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  • richardmitnick 3:41 pm on January 12, 2018 Permalink | Reply
    Tags: , , , , , , , PicSat, PicSat is is one of the few CubeSats worldwide with an astrophysical science goal, Planet transits   

    From ESOblog: “Combining the freedom of a CubeSat with the power of an ESO telescope” 

    ESO 50 Large


    How ESO’s HARPS will help PicSat the CubeSat to unravel the mysteries of the Beta Pictoris star system.

    12 January 2018

    A shoebox-sized satellite called PicSat, developed in record time by a small team of scientists and engineers at the Paris Observatory in France, has just been launched into space to study the Beta Pictoris star system. PicSat will be assisted in its mission by the HARPS instrument on the ESO 3.6-metre telescope, which will make follow-up observations to PicSat’s detections. This will be the first time that a small modular satellite — a CubeSat — and a ground-based telescope work together to address some of the mysteries of the Universe. We speak to Sylvestre Lacour, an astrophysicist and instrumentalist who leads the PicSat team, to find out more about this exciting project.


    Q. First of all, tell us a bit about why you chose to look at the Beta Pictoris star system.

    A. Having celebrated only roughly 23 million years of life, Beta Pictoris is a very young star, astronomically speaking. At about twice the mass and size of the Sun, and just 63.4 light years away, it is relatively easy to observe. Over the past decades, Beta Pictoris has been a popular target for astronomers studying the early stages of star and planet formation, with those astronomers often using ESO facilities. In 2008 a team of French astronomers discovered a giant gas planet orbiting Beta Pictoris. The planet, baptised Beta Pictoris b, has about seven times the mass of Jupiter and orbits its host star at around ten Astronomical Units (AU). The distance between Beta Pictoris and Beta Pictoris b is similar to that between the Sun and our neighbouring ringed planet, Saturn.

    Satellite and ground-based telescopic observations of Beta Pictoris revealed the presence of an outer, dusty, debris disk and an inner clear zone about the size of our Solar System. In 2008, infrared observations from ESO telescopes provided evidence for a giant planet.
    Credit: ESO/A.-M. Lagrange et al.

    A few years ago it became clear that from the viewpoint of the Earth, either Beta Pictoris b, or at least its Hill Sphere, will transit in front of Beta Pictoris. The Hill Sphere of a planet is its gravitational sphere of influence — the region around it that dominates the attraction of rings and moons. Observing a planetary transit would tell us more about the young planet, for example about its size and the chemical composition of its atmosphere. Observing a Hill Sphere transit could tell us about the properties of objects around Beta Pictoris b, for example, its moons or rings.

    Q. Sounds exciting! So what exactly happens during a transit?

    A. During a transit, the planet blocks the light from a small part of the star, diminishing the amount of starlight that reaches us. A telescope captures the light from the star, and a sensitive instrument called a photometer accurately measures the amount of light received. The main goal of PicSat will be exactly that — to monitor the brightness of Beta Pictoris continuously, so as to capture the little revealing dip in its lightcurve as the planet Beta Pictoris b, or its Hill Sphere, passes in front of it.

    A transit of Beta Pictoris b itself would take a few hours and would show a clear dip in the light curve. Because the reach of the Hill Sphere extends a very long way from the planet, a transit of only the Hill Sphere could take up to several months and could result in a more irregular light curve as several rings or moons pass by.

    A diagram showing the dip in brightness of a host star as it is transited by a planet. By measuring the amount of dip in brightness and knowing the size of the star, scientists can determine the size of the planet. Credit: NASA Ames

    Q. And why did you choose to build PicSat for this job? Couldn’t an existing ground-based telescope do exactly the same thing?

