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Contact:
Dr Sandra Jeffers
University of Göttingen
Institute for Astrophysics
Friedrich-Hund-Platz 1, Göttingen, Germany
Email: jeffers@astro.physik.uni-goettingen.de
Professor Stefan Dreizler
Institute for Astrophysics
Friedrich-Hund-Platz 1, Göttingen, Germany
Tel: +49 (0) 1781796035
Email: dreizler@astro.physik.uni-goettingen.de
Artist’s concept of Gliese 887b and Gliese 887c orbiting their red dwarf star. Image via Mark Garlick/ University of Göttingen.
International researchers led by University of Göttingen find multiple planet system orbiting Gliese 887.
The nearest exoplanets to us provide the best opportunities for detailed study, including searching for evidence of life outside the Solar System. In research led by the University of Göttingen, the RedDots team of astronomers has detected a system of super-Earth planets orbiting the nearby star Gliese 887, the brightest [1] red dwarf star in the sky.
ESO Red Dots Campaign
Super-Earths are planets which have a mass higher than the Earth’s but substantially below those of our local ice giants, Uranus and Neptune. The newly discovered super-Earths lie close to the red dwarf’s habitable zone, where water can exist in liquid form, and could be rocky worlds. The results were published in the journal Science.
The RedDots team of astronomers monitored the red dwarf, using the HARPS spectrograph at the European Southern Observatory in Chile.
ESO/HARPS at La Silla ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.
They used a technique known as “Doppler wobble”, which enables them to measure the tiny back and forth wobbles of the star caused by the gravitational pull of the planets. The regular signals correspond to orbits of just 9.3 and 21.8 days, indicating two super-Earths – Gliese 887b and Gliese 887c – both larger than the Earth yet moving rapidly, much faster even than Mercury. Scientists estimate the temperature of Gliese 887c to be around 70oC.
Gliese 887 is one of the closest stars to the Sun at around 11 light years away. It is much dimmer and about half the size of our Sun, which means that the habitable zone is closer to Gliese 887 than Earth’s distance from the Sun. RedDots discovered two more interesting facts about Gliese 887, which turn out to be good news not only for the newly discovered planets but also for astronomers. The first is that the red dwarf has very few starspots, unlike our Sun. If Gliese 887 was as active as our Sun, it is likely that a strong stellar wind – outflowing material which can erode a planet’s atmosphere – would simply sweep away the planets’ atmospheres. This means that the newly discovered planets may retain their atmospheres, or have thicker atmospheres than the Earth, and potentially host life, even though GJ887 receives more light than the Earth. The other interesting feature the team discovered is that the brightness of Gliese 887 is almost constant. Therefore, it will be relatively easy to detect the atmospheres of the super-Earth system, making it a prime target for the James Webb Space Telescope, a successor to the Hubble Telescope.
Dr Sandra Jeffers, from the University of Göttingen and lead author of the study, says: “These planets will provide the best possibilities for more detailed studies, including the search for life outside our Solar System.”
Original publication: Jeffers et al. (2020), A multiple planet system of super-Earths orbiting the brightest red dwarf star GJ887. Science
[1] See recons.org (Research Consortium on Nearby Stars)
RedDots: in 2016, the astronomy team found the closest exoplanet to the Sun, which is roughly Earth-mass and orbits Proxima Centauri. This was followed in 2018 with the announcement of a super-Earth orbiting Barnard’s star, the second closest star to the Sun. A system of three planets orbiting the red dwarf star GJ 1061, just slightly further away from us than GJ 887, was also announced by the team in 2019.
In January 2016, a pioneering outreach research campaign called Pale Red Dot was launched. It not only aimed to search for Earth-like exoplanets around Proxima Centauri, the closest star to the Sun, but also to give the public the opportunity to follow that quest as it happened. The result was amazing: an Earth-mass exoplanet was found orbiting in the habitable zone around Proxima Centauri! This year, the team behind the Pale Red Dot campaign is back with another initiative called Red Dots, looking for exoplanets using ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) and other instruments around the globe. The project is even more ambitious as it expands to hunt for exoplanets around two more of our closest neighbouring stars: Barnard’s Star (6 light-years away) and Ross 154 (9.7 light-years away). Plus, to add to the excitement, the general public and the scientific community now both have access to observational data from Proxima Centauri and can participate in the search themselves. For a first-hand look at the campaign, the science and the people that make it happen, we had a chat with Guillem Anglada-Escudé, the lead scientist of the Red Dots team.
