The largest haul of confirmed planets obtained since the space observatory transitioned to a different mode of observing includes a planetary system comprising four promising planets that could be rocky. An international team of astronomers led by the University of Arizona has discovered and confirmed a treasure trove of new worlds using NASA’s Kepler spacecraft on its K2 mission.
Credit: Third Party Reference
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 four promising planets that could be rocky.
The planets, all between 20 and 50 percent 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 five and a half to 24 days, and two 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, according to lead author Ian Crossfield, a Sagan Fellow at the University of Arizona’s Lunar and Planetary Laboratory.
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 in Hawaii, the Automated Planet Finder of the University of California Observatories, and the Large Binocular Telescope operated by the University of Arizona. The discoveries are published online in the Astrophysical Journal Supplement Series.
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Both Kepler and its K2 mission discovered 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 orbiting stars similar to our sun whose sizes and temperatures might be similar to Earth’s.
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 began its K2 mission, offering a wider view of the sky for Earth-based observatories in both hemispheres. The K2 mission is fully driven by the community, with targets chosen by scientists. Since it observes more of the sky, the K2 mission can detect more cooler, smaller red-dwarf stars, which are much more common in the Milky Way than sun-like stars, meaning nearby stars will mostly 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, the researchers obtained high-resolution images of the planet-hosting stars and high-resolution optical spectroscopic data. By dispersing starlight as through a prism, the spectrographs allowed the researchers to infer the physical properties of a star, such as mass, radius, and temperature, from which the properties of any planets orbiting it could be inferred.
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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.
“This bountiful list of validated exoplanets from the K2 mission highlights the fact that the targeted examination of bright stars and nearby stars along the ecliptic is providing many interesting new planets,” said Steve Howell, project scientist for Kepler and K2 at NASA’s Ames Research Center in Moffett Field, California.
This allows the astronomical community to follow up and characterize them more easily, thus facilitating a deeper understanding of these celestial objects and their unique properties.
Additionally, it highlights a few gems for the first study by the James Webb Space Telescope, which could provide invaluable information about their atmospheres, including the chemical compositions, potential weather patterns, and any signs of habitability that may exist within these distant worlds.
This unprecedented ability to analyze such features opens up exciting new avenues for research and exploration. It will potentially reshape our knowledge of the universe and our place within it.
