Category Archives: Exoplanets

ESO: New ExTrA observatory to look for and study Earth-sized planets orbiting red dwarf stars

A new report from ESO  (European Southern Observatory):

First Light for Planet Hunter ExTrA at La Silla

The ExTrA telescopes are sited at ESO’s La Silla Observatory in Chile. They will be used to search for and study Earth-sized planets orbiting nearby red dwarf stars. ExTrA’s novel design allows for much improved sensitivity compared to previous searches. This nighttime view shows the three ExTra domes in the foreground and many of the other telescopes at ESO’s La Silla Observatory behind. [Hi-res images.]
A new national facility at ESO’s La Silla Observatory has successfully made its first observations. The ExTrA telescopes will search for and study Earth-sized planets orbiting nearby red dwarf stars. ExTrA’s novel design allows for much improved sensitivity compared to previous searches. Astronomers now have a powerful new tool to help in the search for potentially habitable worlds.

The newest addition to ESO’s La Silla observatory in northern Chile, Exoplanets in Transits and their Atmospheres (ExTrA), has made its first successful observations. ExTrA is designed to search for planets around nearby red dwarf stars and study their properties. ExTrA is a French project funded by the European Research Council and the French Agence National de la Recherche. The telescopes will be operated remotely from Grenoble, France.

The ExTrA telescopes are sited at ESO’s La Silla Observatory in Chile. They will be used to search for and study Earth-sized planets orbiting nearby red dwarf stars. ExTrA’s novel design allows for much improved sensitivity compared to previous searches. This view shows one of the three ExTrA in its dome. [Hi-res images]
To detect and study exoplanets, ExTrA uses three 0.6-metre telescopes [1]. They regularly monitor the amount of light received from many red dwarf stars and look for a slight dip in brightness that could be caused by a planet passing — transiting — across a star’s disc and obscuring some of its light.

La Silla was selected as the home of the telescopes because of the site’s excellent atmospheric conditions,” explains the project’s lead researcher, Xavier Bonfils. “The kind of light we are observing — near-infrared — is very easily absorbed by Earth’s atmosphere, so we required the driest and darkest conditions possible. La Silla is a perfect match to our specifications.

The transit method involves comparing the brightness of the star under study with other reference stars to spot tiny changes. However, from the ground it is difficult to make sufficiently precise measurements this way to detect small, Earth-sized planets [2]. By using a novel approach that also incorporates information about the brightness of the stars in many different colours, however, ExTrA overcomes some of these limitations.

The three ExTra telescopes collect light from the target star and four comparison stars and that light is then fed through optical fibres into a multi-object spectrograph. This innovative approach of adding spectroscopic information to traditional photometry helps to mitigate the disruptive effect of Earth’s atmosphere, as well as effects introduced by instruments and detectors — increasing the precision achievable.

Because a transiting planet will block a greater proportion of the light from a smaller star, ExTrA will focus on targeting nearby examples of a specific kind of small, bright star known as M dwarfs, which are common in the Milky Way. Such stars are expected to host many Earth-sized planets, making them prime targets for astronomers looking to discover and study distant worlds that could be amenable to life. The nearest star to the Sun, Proxima Centauri, is an M dwarf and has been found to have an orbiting Earth-mass planet.

The ExTrA telescopes are sited at ESO’s La Silla Observatory in Chile. They will be used to search for and study Earth-sized planets orbiting nearby red dwarf stars. ExTrA’s novel design allows for much improved sensitivity compared to previous searches. This view shows one of the three ExTrA domes with its access door open.[Hi-res images]
Finding these previously undetectable Earth-like worlds is only one of two key objectives for ExTrA. The telescope will also study the planets it finds in some detail, assessing their properties and deducing their composition to determine how similar to Earth they could be.

With ExTrA, we can also address some fundamental questions about planets in our galaxy. We hope to explore how common these planets are, the behaviour of multi-planet systems, and the sorts of environments that lead to their formation,” adds team member Jose-Manuel Almenara.

Bonfils is excited for the future:

With the next generation of telescopes, such as ESO’s Extremely Large Telescope, we may be able to study the atmospheres of exoplanets found by ExTra to try to assess the viability of these worlds to support life as we know it. The study of exoplanets is bringing what was once science fiction into the world of science fact.

