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  • richardmitnick 12:53 pm on August 24, 2016 Permalink | Reply
    Tags: , , , PALE RED DOT, ,   

    From ESO: “Planet Found in Habitable Zone Around Nearest Star” 

    ESO 50 Large

    European Southern Observatory

    24 August 2016
    Guillem Anglada-Escudé (Lead Scientist)
    Queen Mary University of London
    London, United Kingdom
    Tel: +44 (0)20 7882 3002
    Email: g.anglada@qmul.ac.uk

    Pedro J. Amado (Scientist)
    Instituto de Astrofísica de Andalucía – Consejo Superior de Investigaciones Cientificas (IAA/CSIC)
    Granada, Spain
    Tel: +34 958 23 06 39
    Email: pja@iaa.csic.es

    Ansgar Reiners (Scientist)
    Institut für Astrophysik, Universität Göttingen
    Göttingen, Germany
    Tel: +49 551 3913825
    Email: ansgar.reiners@phys.uni-goettingen.de

    James S. Jenkins (Scientist)
    Departamento de Astronomia, Universidad de Chile
    Santiago, Chile
    Tel: +56 (2) 2 977 1125
    Email: jjenkins@das.uchile.cl

    Michael Endl (Scientist)
    McDonald Observatory, The University of Texas at Austin
    Austin, Texas, USA
    Tel: +1 512 471 8312
    Email: mike@astro.as.utexas.edu

    Richard Hook (Coordinating Public Information Officer)
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: proxima@eso.org

    Martin Archer (Public Information Officer)
    Queen Mary University of London
    London, United Kingdom
    Tel: +44 (0) 20 7882 6963
    Email: m.archer@qmul.ac.uk

    Silbia López de Lacalle (Public Information Officer)
    Instituto de Astrofísica de Andalucía
    Granada, Spain
    Tel: +34 958 23 05 32
    Email: silbialo@iaa.es

    Romas Bielke (Public Information Officer)
    Georg August Universität Göttingen
    Göttingen, Germany
    Tel: +49 551 39-12172
    Email: Romas.Bielke@zvw.uni-goettingen.de

    Natasha Metzler (Public Information Officer)
    Carnegie Institution for Science
    Washington DC, USA
    Tel: +1 (202) 939 1142
    Email: nmetzler@carnegiescience.edu

    David Azocar (Public Information Officer)
    Departamento de Astronomia, Universidad de Chile
    Santiago, Chile
    Email: dazocar@das.uchile.cl

    Rebecca Johnson (Public Information Officer)
    McDonald Observatory, The University of Texas at Austin
    Austin, Texas, USA
    Tel: +1 512 475 6763
    Email: rjohnson@astro.as.utexas.edu

    Hugh Jones (Scientist)
    University of Hertfordshire
    Hatfield, United Kingdom
    Tel: +44 (0)1707 284426
    Email: h.r.a.jones@herts.ac.uk

    Jordan Kenny (Public Information Officer)
    University of Hertfordshire
    Hatfield, United Kingdom
    Tel: +44 1707 286476
    Cell: +44 7730318371
    Email: j.kenny@herts.ac.uk

    Yiannis Tsapras (Scientist)
    Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg
    Heidelberg, Germany
    Tel: +49 6221 54-181
    Email: ytsapras@ari.uni-heidelberg.de

    1

    Pale Red Dot campaign reveals Earth-mass world in orbit around Proxima Centauri

    Pale Red Dot

    Astronomers using ESO telescopes and other facilities have found clear evidence of a planet orbiting the closest star to Earth, Proxima Centauri.

    The long-sought world, designated Proxima b, orbits its cool red parent star every 11 days and has a temperature suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth and is the closest exoplanet to us — and it may also be the closest possible abode for life outside the Solar System. A paper describing this milestone finding will be published in the journal Nature on 25 August 2016.

    Just over four light-years from the Solar System lies a red dwarf star that has been named Proxima Centauri as it is the closest star to Earth apart from the Sun. This cool star in the constellation of Centaurus is too faint to be seen with the unaided eye and lies near to the much brighter pair of stars known as Alpha Centauri AB.

    During the first half of 2016 Proxima Centauri was regularly observed with the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile and simultaneously monitored by other telescopes around the world [1]. This was the Pale Red Dot campaign, in which a team of astronomers led by Guillem Anglada-Escudé, from Queen Mary University of London, was looking for the tiny back and forth wobble of the star that would be caused by the gravitational pull of a possible orbiting planet [2].

    As this was a topic with very wide public interest, the progress of the campaign between mid-January and April 2016 was shared publicly as it happened on the Pale Red Dot website and via social media. The reports were accompanied by numerous outreach articles written by specialists around the world.

    Guillem Anglada-Escudé explains the background to this unique search: “The first hints of a possible planet were spotted back in 2013, but the detection was not convincing. Since then we have worked hard to get further observations off the ground with help from ESO and others. The recent Pale Red Dot campaign has been about two years in the planning.”

    The Pale Red Dot data, when combined with earlier observations made at ESO observatories and elsewhere, revealed the clear signal of a truly exciting result. At times Proxima Centauri is approaching Earth at about 5 kilometres per hour — normal human walking pace — and at times receding at the same speed. This regular pattern of changing radial velocities repeats with a period of 11.2 days. Careful analysis of the resulting tiny Doppler shifts showed that they indicated the presence of a planet with a mass at least 1.3 times that of the Earth, orbiting about 7 million kilometres from Proxima Centauri — only 5% of the Earth-Sun distance [3].

    Guillem Anglada-Escudé comments on the excitement of the last few months: “I kept checking the consistency of the signal every single day during the 60 nights of the Pale Red Dot campaign. The first 10 were promising, the first 20 were consistent with expectations, and at 30 days the result was pretty much definitive, so we started drafting the paper!”

    Red dwarfs like Proxima Centauri are active stars and can vary in ways that would mimic the presence of a planet. To exclude this possibility the team also monitored the changing brightness of the star very carefully during the campaign using the ASH2 telescope at the San Pedro de Atacama Celestial Explorations Observatory in Chile and the Las Cumbres Observatory telescope network. Radial velocity data taken when the star was flaring were excluded from the final analysis.

    2
    ASH2 telescope at the San Pedro de Atacama Celestial Explorations Observatory in Chile

    LCOGT Las Cumbres Observatory Global Telescope Network, Haleakala Hawaii, USA
    LCOGT Las Cumbres Observatory Global Telescope Network, Haleakala Hawaii, USA

    Although Proxima b orbits much closer to its star than Mercury does to the Sun in the Solar System, the star itself is far fainter than the Sun. As a result Proxima b lies well within the habitable zone around the star and has an estimated surface temperature that would allow the presence of liquid water. Despite the temperate orbit of Proxima b, the conditions on the surface may be strongly affected by the ultraviolet and X-ray flares from the star — far more intense than the Earth experiences from the Sun [4].

    Two separate papers discuss the habitability of Proxima b and its climate. They find that the existence of liquid water on the planet today cannot be ruled out and, in such case, it may be present over the surface of the planet only in the sunniest regions, either in an area in the hemisphere of the planet facing the star (synchronous rotation) or in a tropical belt (3:2 resonance rotation). Proxima b’s rotation, the strong radiation from its star and the formation history of the planet makes its climate quite different from that of the Earth, and it is unlikely that Proxima b has seasons.

    This discovery will be the beginning of extensive further observations, both with current instruments [5] and with the next generation of giant telescopes such as the European Extremely Large Telescope (E-ELT). Proxima b will be a prime target for the hunt for evidence of life elsewhere in the Universe. Indeed, the Alpha Centauri system is also the target of humankind’s first attempt to travel to another star system, the StarShot project.

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker
    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    Guillem Anglada-Escudé concludes: “Many exoplanets have been found and many more will be found, but searching for the closest potential Earth-analogue and succeeding has been the experience of a lifetime for all of us. Many people’s stories and efforts have converged on this discovery. The result is also a tribute to all of them. The search for life on Proxima b comes next…”

    Note: We are aware that there have been rumours regarding this discovery. These rumours have never been confirmed and have not contained any research content. Whilst the rumours are in the public domain and can be reported, the information in this release, the paper itself and the associated visuals have been provided on an embargoed basis and therefore remain strictly under embargo until 19:00 CEST on 24 August 2016. We would be grateful if any questions or concerns are addressed to us before any action is taken. We thank you for your consideration in this matter.
    Notes

    [1] Besides data from the recent Pale Red Dot campaign, the paper incorporates contributions from scientists who have been observing Proxima Centauri for many years. These include members of the original UVES/ESO M-dwarf programme (Martin Kürster and Michael Endl), and exoplanet search pioneers such as R. Paul Butler. Public observations from the HARPS/Geneva team obtained over many years were also included.

    [2] The name Pale Red Dot reflects Carl Sagan’s famous reference to the Earth as a pale blue dot. As Proxima Centauri is a red dwarf star it will bathe its orbiting planet in a pale red glow.

    [3] The detection reported today has been technically possible for the last 10 years. In fact, signals with smaller amplitudes have been detected previously. However, stars are not smooth balls of gas and Proxima Centauri is an active star. The robust detection of Proxima b has only been possible after reaching a detailed understanding of how the star changes on timescales from minutes to a decade, and monitoring its brightness with photometric telescopes.

    [4] The actual suitability of this kind of planet to support water and Earth-like life is a matter of intense but mostly theoretical debate. Major concerns that count against the presence of life are related to the closeness of the star. For example gravitational forces probably lock the same side of the planet in perpetual daylight, while the other side is in perpetual night. The planet’s atmosphere might also slowly be evaporating or have more complex chemistry than Earth’s due to stronger ultraviolet and X-ray radiation, especially during the first billion years of the star’s life. However, none of the arguments has been proven conclusively and they are unlikely to be settled without direct observational evidence and characterisation of the planet’s atmosphere. Similar factors apply to the planets recently found around TRAPPIST-1.

    [5] Some methods to study a planet’s atmosphere depend on it passing in front of its star and the starlight passing through the atmosphere on its way to Earth. Currently there is no evidence that Proxima b transits across the disc of its parent star, and the chances of this happening seem small, but further observations to check this possibility are in progress.

    More information

    The team is composed of Guillem Anglada-Escudé (Queen Mary University of London, London, UK), Pedro J. Amado (Instituto de Astrofísica de Andalucía – CSIC, Granada, Spain), John Barnes (Open University, Milton Keynes, UK), Zaira M. Berdiñas (Instituto de Astrofísica de Andalucia – CSIC, Granada, Spain), R. Paul Butler (Carnegie Institution of Washington, Department of Terrestrial Magnetism, Washington, USA), Gavin A. L. Coleman (Queen Mary University of London, London, UK), Ignacio de la Cueva (Astroimagen, Ibiza, Spain), Stefan Dreizler (Institut für Astrophysik, Georg-August-Universität Göttingen, Göttingen, Germany), Michael Endl (The University of Texas at Austin and McDonald Observatory, Austin, Texas, USA), Benjamin Giesers (Institut für Astrophysik, Georg-August-Universität Göttingen, Göttingen, Germany), Sandra V. Jeffers (Institut für Astrophysik, Georg-August-Universität Göttingen, Göttingen, Germany), James S. Jenkins (Universidad de Chile, Santiago, Chile), Hugh R. A. Jones (University of Hertfordshire, Hatfield, UK), Marcin Kiraga (Warsaw University Observatory, Warsaw, Poland), Martin Kürster (Max-Planck-Institut für Astronomie, Heidelberg, Germany), María J. López-González (Instituto de Astrofísica de Andalucía – CSIC, Granada, Spain), Christopher J. Marvin (Institut für Astrophysik, Georg-August-Universität Göttingen, Göttingen, Germany), Nicolás Morales (Instituto de Astrofísica de Andalucía – CSIC, Granada, Spain), Julien Morin (Laboratoire Univers et Particules de Montpellier, Université de Montpellier & CNRS, Montpellier, France), Richard P. Nelson (Queen Mary University of London, London, UK), José L. Ortiz (Instituto de Astrofísica de Andalucía – CSIC, Granada, Spain), Aviv Ofir (Weizmann Institute of Science, Rehovot, Israel), Sijme-Jan Paardekooper (Queen Mary University of London, London, UK), Ansgar Reiners (Institut für Astrophysik, Georg-August-Universität Göttingen, Göttingen, Germany), Eloy Rodriguez (Instituto de Astrofísica de Andalucía – CSIC, Granada, Spain), Cristina Rodriguez-Lopez (Instituto de Astrofísica de Andalucía – CSIC, Granada, Spain), Luis F. Sarmiento (Institut für Astrophysik, Georg-August-Universität Göttingen, Göttingen, Germany), John P. Strachan (Queen Mary University of London, London, UK), Yiannis Tsapras (Astronomisches Rechen-Institut, Heidelberg, Germany), Mikko Tuomi (University of Hertfordshire, Hatfield, UK) and Mathias Zechmeister (Institut für Astrophysik, Georg-August-Universität Göttingen, Göttingen, Germany).

