Image montage showing the Maunakea Observatories, Kepler Space Telescope, and night sky with K2 Fields and discovered planetary systems (dots) overlaid. An international team of scientists discovered more than 100 planets based on images from Kepler operating in the ‘K2 Mission’. The team confirmed and characterized the planets using a suite of telescopes worldwide, including four on Maunakea (the twin telescopes of Keck Observatory, the GeminiÂNorth Telescope, and the Infrared Telescope Facility). The planet image on the right is an artist’s impression of a representative planet. Credit: Karen Teramura (UHIfA) based on night sky image of the ecliptic plane by Miloslav Druckmüller and Shadia Habbal, and Kepler Telescope and planet images by NASA.
An international team has discovered and confirmed a treasure trove of new worlds using NASA’s Kepler spacecraft on its K2 mission. Among the findings tallying 197 initial planet candidates, scientists have confirmed 104 planets outside our solar system. Among the confirmed is a planetary system comprising 4 promising planets that could be rocky.
The planets, all between 20 and 50% larger than Earth by diameter, are orbiting the M dwarf star K2-72, found 181 light years away in the direction of the Aquarius constellation. The star is less than half the size of the sun and less bright. The planets’ orbital periods range from 5.5 to 24 days, and 2 of them may experience irradiation levels from their star comparable to those on Earth. Despite their tight orbits – closer than Mercury’s orbit around the sun – the possibility that life could arise on a planet around such a star cannot be ruled out.
The researchers achieved this extraordinary “roundup” of exoplanets by combining data with follow-up observations by earth-based telescopes including the North Gemini telescope and the W. M. Keck Observatory, HI, Automated Planet Finder of the Uni of CA Observatories, and the Large Binocular Telescope operated by the Uni of Arizona.
Both Kepler and its K2 mission discover new planets by measuring the subtle dip in a star’s brightness caused by a planet passing in front of its star. In its initial mission, Kepler surveyed just one patch of sky in the northern hemisphere, measuring the frequency of planets whose size and temperature might be similar to Earth orbiting stars similar to our sun. In the spacecraft’s extended mission in 2013, it lost its ability to precisely stare at its original target area, but a brilliant fix created a second life for the telescope that is proving scientifically fruitful.
After the fix, Kepler started its K2 mission, which has provided an ecliptic field of view with greater opportunities for Earth-based observatories in both the northern and southern hemispheres. Additionally, the K2 mission is entirely community-driven with all targets proposed for by the scientific community. As it covers more of the sky, the K2 mission is capable of observing a larger fraction of cooler, smaller, red-dwarf type stars, and because such stars are much more common in the Milky Way than sun-like stars, nearby stars will predominantly be red dwarfs.
“An analogy would be to say that Kepler performed a demographic study, while the K2 mission focuses on the bright and nearby stars with different types of planets,” said Ian Crossfield. “The K2 mission allows us to increase the number of small, red stars by a factor of 20, significantly increasing the number of astronomical ‘movie stars’ that make the best systems for further study.”
To validate candidate planets identified by K2, they obtained high-resolution images of the planet-hosting stars and high-resolution optical spectroscopy data. The spectrographs allowed the researchers to infer the physical properties of a star – eg mass, radius and temperature – from which the properties of any planets orbiting it can be inferred.
These observations represent a natural stepping stone from the K2 mission to NASA’s other upcoming exoplanet missions such as the Transiting Exoplanet Survey Satellite and James Webb Space Telescope. https://uanews.arizona.edu/story/ualed-team-confirms-100-exoplanets-kepler
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