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A new exoplanet is a real blast from the past.
Astronomers just confirmed the existence of KOI-5Ab, which was first flagged as a potential planet by the pioneer NASA Kepler Space Telescope in 2009.
The elusive alien world was the second ‘candidate’ ever identified by Kepler, who hunted planets on two different missions from 2009 to 2018. Kepler used the “transit method,” spotting the telltale drops in brightness caused when alien worlds crossed the faces of their host stars from the spacecraft’s perspective.
Related: Kepler’s 7 Greatest Exoplanet Discoveries
This work has been incredibly productive. Almost two thirds of the 4300 known exoplanets were discovered by Kepler, and analyzes of the telescope’s massive dataset continue to reveal new findings.
KOI-5Ab fell through the cracks more than a decade ago, in part because of this deluge of data. The Kepler team spotted an apparent transit signal belonging to a planet the size of Neptune that revolved around a sun-like star every five Earth days. This star and the apparent planet are located about 1,800 light years from Earth, in the constellation Cygnus.
But further investigation revealed that the parent star had a companion star, making analyzes much more difficult. And there were a lot of other candidates to check.
Thus, KOI-5Ab “was quickly abandoned, mainly because it got complicated,” said David Ciardi, chief scientist at NASA’s Exoplanet Science Institute, located at the Center for Infrared Processing and Analysis. from the California Institute of Technology in Pasadena, in a press conference Monday (Jan. 11) at the 237th meeting of the American Astronomical Society (AAS).
Indeed, KOI-5Ab was even more complicated than researchers thought at the time. In 2014, Ciardi and other scientists determined that the KOI-5 system actually housed three stars. And it still wasn’t clear if KOI-5Ab actually existed, or if the 2009 signal was generated by one of the companion stars.
KOI-5Ab returned to the spotlight thanks to Kepler’s successor, NASA Survey satellite on exoplanets in transit (TESS), launched in 2018. TESS also spotted a signal in the KOI-5 system, generated by a potential planet with an orbital period of five Earth days.
“I thought to myself, ‘I remember that goal’,” Ciardi said in a press release.
So he carefully examined all the information about the system – transit observations by Kepler and TESS, as well as radial speed data collected by ground-based instruments such as the Keck Observatory in Hawaii. (Radial velocity measurements quantify how much an orbiting planet pulls gravitationally on its parent star. Such work can reveal the approximate mass of an exoplanet, while transit observations give a rough idea of its size.)
Related: 7 ways to discover alien planets
Taken together, the data confirmed that KOI-5Ab is indeed a planet, about half the massive size of Saturn. The new research, which Ciardi detailed at the AAS meeting on Monday, also revealed other details of the KOI-5 system. For example, the main star on which KOI-5Ab orbits (star A) has a close companion (star B); this duo orbit once every 30 Earth years. The third star in the system (star C) is much further away, orbiting the AB pair every 400 years.
Furthermore, KOI-5Ab’s orbital plane is misaligned with that of star B, suggesting that the star may have given the planet a gravitational boot at some point in the system’s history, have said researchers. (Stars and their planets form from the same cloud of gas and dust, so their orbital planes usually match initially.)
KOI-5Ab is far from the first planet to be discovery in a multistar system. But these systems seem to host planets less frequently than single-star solar systems like ours, for reasons scientists don’t yet understand.
“Stellar companions can partially extinguish the process of planet formation,” Ciardi said. “We still have a lot of questions about how and when planets can form in multi-star systems and how their properties compare to planets in single-star systems. how the universe makes planets. “
Mike Wall is the author of “Over there“(Grand Central Publishing, 2018; illustrated by Karl Tate), a book on the search for extraterrestrial life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
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