Q: Considering the success of the Pale Red Dot campaign and the addition of two more stars to the search, what are your expectations for Red Dots?
A: In terms of the science, we hope to repeat in-depth searches on a few more very nearby M dwarf stars. Pale Red Dot showed that focusing the campaign on specific objects, as opposed to surveying, is more efficient for detecting these very challenging signals of exoplanets.
The question of how research develops is not that simple and it’s hard to predict. Along with ESO’s HARPS, we’re also obtaining data from other observatories — including the planet hunter CARMENES — on the same and some extra stars, plus there are other follow-up efforts going on.
Calar Alto CARMENESCalar Alto Observatory located in Almería province in Spain on Calar Alto, a 2,168-meter-high (7,113 ft) mountain in Sierra de Los Filabres
As more information is coming in and other people keep researching the field, we need to continuously adapt our strategy to provide solid and credible results.
Using well-educated guesses from what we know about exoplanets in general, we expect that either Barnard’s Star or Ross 154 should be home to a couple of interesting planets. But it’s another story whether or not our observations will be able to confirm the existence of these planets. We already obtained abundant data on Barnard’s Star and it looked promising because it’s a rather old and quiet star. Ross 154 is younger and more active. We clearly see it varying quite a bit, like shaking back and forth in tune with its rotation period. However, we think we might be able to handle this variability in this kind of intensive campaign. A lot of work is ahead for sure. We’ll see!
Q: How does it feel to being part of something that can trigger the next huge discovery?
A: Not knowing the result in advance, but knowing there is potential for a breakthrough, is very exciting, especially when you’re given the resources to try something that hasn’t been tried before and you’re convinced that you can make a big difference.
But it’s important to note that most of the time, things don’t work out like we expect. I’d say only one tenth of the things one tries leads to a significant breakthrough. Also, from the conception to the execution of the observations, there’s not much to do but wait, which is why we astronomers tend to multitask quite a bit. Speaking realistically, it’s possible (even likely!) that the next breakthrough I will participate in will actually have nothing to do with Red Dots or even Proxima b.
This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Credit: ESO/M. Kornmesser
Q: This project aims to bridge the gap between astronomers and the general public — you’re communicating science as it happens. This is not how scientists usually work. Why are you taking this approach?
A: We felt that as with the Pale Red Dot campaign, which was a deep search for planets around Proxima Centauri, people would get naturally excited about this. During Pale Red Dot we tried to explain the science as it happened while putting things in context with our outreach and with guest articles from specialists. It worked well because the community reacted enthusiastically — and, being realistic, because we got an awesome result. But there seemed to be a need to go deeper into the detail, or at least give people the opportunity to watch the process more closely, by either providing them access to the data or by showing the discussions and activity logs around the observations.
Why we are doing this? It seemed to be the right thing to do, plus there is a demand for transparency and understanding of the processes of science at a global scale. I think there is intrinsic value in doing research and holding discussions in an open environment. You never know what people could contribute; plus, it might help make the world a bit better.
One good thing about science, or at least the basic physical sciences, is that it doesn’t make cultural or political judgements. The knowledge science provides is objectively beneficial for all. This leads to very fruitful international collaborations, even between scientists from countries in open conflict. The act of working together needs to be tested and learned, and communicating science and being open to seriously receive feedback — even cooperate — is part of that.
I personally believe that research institutions should either encourage scientists to do serious communication of their work as part of their duties, or they should provide the means make it happen.
Q: What has been the response from the community?