    Links

    Research paper in Nature
    Two new papers on Habitability on Proxima b

    See the full article here .

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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    Atacama Pathfinder Experiment (APEX) Telescope

     
  • richardmitnick 5:10 am on July 7, 2016 Permalink | Reply
    Tags: , , PALE RED DOT, Peer Review   

    From Pale Red Dot via Oanu Sandu: “Peer review — or how an experiment becomes scientific literature” 

    Pale Red Dot

    Pale Red Dot

    July 5, 2016

    What is happening now?

    Now that the data collection and analysis are complete and the results written in a paper, the next step is for the paper to be verified by the scientific community before going public. Peer review is the process the scientific community uses for quality control of results. While a new exoplanet or supernova might have little impact on our immediate life, mistakes in some scientific disciplines (e.g. biomedical research, chemistry, climate change,.. ) can have very serious consequences. Requests for research funding, patents, space missions and even new medicines are generally not accepted unless they rely on publicly available, peer reviewed research.

    An important component of the peer review process are the scientific journals. Some journals will publish anything as long as it is scientifically correct, while some others will only publish results that are deemed novel or represent a very significant advance.

    Who decides what it is correct and significant?

    For each paper, there are at least two key people that are responsible for assessing correctness and significance. They are the editor and the referee(s). To understand how peer review works, it is better to explain the life cycle of a scientific paper.

    1
    Flow chart of the peer review process. The approximate status of our paper as of July 1st, is marked with the red dot. No image credit.

    Submission

    The authors must choose to submit their paper to a journal of their choice. Once the journal receives the manuscript, a scientific editor is assigned to it. This editor manages and supervises the process. Editors are respected senior scientists that work full-time for the journal, or work at a University and part-time for the journal. Papers can be rejected at this stage because the editor considers there is not sufficient original science in the result, or because the article does not match the philosophy of the journal.

    Paper sent to review

    After a preliminary quality assessment, the editor will search for experts to provide a more detailed revision. These experts (called referees) are scientists not involved in the result but are experts in the field to which the paper relates. One or more referees can be assigned to a paper, and they are asked to submit a report within a few weeks.

    Referees’ opinions have a lot of leverage over the fate of a scientific result. Since referees are likely to be working on a related topic, conflicts of interest can arise and it is the editors job to carefully monitor the process. For example, if a reviewer is exceedingly enthusiastic, aggressive (or even careless), editors can search for additional referees or ignore a review. Referees are asked to follow strict ethical rules and confidentiality. The identity of the referees is not revealed to the authors to protect their independence.

    First revision

    After a while referee reports are sent to the editor and s/he then decides whether or not to proceed with the publication. Passing first revision is an important milestone because serious show stoppers are often identified at this stage. If the referee reports are not negative, the editor forwards them to the authors, and they are given some time to address comments and criticisms. Typical requests consist of providing additional data, analyses, adding references to previous work, and providing better discussion on obscure points of the original manuscript.

    This is where we are with our Proxima paper!

    After implementing the changes, the authors re-submit the article together with responses to the referee reports. The editor forwards all this information to the referees, and the process is iterated until the editor accepts it.

    Acceptance

    At acceptance the editor has become convinced that the paper meets the quality standards of the journal. They then write an acceptance notification which is met with great delight by the authors.

    We hope to reach that point soon!

    … but it is not over yet

    Acceptance only concerns the content. At this stage authors might need to remake plots, prepare final tables and even rewrite some small parts of the paper. This process is done in collaboration with the production teams of the journal and can take from a few days to a few weeks. Final editing is performed in collaboration with professional writers who take account of English language and style.

    As in any other professionally published work, the last editorial step consists of sending the paper in its very final format (commonly called ‘galley proofs’) to the authors for their final approval. When this is done, a publication date is assigned and the peer review process is complete.

    hooray!

    Scientific results can also be presented in conferences or other media, but these are not considered valid references unless they are published in a peer review journal. Alternative peer review procedures are being tested, but still the vast majority of scientific production goes through this classic peer review system.

    … reaching the public!

    It is becoming increasingly important to raise awareness of new scientific (peer reviewed) discoveries, and to be clear of what they mean to all of us. Scientists often don’t have time nor the skills to do that, so this falls into the hands of outreach, press offices, science writers and science communicators in general. When a significant result is achieved, the information needs to be transformed from the dry rigour of a scientific paper to something non-specialised audiences can digest. This includes the so-called general public, but also companies, governments and policy makers who might need to decide on crucial matters based on the most updated evidence.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What is PALE RED DOT?

    It is an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely are there Earth-like planets around the nearest stars?

    Why we call it PALE RED DOT?

    In 1990, Voyager 1, on its trek towards interstellar space, sent back a picture of the Inner Solar System on which the Earth occupied less than a pixel. This image of Earth was called Pale Blue Dot, and inspired the late Carl Sagan’s essay ‘Pale Blue Dot : A vision of the human future in Space’, which in turn has been the source of inspiration for a generation of exoplanet hunters. Given that Proxima Centauri — or just Proxima — is a red dwarf star, such a planet would show reddish tints. Even if successful, we will only obtain information about its orbital period and mass — even less than Voyager 1’s pale blue pixel… at least for now!

    What is special about the project?

    Proxima Centauri is the nearest star to the Sun. The discovery of a planet with some characteristics like Earth in our immediate vicinity would be momentous. After years of data acquisition by many researchers and teams, a signal has been identified which may indicate the presence of an Earth-like planet. The Pale Red Dot project will carry out further detailed observations with the aim to confirm or refute the presence of the planet. By broadcasting the progress and results of the observations through all media channels available e.g. press, website, and social media, the Pale Red Dot project aims to promote Science Technology Engineering and Mathematics (STEM) in the broader society, inform the public and hopefully inspire a new generation of scientists.

    How such a scientific program is organized?

    The planned observation campaign is based on a proposal submitted by the involved scientists to ESO, LCOGT and BOOTES observatories. The proposals, in turn, are based on the analysis of data accumulated and obtained over the years by ourselves or by other researchers abroad. Observatories and other advanced research facilities are mostly supported by public resources, large international consortia and private foundations.

    How the results will be reported?

    As in any professional scientific work, final results need to be reviewed by the community before being announced. After the campaign is finished by April 1st, the really tough process of analyzing the data, drawing conclusions and presenting them in a credible manner will begin. After that, the analysis will be summarized in an article and submitted to a scientific journal. At that point, one or more scientists NOT involved in the project will critically revise the work, suggest modifications and even reject its publication if fundamental flaws are spotted. This last step of peer-review can take any time between a few months to a year or two. Hopefully, the data will prove to be high quality and the observations will have a straightforward interpretation, but that is just a hope. A few key milestones of the peer-review process will also be reported on the website, which might remain active at a lower activity level after the observing campaign has finished.

     
  • richardmitnick 8:22 pm on April 21, 2016 Permalink | Reply
    Tags: , , Interview to Didier Queloz — ‘From 51 Pegasi to the search for life around small stars’, PALE RED DOT   

    From PALE RED DOT: “Interview to Didier Queloz — ‘From 51 Pegasi to the search for life around small stars’ “ 

    Pale Red Dot

    Pale Red Dot

    April 21, 2016

    Interview to Prof. Didier Queloz at University of Cambridge/UK, by Guillem Anglada-Escude

    In the early 90’s the search for extra-solar planets was not even a research topic. What can you tell us about those first days?

    At the end of the 80’s and early 90’s, exoplanets were not fashionable at all. I was involved in the design and building of a new type of instrument specifically designed to find planets around other stars. Our team were very successful in making key design decisions, so as soon we had the instrument on the telescope, we quickly identified one with quite a different variability from the others. It was 51 Peg.

    The spectrograph concept was developed by a team under the direction of Prof. Michel Mayor. Who created the optical design? I heard that a French professor called Andre Baranne was a key person at that stage…

    ESO VLT GIRAFFE spectrograph
    ESO VLT GIRAFFE spectrograph

    Yes, in any instrument, there is always an expert in precision optics. The person for that project was Prof. Andre Baranne. He was the creator of the so-called ‘white-pupil’ design, which is now adopted by most high resolution spectrometers. Before Andre’s work, spectrometers were huge, photon-eating devices. Thanks to that improvement, instruments became compact and efficient. He was close to retirement but he became very active in the project. The spectrometer was build at Observatoire de Haute Provence (OHP).

    L'Observatoire de Haute-Provence
    Observatoire de Haute-Provence

    In those days they had very sensitive cameras for faint objects, but a lot of telescope time could not be used because of background contamination by the moon. This is when Michel Mayor came forward offering a high resolution spectrometer for stellar astrophysics that, at the same time, would be able to detect radial velocities with unprecedented precision. Because it was a joint effort of Micheal’s team and the observatory, quite a lot of people were behind the design of the numerous subsystems.

    1
    The ELODIE spectrograph ready for operation at the 193 cm Telescoep of l’Observatoire de Haute Provence. Image credit : CNRS / OHP

    You and Micheal Mayor were at the Geneva Observatory at the time but the spectrograph was made by OHP?

    Yes, OHP built it but most participating astronomers were from Geneva. Michel already had a working instrument at OHP called CORAVEL, so it was a natural choice for him to to build the new one with them. The deal was the following; OHP would build two spectrometers, and the second one would be installed at the Swiss telescope at la Silla in Chile (CORALIE).

    ESO Swiss 1.2 meter Leonhard Euler Telescope
    ESO Swiss 1.2 meter Leonhard Euler Telescope at La Silla

    For a number of reasons, the OHP one -ELODIE- was at the telescope first, which is where I spent most of my PhD time testing the new hardware, detectors, optical fibres, wavelength calibration using Thorium-Argon lamps and simultaneous tracking. These are obvious things to do today, but they were completely new concepts at the time. ELODIE was the first of a series of instruments that led to HARPS.

    ESO 3.6m telescope & HARPS at LaSilla
    ESO/HARPS
    ESO/HARPS

    1
    World-renowned Swiss astronomers Didier Queloz and Michel Mayor of the Geneva Observatory are seen here in front of ESO’s 3.6-metre telescope at La Silla Observatory in Chile. The telescope hosts HARPS, the world’s leading exoplanet hunter. Image credits : L. Weinstein/Ciel et Espace Photos/ESO

    So what was the key element that made possible the breakthrough of finding the first planet in 1995?

    Two really important things. We had enough telescope time to look at a meaningful sample of stars. And second, of course, we also had the machine to do it. We could regularly obtain data with a precision better than 10 m/s, which had not been possible before… and the signals were just there. Once you have done the really hard work of getting that kind of precision, the planets come for free (‘almost’). The previous precision was 50–100 m/s with instruments similar to CORAVEL, and even some first results reported by G. Marcy’s team , were in the 20–30 m/s level. When Marcy & Butler managed to get down to 5–10 m/s level, the planets started to show-up in their data too. The same for us. This new machine started delivering better than 10 m/s since the beginning, so with all this hard work done you can only start finding those planets.

    How was finding 51 Peg, and more importantly, how sure were you that it was a planet? Lots of people were skeptical those days, arguing that it was an instrumental error?..an astrophysical artifact?..a binary?