Notes

[1] The telescopes and their mounts were supplied by Astrosysteme Austria, the domes come from the German company ScopeDome and the infrared camera was made by the US company Princeton Instruments with the detector array from the Belgium company Xenics. Additional information about the facility is available here.

[2] This approach, known as differential photometry, involves observing the target star along with other stars nearby in the sky. By correcting for variations that are common to all stars due to the Earth’s disruptive atmosphere, more accurate measurements can be obtained for the target star. However, the dips in light caused by Earth-sized planets are so slight that even this technique is not always sufficient.

Video: Google neural network used to discover exoplanet

A NASA / Google collaboration used artificial intelligence (AI) techniques to discover an eighth planet around the star Kepler-90i, which resides just over 2500 light years from earth.

Here is the NASA press release:

Artificial Intelligence, NASA Data Used to Discover Exoplanet | NASA

Our solar system now is tied for most number of planets around a single star, with the recent discovery of an eighth planet circling Kepler-90, a Sun-like star 2,545 light-years from Earth. The planet was discovered in data from NASA’s Kepler Space Telescope.

The newly-discovered Kepler-90i – a sizzling hot, rocky planet that orbits its star once every 14.4 days – was found using machine learning from Google. Machine learning is an approach to artificial intelligence in which computers “learn.” In this case, computers learned to identify planets by finding in Kepler data instances where the telescope recorded signals from planets beyond our solar system, known as exoplanets.

NASA will host a Reddit Ask Me Anything at 3 p.m. EST [Thursday, Dec.14.2017] on this discovery.

“Just as we expected, there are exciting discoveries lurking in our archived Kepler data, waiting for the right tool or technology to unearth them,” said Paul Hertz, director of NASA’s Astrophysics Division in Washington. “This finding shows that our data will be a treasure trove available to innovative researchers for years to come.” 

The discovery came about after researchers Christopher Shallue and Andrew Vanderburg trained a computer to learn how to identify exoplanets in the light readings recorded by Kepler – the minuscule change in brightness captured when a planet passed in front of, or transited, a star. Inspired by the way neurons connect in the human brain, this artificial “neural network” sifted through Kepler data and found weak transit signals from a previously-missed eighth planet orbiting Kepler-90, in the constellation Draco.

While machine learning has previously been used in searches of the Kepler database, this research demonstrates that neural networks are a promising tool in finding some of the weakest signals of distant worlds.

Other planetary systems probably hold more promise for life than Kepler-90. About 30 percent larger than Earth, Kepler-90i is so close to its star that its average surface temperature is believed to exceed 800 degrees Fahrenheit, on par with Mercury. Its outermost planet, Kepler-90h, orbits at a similar distance to its star as Earth does to the Sun.

“The Kepler-90 star system is like a mini version of our solar system. You have small planets inside and big planets outside, but everything is scrunched in much closer,” said Vanderburg, a NASA Sagan Postdoctoral Fellow and astronomer at the University of Texas at Austin.

Shallue, a senior software engineer with Google’s research team Google AI, came up with the idea to apply a neural network to Kepler data. He became interested in exoplanet discovery after learning that astronomy, like other branches of science, is rapidly being inundated with data as the technology for data collection from space advances.

“In my spare time, I started googling for ‘finding exoplanets with large data sets’ and found out about the Kepler mission and the huge data set available,” said Shallue. “Machine learning really shines in situations where there is so much data that humans can’t search it for themselves.”

Kepler’s four-year dataset consists of 35,000 possible planetary signals. Automated tests, and sometimes human eyes, are used to verify the most promising signals in the data. However, the weakest signals often are missed using these methods. Shallue and Vanderburg thought there could be more interesting exoplanet discoveries faintly lurking in the data.

First, they trained the neural network to identify transiting exoplanets using a set of 15,000 previously-vetted signals from the Kepler exoplanet catalogue. In the test set, the neural network correctly identified true planets and false positives 96 percent of the time. Then, with the neural network having “learned” to detect the pattern of a transiting exoplanet, the researchers directed their model to search for weaker signals in 670 star systems that already had multiple known planets. Their assumption was that multiple-planet systems would be the best places to look for more exoplanets.

“We got lots of false positives of planets, but also potentially more real planets,” said Vanderburg. “It’s like sifting through rocks to find jewels. If you have a finer sieve then you will catch more rocks but you might catch more jewels, as well.”

