Talk about your happy accidents: the Kepler space telescope’s broken pointing system is being credited for helping an international team of researchers discover more than 100 confirmed new exoplanets – the largest find since Kepler began its K2 mission.
The findings, which included the first planetary system comprised of four planets that could be potentially similar to Earth, were confirmed by follow-up observations conducted using ground-based telescopes including the W. M. Keck Observatory on Maunakea, Hawaii. The researchers have published their findings online in The Astrophysical Journal Supplement Series.
During the original phase of its mission, Kepler surveyed specific areas in the skies above the northern hemisphere, searching for Earth-like planets orbiting Sun-like stars. In 2013, however, it lost the ability to closely examine its original target area, forcing engineers to repurpose it to examine multiple independent target areas in both hemispheres.
The now community-driven K2 mission gave Kepler new life, and enabled researchers to use it along with ground-based observatories to examine a larger percentage of smaller and cooler red dwarf stars, which are far more common in our galaxy than Sun-like stars, the team explained.
“Kepler’s original mission observed a small patch of sky as it was designed to conduct a demographic survey of the different types of planets,” lead investigator Ian Crossfield, a Sagan Fellow at the University of Arizona’s Lunar and Planetary Laboratory, said in a statement. “This approach effectively meant that relatively few of the brightest, closest red dwarfs were included in Kepler’s survey. The K2 mission allows us to increase the number of small, red stars by a factor of 20 for further study.”
Techniques could ‘triple’ the number of known Earth-like planets
Using data obtained by Kepler, and confirming those observations with others made at the Keck Observatory, the Gemini telescopes on Maunakea and in Chile, the Automated Planet Finder of the University of California Observatories, and the Large Binocular Telescope at the University of Arizona, Crossfield’s team managed to find 197 candidates and 104 verified planets.
Among the new worlds they were able to discover was a system of four potentially rocky planets that were each 20% to 50% larger than Earth, and which orbit a star less than half as large as our Sun. The orbits of these worlds range from 5.5 to 24 days, and while their host star gives off less light than the Sun, two of the worlds may experience radiation levels comparable to ours.
While their orbits bring them closer to their host star than Mercury’s orbit does to the Sun, there is still a possibility that such planets could be habitable, Crossfield explained. “Because these smaller stars are so common in the Milky Way, it could be that life occurs much more frequently on planets orbiting cool, red stars rather than planets around stars like our sun,” he said.
Once the planets were identified by K2, the researchers used Keck Observatory’s near infrared camera (NIRC2) and other instruments to obtain high-resolution images of the stars, and the high resolution spectrograph (HIRES) instrument at the Maunakea facility and the Automated Planet Finder to gather high-resolution optical spectroscopy data to verify the candidate planets.
Using the spectrographs allowed the researchers to disperse the starlight and measure the mass, radius, temperature and other physical properties of the star, the study authors said. This, in turn, made it possible for them to infer the characteristics of each planet orbiting those stars, and by applying these techniques to future K2 findings, Crossfield said that he believes that they will be able to “double or triple the number of relatively small planets orbiting nearby, bright stars.”
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Image credit: NASA
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