A Story of a Planetary Resurrection – Pasadena now

Shortly after NASA’s Kepler mission began operations back in 2009, it identified what was thought to be a planet about the size of Neptune. Called KOI-5Ab, the planet, which was the second new planet finder discovered by the mission, was eventually forgotten as Kepler unleashed more and more planetary missions. By the end of his mission in 2018, Kepler had discovered 2,394 exoplanets, or planets erupting stars outside our solar system, and an additional 2,366 exoplanet candidates, including KOI-5Ab.

Now, David Ciardi, chief scientist at NASA’s Exoplanet Science Institute (NExScI), based at IPAC Caltech, says he has “resurrected KOI-5Ab from the dead,” thanks to new ideas from NASA TESS (Transiting Exoplanet Survey Satellite) mission.

“KOI-5Ab fell off the table and was forgotten,” said Ciardi, who presented the findings at a preliminary meeting of the Astronomical Society of America (AAS). Prior to 2014, Ciardi and other researchers had used the WM Keck Observatory in Hawaii, the Palomar Caltech Observatory near San Diego, and Gemini North in Hawaii to show that the star is surrounded by KOI-5Ab as a single member. of a three-star system called KOI- 5. But they were not sure if the KOI-5 system was actually hosting a planet or if they were seeing an erroneous signal from one of the other two stars.

Then, in 2018, TESS came forward. Like Kepler, TESS is looking to emit a star light that comes when a planet orbits in front of it, or moves over a star. TESS saw a portion of Kepler’s field of view, including the KOI-5 system. Certainly, TESS also identified KOI-5Ab as a candidate planet (although TESS calls TOI-1241b). TESS, like Kepler, discovered that the planet erupted its star about every five days. But at that point, it was not yet clear if the planet was real.

“I was thinking to myself,‘ I remember this target, ’” Ciardi said, after seeing the TESS data. He then went back and retweeted all the data, including that from California Planet Research, led by Caltech astronomy professor Andrew Howard. Planet California Search uses ground-based telescopes, including the Keck Observatory, to detect the telltale wobble in a star that occurs when a planet orbits around it and removal of gravity thatch.

“If it weren’t for TESS looking at the planet again, I would never have returned and done this detective work,” Ciardi said.

Jessie Dotson, Kepler / K2 project scientist at NASA’s Ames Research Center, said, “This research confirms the importance of NASA’s entire fleet of space telescopes and their collaboration with ground-based systems. Finds like this can be very long. “

Together, the data from the space-based and ground-based telescopes helped confirm that KOI-5Ab is a planet. KOI-5Ab is about half the mass of Saturn and orbiting a star (star A) with a relatively close companion (star B). Star A and star B orbit each other every 30 years. A third star with a grave connection (star C) moves stars A and B every 400 years.

The combined data set also shows that the planet’s orbital plane is not aligned with the orbital plane of the second inner star (star B) as would be expected if all the stars and planet were formed. from the same disc of swirling material. It is thought that three-star star systems, which make up about 10 percent of all star systems, when three stars are born together out of the same disk of gas and dust.

Astronomers are not sure what caused the KOI-5Ab mismatch but claim that the planet’s second star suddenly exploded during its development, sliding its orbit and causing her to migrate inside.

This is not the first evidence for planets in double and triple star systems. One interesting case involves the GW Orionis three-star system, in which a planet-shaped disk was torn into special unmarked rings, where planets could form. But despite hundreds of discoveries on multi-star system planets, the frequency of planet formation in these systems is lower than in single-star systems. This could be due to observational bias (it is easier to find single-star planets) or because planetary formation is indeed so common in multi-star systems.

Future instruments, such as the Palomar Radial Velocity Instrument (PARVI) at Palomar’s 200-inch Hale Telescope and Keck’s Keck Planet Finder, will open up new avenues for better answering these questions.

“Stellar companions may partially shut down the planet-making process,” Ciardi said. “We still have many questions about how and when planets can be in multi-star systems and how their properties compare to planets in single-star systems. By examining the KOI-5 system in more detail, we may gain an understanding of how the universe makes planets. ”