    In a sense, people were right to be skeptical. We were as well. You have to realize there were no known exoplanets in those days. It was a rather special situation. Today is very different. You can now publish, or claim detections of planets, even if you are not 100% sure because there are many of them so one more or less is not that transcendental. That was not the case back then. You REALLY needed to be sure. In our case, it was a new instrument and nobody was expecting to find a planet at such short period. I was the first not to expect it, and the same for Michel Mayor. Michel was on sabbatical, so I started the observation program more or less alone. Quite early on I picked up a strange object. It was weird, that star was clearly not stable above those 10 m/s, but it was known to be a very non-active sun-like star too. I kind of felt responsible for the operation of the spectrograph and all the software, so I became completely obsessed with it. I observed 51 Peg much more often than was planned. Consequently I found that there was a periodicity to the signal. Then I took quite some time to convince myself first that the signal was a planet without telling anybody. Convincing myself implied reviewing all the data-processing, the way the velocity was measured, that the period was not related to some instrumental issue and review the other stars in the sample. Once there was no more to check, I sent a fax to Michel who was in Hawaii. “Michel, I think I have found a planet with this period”. Michel responded “Yes, ok… maybe, I’ll see when I come back”. He was really puzzled. We then reviewed everything from the start again, thinking there might be a bug somewhere… even what we knew from the star itself; star-spots on it could create a signal.

    3
    Radial velocity curve of 51 Peg as measured by ELODIE. The radial velocity variations follow an amplitude of 59 m/s and have a period of 4.23 days. Source : OHP

    It’s kind of funny for me, because most of what has been done later—looking at activity features and comparing it to the orbits of the possible planets—we did all these in that first paper too. I suspect nobody understood the reason for all those tests and complexity (read about the reasons in X. Dumusque’s article here). The detection of the signal was the easy part! The hard part was to be completely sure that it was a planet, and nothing else. When we had all this, we submitted the paper, and it barely got accepted. It felt a bit like magic because it was shaking the currently held theory. In a way, when we announced it at the Florence meeting, we were lucky that G.Marcy & P. Bulter were at the telescope at that very moment. G. Marcy later confessed that he thought the signal was a complete fraud, so they were also really surprised when they could confirm the signal after only a few days. This was kind of the key point of my PhD, and a big relief. That meant that the data was fine, the spectrograph was working and the period was also fine. Then we had to struggle a lot with the community. For example, many argued this could not be a planet but the atmosphere of a star changing over time. In science when you make a big claim you typically get heavily attacked, and if you survive you come back even stronger. So it took us a couple of years to convince everybody, but the final blow came in 2000 when the first of these planets was found to transit in front of the star.

    51 Peg, and the planets we familiarly know as hot-Jupiters, are still a mystery and a challenge. We know a lot about these hot-Jupiters, we probe their atmospheres, we can see if their orbits are aligned with the star. But it is still a mystery how they fit in the big picture of how we think planets should form. We now know that those planets are relatively rare (about <2% of the stars have them). But with these odds, you pick up 50 stars at random and this is what you get. True enough, there was only one hot-Jupiter in our sample. In a sense, you need to be lucky to find a planet. You need the right instrument and the right strategy, and the planet needs to be there.

    But one needs to push his luck…

    Sure, what we were really ‘lucky’ about is that the other team didn’t get it first! Geoff Marcy started 2 years before so they could have found it two years earlier.

    There were issues with resources if you ask Paul Butler (see story here!)… Are there other discoveries after 51 Peg that you feel proud of as well?

    Well, I think the discovery of 51 Peg was the key to this threshold—it changed the whole game, it opened up the field of exoplanets. So I came out in this strange situation, my best ever result and highest impact paper is that first one. I mean, we created the field with 51 Peg in 1995. Before it was a weird topic, after ’95 it was a scientific topic, and the theme has been made broader because it is related to the search for life in the universe. 51 Peg was key. Of course, I have been doing lots and lots of other things, and working on other techniques like transit searches and astrometry.

    What is driving your research these days?

    Oh, this is simple. We have a long list of questions now. 51 Peg was the entry point. There are numerous scientific questions to answer, and a handful that are really important and deep ones. For example, the formation of our Solar System in the context of other planetary systems. We need to detect lots of planets and characterize their atmospheres to understand how planetary systems form and evolve…

    …but the real question that is driving my efforts is looking for life in the universe. After finding the first planet, this is the next big thing. From a practical point of view; can we define a robust and affordable strategy to do this? I am getting more and more convinced that a step-by-step process is realistic, but it will require out-of-the-box thinking in terms of support of the science. So now I invest a lot of time to try to explain to people that the Victorian division of the sciences like Chemistry, Physics, Astrophysics, Biology doesn’t make sense in this context anymore. The question of life in the universe is a multi-disciplinary problem that needs to be tackled in a different way. I try to convince agencies, and the universities, that all the work I have been doing is about promoting this new kind of work. I might not be doing it myself because I am getting too old, but I really think that the task of the next generation of scientists won’t be searching for the planets, it will be about figuring out whether there is life on these planets.

    From all the proposals to search for evidence of life around exoplanets, do you have a favorite one?

    There are plenty of ways to look for evidence of life on other planets. The difference is in the practicalities. It will be enormously difficult to detect and characterize an Earth-analog around a star like the Sun. It will be done, I am pretty sure, we will eventually have pictures of such a world, we will see continents, rotation… that will happen, I am confident, nothing will stop. It is just that, being realistic, the technology we need is not there. As scientists we want to think big and far, but we also need to look at what the technology of today can achieve. Along these lines, there are a number of experiments that allow us to push pretty far in the understanding of exoplanets (post by Don Polacco). The transit technique gives potential access to the atmospheres, so we need to work on that. And the direct imaging method has finally made great progress and soon will be providing abundant information about the atmosphere of planets (gas giants first).

    Can we do well enough to be able to find life? This is where we need to go back to the books. People have been thinking about this for a long time. What would an Early-Earth atmosphere look like. What about the early UV and X-ray fluxes? All the assumptions made so far were very simplistic and the habitable zone concept much tied to the Earth’s… you add some hydrogen into the atmosphere and the possible climates change completely. We need studies at telescopes, but also in the lab. My idea is being as open-minded as I can. The real drive of the field has been finding and reporting the unexpected. We really need to get away from being over-simplistic.

    Today, there are kinds of stars where we might be able to do it, because it is easier. These are very very small stars (like Proxima). With the available technology of today, there are realistic chances of finding the first hints of life in planets around them. This is an amazing field of research. It is extremely exciting to begin the transition from exoplanet detection towards the search for life. These planets must be very different than Earth. Nobody has thought much about taking an Earth and putting it so close to the star. The amount of UV fluxes, tidal interactions, the nature of the atmosphere and climates… all can be so different! We have to go to the drawing board and broaden our expectations. In this sense, I think Pale Red Dot is the kind of project that is opening up where these planets are, it can lead to the new science that will explode soon. There will be some chance of seeing hints of organic activity, but let’s make it more simple… let’s look for something that tells us that an atmosphere is out-of-balance. Life takes the Earth atmosphere out of balance. This is something that cannot happen without an active agent on the planet surface. So, let’s search for signs of these atmospheres being out of balance. This will be a new big window that can potentially open the field as the first planet did. I’m willing to invest time enabling this new era.

    We all have high hopes of that… so how do you see the mid-term future? Do you see a large class mission in space anytime soon?

    I have experience with space missions. Careful! Space business is about minimizing risk. Space missions and agencies run away from doing new technology. On the other hand, you can do many more technological cycles from the ground. The low-mass stars can be done from the ground. And this is the problem. There is no big experiment systematically preparing to investigate planets around these very low-mass stars. There are small attempts but we really need more. The one program I am aware of is SPECULOOS, and there can be many more of these programs.

    SPECULOOS  four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory
    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory

    But these are on small class telescopes and the goal is finding them, not characterizing them… Is there a plan for the big telescopes? No, there isn’t! We can do it and we should do it. Infrared, stabilized spectrographs on the VLT do not need a 100M € investment. So a lot can be done from the ground.

    ESO/VLT
    ESO/VLT at Cerro Paranal

    Space is great, but space is not the place for innovation and development. You need to first to have the technology, show that it will definitely work, and setup long and expensive technology development programs. The European Space Agency (ESA) is not good at that. The budget is really limited compared to larger agencies like NASA. For example, ESA could not launch something like JWST [neither could NASA, without its partners, ESA and CSA].

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    Given that this is our working framework, we should be promoting and strongly developing our ground based facilities. We could be world-leading, and we are not doing that. There are exoplanet detection programs attached to some instrument developments but, given the weight and influence of the field, we don’t have enough. We are not investing enough to go for the big challenge that is the search for life. I will be happy to change my mind if a revolutionary idea (and resources) show up. But we need to be very careful in thinking that space is the solution to all our needs.

    For example, look at the gravitational wave experiments.

    Caltech/MIT Advanced aLIGO Hanford Washington USA installation
    Caltech/MIT Advanced aLIGO Hanford Washington USA installation

    It took 30 years to build up and refine the experiments needed to finally be successful, and they might also get a space mission.

    ESA/LISA Pathfinder
    ESA/LISA Pathfinder

    We are now in a similar situation. I think we need a bit more progress. We should be looking for life around these low-mass stars. Once we find it (or evidence for it), that will completely change the field (as 51 Peg did) . The current designs of big missions are not appropriate to search for evidence of life. People designed the missions to detect planets orbiting G,K and early M-stars. That is not what is needed in the most immediate time-frame to move forward in the search for life. My hope? When we start detecting and investigating these planets around low-mass stars, we will realize we haven’t built the right instrument and we will react to it.

    A paradigm change then…

    Yes, I think with experiments like Pale Red Dot and SPECULOOS it will become obvious these planets are probably there in large numbers; and then we won’t be looking for the planets themselves, we will start looking for life. The experiments and the field become different. I don’t want to minimize the importance of other questions like origins and formation of planetary systems. It is crucial to understand how the solar system started and put it in context. But if you really want to look ahead, the goal is to search for life, nothing else. By finding hints of life around these small stars, the argument will become strong and solid enough to promote and narrow-down the design of THE space mission that will address the question of life in the universe in a broader context.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What is PALE RED DOT?

    It is an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely are there Earth-like planets around the nearest stars?

    Why we call it PALE RED DOT?

    In 1990, Voyager 1, on its trek towards interstellar space, sent back a picture of the Inner Solar System on which the Earth occupied less than a pixel. This image of Earth was called Pale Blue Dot, and inspired the late Carl Sagan’s essay ‘Pale Blue Dot : A vision of the human future in Space’, which in turn has been the source of inspiration for a generation of exoplanet hunters. Given that Proxima Centauri — or just Proxima — is a red dwarf star, such a planet would show reddish tints. Even if successful, we will only obtain information about its orbital period and mass — even less than Voyager 1’s pale blue pixel… at least for now!

    What is special about the project?

    Proxima Centauri is the nearest star to the Sun. The discovery of a planet with some characteristics like Earth in our immediate vicinity would be momentous. After years of data acquisition by many researchers and teams, a signal has been identified which may indicate the presence of an Earth-like planet. The Pale Red Dot project will carry out further detailed observations with the aim to confirm or refute the presence of the planet. By broadcasting the progress and results of the observations through all media channels available e.g. press, website, and social media, the Pale Red Dot project aims to promote Science Technology Engineering and Mathematics (STEM) in the broader society, inform the public and hopefully inspire a new generation of scientists.

    How such a scientific program is organized?

    The planned observation campaign is based on a proposal submitted by the involved scientists to ESO, LCOGT and BOOTES observatories. The proposals, in turn, are based on the analysis of data accumulated and obtained over the years by ourselves or by other researchers abroad. Observatories and other advanced research facilities are mostly supported by public resources, large international consortia and private foundations.

    How the results will be reported?

