Rare planet with three suns has a super strange orbit

Astronomers have confirmed the existence of a three-star exoplanet located 1,800 light years from Earth. Planets stationed in multi-star systems are rare, but this object is particularly unusual due to its inexplicably strange orbital alignment.

The first trace of KOI-5Ab was spotted by NASA’s Kepler Space Telescope in 2009, but it was very early in the mission, so the exoplanetary candidate was cast aside. in favor of easier targets. Not a terrible decision, given that Kepler, during his illustrious nine-year career, spotted 4,760 exoplanet candidates.s, of which about half have yet to be confirmed.

“KOI-5Ab was dropped because it was complicated, and we had thousands of applicants,” David Ciardi, chief scientist at NASA’s Exoplanet Science Institute, explained in a NASA article. declaration. “There were easier choices than KOI-5Ab, and we were learning something new from Kepler every day, so KOI-5 was almost forgotten.”

Ciardi, along with his colleagues, have now looked at KOI-5Ab with new eyes, namely NASA’s Transiting Exoplanet Survey Satellite and several ground-based telescopes, including the Keck Observatory in Hawai’i. The team was ultimately able to confirm that KOI-5Ab was a bona fide exoplanet, and in the process of uncovering fascinating – if not completely puzzling – aspects about its stellar environment. Ciardi, a research astronomer at Caltech, recently presented his team’s findings during a virtual meeting from the American Astronomical Society.

Confirmation of KOI-5Ab was made with the proven transit method, in which an orbiting planet passes in front of its star from our point of view, causing a brief attenuation. The confirmation was further validated by another technique, the oscillation method, in which the slight gravitational pulling of an orbiting planet causes a detectable flicker in its host star. TESS was used for the transit method, while Keck was used to detect oscillation. The combined data allowed researchers to rule out other possibilities, such as a fourth star.

KOI-5Ab is probably a gas giant, similar to Neptune in terms of size. It resides in a three-star system, and although its orbit is a bit odd, its overall environment is less chaotic than it looks.

Although it has three stellar companions, KOI-5Ab revolves around a single star, KOI-5A, once every five days. This host star is taken in a mutual orbit with a nearby star called KOI-5B, and the two revolve around each other once every 30 years. A more distant star, KOI-5C revolves around this pair once every 400 years.

The problem has to do with the orbital alignment of KOI-5Ab relative to KOI-5B. The two objects do not share the same orbital plane, which is an unexpected result – one that challenges conventional theories of planetary formation, such as the way such objects are thought to be form from a single protostellar disc.

“We don’t know a lot of planets that exist in three-star systems, and this one is very special because it has a skewed orbit,” 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. By studying this system in more detail, perhaps we can get some insight into how the universe makes planets.

Ciardi and his colleagues don’t know the reason for the misalignment, but their working theory is that KOI-5B exerted a gravitational shrug during the development of the system, disrupting KOI-5Ba’s orbit and causing it to migrate to its host star.

About 10% of all star systems involve three stars, according to NASA. Planets have been spotted in three-star systems before, and also in binary star systems, but such discoveries remain rare. Multiple star systems, it seems, don’t tend to host many planets. This could mean that the conditions for the formation of planets are not ideal in these contexts, but it could be the result of an observational selection effect, in that it could be more difficult for astronomers to spot planets in multi-star systems versus single-star systems.

The answer to this question is important, as it has serious implications in the search for extraterrestrial life. Multi-star systems represent more than 85% of all the star systems in the Milky Way galaxy. If we confirm that multi-star systems tend to have far fewer planets, and therefore fewer life-bearing planets, astrobiologists and scientists at SETI should focus their attention on single-star systems.

This list can be reduced even further. A whopping three-quarters of all stars in the Milky Way are red dwarfs, which, due to their propensity to explosion neighboring planets with solar flares could also be poor candidates in the search for extraterrestrial life.

Considering these factors, it is easy to get the feeling that life must be unusually scarce in the galaxy. It just might be, but it’s important to remember that the Milky Way has around 100 billion stars. That still leaves us with plenty of choices, a handful of which could accommodate civilizations asking exactly the same questions as these.