A: A couple of groups have been looking at the data as it comes through. Discussing with them as the campaign unfolds should help us to reach a better consensus on the interpretation of the results at the end. Experiments hardly ever happen as planned. The scientists involved in an experiment often lose perspective, and the scientists outside it can have trouble following the subtleties of the work. I think that making the data public and discussing it on-the-fly is a healthy exercise, at least from time to time. All this said, my colleagues and I were expecting more action, especially a bit more open discussion on what the data was showing. Others were afraid that other scientists would take the data and take advantage of us, but I see none of that happening, meaning we can probably try to be more open in general. In a sense, being open protects us against the possibility of being scooped, because everyone — including our colleagues and journal editors — know where the data is coming from. They would recognise if someone took the data and used it to publish astounding results.
This unusual Picture of the Week showcases the latest data gathered by ESO’s exoplanet hunter, the High Accuracy Radial velocity Planet Searcher (HARPS), during the ongoing Red Dots campaign, a search for terrestrial planets around our nearest three red dwarf stars: Proxima Centauri, Barnard’s Star, and Ross 154. The campaign was launched earlier in 2017 to build on the 2016 discovery of Proxima b around our nearest stellar neighbour, Proxima Centauri. Red Dots is designed as an open notebook science experiment, meaning the public has access to the data and can even contribute observations. Can you see a new exoplanet in these data of Proxima Centauri?
By carefully tracing the movement of a star over time, graphs like these can reveal the presence of exoplanets. Just as a star pulls on its orbiting planets using gravity, planets pull on the star, causing the star to wobble and shift the wavelength of its light by a small but measureable amount. By analysing the predictable, repeating changes, astronomers can infer the presence of a planet. The top left graph displays the 2016 data that confirmed the existence of Proxima b, showing how the planet is causing its parent star, Proxima Centauri, to move towards and away from Earth over time. The curved line represents the wobbling signal of the star, with the regular pattern of changing radial velocities (RV) repeating every 11.2 days.
The top right graph shows new measurements made with HARPS during the Red Dots campaign. The new data once again confirms Proxima b’s signal (in yellow), but also includes additional data patterns — visible here as a downward slope in both the 2016 and 2017 data points — hinting that there may be more to be discovered. To make a firmer statement on what is causing these patterns, astronomers need to use quantitative mathematical tools.
One such mathematical tool is called a periodogram, which searches for repeating signals in the data — displayed here as prominent peaks — that indicate the presence of a planet. The graph on the bottom panel shows the periodogram for the new data. The first signal (in white) corresponds to Proxima b. The second set of possible periods (in red), of around 200 days, are produced from patterns seen in the top panels. The presence of multiple peaks of similar heights means a signal cannot be precisely pinpointed and that its origin remains unclear.
The project will continue acquiring measurements until the end of September this year. You can follow along as the Red Dots campaign unfolds and even contribute observations via the Red Dots website, Facebook, or Twitter accounts. Credit: ESO/G. Anglada-Escudé
Q: How has the scientific community reacted to this project? Is there a difference to how they are getting involved?
A: The reaction of the scientific community is hard to gauge. In official terms, the scientific community expresses itself in research papers, which cite previous relevant work. The paper reporting the detection of Proxima b has certainly been cited many times, so the result itself had a significant impact. Then there is more informal feedback, in terms of receiving invitations to give talks, seminars and visit places. At least personally, I have made quite a number of excursions and gave a lot of public talks last year. So, yes, there seems to be a positive reaction at least from the broader community, although the “community” is not a uniform mass with just one opinion.
Q: You’re involving amateur astronomers. How is that working out? What are your expectations of them?
A: Yes, this is something I personally wanted to try. Firstly, I would have loved to have been given the opportunity to contribute to a professional science experiment when I was younger — I never did this as a child or before becoming a “professional” researcher. Maybe I wasn’t in the right environment when I was young, but I enjoy offering the opportunity to others. Secondly, there are a lot of clever and enthusiastic people in the world, and just because someone is not a career astronomer doesn’t mean they are not ready to perform excellent science. Good science is about formulating relevant questions, and paying attention to the details and context.