    As in any professional scientific work, final results need to be reviewed by the community before being announced. After the campaign is finished by April 1st, the really tough process of analyzing the data, drawing conclusions and presenting them in a credible manner will begin. After that, the analysis will be summarized in an article and submitted to a scientific journal. At that point, one or more scientists NOT involved in the project will critically revise the work, suggest modifications and even reject its publication if fundamental flaws are spotted. This last step of peer-review can take any time between a few months to a year or two. Hopefully, the data will prove to be high quality and the observations will have a straightforward interpretation, but that is just a hope. A few key milestones of the peer-review process will also be reported on the website, which might remain active at a lower activity level after the observing campaign has finished.

     
  • richardmitnick 10:27 am on April 16, 2016 Permalink | Reply
    Tags: , , PALE RED DOT,   

    From PALE RED DOT: “Campaign Highlights 1” 

    Pale Red Dot

    Pale Red Dot

    1

    Observing flares on Proxima! For a short time Proxima became 10% brighter! Imagine what would happen if the Sun did that!!

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What is PALE RED DOT?

    It is an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely are there Earth-like planets around the nearest stars?

    Why we call it PALE RED DOT?

    In 1990, Voyager 1, on its trek towards interstellar space, sent back a picture of the Inner Solar System on which the Earth occupied less than a pixel. This image of Earth was called Pale Blue Dot, and inspired the late Carl Sagan’s essay ‘Pale Blue Dot : A vision of the human future in Space’, which in turn has been the source of inspiration for a generation of exoplanet hunters. Given that Proxima Centauri — or just Proxima — is a red dwarf star, such a planet would show reddish tints. Even if successful, we will only obtain information about its orbital period and mass — even less than Voyager 1’s pale blue pixel… at least for now!

    What is special about the project?

    Proxima Centauri is the nearest star to the Sun. The discovery of a planet with some characteristics like Earth in our immediate vicinity would be momentous. After years of data acquisition by many researchers and teams, a signal has been identified which may indicate the presence of an Earth-like planet. The Pale Red Dot project will carry out further detailed observations with the aim to confirm or refute the presence of the planet. By broadcasting the progress and results of the observations through all media channels available e.g. press, website, and social media, the Pale Red Dot project aims to promote Science Technology Engineering and Mathematics (STEM) in the broader society, inform the public and hopefully inspire a new generation of scientists.

    How such a scientific program is organized?

    The planned observation campaign is based on a proposal submitted by the involved scientists to ESO, LCOGT and BOOTES observatories. The proposals, in turn, are based on the analysis of data accumulated and obtained over the years by ourselves or by other researchers abroad. Observatories and other advanced research facilities are mostly supported by public resources, large international consortia and private foundations.

    How the results will be reported?

    As in any professional scientific work, final results need to be reviewed by the community before being announced. After the campaign is finished by April 1st, the really tough process of analyzing the data, drawing conclusions and presenting them in a credible manner will begin. After that, the analysis will be summarized in an article and submitted to a scientific journal. At that point, one or more scientists NOT involved in the project will critically revise the work, suggest modifications and even reject its publication if fundamental flaws are spotted. This last step of peer-review can take any time between a few months to a year or two. Hopefully, the data will prove to be high quality and the observations will have a straightforward interpretation, but that is just a hope. A few key milestones of the peer-review process will also be reported on the website, which might remain active at a lower activity level after the observing campaign has finished.

     
  • richardmitnick 4:04 pm on April 9, 2016 Permalink | Reply
    Tags: , , Magnetic Open Cluster Stars of a Peculiar Kind observed with HARPS-POL, PALE RED DOT   

    From PALE RED DOT: “Magnetic Open Cluster Stars of a Peculiar Kind observed with HARPS-POL” 

    Pale Red Dot

    Pale Red Dot

    April 6, 2016
    James Silvester, Uppsala University

    Magnetic fields play a fundamental role in the atmospheric physics of a significant fraction of stars on the Hertzsprung–Russell diagram. The magnetic fields of the chemically peculiar magnetic A and B type stars (Ap/Bp) have quite different characteristics than, for example, cooler stars like the Sun. In these magnetic Ap/Bp stars the large-scale surface magnetic field is static on time-scales of at least many decades, and appears to be “frozen” into a rigidly rotating atmosphere. The magnetic field is globally organised, permeating the entire stellar surface, with a high field strength (typically of a few hundreds up to a few tens of thousands of gauss—by comparison the sun has a polar field strength of one to two gauss). These stars are so called “chemically peculiar” as a result of having peculiar abundances (amounts) of certain chemical elements compared to what is seen in the Sun or other solar type stars.

    1
    This figure shows a comparison between a solar abundance model spectrum (red dashes, T=5800 K) and typical peculiar abundance spectrum for a hotter star (solid green, T=13000 K). No image credits.

    It is thought that the presence of this magnetic field strongly influences energy and mass transport, and results in strong chemical abundance non-uniformities within the atmosphere. These uniformities can take the form of large abundance structures in certain layers in the atmosphere.

    Originally the magnetic field geometries of these chemically peculiar Ap/BP stars were modelled in the context of a simple dipole field (think of a bar magnet stuck in the star). However, with the acquisition of increasingly sophisticated data, it has become clear that the large-scale field topologies exhibit important differences from a simple pure dipole model. Through the advent of high-resolution circular and linear polarisation spectroscopy we have found the presence of strong, small-scale complex field structures, which were completely unexpected based on earlier modelling.

    How do we measure magnetic fields of Ap/Bp Stars

    In 1897 Dutch physicist Pieter Zeeman discovered that in the presence of an external magnetic field; light is polarised circularly if viewed parallel to the direction of the magnetic field and is plane (or linearly) polarised if viewed perpendicular to the magnetic field. In addition, spectral lines in the presence of such a field can be split into discrete levels—the so called Zeeman effect—where the strength of the magnetic field is proportional to the width of the splitting within the spectral lines.

    The figure below illustrates how both a spectral line and how the linear and circular polarisation signature can change in the presence of a strong magnetic field, in the case of when the field is either perpendicular or parallel to the line of sight of the observer.

    2
    Spectral line shapes in different polarization states.

    We use these effects to study the magnetic field of stars with the aid of a spectropolarimeter. The form of the polarised light we receive tells us about the direction of the field on the surface of the star with respect to the observer, and the level of Zeeman splitting within a given spectral line or set of lines allows us to determine the strength of the magnetic field.

    In cases where the polarisation signal is too weak to effectively measure in individual spectral lines, we can use line averaging techniques to improve the signal by averaging all the lines in the spectrum showing polarisation signatures into one line.
    The recent advances in tomographic imaging techniques and the new generation of spectropolarimeters such as ESPaDOnS (at the CFHT), NARVAL (at the TBL, Pic du Midi) and HARPS-pol (ESO 3.6 at La Silla) offer the opportunity to improve our understanding of the magnetic field of Ap/Bp stars by allowing us to map the magnetic field and chemical surface structure in quite some detail. (For the finer details of how we map magnetic fields see the great article by Élodie Hébrard and Rakesh Yadav).

    3
    The extended magnetic field topology map for the Ap star HD 32633, the number in the right hand corner is the phase of rotation.

    Even though we are able to very successfully map the magnetic fields of Ap/Bp stars, there are however some questions that remain open. Notably the origin of these magnetic fields is not fully understood and importantly neither is the evolution of such magnetic fields and the atmospheric chemical structures with time. This is where Ap/Bp stars in open clusters comes in.

    The Current Project – Observations of Cluster Ap/Bp Stars

    The question of the evolution of the magnetic field and chemical surface structures in Ap/Bp stars can be investigated by studying these stars in open clusters. An open cluster is a group of gravitationally bound stars, and whilst it is very difficult to get an precise age for an individual star, it is however possible to get a more precise age for an open cluster, because you have an ensemble of stars which are thought to be of a similar age. Therefore if you can confirm that a star is a true member of a cluster, you have a much more reliable age for that star than if it was an individual star.

    By studying the magnetic fields of stars in different open clusters with different ages, we can in essence look at Ap/Bp stars at different stages of evolution. This allows us to investigate if the magnetic field complexity, or the form the magnetic field takes, varies as a function of age, e.g does the magnetic field structure of an Ap/Bp star evolve with time?

    4
    The cluster NGC 6475 / M7. Image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla Observatory in Chile. Image credits : ESO

    ESO WFI LaSilla 2.2-m MPG/ESO telescope at La Silla
    ESO WFI LaSilla 2.2-m MPG/ESO telescope at La Silla

    MPG/ESO 2.2 meter telescope at La Silla
    MPG/ESO 2.2 meter telescope at La Silla

    ESO/LaSilla
    ESO/LaSilla

    Our team, including astronomers based in Sweden, Canada and France, has begun to obtain observations of cluster Ap/Bp stars using the HARPSpol spectropolarimeter.

    ESO 3.6m telescope & HARPS at LaSilla

    HARPSpol spectropolarimeter on ESO HARPS at La Silla
    HARPSpol spectropolarimeter on ESO HARPS at La Silla

    By measuring the circular polarisation of these magnetic Ap/Bp stars and by obtaining measurements at all phases of rotation, we will be able to create magnetic and surface chemical maps for all the stars we observe. It is hoped that the resulting maps from our target stars will give us insight into how the magnetic field geometries and chemical surface structures of Ap/Bp stars vary with age. Having more information about the evolution of the magnetic field will also provide a powerful constraint for stellar evolution models.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What is PALE RED DOT?

    It is an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely are there Earth-like planets around the nearest stars?

    Why we call it PALE RED DOT?

    In 1990, Voyager 1, on its trek towards interstellar space, sent back a picture of the Inner Solar System on which the Earth occupied less than a pixel. This image of Earth was called Pale Blue Dot, and inspired the late Carl Sagan’s essay ‘Pale Blue Dot : A vision of the human future in Space’, which in turn has been the source of inspiration for a generation of exoplanet hunters. Given that Proxima Centauri — or just Proxima — is a red dwarf star, such a planet would show reddish tints. Even if successful, we will only obtain information about its orbital period and mass — even less than Voyager 1’s pale blue pixel… at least for now!

    What is special about the project?

    Proxima Centauri is the nearest star to the Sun. The discovery of a planet with some characteristics like Earth in our immediate vicinity would be momentous. After years of data acquisition by many researchers and teams, a signal has been identified which may indicate the presence of an Earth-like planet. The Pale Red Dot project will carry out further detailed observations with the aim to confirm or refute the presence of the planet. By broadcasting the progress and results of the observations through all media channels available e.g. press, website, and social media, the Pale Red Dot project aims to promote Science Technology Engineering and Mathematics (STEM) in the broader society, inform the public and hopefully inspire a new generation of scientists.

    How such a scientific program is organized?

    The planned observation campaign is based on a proposal submitted by the involved scientists to ESO, LCOGT and BOOTES observatories. The proposals, in turn, are based on the analysis of data accumulated and obtained over the years by ourselves or by other researchers abroad. Observatories and other advanced research facilities are mostly supported by public resources, large international consortia and private foundations.

    How the results will be reported?

    As in any professional scientific work, final results need to be reviewed by the community before being announced. After the campaign is finished by April 1st, the really tough process of analyzing the data, drawing conclusions and presenting them in a credible manner will begin. After that, the analysis will be summarized in an article and submitted to a scientific journal. At that point, one or more scientists NOT involved in the project will critically revise the work, suggest modifications and even reject its publication if fundamental flaws are spotted. This last step of peer-review can take any time between a few months to a year or two. Hopefully, the data will prove to be high quality and the observations will have a straightforward interpretation, but that is just a hope. A few key milestones of the peer-review process will also be reported on the website, which might remain active at a lower activity level after the observing campaign has finished.

     
  • richardmitnick 3:41 pm on April 9, 2016 Permalink | Reply
    Tags: , , PALE RED DOT, Terrestrial Planets over the Next Decade   

    From PALE RED DOT: “Terrestrial Planets over the Next Decade” 

    Pale Red Dot

    Pale Red Dot

    April 3, 2016
    Don Pollaco, Warwick University, UK

    There can be no doubt that NASA’s Kepler mission has been a resounding success.