    A. So far it has only been possible to estimate an approximate time for the moment of transit — we believe that it should occur by summer 2018. Because of this uncertainty, we needed something that could continuously monitor the star system. Ground-based telescopes can only observe at night and are in high-demand — they are too busy to make continuous observations. So we decided that sending a satellite into space would be the only way to ensure that we capture this phenomenon. PicSat will orbit around the Earth from pole to pole, as the Earth rotates below it. This means that PicSat can always see to either side of the Earth without its view being blocked, allowing it to continuously observe Beta Pictoris.

    With a polar orbit, PicSat will pass over the poles of the Earth, constantly keeping an eagle eye on Beta Pictoris.
    Credit: NASA illustration by Robert Simmon

    The fully assembled PicSat, which consists of three cubic units stacked on top of each other.
    Credit: PicSat CubeSat

    When PicSat observes photometrically that a transit is taking place, we will use an online form to alert people working at the ESO 3.6-m telescope. As soon as possible after they have been alerted, they will use the HARPS (High Accuracy Radial velocity Planet Searcher) instrument to make detailed spectroscopic observations. The photometric (measurement of the amount of light) and spectroscopic (measurement of the wavelength distribution of light) observations can then be combined to find out much more about the star system.

    Q. We’d love to hear a bit more about PicSat itself.

    A. PicSat, a contraction of Beta Pictoris and Satellite, is composed of three standard cubic units with side lengths of 10 cm. The project started in 2014 when I proposed using CubeSat technology to observe the predicted transit. I gathered a small local team and together we worked hard to design and build PicSat. It is incredible that in less than four years we have reached a stage where PicSat is being launched!

    One really cool thing about PicSat is that it is one of the few CubeSats worldwide with an astrophysical science goal, and is the first CubeSat aiming to provide answers in the challenging field of exoplanetary science.

    Q. You say that PicSat is made of three cubic units — do these units each have different roles in the operation of the satellite?

    A. Absolutely! The top and middle cubic units house the “science payloads”, whilst the bottom unit contains the onboard computer.

    More specifically, the top cubic unit of PicSat contains a small telescope. Thanks to the brightness of Beta Pictoris, the mirror of this telescope can have a diameter of just 5 cm.

    This telescope sends the light from Beta Pictoris down into the middle unit. Here, a tiny optical fibre, three micrometres in diameter (or about a fifth of the size of a thin human hair) collects the light and guides it onto a sensitive photodiode that accurately measures the arrival time of each individual photon. Because light will be guided by the tube-shaped fibre, unwanted light will be prevented from entering the photodiode. This allows for a very accurate measurement of the star’s brightness. Imagine looking through a tube — you are able to focus much more easily on a distant object than if you use just your unaided eye because the tube prevents peripheral light from entering your eye. Optical fibres are often used in ground-based telescopes, but this will be the first time an optical fibre is flown in space for astronomical observations.

    However, PicSat will wiggle and wobble a little as it orbits the Earth, so the accuracy with which it points at Beta Pictoris wouldn’t be good enough for the telescope to send all the light from the star into the small fibre all the time. We devised an innovative solution to this problem by connecting the optical fibre to a small plate, a “piezoelectric actuator”, that can track the star and immediately follow it to remain on target.

    A “naked” PicSat, with its cover removed so that its science payload is visible. The optical fibre is in the centre of the image.
    Credit: NASA illustration by Robert Simmon

    The bottom unit of PicSat contains the onboard computer for operating the satellite, communicating with Earth, raw pointing of the telescope and other important monitoring tasks. The whole satellite is clothed in solar panels that provide the satellite with energy, but it does not need a lot. In fact, the total power consumption of PicSat is about 5 watts, similar to a small light bulb!

    PicSat’s compact optical system collects the light from Beta Pictoris and the electronics track the star’s position. Inbuilt electronics include a precision stage for moving the optical fibre and a state-of-the-art photodiode.
    Credit: PicSat CubeSat

    Q. And what exactly will happen when PicSat observes a transit?

    A. If PicSat detects the beginning of a transit, whether it be Beta Pictoris b, its Hill Sphere, or any other transit like phenomena, ESO’s 3.6-metre telescope will immediately be put into action. Dr Flavien Kiefer from the Institut d’Astrophysique de Paris will lead the ground-based observations and has guaranteed time using HARPS to support PicSat. He will be the one to respond quickly to our online alert.