Technology is awesome these days, and flexibility and availability can be more valuable than a massive investment on large facilities. Amateur, or “pro-am”, astronomers are a perfect example of this. Again, the knowledge gained will be for all at the end, so everyone should have the chance to participate at some level. I must say that some of the light curves being produced by pro-am are of amazing quality, much better that what I could do. I am sure that a lot of the measurements will be used in the papers to come, and I would really like to work on new projects with them in the future.
Q: You’ve started vlogs — what are they about? What should we expect from these?
A: Our video blogs, or vlogs, are summaries of the activities of the last few weeks. The idea behind them is that, since our articles have a limited audience, we thought we might be able to offer the same content in a format that is easier to digest. I was lucky to have a summer intern (Harriet Brettle) and a PhD student (Clark Baker) here, who could work in tandem to manage the social media, prepare summaries and film the vlogs. Clark was especially keen, so we did it as an experiment. I can tell you that we didn’t get millions of YouTube hits, but some of our audience seem to better appreciate this format. It took a while to determine the structure and format (including length and content style, logos, and timing), but it’s easier now. It’s not as hard or as time consuming as I imagined, so with some more resources we’ll do great next time.
Our magnificent Milky Way galaxy is radiant over La Silla Observatory. The ESO 3.6-metre telescope is shown to the right, now home to the world’s foremost extrasolar planet hunter: High Accuracy Radial velocity Planet Searcher (HARPS), a spectrograph with unrivalled precision. Credit:
ESO/B. Tafreshi (http://twanight.org)
Q: And for the final question…do you think there’s life elsewhere in the Universe? And will we ever be able to find it?
A: There must be life somewhere else. I tend to be very optimistic about detecting evidence of it on nearby planets in the Solar System or around nearby stars. However, complex and technological civilisations do not seem to be the rule. Extrapolating our rate of progress, we should be able to “conquer” the Solar System in a few hundred years — or maybe thousands, but still a negligible period of time — and make our presence obvious to others who are searching. However, we see no clear evidence of this happening elsewhere, and people on Earth are seriously looking. This makes me think that either technological civilisations have short lifespans (we might be the next example…), or life is not as flexible as we think and it only thrives under very specific Earth-like conditions. Either way, we or our grandchildren might be able to find out pretty soon!
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/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 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.
VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.
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 levelSPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea levelESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level
A screen shot from Abel Méndez’s lab note titled “Strange Signals from the Nearby Red Dwarf Star Ross 128.” Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo/Aladin Sky Atlas.
Frank Elmore Ross (1874-1960), an American astronomer and physicist, became the successor to E. E. Barnard at Yerkes Observatory.
U Chicago Yerkes Observatory
U Chicago Yerkes Observatory interior
Barnard, of course, is the discoverer of the high proper motion of the star named after him, alerting us to its proximity.
And as his successor, Ross would go on to catalog over 1000 stars with high proper motion, many of them nearby. Ross 128, now making news for what observers at the Arecibo Observatory are calling “broadband quasi-periodic non-polarized pulses with very strong dispersion-like features,” is one of these, about 11 light years out in the direction of Virgo.
NAIC/Arecibo Observatory, Puerto Rico, USA
Any nearby stars are of interest from the standpoint of exoplanet investigations, though thus far we’ve yet to discover any companions around Ross 128. An M4V dwarf, Ross 128 has about 15 percent of the Sun’s mass. More significantly, it is an active flare star, capable of unpredictable changes in luminosity over short periods. Which leads me back to that unusual reception. The SETI Institute’s Seth Shostak described it this way in a post:
“What the Puerto Rican astronomers found when the data were analyzed was a wide-band radio signal. This signal not only repeated with time, but also slid down the radio dial, somewhat like a trombone going from a higher note to a lower one.”
And as Shostak goes on to say, “That was odd, indeed.”