    NASA/Kepler Telescope
    NASA/Kepler Telescope

    In particular, much of what we know about rocky planets has come from this mission. After saying that, ground-based radial velocity surveys had already indicated the existence of super-Earths—a class of planet not found in our solar system (ignoring Planet 9!), and the first exo-rocky planet discovered was found through the French-ESA CoRoT mission (Corot-7b).

    ESA/CoRoT
    ESA/CoRoT

    The list of “firsts” from Kepler is truly amazing:

    1. Planetary size distribution
    2. The commonality of multi-planet systems
    3. The application of transit timing techniques to derive planetary masses and the recovery of unseen components
    4. The detection and modelling of the first circumbinary systems
    5. The diversity of low mass planets
    6. The evaporation and breakup of small planets

    and so, while some results are less good, e.g. estimate of eta-Earth (number of habitable zone planets per star) and the masses of low-mass planets, Kepler’s place in history is assured. To me though, Kepler’s greatest result is really the ubiquity of exoplanets; specifically small planets.

    Almost as impressive has been Kepler’s contribution to the proving of stellar asteroseismology. Whilst these techniques had been applied to the Sun and individual stars, Kepler has been used to derive stellar parameters for hundreds of stars at a level never before achieved en masse.

    Kepler Small Planets

    Kepler has given us a tantalizing first glimpse of the small/rocky planet population and some of the results have been absolutely awesome (Figure 1). For example, masses for the fantastic seven planet Kepler-11 system have been derived through modelling the gravitational perturbations giving rise to the transit time variations, and show these planets are much bigger than expected for their masses—maybe they are mini gas planets or have fluffy extended atmospheres.

    1
    Figure 1. The known small planet population in the mass-radius plane (x-axis’ units are Earth masses) compared to different compositions and compared to rocky planets in our solar system There is far more diversity than originally expected.

    At the other extreme is Kepler-10c. Kepler-10b (mass 3.33ME, radius 1.47RE, Period 0.84d) was well known as Kepler’s first rocky planet, and spectroscopic observations from the ground with HARPS-N on La Palma not only confirmed this, but also detected the stellar reflex motion from the long period Kepler-10c component.

    Telescopio Nazionale Galileo - Harps North
    Telescopio Nazionale Galileo – Harps North

    Surprisingly, the mass turned out to be 17.2ME, but the Kepler (2.3RE) radius suggested we were still most likely looking at a massive super-Earth. Given that we struggle to understand the internal structure of the Earth, we are quite mystified to explain that of Kepler-10c. These results and others lead us to believe the small planet population is much more diverse than we originally believed.

    When Kepler was being designed, it was generally agreed that there would be little variation of compositions in this population, so that from a measurement of planetary radius its mass could be directly inferred. Consequently, it was assumed that there would be little need for follow up observations. Kepler showed us the need to determine the planetary mass directly.

    Radial Velocity Surveys: Masses of Kepler Planets

    Since the first discovery of a planet around a Sun-like star (Mayor and Queloz 1995), radial velocity surveys—searching for the reflex motion induced in the star—were often the most efficient discovery technique. Compared to the transit method’s strict requirement on the orbital geometry, radial velocity detection is far more lenient. However, without knowledge of the orbital inclination to our line of sight, all we can determine is the planetary minimum mass. Basically, from radial velocity information alone we can learn about the planetary orbit, but essentially nothing about the planet itself.

    Radial velocity information is most useful when it is used alongside transit data. With radius and, most importantly, orbital information coming from the light curve modelling, solutions of the equations of motion can give an accurate planetary mass. Thus, we can get an accurate estimation of the bulk density/composition of a planet. What should be emphasized here is that to derive the planetary mass and radii requires better accuracy in the stellar parameters; in fact, for the best transit light curves knowledge of the host star is often the factor limiting that of the planetary component. The study of exoplanets has led to a renaissance in stellar research and especially the proving of asteroseismology.

    The low brightness of the Kepler field stars and the prevalence of small planets is a double whammy for our studies of the masses of small planets—the small reflex motion and lack of stellar photons make mass measurements at best somewhat challenging. So while the Kepler photometry has produced highly accurate relative radii, even the brightest Kepler host stars are challenging targets for radial velocity work. It is ironic that the planets with the most accurate accepted masses are massive planets found from ground-based transit surveys such as SuperWASP or HAT.

    As a consequence, researchers have developed our ability to model gravitation perturbations detectable through transit timing variations (as noted earlier) and this is how most Kepler planetary masses have been determined. This has the advantage that they can be derived from the light curve alone and with apparently small errors, but is possible for only a small fraction of the planets. There is still some controversy surrounding the use of masses derived in this way and maybe more importantly in the quoted errors. Maybe this will improve in the future.

    However, one of the big lessons from Kepler (and the ongoing K2 surveys of course) is that we need a host star population as bright as possible so we can derive masses, make planetary atmosphere observations, etc. So given this, what does the future hold?

    Looking forward—the Transit Roadmap

    For exploring the inner parts of solar systems, and in particular the habitable zones, for the next 10–15 years it is likely that transits of bright stars that allow radial velocity observations to be made will dominate (Figure 2). That’s not to say that other techniques and regions of the parameter space will not be important—they will. For example, with SPHERE and GPi we are taking our first steps with dedicated and optimized instruments capable of direct planet detection—at least of luminous, young and massive planets.

    ESO/SPHERE extreme adaptive optics system and coronagraphic facility on the VLT
    ESO/SPHERE extreme adaptive optics system and coronagraphic facility on the VLT

    NOAO Gemini Planet Imager on Gemini South
    NOAO Gemini Planet Imager on Gemini South

    JWST may also be capable of this. Gaia and various microlensing space missions such as WFIRST (~2025) or EUCLID (2021) will allow us to statistically explore the outer parts of solar systems.

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    ESA/Gaia satellite
    ESA/Gaia satellite

    NASA/WFIRST telescope
    NASA/WFIRST telescope

    ESA/Euclid spacecraft
    ESA/Euclid spacecraft

    3
    Figure 2. The funded transit roadmap showing facilities that are used for detection and bulk characterisation. Some of the facilities here can also be used for atmospheric characterisation.

    In terms of transit experiments, we have a crop of ground-based experiments—including the new NGTS [Next-Generation Transit Survey], and the re-tasked Kepler K2 surveys. While still at an early stage, NGTS is proving capable of routinely detecting dips which could be due to Neptune-sized objects. Various experiments have been deployed targeting M dwarf stars, where the low intrinsic brightness and small star size mean that ground based photometry would even be capable of detecting Earth-sized planets in orbits of a few days; corresponding to the habitable zones of the feeblest stars.

    In general, finding small planets (smaller than Neptune, say) in habitable zones is a difficult task and is best done from space. This not only avoids limitations in photometric accuracy from the Earth’s atmosphere, but also the interruptions caused by the day/night cycles. Even still, as we push to higher and higher accuracies stellar activity becomes a bigger issue with less stars being suitable for radial velocity work. However, understanding stellar activity is an area of much research and there is hope that small radial velocity signals will be detectable against the activity signal in the future. Nonetheless, we are fortunate that both NASA and ESA have recognized the need for new surveys and we have a series of missions that have transit detection at their heart.

    CHEOPS is due for launch in 2017 and is ESA first “Small” satellite. This Swiss led mission is designed to look at objects one at a time. CHEOPS has two science drivers:

    The follow up of known planets discovered from radial velocity surveys and especially those targets thought likely to transit, and
    High accuracy light curves of transits from other surveys, notably NGTS.

    ESA/CHEOPS
    ESA/CHEOPS

    So, while CHEOPS is not a survey instrument it will produce extremely accurate photometry of known planets and hence bulk densities. CHEOPS also has many other potential uses such as monitoring transits for timing variations etc.

    NASA’s Transiting exoplanet Survey Satellite, TESS, will be launched around the end of 2017.

    NASA/TESS
    NASA/TESS

    TESS will be orientated into a highly eccentric and inclined orbit which reaches almost to the lunar orbit. For most of the 27 day orbit the satellite will be far from the Earth, enabling accurate photometry. The clever orbit and observation strategy results in sections of the sky being monitored for 27 days before moving to the next section. These sections overlap at the Ecliptic poles and so a small region is monitored for as long as ~1 year. Given this, it is likely that TESS will find many single transiting systems which would benefit from CHEOPS observations.

    TESS is aimed at surveying the nearest and brightest stars (mag) and is therefore preferentially examining M dwarfs. These low luminosity stars have habitable zones close in (periods as short as a week or so for the coolest objects). Furthermore, as these stars are quite small the detection of small planets can be achieved easier. Being extremely red objects they are likely to be ideal targets for the JWST and it is likely that the first observations of the atmosphere of a habitable zone planet will come from TESS.

    The Future: ESA’s M3 PLATO Mission

    ESA/PLATO
    ESA/PLATO

    Over the years, there has been a succession of transit survey concepts studied by ESA, but in 2014, PLATO was finally selected as the “Medium 3” mission with launch date in 2024. PLATO was designed from the outset to characterize habitable zone rocky planets with Sun-like host stars that are bright enough for observation with the new generation of radial velocity spectrograph’s such as ESPRESSO at ESO’s Very Large Telescope (VLT) in Chile.

    ESO/Espresso on the VLT
    ESO/Espresso on the VLT

    PLATO is a multi-telescope system which provides a huge field of view (>2,200 square degrees—about 20 times that of Kepler) with excellent sensitivity and it will be stationed in a thermally stable environment at the L2 point, several million kilometers from Earth. While the dynamic range is from 4–13 magnitude, most of the interesting science will be for stars with magnitudes allowing asteroseismic characterization of accurate stellar parameters including their age. Figure 3 shows the predicted rocky planet catch for stars that can be fully characterized through asteroseismology compared to those from Kepler and TESS.

    4
    Figure 3. Simulations of PLATO transit signal detection performance (in green) for super-Earth planets (less than 2RE) for stars brighter than 11 mag, hence with RV follow-up and host star asteroseismology possible. For comparison, Kepler results are shown (in blue, Fressin et al. 2013) and expected yields for TESS (in red) assuming 27 day observing coverage per field and 2% of the sky observed for 1 year

    The time requirement for the ground-based follow up will be almost entirely driven by the smallest, longest period, planets and will represent a significant investment by the astronomical community. For some of the multi-planet systems, masses will also be available from models of any transit timing variations. While PLATO will certainly produce lots of interesting and no doubt unique systems and maybe even moons, rings, etc., the real PLATO reward will be the database of uniformly characterized planetary systems that can be used for future theoretical and observational experiments.

    By the end of the next decade, we will have fully characterized hundreds of systems containing rocky planets. Many of these will be bright enough to have their atmospheres examined with the instruments of the day. The database of PLATO systems with known ages will allow us to take the first steps in comparing the observed planet population with theoretical studies, hence throwing light on the important processes that are sculpting the architectures of these systems. In many ways PLATO can be considered the descendant of Kepler and indeed one of the options for PLATO is to revisit the Kepler field to examine the variations in transit timing variations accumulated after a delay of some 15 years.

    We live at a very fortunate time. Kepler has opened the window and shown us some of the landscape. The new missions will enable us to make great gains in comparative planetology so that we can understand our place in the Universe.

    Dr Don Pollacco, astro-physicist and planet hunter from Queens University, Belfast.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What is PALE RED DOT?

    It is an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely are there Earth-like planets around the nearest stars?

    Why we call it PALE RED DOT?

    In 1990, Voyager 1, on its trek towards interstellar space, sent back a picture of the Inner Solar System on which the Earth occupied less than a pixel. This image of Earth was called Pale Blue Dot, and inspired the late Carl Sagan’s essay ‘Pale Blue Dot : A vision of the human future in Space’, which in turn has been the source of inspiration for a generation of exoplanet hunters. Given that Proxima Centauri — or just Proxima — is a red dwarf star, such a planet would show reddish tints. Even if successful, we will only obtain information about its orbital period and mass — even less than Voyager 1’s pale blue pixel… at least for now!

    What is special about the project?

