This artist’s concept shows how the planet KOI-5Ab faces a solar star throughout, which is part of a triple star system located 1800 light-years away in the constellation Cygnus. Credit: Caltech / R. Seer (IPAC)
Shortly after NASA’s Kepler mission began operating in 2009, the space telescope saw in a multi-star system that as a planet was about half the size of Saturn. KOI-5Ab was only the second planetary candidate found by the mission, and excitingly as at the time, it was eventually set aside as Kepler gained more and more planetary discoveries.
At the end of the spacecraft’s operation in 2018, Kepler discovered a whopping 2,394 exoplanets, or planets orbiting stars around our sun, and another 2,366 exoplanet candidates still needed.
“KOI-5Ab was abandoned because it was complicated, and we had thousands of candidates,” said David Ciardi, chief scientist at NASA’s Exoplanet Science Institute. “It was easier chosen than KOI-5Ab, and we learned something new from Kepler every day, so KOI-5 was mostly forgotten.”
Now, after a long hunt that stretched over many years and many telescopes, Ciardi said he had ‘raised KOI-5Ab from the dead’. Thanks to new observations from NASA’s second planet-hunting mission, the Transiting Exoplanet Survey Satellite, or TESS, and a number of ground-based telescopes, Ciardi was finally able to disrupt all the evidence surrounding KOI-5Ab and prove its existence. There are some interesting details about it to think about.
Probably a gas giant planet like Jupiter or Saturn in our solar system given its size, KOI-5Ab is unusual because it orbits a star in a system with two other accompanying stars, orbiting an airplane that is not in line with at least one does not. of the stars. The arrangement questions how each member in this system formed from the same swirling clouds of gas and dust. Ciardi, located in Caltech, Pasadena, California, presented the findings at a virtual meeting of the American Astronomical Society.
Pick up the route
After the initial detection by Kepler, Ciardi and other researchers selected the track on the KOI-5Ab as part of a cache of planetary candidates they followed up on. Using data from the WM Keck Observatory in Hawaii, Caltech’s Palomar Observatory near San Diego and Gemini North in Hawaii, Ciardi and other astronomers determined that KOI-5b appears to be one star in a triple-star circle. . However, they still could not bother whether the planetary signal was actually a faulty error of one of the other two stars, or, if the planet was real, which of the stars it orbits.
Then, in 2018, TESS came along. Like Kepler, TESS looks at the twinkling starlight that comes when a planet crosses in front of a star, or passes through. TESS observed a portion of Kepler’s field of view, including the KOI-5 system. Sure enough, TESS has also identified KOI-5Ab as a candidate planet, although TESS calls it TOI-1241b. As Kepler noted earlier, TESS found that the planet orbits its star about every five days.
“I thought to myself, ‘I remember this target,'” Ciardi said after seeing the TESS data. “But we could not yet definitively determine whether the planet was real or whether the blip in the data of another star entered the system – it could have been a fourth star.”
Clues in the wobbles
He then went back and analyzed all the data again and then looked for new clues from telescopes on the ground. The Keck Observatory is frequently used by Kepler and TESS, and is often used for follow-up surveys of exoplanets by measuring the light wobble in a star as a planet orbits it and gravitational pull. Ciardi, along with other scientists through an exoplanet collaboration group called the California Planet Search, searched for any shake-up in Keck’s data on the KOI-5 system. They could bother a pendulum moving through the inner companion star, orbiting the primary star, from the oscillation of the apparent planet as it orbits the primary star. Together, the various collections of data from the space and ground telescopes helped to confirm that KOI-5Ab is indeed a planet orbiting the primary star.
Bingo – it was there! “If it were not for the fact that TESS was looking at the planet again, I would never have done all this detective work,” he said. But it really took a lot of keys in data collected from many different telescopes to eventually nail. on this planet. ”
KOI-5Ab orbits star A, which has a relatively close companion, star B. Star A and star B orbit each other every 30 years. A third gravity-bound star, star C, orbits stars A and B every 400 years.
The KOI-5 galaxy consists of three stars, marked A, B and C in this diagram. Stars A and B rotate each other every 30 years. Star C orbits stars A and B every 400 years. The system houses one known planet, called KOI-5Ab, which was discovered and characterized using data from NASA’s Kepler and TESS (Transiting Exoplanet Survey Satellite) missions, as well as as telescopes on the ground. KOI-5Ab is about half the mass of Saturn and orbit star A approximately every five days. Its orbit is 50 degrees relative to the level of stars A and B. Astronomers suspect that this wrong orbit was caused by star B, which kicked the planet during its evolution, distorted its orbit and caused it to migrate inward. Credit: Caltech / R. Seer (IPAC)
A skewed job
The combined data set also reveals that the orbital plane of the planet is not in line with the orbital plane of star B, the second inner star as might be expected if the stars and planet are all formed from the same disk of swirling material. Astronomers are not sure what caused the misinterpretation of KOI-5Ab, but believe that the second star kicked the planet during its evolution gravitationally, skewed its orbit and caused it to migrate inward. Triple systems make up about 10% of all star systems.
This is not the first evidence of planets in double and triple systems. One notable case is the triple galaxy GW Orionis, in which a planet-forming disk is torn into clear, wrong edges, where planets can form. Despite hundreds of discoveries of planets in multiple galaxies, far fewer planets have been observed than in single galaxies. This may be due to a perceptual bias (single star planets are easier to detect), or because planet formation is actually less common in multiple galaxies.
“This research highlights the importance of NASA’s complete fleet of space telescopes and their synergy with terrestrial systems,” said Jessie Dotson, project scientist for the Kepler Space Telescope at NASA’s Ames Research Center in Silicon Valley, California. “Discoveries like these can be a long way off.”
New and future instruments, such as the Palomar Radial Velocity Instrument at the 200-inch Hale Telescope at Palomar, NASA and the NEID instrument of the National Science Foundation in southern Arizona, and the Keck Planet Finder will offer new ways to learn about exoplanets.
Media contact:
Elizabeth Landau
NASA Headquarters, Washington
202-923-0167
[email protected]
Alison Hawkes
NASA Ames Research Center, Silicon Valley, California.
650-604-4789
[email protected]