It’s this star’s flare activity that stands out for me as I look over the online announcement of its unusual emissions, which were noted during a ten-minute spectral observation at Arecibo on May 12. Indeed, Abel Mendez, director of the Planetary Habitability Laboratory at Arecibo, cited Type II solar flares first in a list of possible explanations, though his post goes on to note that such flares tend to occur at lower frequencies. An additional novelty is that the dispersion of the signal points to a more distant source, or perhaps to unusual features in the star’s atmosphere. All of this leaves a lot of room for investigation.
We also have to add possible radio frequency interference (RFI) into the mix, something the scientists at Arecibo are examining as observations continue. The possibility that we are dealing with a new category of M-dwarf flare is intriguing and would have obvious ramifications given the high astrobiological interest now being shown in these dim red stars.
All of this needs to be weighed as we leave the SETI implications open. The Arecibo post notes that signals from another civilization are “at the bottom of many other better explanations,” as well they should be assuming those explanations pan out. But we should also keep our options open, which is why the news that the Breakthrough Listen initiative has now observed Ross 128 with the Green Bank radio telescope in West Virginia is encouraging.
GBO radio telescope, Green Bank, West Virginia, USA
No evidence of the emissions Arecibo detected has turned up in the Breakthrough Listen data. We’re waiting for follow-up observations from Arecibo, which re-examined the star on the 16th, and Mendez in an update noted that the SETI Institute’s Allen Telescope Array had also begun observations.
SETI/Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, USA
Seth Shostak tells us that the ATA has thus far collected more than 10 hours of data, observations which may help us determine whether the signal has indeed come from Ross 128 or has another source.
“We need to get all the data from the other partner observatories to put all things together for a conclusion,” writes Mendez. “Probably by the end of this week.”
[Shostak]
Or perhaps not, given the difficulty of detecting the faint signal and the uncertainties involved in characterizing it. If you’re intrigued, an Arecibo survey asking for public reactions to the reception is now available.
I also want to point out that Arecibo Observatory is working on a new campaign to observe stars like Ross 128, the idea being to characterize their magnetic environment and radiation. One possible outcome of work like that is to detect perturbations in their emissions that could point to planets — planetary magnetic fields could conceivably affect flare activity. That’s an intriguing way to look for exoplanets, and the list being observed includes Barnard’s Star, Gliese 436, Ross 128, Wolf 359, HD 95735, BD +202465, V* RY Sex, and K2-18.
A final note: Arecibo is now working with the Red Dots campaign in coordination with other observatories to study Barnard’s Star, for which there is some evidence of a super-Earth mass planet. More on these observations can be found in this Arecibo news release.
Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.
7.18.17
by Paul Gilster, writer and author of “Centauri Dreams”
Edited by Zaira M. Berdiñas
The Red Dots campaign to study Proxima Centauri, Barnard’s Star and Ross 154 gives us a cannily chosen set of targets. All red dwarfs much smaller than the Sun, these stars offer us the opportunity of atmospheric analysis of any planets discovered there by future space-and ground-based instruments because all are close. At 4.2 light years, Proxima Centauri is nearest to the Sun, but Barnard’s Star is a scant 6 light years out, making it the closest known star other than the three Alpha Centauri stars. Ross 154 comes in at just under 10 light years, still very much in the local neighborhood in astronomical terms.
The proper motion of Barnard’s Star between the years 1991 and 2007, an indication of its proximity to our own Solar System. No image credit.
But it is not just their proximity that makes these stars interesting. We’d like to know how stars like this age, considering that young M-dwarfs can show strong flare activity. All three of these stars do, with Proxima Centauri and Ross 154 being catalogued as UV Ceti stars; i.e., stars that produce major flares every few days. Barnard’s Star is of a variable category known as BY Draconis, stars that show starspots, variations in luminosity and other activity.
So consider the spread here. Proxima Centauri is thought to be about 4.85 billion years old, while Barnard’s Star is perhaps twice that. Ross 154, however, shows a high rate of rotation — 3.5 ± 1.5 km/s — that indicates a younger star, perhaps one less than a billion years old. Thus we have three stars and possible planets at markedly different stages of development, giving us the ability to take a deeper look into flare activity on M-dwarfs as they age, and to assess flare effects on planetary habitability, assuming Barnard’s Star and Ross 154 do have planets. We’ll also be investigating the prospects for multiple planets around Proxima Centauri itself.