    Proxima Centauri is the nearest star to the Sun. The discovery of a planet with some characteristics like Earth in our immediate vicinity would be momentous. After years of data acquisition by many researchers and teams, a signal has been identified which may indicate the presence of an Earth-like planet. The Pale Red Dot project will carry out further detailed observations with the aim to confirm or refute the presence of the planet. By broadcasting the progress and results of the observations through all media channels available e.g. press, website, and social media, the Pale Red Dot project aims to promote Science Technology Engineering and Mathematics (STEM) in the broader society, inform the public and hopefully inspire a new generation of scientists.

    How such a scientific program is organized?

    The planned observation campaign is based on a proposal submitted by the involved scientists to ESO, LCOGT and BOOTES observatories. The proposals, in turn, are based on the analysis of data accumulated and obtained over the years by ourselves or by other researchers abroad. Observatories and other advanced research facilities are mostly supported by public resources, large international consortia and private foundations.

    How the results will be reported?

    As in any professional scientific work, final results need to be reviewed by the community before being announced. After the campaign is finished by April 1st, the really tough process of analyzing the data, drawing conclusions and presenting them in a credible manner will begin. After that, the analysis will be summarized in an article and submitted to a scientific journal. At that point, one or more scientists NOT involved in the project will critically revise the work, suggest modifications and even reject its publication if fundamental flaws are spotted. This last step of peer-review can take any time between a few months to a year or two. Hopefully, the data will prove to be high quality and the observations will have a straightforward interpretation, but that is just a hope. A few key milestones of the peer-review process will also be reported on the website, which might remain active at a lower activity level after the observing campaign has finished.

     
  • richardmitnick 1:44 pm on April 9, 2016 Permalink | Reply
    Tags: , , PALE RED DOT, Planetary System Dynamics   

    From PALE RED DOT: “Planetary System Dynamics” 

    Pale Red Dot

    Pale Red Dot

    April 7, 2016
    Francisco J. Pozuelos, Instituto de Astrofísica de Andalucía (IAA-CSIC)

    The ultimate goal of exoplanetary research is to place ourselves in the universe. Are we just the result of normal evolution? That is to say, does life tend to appear almost everywhere, which means that the emergence of intelligent life is just a matter of time. Or, on the other hand, are we unique? Something that just happens in a few places in the vast universe? This question has haunted the humankind since consciousness and for the first time in the history we are close to answering it. We are living in exciting times.

    When the next generation of telescopes and instruments point to the sky, we will be able to observe planetary systems as never before. Super-Earths, exotic planets, planetary systems under extreme conditions… We do not know what we are going to find, but for sure it’s going to be surprising.

    1
    Artistic impression of the PLATO spacecraft searching for exotic exoplanetary systems. Credits: DLR (Susanne Pieth).

    ESA/PLATO
    ESA/PLATO

    However, it is necessary to take into account that this new technology just offers us a picture frozen in time. To understand what we observe it is mandatory to develop dynamic studies on the order of the life time of the system, from a few million to billions of years. This is possible thanks to the great advances in computational science in the last decades, which allows us to investigate what causes the planetary systems to become as we see them today and how they are going to evolve in the future. It is also necessary to understand that we need to study the planetary system as a whole, taking into account other planets, planetesimal disks, even the evolution of the host star. Here we comment on a few examples of planetary dynamics which will help us to increase our knowledge about formation and evolution:

    Planet-Planet interaction and Migrations. It seems that multi-planet systems tend to have more circular orbits. This fact decreases the influence of planets on each other, resulting them being stable for very long periods of time. On the other hand, those planetary systems with planets in eccentric orbits generate a chaotic and unstable scenario where the bodies can collide and even be thrown out of the system. In addition, during the first steps of evolution after the formation process, planets can suffer so-called “migrations”. Due to this mechanism planets can evolve to outer or inner orbits; such a scenario can explain the existence of hot Jupiters.

    2
    Simulation showing the evolution of the Solar System. Left: early configuration of the outer planets and planetesimal belt before the Jupiter and Saturn 2:1 resonance . Center: scattering of planetesimals into the inner Solar System after the orbital shift of Neptune (dark blue) and Uranus (light blue). Right: final configuration after ejection of planetesimals by planets. Credits: R. Gomes et al.

    Tidal interactions. Some of the observational techniques used to detect exoplanets are more sensitive to those planets whose orbits are close to the host star. These planets will experience significant tidal forces as a result of this proximity. The relevance of the tides in the evolution of planets in close-in orbits was apparent with the discovery of 51 Peg b, whose semi-major axis was established as only 5% of the Sun-Earth distance. Since then, the tidal interaction between host stars and close-in planets is considered to be the cause of many effects. For example, these tidal forces are generally expected to lead to the alignment of their rotation axes, synchronization of their rotation and orbital periods, a reduction in orbital ellipticity (tidal circularisation), an accompanying reduction in semi-major axis, and a conversion of orbital energy into tidal heating of the planet. This effect of tidal heating in rocky or terrestrial planets and exo-satellites may have significant implications for habitability. For example, in our Solar System, the cool satellite Europa is a rocky body covered by 150 km of water ice crust, for which the tidal heating may maintain a subsurface water ocean. Or, in the case of the Jovian satellite Io, where the extreme violence of the tides provoke intense global volcanism and rapid resurfacing, ruling out any possibility for habitability. Thus, a correct treatment of the tidal interactions is necessary to determine if the planet was/is/will be habitable, and for how long. Of special interest will be those planets in close-in orbits, classified as terrestrial planets and hosted by M stars, where the habitable zone is expected to be in the region where the tides are acting.

    3
    Evolution of the semimajor axis (a), eccentricity (e), and distance of a synthetic planetary system composed by a Jupiter-like and Earth-like planets in presence of tidal interactions. Credits: Francisco J. Pozuelos.

    Debris Disk-Planet interactions. Debris disks, with a qualitative similarity to the main asteroid belt and Kuiper belt in the Solar System, have been observed in various exoplanetary systems.

    Asteroid belt  Mdf
    Asteroid belt. Mdf

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    These debris disks are composed of second-generation material, and their presence implies the existence of a significant planetesimal population. The impact range of these minor bodies and the planets is especially interesting for those planetary systems with planets on the habitable zone. First it is assumed that they are an important source of water and organics once the formation process is finished. On the other hand, a large impact removes any possibility for habitability. This fact was understood with the breathtaking impact of Shoemaker-Levy 9 with Jupiter in 1994, when the impact of two objects in the Solar System was observed for first time.

    All these studies will complement the information obtained from telescopes giving us a better idea of how planetary systems evolve. We are going to be able to determine how rare the Solar System and our planet are.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What is PALE RED DOT?

    It is an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely are there Earth-like planets around the nearest stars?

    Why we call it PALE RED DOT?

    In 1990, Voyager 1, on its trek towards interstellar space, sent back a picture of the Inner Solar System on which the Earth occupied less than a pixel. This image of Earth was called Pale Blue Dot, and inspired the late Carl Sagan’s essay ‘Pale Blue Dot : A vision of the human future in Space’, which in turn has been the source of inspiration for a generation of exoplanet hunters. Given that Proxima Centauri — or just Proxima — is a red dwarf star, such a planet would show reddish tints. Even if successful, we will only obtain information about its orbital period and mass — even less than Voyager 1’s pale blue pixel… at least for now!

    What is special about the project?

    Proxima Centauri is the nearest star to the Sun. The discovery of a planet with some characteristics like Earth in our immediate vicinity would be momentous. After years of data acquisition by many researchers and teams, a signal has been identified which may indicate the presence of an Earth-like planet. The Pale Red Dot project will carry out further detailed observations with the aim to confirm or refute the presence of the planet. By broadcasting the progress and results of the observations through all media channels available e.g. press, website, and social media, the Pale Red Dot project aims to promote Science Technology Engineering and Mathematics (STEM) in the broader society, inform the public and hopefully inspire a new generation of scientists.

    How such a scientific program is organized?

    The planned observation campaign is based on a proposal submitted by the involved scientists to ESO, LCOGT and BOOTES observatories. The proposals, in turn, are based on the analysis of data accumulated and obtained over the years by ourselves or by other researchers abroad. Observatories and other advanced research facilities are mostly supported by public resources, large international consortia and private foundations.

    How the results will be reported?

    As in any professional scientific work, final results need to be reviewed by the community before being announced. After the campaign is finished by April 1st, the really tough process of analyzing the data, drawing conclusions and presenting them in a credible manner will begin. After that, the analysis will be summarized in an article and submitted to a scientific journal. At that point, one or more scientists NOT involved in the project will critically revise the work, suggest modifications and even reject its publication if fundamental flaws are spotted. This last step of peer-review can take any time between a few months to a year or two. Hopefully, the data will prove to be high quality and the observations will have a straightforward interpretation, but that is just a hope. A few key milestones of the peer-review process will also be reported on the website, which might remain active at a lower activity level after the observing campaign has finished.

     
  • richardmitnick 6:46 pm on January 25, 2016 Permalink | Reply
    Tags: , , PALE RED DOT,   

    From PALE RED DOT: “Intensifying the Proxima Centauri Planet Hunt” 

    Pale Red Dot

    Pale Red Dot

    January 24, 2016
    Paul Gilster

    There will always be a ‘proxima’—a star that is closest to our own—but it won’t always be Proxima Centauri, which in tens of thousands of years will doubtless revert to a different name, perhaps Alpha Centauri C or some other designation. We live in a dynamical universe, one in which the red dwarf Ross 248 will (in forty thousand years or so) be the new ‘proxima.’ We can even anticipate stars being much closer than Proxima Centauri is today. Go 1.4 million years into the future and GL 710 will move within 50000 AU (an Astronomical Unit, or AU, being roughly the distance between the Earth and the Sun). In time’s other direction, the bright Alpha Centauri system of today would not have been visible to the naked eye 3 million years ago.

    In this ongoing celestial dance, the closest star will always captivate a technological society looking into life elsewhere and pondering strategies for sending probes across the interstellar gulf. The nearest star is a natural magnet for exoplanet hunters, as is the entire Alpha Centauri system, which comprises Centauri A and B and, if it is indeed gravitationally bound, as seems likely, Proxima itself. What good news that the Pale Red Dot project is now planning a two­-month observing campaign to search for potential Earth-analogs around Proxima Centauri using HARPS, the High Accuracy Radial velocity Planet Searcher spectrograph at the ESO La Silla 3.6m telescope. Nightly monitoring began on January 18th.

    ESO HARPS
    HARPS interior

    ESO 3.6m telescope & HARPS at LaSilla
    ESO 3.6 meter telescope at La Silla with HARPS

    Discovered in 1915, by the Scottish astronomer Robert Innes, Proxima Centauri has been kindling imaginations ever since. For science fiction writer Robert Heinlein, it was the inevitable destination of the starship Vanguard, which carried crews that lived and died aboard the ‘generation ship’ in two 1940’s short stories that became his novel Orphans of the Sky. Murray Leinster had earlier claimed the star as our primary target in his 1935 story Proxima Centauri. And while Centauri B has recently gotten the lion’s share of attention with the still unconfirmed and now doubtful declaration of a Centauri Bb planetary candidate, Proxima Centauri has had a recent run of study that has helped define the parameters of the planet search.

    To Find a Transiting World

    Centauris Alpha Beta Proxima
    The Alpha Centauri system, Alpha, Beta, Proxima From Pics About Space

    Some 4.218 light years away from the Sun, this red dwarf star would be obscure even from a planet around Centauri A or B. Separated from them by 15,000 AU, Proxima is small and dim enough that it might take any Alpha Centauri astronomers some time to realize it was close, making the call only once its large proper motion became obvious. A naked eye object, yes, but at magnitude 3.7, it would hardly dominate the sky. Yet it might exert quite an effect on the two larger stars, with Greg Laughlin and Jeremy Wertheimer (UC­ Santa Cruz) recently speculating that it could have a role in dislodging comets from the circumbinary disk that presumably surrounds both stars, hence delivering water to their planets.

    Whether planets exist around Proxima itself remains an open question. To answer it, various modes of exoplanet detection are being brought into play, the most recent being a transit search by David Kipping’s (CfA) using the Canadian Space Agency’s MOST (Microvariability & Oscillations of STars) space telescope.