    The ESO 3.6-metre telescope at La Silla. This telescope is mounted with the High Accuracy Radial velocity Planet Searcher (HARPS), an instrument dedicated to the discovery of exoplanets. Credit: Y. Beletsky (LCO)/ESO

    Another exciting thing this project might address is that the Beta Pictoris system is rich in objects thought to be comet-like, which have often been observed spectroscopically by ESO telescopes. The presence of these objects has been inferred through the absorption lines of elements such as calcium, sodium and iron present in the object’s tails, which appear in the spectra and disappear again as they transit the star. However, a photometric detection of the dust in a cometary tail passing in front of Beta Pictoris has not yet been achieved. PicSat could well provide us with the first of these observations, which would confirm that these objects are indeed exocomets. If combined with an immediate follow up by HARPS, this would provide new and unique information about such comets and the system as a whole.

    Astrophysicist and PicSat team member Flavien Kiefer (Institut d’Astrophysique de Paris, France) talks about the detection of exocomets in the Beta Pictoris system. Credit: PicSat CubeSat

    Q. And finally, I’m curious to know what could go wrong and how you would deal with any problems that might arise.

    A. As with any space mission, things can, of course, go wrong! This is the first time that our team (and in fact the LESIA lab!) has constructed an entire satellite, and with a small team, low budget and short time-scale, risks are higher than for conventional missions.

    We were most concerned about the launch, but that was a huge success this morning!! So the next stage is to cross our fingers that the automatic initiation sequence that will start PicSat works successfully. At the end of this sequence, antennas will deploy — critical for communication with the satellite. Antenna deployment and pointing at Beta Pictoris have been tested many times in the lab, so we are hopeful that they work in space as well.

    As for how we would deal with it, well that really depends on the problem! Fortunately, we have a varied and intuitive team and we believe can adapt to most situations.

    The PicSat satellite was successfully launched at 05:00 CET on Friday 12 January 2018. Follow the progress of the mission and find out more about the project at https://picsat.obspm.fr.


    PicSat website
    PicSat YouTube channel
    PicSat Flickr account
    PicSat Beta Pictoris Star System Info Sheet
    PicSat Twitter account

    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”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

  • richardmitnick 10:33 am on March 20, 2017 Permalink | Reply
    Tags: , , , , , , , , Planet transits, Sardines in Space   

    From astrobites: “Sardines in Space: The Intensely Densely-Packed Planets Orbiting Kepler-11” 

    Astrobites bloc


    Title: A Closely-Packed System of Low-Mass, Low-Density Planets Transiting Kepler-11
    Authors: Jack J. Lissauer, Daniel C. Fabrycky, Eric B. Ford, et al.
    Lead Author’s Institution: NASA Ames Research Center, Moffett Field, CA, 94035, USA

    Status: Published in Nature 2011 [open access]

    The dawn of the Kepler Space Telescope data has unearthed a treasure trove of new and unusual celestial objects. Among these new discoveries is the planetary system Kepler-11. The system contains six transiting planets that are packed incredibly close around the Sun-like star, much like sardines are packed very closely in cans. The first five of these planets fall within the orbit of Mercury, and the sixth one falls well within the orbit of Venus. Few systems like this have been discovered; most planetary systems have a much larger separation between the planets, yet this system has its planets arranged in an extremely packed, yet extraordinarily still stable, way.

    Figure 1: This figure from the NASA website is a visual representation of the Kepler-11 system, overlaid with the orbits of Mercury and Venus.

    When a single planet orbits a star, its period follows Kepler’s Laws to a tee; however, when other planets are introduced in the system, the orbiting bodies tend to perturb each other’s orbits. Their periods differ slightly according to the gravitational perturbations, and this variation is called a transit timing variation (TTV). Since Kepler-11 has five planets orbiting in extreme proximity to one another, it is the perfect illustration of measurements from transit-timing variations.