Barnard’s Star has already produced its own share of notoriety. Working at the Sproul Observatory (Swarthmore College, Pennsylvania), astronomer Peter van de Kamp examined 2,413 photographic plates of the star taken between 1916 and 1962. The astronomer observed what he believed to be a telltale wobble in the motion of Barnard’s Star that fit the profile of a planet about 1.6 times Jupiter’s mass in an orbit at 4.4 AU [1]. He would later suggest the possibility of two gas giants here [2], and by 1973, Oliver Jensen (University of British Columbia) and Tadeusz Ulrych had upped the number to three [3].
Peter van de Kamp (right) and the the 61 cm Sproul refracting telescope (left) he used in his work on Barnard’s Star.
If confirmed, these would have been the first planets ever detected outside our Solar System, but it was not to be. Follow-up studies by George Gatewood (University of Pittsburgh) and John Hershey (also at the Sproul Observatory) found systematic errors in van de Kamp’s work. The culprit: Lens adjustments to the Swarthmore instrument that were later confirmed by Hershey when he found an identical wobble in the M-dwarf Gliese 793 [4]. Subsequent work by Gatewood and, later, Jieun Choi (UC Berkeley) would be able to detect no planets [5],[6].
Figure from Gatewood & Eichhorn that shows the disagreement between their data (black dots) and the model fitted by Van de Kamp using the data from the Sproul Observatory (dashed line).
Peter van de Kamp’s tool was astrometry, meaning he used precise measurements in the proper motion of the star to look for the presence of planets, finding minute variations on photographic plates that were consistent with the hypothesis. His observational skills and persistence were rightly praised, but errors in his instrument negated what would have been a major discovery.
So what do we have today? We can rule out gas giants at Barnard’s Star thanks to continuing Doppler monitoring, but we can’t yet rule out small rocky planets of the kind we are now turning up around other M-dwarfs in data from the Kepler mission.
NASA/Kepler Telescope
Kepler has shown us that planets of a few times Earth-mass are not uncommon, while a 2013 study by Ravi Kopparapu (Pennsylvania State) found that about half of all M-dwarfs should have Earth-size planets in the habitable zone[7]. What might Red Dots uncover around this tantalizingly close star?
It was Peter van de Kamp’s work that helped the energetic team of starship designers behind the British Interplanetary Society’s Project Daedalus choose Barnard’s Star as their destination. And physicist Robert Forward, no stranger to fiction, would use a planetary system around Barnard’s Star as the setting for his novel Rocheworld (1984). The system is reached by a lightsail beamed by a laser array, a concept not unfamiliar to today’s Breakthrough Starshot (read the article by Avi Loeb), which envisions sending small sails by laser to Proxima Centauri.
How fitting, then, that Red Dots should home in on this interesting system, along with a return to Proxima Centauri and a deep exploration of Ross 154 as well. Red dwarf stars like these account for as much as 80 percent of the stars in our galaxy. The new campaign will let us see, in real time, no less, just how this inspiring search of nearby dwarfs proceeds.
References:
van de Kamp, P. “Astrometric study of Barnard’s star from plates taken with the 24-inch Sproul refractor”, Astronomical Journal, 68, 515, (1963).
van de Kamp, P. “Alternate dynamical analysis of Barnard’s star”, Astronomical Journal, 74, 757, (1969).
Jensen, O. G. & Ulrych, T. “An analysis of the perturbations on Barnard’s Star”, Astronomical Journal, 78, 1104, (1973).
Hershey, J. L. “Astrometric analysis of the field of AC +65 6955 from plates taken with the Sproul 24-inch refractor”, Astronomical Journal, 78, 421, (1973).
Gatewood, G. & Eichhorn, H. “An unsuccessful search for a planetary companion of Barnard’s star BD +4 3561”, Astronomical Journal, 78, 769, (1973).
Choi, J. et al. “Precise Doppler Monitoring of Barnard’s Star”, Astrophysical Journal, 764, 131, (2013).