    CSA MOST
    CSA MOST

    Begun in the summer of 2014, the project took 13 days of data that year and an additional 30 in 2015. Results are to be announced by the summer of 2016. A small and inexpensive instrument, MOST is best known as the telescope that found transits of 55 Cancri e, making its primary the first naked eye star found with a transiting planet.

    A transit detection, tracing the dip in starlight as a planet passed in front of the star as seen from MOST, would put the space telescope in the history books. Transit studies have advantages when it comes to small stars like Proxima Centauri. Proxima’s size is roughly one-tenth that of our Sun. Any habitable planet around it should produce a relatively deep transit signature in the star’s light curve, because the size of the planet in relation to the star is significant as opposed to small worlds around much larger G­- or F-­class stars. For the same reason, the likelihood of a transit alignment is enhanced.

    A Planet through Gravity’s Lens

    Gravitational microlensing also offers up prospects for tracking down Proxima planets, as noted in 2013 by Kailash Sahu (Space Telescope Science Institute), who realized that a star with such high angular motion across the sky might frequently occult a more distant object. In microlensing, the nearer object creates a ‘lensing’ of the background source as light flows along curved spacetime, an effect predicted by [Albert] Einstein. An occultation of a distant star by Proxima might allow one or more planets to be revealed as they create their own lensing effect following the occultation by Proxima Centauri itself, slightly brightening the image of the background star.

    Sahu found two occultation events, the first being passage in front of a 20th-­magnitude background star in October of 2014, the second an occultation of a 19.5­-magnitude star in February of 2016. Using both, it should be possible to measure Proxima’s mass to an accuracy of five percent. The Hubble Space Telescope, the European Southern Observatory’s Very Large Telescope (Chile) and ESA’s Gaia space telescope are all capable of measuring down to 0.2 milliarcseconds, while the displacement of the two background stars induced by Proxima’s mass is estimated at 0.5 milliarcseconds and 1.5 milliarcseconds respectively.

    NASA Hubble Telescope
    NASA/ESA Hubble

    ESO VLT Interferometer
    ESO/VLT

    ESA Gaia satellite
    ESA/Gaia

    Probing Stellar ‘Wobbles’

    Gravitational microlensing may or may not yield a Proxima Centauri planet, but the star has also been subjected to several radial velocity studies, in which we look for and analyze a characteristic stellar motion. This signal manifests as an extremely faint Doppler shift caused by the effect of an orbiting planet as the star moves slightly further away from us, then closer again. We can track this apparent ‘wobble’ with exquisitely sensitive spectrographs, as Michael Endl (UT­Austin) and Martin Kürster (Max­Planck­Institut für Astronomie) have done for Proxima Centauri using seven years of data from the UVES spectrograph at the Very Large Telescope in Paranal (Chile).

    ESO UVES
    ESO/ UVES at the VLT

    No planet has been detected, but we’re only part way into the game, for we are beginning to see what kind of planets we can exclude from the realm of possibility. Endl and Kürster find no planet with Neptune’s mass or above, for instance, out to about 1 AU from the star. We can also make a statement about ‘super­-Earths’—rocky worlds more massive than our own—the researchers find no such worlds larger than 8.5 Earth masses in orbits of less than 100 days.

    We are not, then, excluding the possibility of planets, but only beginning to declare what we have not yet found. Scientists consider a star’s habitable zone to be the region where liquid water could exist on the surface of a planet. In Proxima Centauri’s case, that zone should reach between 0.022 and 0.054 AU, corresponding to orbits between 3.6 and 13.8 days. The Proxima investigations have yet to find anything in this window, but so far the most we can say is that super­-­­Earths of 2­3 times the mass of the Earth in circular orbits have been ruled out.

    With these limits in mind, it’s worth noting an astrometric study, led by G. Fritz Benedict (McDonald Observatory) in the 1990s, used the Hubble telescope to scrutinize the precise position of Proxima Centauri in the sky. In conjunction with a 2013 astrometric study by Lurie (Research Consortium on Nearby Stars), the results produced no planet. These studies indicate that Proxima can have no planet with a mass greater than Jupiter in orbits from 0.14 to 12.6 years.

    What Pale Red Dot Might Find

    The Pale Red Dot campaign’s radial velocity studies sharpen our focus on a target that is rife with possibilities. What about the prospects for life if we do locate a planet within the Proxima Centauri habitable zone? Here we have two issues to contend with. Like many younger M-­dwarfs, Proxima is prone to sudden, violent flares, producing sudden changes in brightness to Earth observers and cascades of deadly particles for any life forms on a planet. This may or not create an evolutionary niche as creatures adapt themselves over time to the incoming sleet of energetic particles; how such adaptations would succeed can only be speculated about.

    Just as significant is the prospect of a planet in the habitable zone being so close to the parent star that it becomes tidally locked, forever putting the same face forward to its star. In a world like this, where the star does not move in the sky, we have permanent night on one presumably very cold side, and permanent day on the other. Fortunately, models developed by Jérémy Leconte (University of Toronto) and colleagues suggest that the presence of an atmosphere can largely overcome this difficulty by distributing hot and cold air so as to moderate temperatures around the planet.

    Moreover, 3­D weather simulations by Jun Yang and Dorian Abbot (both of the University of Chicago) and Nicholas Cowan (Northwestern University) show that the side of a tidally locked planet facing the star would develop highly reflective clouds at the ‘sub­stellar’ region directly below the star’s position in the sky. Such cloud coverage could stabilize the atmosphere and produce a cooling effect that bodes well for temperate regions on the day side. There is even the prospect in recent work by Xavier Delfosse (IPAG, Grenoble) that close-­in habitable worlds may be captured into a spin­orbital resonance, but not necessarily into synchronous rotation. The possibility of life on red dwarf planets thus remains open.

    Red dwarfs like Proxima Centauri are thought to comprise up to 80 percent of the stars in our galaxy, giving us tens of billions of planets likely to be in the habitable zone of their host stars. Some 100 are relatively close to the Sun, but Proxima retains pride of place as the nearest star to our own. At 4.2 light years, it is a destination we may one day be able to cross using technologies like beamed sails driven by laser or microwaves, but even at a tenth of the speed of light, any probes will take four decades to reach their destination. What could impel us to press ahead is the discovery of a potentially habitable world, a prospect all scientists working on the exoplanet hunt would applaud. The enticing presence of the K-­class Centauri B and solar-like G­-class Centauri A, just 15,000 AU further, is all the more reason we may one day make the crossing.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What is PALE RED DOT?

    It is an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely are there Earth-like planets around the nearest stars?

    Why we call it PALE RED DOT?

    In 1990, Voyager 1, on its trek towards interstellar space, sent back a picture of the Inner Solar System on which the Earth occupied less than a pixel. This image of Earth was called Pale Blue Dot, and inspired the late Carl Sagan’s essay ‘Pale Blue Dot : A vision of the human future in Space’, which in turn has been the source of inspiration for a generation of exoplanet hunters. Given that Proxima Centauri — or just Proxima — is a red dwarf star, such a planet would show reddish tints. Even if successful, we will only obtain information about its orbital period and mass — even less than Voyager 1’s pale blue pixel… at least for now!

    What is special about the project?

    Proxima Centauri is the nearest star to the Sun. The discovery of a planet with some characteristics like Earth in our immediate vicinity would be momentous. After years of data acquisition by many researchers and teams, a signal has been identified which may indicate the presence of an Earth-like planet. The Pale Red Dot project will carry out further detailed observations with the aim to confirm or refute the presence of the planet. By broadcasting the progress and results of the observations through all media channels available e.g. press, website, and social media, the Pale Red Dot project aims to promote Science Technology Engineering and Mathematics (STEM) in the broader society, inform the public and hopefully inspire a new generation of scientists.

    How such a scientific program is organized?

    The planned observation campaign is based on a proposal submitted by the involved scientists to ESO, LCOGT and BOOTES observatories. The proposals, in turn, are based on the analysis of data accumulated and obtained over the years by ourselves or by other researchers abroad. Observatories and other advanced research facilities are mostly supported by public resources, large international consortia and private foundations.

    How the results will be reported?

    As in any professional scientific work, final results need to be reviewed by the community before being announced. After the campaign is finished by April 1st, the really tough process of analyzing the data, drawing conclusions and presenting them in a credible manner will begin. After that, the analysis will be summarized in an article and submitted to a scientific journal. At that point, one or more scientists NOT involved in the project will critically revise the work, suggest modifications and even reject its publication if fundamental flaws are spotted. This last step of peer-review can take any time between a few months to a year or two. Hopefully, the data will prove to be high quality and the observations will have a straightforward interpretation, but that is just a hope. A few key milestones of the peer-review process will also be reported on the website, which might remain active at a lower activity level after the observing campaign has finished.

     
  • richardmitnick 11:39 am on January 20, 2016 Permalink | Reply
    Tags: , , , PALE RED DOT   

    From Pale Red Dot: “Pale Blue Dot, Pale Red Dot, Pale Green Dot, …” 

    Pale Red Dot

    Pale Red Dot

    1.14.16
    Alan Boss, Carnegie Institution for Science

    Even Carl Sagan would be astonished by what has transpired in the 20 years since the first reproducible evidence for a giant planet in orbit around a sun-like star was announced in October 1995. The announcement of the discovery of a giant planet in orbit around the near-solar twin 51 Pegasus by Michel Mayor and Didier Queloz, followed by its confirmation a few weeks later by Geoff Marcy and Paul Butler, was completely unexpected, not because 51 Peg b has a mass of about half that of Jupiter, or a circular orbit, but because 51 Peg b orbits its star at a distance just 1/100 that of Jupiter, twenty times closer to 51 Peg than the Earth is to the Sun. Theorists such as myself could not imagine forming a presumably gas giant planet that close to a star, a confined space lacking in the raw materials necessary for forming any giant planet. We also feared that if a giant planet formed at a more reasonable distance, similar to Jupiter’s present orbit, subsequent gravitational interactions between the giant planet and the residual planet-forming disk of gas and dust might result in unchecked inward orbital migration of the giant planet toward the growing central protostar that could only result in the planet being swallowed by the voracious youngster. 51 Peg b proved planet formation theorists to be wrong, and we have been playing catch-up ever since.

    Temp 1
    Changes in the velocity of the Sun-like star 51 Peg were used by M. Mayor and D. Queloz to infer the presence of a planet in a short period orbit around the star. Source : arXiv:astro-ph/0310261

    Two months after the announcement of 51 Peg b, Carl Sagan sent letters to George Wetherill and me regarding his claim to have predicted theoretically the formation of a planet similar to 51 Peg b. Sagan had published a paper with a colleague in 1977 that used a simple model of the planet formation process to predict that if a protoplanetary disk happened to have all of its mass concentrated close to the protostar, then a single, massive planet orbiting at 10 times the distance of 51 Peg b might form. Their 1977 paper concluded, however, that such a formation mechanism was “highly questionable”. With the discovery of 51 Peg b, Sagan was ready to drop the “highly questionable” qualifier, and take credit for the first theoretical prediction of an extrasolar planet. Wetherill and I discussed Sagan’s claim, but had several objections of our own: first, whether the initial conditions assumed for the disk by Sagan were at all feasible, and, second, whether the simple model used was up to the task. Detailed computational models of planet formation were Wetherill’s specialty, building on the firm analytical foundation built by Victor Safronov and his colleagues, and Wetherill considered the simple model used in the 1977 paper to be closer to numerology than to proper physics. We politely refrained from supporting Sagan’s claim to theoretical ownership of 51 Peg b.

    One year later, Carl Sagan died at the untimely age of 62 of a rare bone marrow disease, a shock to all of us who knew him as the prophet of the search for life beyond Earth. Just as I remember my seventh-grade classroom where I first heard about the assassination of President Kennedy in 1963, I remember the traffic light I was stopped at when a radio news show reported the death of Carl. By the time of his death, the roster of exoplanets discovered by Doppler spectroscopy (see http://home.dtm.ciw.edu/users/boss/planets.html/) had grown from one to seven, five of which were discovered by Butler and Marcy. The list of exoplanet candidates was now growing at the rate of a planet every month. Carl was a visionary prophet who lived long enough to catch a glimpse of the Promised Land beyond Earth, but not long enough to fully comprehend the prevalence of extrasolar planets.

