The largest haul of confirmed planets has been obtained. This occurred after the space observatory transitioned to a different mode of observing. It includes a planetary system with four promising planets. These planets be rocky.
UNIVERSITY OF ARIZONA
Led by the University of Arizona, an international team of astronomers has discovered many new worlds. They confirmed this using NASA’s Kepler spacecraft on its K2 mission. Among the findings tallying 197 first planet candidates, scientists have confirmed 104 planets outside our solar system. Among the confirmed is a planetary system comprising four promising planets that are rocky.
The planets are all between 20 and 50 percent larger than Earth by diameter. They orbit the M dwarf star K2-72. This star is 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. Two of them experience irradiation levels from their star that are comparable to those on Earth.
Their orbits are tight and closer than Mercury’s orbit around the sun. Despite this, the possibility of life arising on a planet around such a star remains. Lead author Ian Crossfield is a Sagan Fellow at the University of Arizona’s Lunar and Planetary Laboratory. He does not rule this out.
The researchers combined the initial data with follow-up observations from several leading ground-based telescopes. These included the Gemini North Telescope, the W. M. Keck Observatory in Hawaii, the University of California Observatories’ Automated Planet Finder, and the Large Binocular Telescope operated by the University of Arizona. The discoveries were published online in the Astrophysical Journal Supplement Series.
Kepler discovered new planets by measuring the subtle dip in a star’s brightness. This was caused by a planet passing in front of its star. The K2 mission continued this work. In its first mission, Kepler surveyed just one patch of sky in the northern hemisphere. It measured the frequency of planets. These planets have a size and temperature comparable to Earth. They orbit stars akin to our sun. In the spacecraft’s extended mission in 2013, it lost its ability to precisely stare at its original target area. Yet, a brilliant fix created a second life for the telescope. This fix is proving scientifically fruitful.
Kepler started its K2 mission after the fix. This mission has provided an ecliptic field of view. It offers 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 by the scientific community.
The K2 mission covers more of the sky. It is capable of observing a larger fraction of cooler, smaller, red-dwarf-type stars. Such stars are much more common in the Milky Way than sun-like stars. Thus, nearby stars will predominantly be red dwarfs.
“Kepler performed a demographic study. In contrast, 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. This significantly increases the number of astronomical ‘movie stars’. These stars make the best systems for further study.”
The researchers obtained high-resolution images of the planet-hosting stars. They also acquired high-resolution optical spectroscopy data to confirm candidate planets identified by K2. The spectrographs dispersed the starlight as through a prism. This dispersion allowed the researchers to infer the physical properties of a star, like mass, radius, and temperature. From these properties, they inferred the characteristics of any planets orbiting it.
These observations are a natural progression from the K2 mission. They lead to NASA’s other upcoming exoplanet missions. Examples include the Transiting Exoplanet Survey Satellite and James Webb Space Telescope.
“This bountiful list of validated exoplanets from the K2 mission is significant. Steve Howell is the project scientist for Kepler and K2 at NASA’s Ames Research Center in Moffett Field, California. He said that examining bright and nearby stars along the ecliptic provides many interesting new planets.
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