Kopparapu, R. K. “A Revised Estimate of the Occurrence Rate of Terrestrial Planets in the Habitable Zones around Kepler M-dwarfs”, Astrophysical Journal, 767, L8, (2013).
Red dots is a project to attempt detection of the nearest terrestrial planets to the Sun. Terrestrial planets in temperate orbits around nearby red dwarf stars can be more easily detected using Doppler spectroscopy, hence the name of the project.
ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.ESO/HARPS at La SillaCentauris Alpha Beta Proxima 27, February 2012. Skatebiker
Following the announcement of the discovery of Proxima b, the Red Dots campaign aims at detecting additional small planetary sized companions to Proxima Centauri. But we already have hints of variability in the star’s radial velocities not explained by the presence of Proxima b alone. There is more to the star than Proxima b.
We explained in our paper last year [1] that there was evidence for variability at a period of roughly 215 days in the radial velocity data from two instruments: HARPS (including the Pale Red Dot observing run in 2016) at ESO observatory at La Silla, ESO’s UVES instrument at VLT in Paranal, Chile. This variability is much more dominant on these relatively longer periods than the signal caused by Proxima b and is especially clearly visible when looking at the unbinned data (Fig. 1) — it is certainly amplified with respect to that in the nightly binned data presented in the Proxima b discovery paper. But although we labelled this variability as activity and removed it in order to study the signal of Proxima b at a shorter period, in reality, we do not know its origin. Different hypotheses range from instrumental instability to activity of the stellar surface to Doppler signature of another planet orbiting the star.
Red dots is a project to attempt detection of the nearest terrestrial planets to the Sun. Terrestrial planets in temperate orbits around nearby red dwarf stars can be more easily detected using Doppler spectroscopy, hence the name of the project.
ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.ESO/HARPS at La Silla
19 June 2017
Oana Sandu
Community Coordinator & Communication Strategy Officer
ESO education and Public Outreach Department
+49 89 320 069 65
osandu@partner.eso.org
ESO Joins Open Notebook Science Experiment
ESO Red Dots Campaign
The team behind the Pale Red Dot campaign, who last year discovered a planet around the closest star to our Sun (eso1629), are resuming their search for Earth-like planets and launching another initiative today. The Red Dots campaign will follow the astronomers as they use ESO’s exoplanet-hunter to look for planets around some of our nearest stellar neighbours: Proxima Centauri, Barnard’s Star and Ross 154. ESO is joining this Open Notebook Science experiment — real science presented in real time — that will give the public and the scientific community access to observational data from Proxima Centauri as the campaign unfolds.
The scientific team [1] led by Guillem Anglada-Escudé from Queen Mary University of London will acquire and analyse data from ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) and other instruments across the globe [2] over approximately 90 nights.
ESO/HARPS at La Silla ESO 3.6m telescope & HARPS at LaSilla
Photometric observations began on 15 June and spectrographic observations start on 21 June.
HARPS is a spectrograph with unrivalled precision — the most successful finder of low-mass exoplanets to date. Attached to the ESO 3.6-metre telescope at La Silla.
ESO/Cerro LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.
HARPS searches nightly for exoplanets, looking for the minute wobbles in the star’s motion generated by the pull of an exoplanet in orbit. HARPS picks up motion which can be as little as a gentle walking pace — just 3.5 km/h — from trillions of kilometres away.
Among the stars targeted by Red Dots will be Proxima Centauri, which scientists suspect has more than one terrestrial planet in orbit around it.
Centauris Alpha Beta Proxima 27, February 2012. Skatebiker
Proxima Centauri is the closest star to our Sun, only 4.2 light-years away. It may be one of the most suitable places to look for life beyond our Solar System, as our instruments and technologies advance.
Earlier this year, ESO announced a partnership with the Breakthrough Initiatives, which aims to demonstrate proof of concept for a new technology that will enable ultra-light unmanned space flight at 20% of the speed of light. Such nanocraft could be sent to the three stars of the Alpha Centauri system, of which Proxima Centauri is the closest to our Sun.
