A newly discovered exoplanet is a real blast from the past.
Astronomers have just confirmed the existence of KOI-5Ab, which was first identified as a potential planet by NASA’s pioneering work. Kepler Space Telescope back in 2009.
The elusive alien world was the second “candidate” ever identified by Kepler, who hunted for planets on two different missions from 2009 to 2018. Kepler uses the ‘transit method’, and notices the luminosity dips that are seen as alien worlds cross their host stars’ faces from the perspective of the spacecraft.
Related: Kepler’s 7 Greatest Exoplanet Discoveries
This work was incredibly productive. Nearly two-thirds of the approximately 4,300 known exoplanet was discovered by Kepler, and the analysis of the telescope’s large data set continues to yield new findings.
KOI-5Ab slipped through the cracks more than a decade ago, in part due to the data flood. The Kepler team saw an apparent transit signal belonging to an approximately Neptune planet that swept around a sunny star every five days. This star and the apparent planet lie about 1800 light-years from Earth in the constellation Cygnus.
But further investigation revealed that the parent star had a companion star, making analyzes significantly more difficult. And there were many other candidates to vet.
Thus, KOI-5Ab “was rapidly abandoned, mostly because it became complex,” said David Ciardi, chief scientist at NASA’s Exoplanet Science Institute, located in the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. during a news conference Monday (January 11) at the 237th meeting of the American Astronomical Society (AAS).
Indeed, KOI-5Ab was even more complicated than researchers realized at the time. By 2014, Ciardi and other scientists determined that the KOI-5 system actually contained three stars. And it was still not clear if KOI-5Ab really existed, or if the 2009 signal was generated by one of the companions.
KOI-5Ab is back in the spotlight thanks to Kepler’s successor, NASA Transit satellite for exoplanet survey (TESS), which was 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 this target, ” Ciardi said in a statement.
Therefore, he looked closely at all the information on the system – transit observations by Kepler and TESS, as well as radial velocity data collected by instruments on the ground such as the Keck Observatory in Hawaii. (Radial velocity measurements quantify how much a planet draws around its older star gravity. Such work can reveal the approximate mass of an exoplanet, while observations by transit give a rough idea of its size.)
Related: 7 ways to discover alien planets
Taken together, the data confirm that KOI-5Ab is indeed a planet, one that is about half as massive as Saturn. The new research, which Ciardi outlined during the AAS meeting on Monday, also revealed other details of the KOI-5 system. For example, the main star orbiting KOI-5Ab (star A) has a close companion (star B); this duo revolves around each other once every 30 Earth years. The third star in the system (star C) is much further removed and orbits the AB pair every 400 years.
In addition, the orbital level of KOI-5Ab has been misaligned to that of star B, suggesting that the star may have given the planet some gravity somewhere in history, researchers said. (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 that was there discovered in a multisystem. But such systems appear to house planets less frequently than single-star solar systems such as our own, for reasons that scientists do not yet understand.
“Star companions can partially extinguish the process of planet formation,” Ciardi said. “We still have many questions about how and when planets can form in multiple galaxies and how their properties compare to planets in single galaxies. By studying the KOI-5 system in more detail, we may be able to gain insight into how the universe makes planets. . ‘
Mike Wall is the author of “Out there“(Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.