    Planet transit. NASA/Ames

    The photometric Kepler data marked the discovery of this system. The transits for each of the planets appeared separately in the light curve of the system. The light curve is just a measurement of the brightness of the star over time, so when a planet passes in front of the star, the brightness decreases, causing the dip in the light curve. The shape varies with each planet based on differences in size of the planet and orbital radius. From this data, it is possible to measure the radius of the transiting planet. This team followed up their photometric data with spectroscopic analysis from the Keck I telescope. This additional data allowed for the precise measurements of transit-timing variations, which yielded mass measurements for the inner five planets.

    For the first five planets, the TTVs were successfully measured, and with this information, the research team found the densities of the inner five planets, which yielded a surprising result. These planets, despite being densely packed, are not made of very dense material. Kepler-11b is both closest to the Sun and densest, but only with an overall density of 3.31 g/cm3. For comparison, Earth has an overall density of about 5.5 g/cm3. The densities of the planets orbiting Kepler-11 are depicted in Figure 2.

    Figure 2: This shows the mass versus radius of the planets in the Kepler-11 system. The planets orbiting Kepler-11 are represented by the filled in circles. The other marking on the graph indicate planets in our solar system, shown for comparison. Figure 5 from today’s paper.

    While transit timing variations worked like a charm for the inner five planets, the sixth planet (Kepler-11g) was too distant from the others for this method to work well, so to confirm this planet, another method was employed. This team used several simulations to rule out alternate scenarios, which include chance alignment of the Kepler-11 system with and eclipsing star or with another star-planet system. This analysis successfully confirmed Kepler-11g , but because no TTVs could be measured for this particular planet, its mass and radius remain unknown.

    Even though this system has been more closely studied than most, the measurements have raised nearly as many questions as they have answered. The inner five have small inclinations and eccentricities, which implies some planetary migration process. However, since the periods of these planets are not in resonance, slow and convergent migration theories—which would naturally force the planets into resonant orbits—seem unlikely to be at play in this system. Formation of such a system is still a bit of a mystery. After all, such low-density planets are unusual and do not completely fit within the current understanding of planet formation.

    Kepler-11 continues to be one of the more intriguing planetary systems discovered, and its formation is not fully understood. Even though this system has been more closely studied than most, the measurements have raised nearly as many questions as they have answered. Systems like this extend our understanding of astrophysics, perhaps in a bit of an unexpected way; these closely packed planets have so much more to teach us about their system formation.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
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    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

  • richardmitnick 1:08 pm on December 22, 2016 Permalink | Reply
    Tags: , , , , Planet transits   

    From Kavli: “Revealing the Orbital Shape Distributions of Exoplanets with China’s LAMOST Telescope” 


    The Kavli Foundation


    Using data from China’s LAMOST telescope, a team of astronomers have derived how the orbital shapes distribute for extrasolar planets. The work is recently published in the journal Proceedings of the National Academy of Sciences of the United States of America” (PNAS). The lead authors are Prof. Jiwei Xie from Nanjing University and Prof. Subo Dong, a faculty member of the Kavli Institute of Astronomy & Astrophysics (KIAA) at Peking University.

    LAMOST telescope located in Xinglong Station, Hebei Province, China
    The Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) telescope in Hebei, China. It is the most efficient spectroscopy machine in the world.

    Until two decades ago, the only planetary system known to mankind was our own solar system. Most planets in the solar system revolve around the Sun on nearly circular orbits, and their orbits are almost on the same plane within about 3 degrees on average (i.e., the averaged inclination angle is about 3 degrees). Astronomers use the parameter called eccentricity to describe the shape of a planetary orbit. Eccentricity takes the value between 0 and 1, and the larger the eccentricity, the more an orbit deviates from circular. The averaged eccentricity of solar system planets is merely 0.06. Hundreds of years ago, motivated by circular and coplanar planetary orbits, Kant and Laplace hypothesized that planets should form in disks, and this theory has developed into the “standard model” on how planets form.