Kepler-90i wasn’t the only jewel this neural network sifted out. In the Kepler-80 system, they found a sixth planet. This one, the Earth-sized Kepler-80g, and four of its neighboring planets form what is called a resonant chain – where planets are locked by their mutual gravity in a rhythmic orbital dance. The result is an extremely stable system, similar to the seven planets in the TRAPPIST-1 system.

Their research paper reporting these findings has been accepted for publication in The Astronomical Journal. Shallue and Vanderburg plan to apply their neural network to Kepler’s full set of more than 150,000 stars.

Kepler has produced an unprecedented data set for exoplanet hunting. After gazing at one patch of space for four years, the spacecraft now is operating on an extended mission and switches its field of view every 80 days.

“These results demonstrate the enduring value of Kepler’s mission,” said Jessie Dotson, Kepler’s project scientist at NASA’s Ames Research Center in California’s Silicon Valley. “New ways of looking at the data – such as this early-stage research to apply machine learning algorithms – promises to continue to yield significant advances in our understanding of planetary systems around other stars. I’m sure there are more firsts in the data waiting for people to find them.”

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate in Washington. NASA’s Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. This work was performed through the Carl Sagan Postdoctoral Fellowship Program executed by the NASA Exoplanet Science Institute.

For more information on this announcement, visit: https://www.nasa.gov/mediaresources

For more information about the Kepler mission, visit: https://www.nasa.gov/kepler

Video: Kepler introduces the Era of Exoplanets

A video of recent public lecture at the SETI Institute giving an overview of the exoplanet discoveries of the Kepler space telescope: The Era of Exoplanets Has Arrived – Jeff Coughlin & Geert Barentsen (SETI Talk 2017) – 

NASA’s Kepler space telescope was launched in 2009 and measured the brightness of 200,000 stars at unprecedented precision for over four years, with the prime mission goal of detecting Earth-sized exoplanets. Now after another four, Kepler’s final planet catalog is complete — over 4,000 planet candidates have been found, with 50 of them possibly rocky and capable of having liquid water. For the first time in human history, we can calculate how common planets the same size and temperature as Earth are, a key component to SETI’s goal of figuring out how common life may be in the universe.

The K2 mission began three years ago, and uses the Kepler spacecraft to stare at many different parts of the sky for 80 days at a time. A broad portion of the Astronomical community chooses what targets to observe, resulting in a wide variety of science, including supernovae, galaxies, stars, and of course exoplanets. K2 has found over 300 confirmed exoplanets and an additional 500 candidates. Some of these are likely to be habitable, and many of them are prime targets to be observed by future missions, such as the James Webb space telescope. We’ll discuss what we may learn about these worlds over the next few decades, and what future missions are being planned to find planets to which our descendants may one day travel.

 

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Video: “A Planet for Goldilocks: Kepler & the Search for Living Worlds” – Dr. Natalie Batalha

Dr. Natalie Batalha of NASA’s Kepler Mission Project gives a public lecture about A Planet for Goldilocks: Kepler & the Search for Living Worlds

NASA’s Kepler Mission launched in 2009 with the objective of finding “Goldilocks planets” orbiting other stars like our Sun. The space telescope opened our eyes to the many terrestrial-sized planets that populate the galaxy (including several right in our neighborhood,) as well as to exotic worlds unlike anything that exists in the solar system. Dr. Batalha gives an overview of the science legacy of the Kepler Mission and other key planet discoveries (including some results only a few weeks old). She also gives a preview of planet-finding missions to come.

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Video: “How to Find an Inhabited Exoplanet”

Here is an excellent overview for a general public audience of the question, “How to Find an Inhabited Exoplanet”:

The speaker is David Charbonneau of Harvard University. He gave the presentation at the Space Telescope Science Institute in Baltimore, Maryland for one of their public lectures:

Over the past couple decades, research has uncovered thousands of exoplanets in orbit around other stars. In particular, the NASA Kepler Mission taught us that Earth-sized planets are commonplace throughout the Galaxy.  But the big question remains – did life take root on any of these distant worlds? Using upcoming large telescopes, astronomers will examine the atmospheres of Earth-like planets for the telltale chemical fingerprints of life. The search for life in the universe has entered an exciting new phase.