The other two stars observed during the Red Dots campaign are Barnard’s star, a low mass red dwarf almost 6 light-years away, and Ross 154, another red dwarf, 9.7 light-years away. Barnard’s star is a popular star in science fiction culture and has also been proposed as the target for future interstellar missions such as the Daedalus project.
The telescope observations will be complemented by an outreach campaign supported by ESO and other partners [3]. The Pale Red Dot campaign revealed the methods and steps of doing science, but the results were presented only after the peer review process. This time, observational data from Proxima Centauri will be revealed, analysed and discussed in real time.
Pro-am collaborations and contributions by interested citizens and scientists will be encouraged via social media and a forum tool, as well as via support tools from the American Association of Variable Star Observers (AAVSO).
Any observations presented during this time will of course be preliminary only and they must not be used or cited in refereed literature. The team will not produce conclusive statements, nor claim any finding until a suitable paper is written, peer-reviewed and accepted for publication.
The Red Dots campaign will keep the public informed via the reddots.space website, where weekly updates will be posted, together with supporting articles and highlights of the week including featured contributions by the community. Conversations will take place also on the Red Dots Facebook page, the Red Dots Twitter account and the hashtag #reddots.
No one can say for sure what the outcome of the Red Dots campaign will be. After data acquisition and data analysis together with the community, the scientific team will submit the results for formal peer review. If exoplanets are indeed discovered around these stars, ESO’s Extremely Large Telescope, due to see first light in 2024, should be able to directly image them and characterise their atmospheres, a crucial step towards searching for evidence of life beyond the Solar System.
Notes
[1] The team of astronomers leading the observations and outreach campaign are: Guillem Anglada-Escudé, John Strachan, Richard P. Nelson, Harriet Brettle (Queen Mary University of London, UK), John Barnes (Open University, UK), Mikko Tuomi, Hugh R. A. Jones (University of Hertfordshire, UK), Cristina Rodríguez-Lopez, Eloy Rodriguez, Pedro J. Amado, María J. López-González, Nicolás Morales, José Luís Ortiz (Instituto de Astrofisica de Andalucia, Spain), Enric Pallé, Victor J. Sanchez Bejar, Felipe Murgas (Instituto de Astrofísica de Canarias, Spain), Ignasi Ribas, Enrique Herrero Casas (Institut de Ciències de l’Espai, Spain), Ansgar Reiners, Mathias Zechmeister, Stefan Dreizler, Lev Tal-Or, Sandra Jeffers (University of Goettingen, Germany), Yiannis Tsapras (Astronomisches Rechen-Institut, University of Heidelberg, Germany), Rachel Street (LCOGT.net), James Jenkins, Zaira Modroño Berdiñas (Universidad de Chile, Chile), Aviv Ofir (Weizmann Institute, Israel), Julien Morin (Université de Montpellier and CNRS, France), Gavin Coleman (University of Bern, Switzerland).
[2] The facilities used during the Red Dots campaign are: HARPS/ESO in Chile (Spectroscopy/Doppler measurements and more); and an extended network of small telescopes for photometric monitoring including: Las Cumbres Global Observatory Telescope network; SpaceObs ASH2 in Chile; Observatorio de Sierra Nevada, in Spain; and Observatori Astronomic del Montsec, Spain. In addition to new data, the team will make extensive use of public observations of all three stars from the ESO archives (HARPS and UVES/VLT) and the ASAS photometric survey.
LCOGT Las Cumbres Observatory Global Telescope Network, Haleakala Hawaii, USA
SpaceObs ASH2 in Chile
Observatorio de Sierra Nevada, in Spain
Observatori Astronòmic del Montsec (OAdM), Spain
[3] The outreach campaign is coordinated by members of the science team with support from the outreach departments of ESO, Queen Mary University of London, Instituto de Astrofisica de Andalucia/CSIC, Universidad de Chile and University of Goettingen.
Links
See the full ESO article for the many links associated with this campaign
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/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 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
VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level
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
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