    In 1995, astronomers discovered the first exoplanet around a Sun-like star 51 Pegasi with a technique called Radial Velocity, and this discovery started an exciting era of exoplanet exploration. At the beginning of the 21st Century, people had discovered hundreds of exoplanets with the Radial Velocity technique, and most of them are giant planets comparable in mass with the Jupiter. These Jovian planets are relatively rare, found around approximately one tenth of stars studied by the Radial Velocity technique. The shapes of their orbits were a big surprise: a large fraction of them are on highly eccentric orbits, and all the giant planets found by Radial Velocity have a mean eccentricity of about 0.3. This finding challenges the “standard model” of planet formation and raises a long-standing puzzle for astronomers – are the nearly circular and coplanar planetary orbits in the solar system common or exceptional?

    The Kepler satellite launched by NASA in 2009 has discovered thousands of exoplanets by monitoring tiny dimming in the brightness of stars when their planets happen to cross in the front (called “transit”).

    Planet transit. NASA/Ames
    Planet transit. NASA/Ames

    Many of the planets discovered by Kepler have sizes comparable to that of the Earth. Kepler’s revolutionary discoveries show that Earth-size planets are prevalent in our galaxy. However, data from the Kepler satellite alone cannot be used to measure the shape of a transiting exoplanet’s orbit. To do so, one way is to use the size of the planet host star as a “ruler” to measure against the length of the planet transit, while implementing this method needs precise information on the host star parameters such as size and mass. This method has previously been applied to the host stars characterized with the asteroseismology technique but the sample is limited to a relatively small number of stars with high-frequency, exquisite brightness information required by asteroseismology.

    With its innovative design, the LAMOST telescope in China can observe spectra of thousands of celestial objects simultaneously within its large field of view, and it is currently the most efficient spectroscopy machine in the world (Figure 1). In recent years, LAMOST has obtained tens of thousands of stellar spectra in the sky region where the Kepler satellite monitors planet transits, and they include many hundreds of stars hosting transiting exoplanets. By comparing with other methods such as asteroseismology, the research team finds that, high-accuracy characterization of stellar parameters can be reliably obtained from LAMOST spectra, and they can subsequently be used to measure the the orbital shape distributions of Kepler exoplanets.

    They analyze a large sample of about 700 exoplanets whose host stars have LAMOST spectra, and with the LAMOST stellar parameters and Kepler transit data, they measure the eccentricity and inclination angle distributions. They find that about 80% of the analyzed planet orbits are nearly circular (averaged eccentricity less than 0.1) like those in the solar system, and only about 20% of the planets are on relatively eccentric orbits that significantly deviate from circular (average eccentricity large than 0.3). They also find that the average eccentricity and inclination angle for the Kepler systems with multiple planets fit into the pattern of the solar system objects (Figure 2).

    Therefore, circular orbits are not exceptional for planetary systems, and the orbital shapes of most planets inside and outside the solar system appear to distribute in a similar fashion. This implies that the formation and evolution processes leading to the distributions of the orbital shapes of the solar system may be common in the Galaxy.

    See the full article here .

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    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

    • vegetarian dash diet meal pla 1:39 pm on December 22, 2016 Permalink | Reply

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      I most certainly will recommend this website!


      • richardmitnick 2:27 pm on December 22, 2016 Permalink | Reply

        Thanks, I am just glad my work is appreciated. I do it for the love of bringing this material which the press ignores to the public. I have about 800 readers in North America , Europe, East Asia, Africa, and the Middle East. No contests.