    51 Peg b was not in any way the first claimed discovery of an exoplanet. The most famous of these was the gas giant planet thought to orbit around Barnard’s Star, a red dwarf star similar to Proxima Centauri that is our nearest neighbour after the Alpha Centauri AB/Proxima Centauri triple system.

    Temp 5
    Shining brightly in this Hubble image is our closest stellar neighbour: Proxima Centauri.
    Proxima Centauri lies in the constellation of Centaurus (The Centaur), just over four light-years from Earth. Although it looks bright through the eye of Hubble, as you might expect from the nearest star to the Solar System, Proxima Centauri is not visible to the naked eye. Its average luminosity is very low, and it is quite small compared to other stars, at only about an eighth of the mass of the Sun.

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Hubble WFPC2
    WFPC2 [no longer in service]

    However, on occasion, its brightness increases. Proxima is what is known as a “flare star”, meaning that convection processes within the star’s body make it prone to random and dramatic changes in brightness. The convection processes not only trigger brilliant bursts of starlight but, combined with other factors, mean that Proxima Centauri is in for a very long life. Astronomers predict that this star will remain middle-aged — or a “main sequence” star in astronomical terms — for another four trillion years, some 300 times the age of the current Universe.
    These observations were taken using Hubble’s Wide Field and Planetary Camera 2 (WFPC2). Proxima Centauri is actually part of a triple star system — its two companions, Alpha Centauri A and B, lie out of frame.
    Although by cosmic standards it is a close neighbour, Proxima Centauri remains a point-like object even using Hubble’s eagle-eyed vision, hinting at the vast scale of the Universe around us.
    Date 28 October 2013

    Temp 6
    The two bright stars are (left) Alpha Centauri and (right) Beta Centauri. The faint red star in the center of the red circle is Proxima Centauri. Taken with Canon 85mm f/1.8 lens with 11 frames stacked, each frame exposed 30 seconds.
    2012-02-27
    Skatebiker

    Peter van de Kamp announced in 1963 the discovery of this planet, 60% more massive than Jupiter, and with an orbital period twice that of Jupiter’s twelve years. This planet made a lot more sense to the theorists than 51 Peg b, and it was accepted as a real detection. Van de Kamp used the astrometric method to search for the wobbles of the central star caused by an unseen planet, where multiple images are taken over a decade or longer. Ten years later, in 1973 George Gatewood published an independent set of astronomical plates that showed that the wobbles that van de Kamp thought were caused by a planet around Barnard’s star were caused instead by changes in the 24-inch refractor used by van de Kamp and in the photographic emulsions used for the exposures. As of 1973, there were no good examples of planets outside our solar system, leaving theorists to continue to concentrate solely on the puzzles associated with the formation of the our own collection of rocky planets, gas giants, and ice giants.

    There were other claims for exoplanet discoveries in the two decades between 1973 and 1995. Gordon Walker and Bruce Campbell started one of the first Doppler spectroscopy searches in 1983, and after twelve years of observing, published their final paper in early 1995, concluding that they had found no firm evidence of planets with masses greater than that of Jupiter. In 1988, they thought they had found evidence for a Jupiter in orbit around Gamma Cephei, but after taking more data, in 1992 they published a retraction of the claim. The case for an exoplanet around Gamma Cephei is still debated (see http://exoplanet.eu/catalog/gamma_cephei_b/).

    In 1988 another Doppler detection appeared, that of an object orbiting the star HD114762, discovered by David Latham and Michel Mayor. This object, however, had a minimum mass of about 11 Jupiter masses, perilously close to the critical value of 13.5 Jupiter masses, which separates Brown dwarfs from Jupiters. Brown dwarfs are massive enough to burn deuterium during their early evolution, whereas planets are forbidden to enjoy the energy generated by hydrogen fusion reactions (see http://home.dtm.ciw.edu/users/boss/definition.html/). Alexander Wolszczan and Dale Frail used the most exotic method of all to discover planetary-mass objects: in 1992 they published evidence from precise timing of the radio wave pulses emitted by the pulsar PSR1257+12 of the presence of not one, but two planets with masses of several times that of the Earth. The fact that these objects orbited in the deadly radiation field of a neutron star that presumably resulted from a supernova explosion made for a fascinating discovery, but one that held little interest for those of us who were fixated on searching for potentially habitable Earth-mass planets around solar-type stars.

    Temp 2
    Artists impression of extrasolar planets in the pulsar, PSR B1257+12.
    NASA/JPL-Caltech/R. Hurt (SSC) – http://photojournal.jpl.nasa.gov/catalog/PIA08042

    In 2004, Butler and his colleagues announced the discovery of the first example of a new class of exoplanets: super-Earths. They showed that the M dwarf star Gliese 436 was orbited by a planet with a mass as small as 21 times that of the Earth, a mass that suggested a composition lacking in gas but rich in rock and ice. Doppler spectroscopy surveys have found hundreds of exoplanets and super-Earths in the intervening years, enough so that by 2009, the prediction could be made that roughly 1/3 of all M dwarf stars were orbited by super-Earths. M dwarfs are at most about 1/2 the mass of the Sun, with much lower luminosities, leading to their having habitable zones much closer to their stars than Earth is to the Sun, but this remarkably high estimate of M dwarf exoplanets was a strong encouragement that the same high abundances would turn out to be the case for G dwarf stars like the Sun.

    Proving this point would fall to NASA’s first space telescope designed specifically for exoplanet detection, the Kepler Space Telescope (see http://kepler.nasa.gov/).

    NASA Kepler Telescope
    NASA/Kepler

    Kepler was the brainchild of William Borucki, who struggled for decades to convince his colleagues (and NASA) of the incredible power of a space telescope for discovering exoplanets by the transit photometry technique. Launched in March 2009, Kepler has more than repaid the America taxpayers who funded its development and operations, having discovered nearly 5,000 exoplanet candidates (at a cost of roughly $100K each) and over 1,000 confirmed planets. Kepler has proven that exoplanets are everywhere, even around G dwarf stars, in startling abundances. Estimates range as high as there being one habitable Earth-like planet for every star in our galaxy.

    Temp 3
    Kepler Objects of Interest (many of them are most likely planets) as of July 23, 2015. Credits : NASA Ames/W. Stenzel – Licensed under Public Domain via Commons

    As someone who has lived through the ups and downs of the history of the field of planet formation and detection, this revelation never fails to amaze me, and often chokes me up when giving public lectures. I cannot imagine that Carl Sagan would feel otherwise were he to have survived long enough to survey the entirety of this Promised Land. We now dream not just of pale blue dots, but of pale green dots indicative of chlorophyll worlds, of not-too-distant future space telescopes capable of the direct imaging of nearby habitable worlds, telescopes powerful enough to sample the compositions of the atmospheres of these worlds in search of molecules associated with habitable and even inhabited planets. Proxima Centauri is a sterling example of such a nearby star that we will continue to scrutinize in the coming years.

    Carl Sagan lived at a time when the optimists among us hoped that maybe one out of a hundred stars might have a planet of some sort in orbit around it. His famous reference to the Earth as a pale blue dot hinted at the likely fragility of life in the Milky Way galaxy, life quite possibly confined to a single refuge in the immense void of an otherwise uncaring and oblivious universe. We now know that nearly every star we can see in the night sky has at least one planet, and that a goodly fraction of those are likely to be rocky worlds orbiting close enough to their suns to be warm and perhaps inhabitable. The search for a habitable world around Proxima Centauri is the natural outgrowth of the explosion in knowledge about exoplanets that human beings have achieved in just the last two decades of the million-odd years of our existence as a unique species on Earth. If Pale Red Dots are in orbit around Proxima, we are confident we will find them, whether they are habitable or not.

    Temp 4
    Dr. Alan Boss explains science results during the NASA Science update. Tuesday, March 22, 2005. Photo Credit: “NASA/Bill Ingalls”

    About the author. Dr. Alan Boss is a Research Scientist at the Carnegie Institution for Science’s Department of Terrestrial Magnetism. He is an internationally recognized theoretical astrophysicist, whose research interests include the study of star formation, evolution of the solar nebula and other protoplanetary disks, and the formation and search for extrasolar planets. Dr. Boss has served on manifold NASA review panels, and has led both NASA and community working groups on extrasolar planet studies, including Chair of the NASA Astrophysics Subcommittee, Chair of NASA Planetary Systems Science Working Group, Chair of NASA Origins of Solar Systems MOWG, Chair of the IAU Working Group on Extrasolar Planets, President of IAU Commissions 51 and 53, and Chair of the AAAS Section on Astronomy. He received a NASA Group Achievement award in 2008 for his role in the Astrobiology Roadmap and another in 2010 for his role in the SIM Planet Finding Capability Study Team. He is a member and Fellow of several professional organizations including the American Astronomical Society, AGU, AAAS, Meteoritical Society, and the American Academy of Arts and Sciences. He has received numerous NASA and NSF grants, served on many professional committees, and is a Series Editor of the Cambridge Astrobiology Series. He has published two books about the search for planets outside the Solar System, “Looking for Earths: The Race to Find New Solar Systems” in 1998, and “The Crowded Universe: The Search for Living Planets” in 2009. Boss is currently the Chair of the NASA Exoplanet Exploration Program Analysis Group, as well as Chair of NASA’s Exoplanet Technology Assessment Committee and WFIRST/AFTA Coronagraph and Infrared Detectors Technology Assessment Committees.

    See the full article here.

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    What is PALE RED DOT?

    It is an outreach project to show to the public how scientists are working to address a major question that could affect us all, namely are there Earth-like planets around the nearest stars?

    Why we call it PALE RED DOT?

    In 1990, Voyager 1, on its trek towards interstellar space, sent back a picture of the Inner Solar System on which the Earth occupied less than a pixel. This image of Earth was called Pale Blue Dot, and inspired the late Carl Sagan’s essay ‘Pale Blue Dot : A vision of the human future in Space’, which in turn has been the source of inspiration for a generation of exoplanet hunters. Given that Proxima Centauri — or just Proxima — is a red dwarf star, such a planet would show reddish tints. Even if successful, we will only obtain information about its orbital period and mass — even less than Voyager 1’s pale blue pixel… at least for now!

    What is special about the project?

    Proxima Centauri is the nearest star to the Sun. The discovery of a planet with some characteristics like Earth in our immediate vicinity would be momentous. After years of data acquisition by many researchers and teams, a signal has been identified which may indicate the presence of an Earth-like planet. The Pale Red Dot project will carry out further detailed observations with the aim to confirm or refute the presence of the planet. By broadcasting the progress and results of the observations through all media channels available e.g. press, website, and social media, the Pale Red Dot project aims to promote Science Technology Engineering and Mathematics (STEM) in the broader society, inform the public and hopefully inspire a new generation of scientists.

    How such a scientific program is organized?

    The planned observation campaign is based on a proposal submitted by the involved scientists to ESO, LCOGT and BOOTES observatories. The proposals, in turn, are based on the analysis of data accumulated and obtained over the years by ourselves or by other researchers abroad. Observatories and other advanced research facilities are mostly supported by public resources, large international consortia and private foundations.

    How the results will be reported?

    As in any professional scientific work, final results need to be reviewed by the community before being announced. After the campaign is finished by April 1st, the really tough process of analyzing the data, drawing conclusions and presenting them in a credible manner will begin. After that, the analysis will be summarized in an article and submitted to a scientific journal. At that point, one or more scientists NOT involved in the project will critically revise the work, suggest modifications and even reject its publication if fundamental flaws are spotted. This last step of peer-review can take any time between a few months to a year or two. Hopefully, the data will prove to be high quality and the observations will have a straightforward interpretation, but that is just a hope. A few key milestones of the peer-review process will also be reported on the website, which might remain active at a lower activity level after the observing campaign has finished.

     
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