  • richardmitnick 3:48 pm on March 1, 2016 Permalink | Reply
    Tags: , , ET Search: Look for the Aliens Looking for Earth, , Planet transits,   

    From SA- “ET Search: Look for the Aliens Looking for Earth” 

    Scientific American

    Scientific American

    March 1, 2016
    Alexandra Witze

    Planet transit
    Light Curve of a Planet Transiting Its Star. NASA/Kepler

    By watching how the light dims as a planet orbits in front of its parent star, NASA’s Kepler spacecraft has discovered more than 1,000 worlds since its launch in 2009.

    NASA Kepler Telescope

    Now, astronomers are flipping that idea on its head in the hope of finding and talking to alien civilizations.

    Scientists searching for extraterrestrial intelligence should target exoplanets from which Earth can be seen passing in front of the Sun, says René Heller, an astronomer at the Max Planck Institute for Solar System Research in Göttingen, Germany. By studying these eclipses, known as transits, civilizations on those planets could see that Earth has an atmosphere that has been chemically altered by life. “They have a higher motivation to contact us, because they have a better means to identify us as an inhabited planet,” Heller says.

    About 10,000 stars that could harbour such planets should exist within about 1,000 parsecs (3,260 light years) of Earth, Heller and Ralph Pudritz, an astronomer at McMaster University in Hamilton, Canada, report in the April issue of Astrobiology. They argue that future searches for signals from aliens, such as the US$100-million Breakthrough Listen project, should focus on these stars, which fall in a band of space formed by projecting the plane of the Solar System out into the cosmos.

    Breakthough Listen
    Breakthrough Listen Project

    Breakthrough Listen currently has no plans to search this region; it is targeting both the centre and the plane of our galaxy, which is not the same as the plane of the Solar System, as well as stars and galaxies across other parts of the sky.

    The idea of searching for worlds whose inhabitants could see Earth transits dates back to at least the 1980s. But astronomers can now update and revise their ideas thanks to what they have learned from Kepler, Heller says.

    In the zone

    The zone of space in which Earth transits would be visible is a relatively narrow strip. It gets even narrower if restricted to geometries in which the Earth passes less than half a solar radius from the Sun’s centre—which gives a transit that should be easily visible, if aliens have a tool similar to Kepler.

    Heller and Pudritz went through a catalogue of stars compiled using data from the Hipparcos satellite and found 82 Sun-like stars in this zone that are within 1,000 parsecs of Earth. Because not all of the stars in this region of space have been discovered, Heller and Pudritz extrapolated the number of known stars to the number that probably exists and came up with roughly 10,000 candidate stars. If these stars have planets, and if the planets have intelligent life forms, they could have long ago spotted the blink of an Earth transit and begun beaming signals towards us, Heller says.

    One of the closest known stars in the zone is Van Maanen’s Star, only 4 parsecs away. It is a white dwarf star, the remains of a stellar explosion, and may or may not have planets orbiting it. But if they did exist, they would provide a ringside seat for watching Earth. “If any civilization survived the death of their star, they could see us transiting our own Sun,” says Heller.

    For four days in 2010, the Allen Telescope Array in northern California looked for signals coming from the region of space directly opposite the Sun, says Seth Shostak, an astronomer at the SETI (search for extraterrestrial intelligence) Institute in Mountain View, California.

    Allen Telescope Array
    Allen Telescope Array

    The goal was to test whether extraterrestrials might be timing any transmissions to reach Earth just as they see it transiting the Sun. No signs of aliens were found, and no follow-up is planned.

    “Unfortunately, there are more good ideas for SETI experiments than there are SETI experimenters to act on them,” says Andrew Siemion, an astronomer at the University of California, Berkeley.

    In the next five or so years, the European Space Agency’s Gaia satellite is likely to discover most of the nearby stars in the Earth transit zone, Heller says.

    ESA Gaia satellite

    Until then, he and Pudritz plan to use data from K2, the Kepler follow-on mission, to hunt directly for planets in the zone—and to look for aliens who might be looking for us.

    See the full article here .

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    Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.

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