Astronomers have confirmed the existence of a three-star exoplanet located 1,800 light-years from Earth. Planets parked in multi-star systems are rare, but this object is particularly unusual due to the strangely inexplicably orbital alignment.
The first trace of the KOI-5Ab was seen by NASA’s Kepler space telescope in 2009, but it was very early in the mission, so the exoplanetary candidate was left out. in favor of lighter targets. It’s not a terrible decision, given that Kepler, during his illustrious nine-year career, has seen 4,760 candidates for the exoplanet.s, of which about half still need to be confirmed.
“KOI-5Ab was abandoned because it was complicated and we had thousands of candidates,” David Ciardi, chief scientist at NASA’s Exoplanet Science Institute, told NASA. statement. “It was an easier choice than the KOI-5Ab, and I learned something new from Kepler every day, so the KOI-5 was largely forgotten.”
Ciardi, along with his colleagues, now looked at the KOI-5Ab with new eyes, namely the Transiting Exoplanet Survey Satellite and several ground-based telescopes, including the Keck Observatory in Hawai’i. The team finally managed to confirm KOI-5Ab as a bona fide exoplanet and, in the process, discovered some fascinating – if not completely puzzling – aspects of its stellar environment. Ciardi, a research astronomer at Caltech, recently presented his team’s findings to a virtual meeting of the American Astronomical Society.
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The confirmation of KOI-5Ab was made with the tried and true transit method, in which an orbiting planet passes in front of its star from our perspective, causing a brief fading. The confirmation was further validated by another technique, the oscillation method, in which light gravitational towing of an orbiting planet causes a detectable leak in its host star. TESS was used for the transit method, while Keck was used to detect the oscillation. The combined data allowed researchers to rule out other possibilities, such as the fourth star.
KOI-5Ab is probably a gas giant, similar to Neptune in size. It is in a three-star system and, although its orbit is a bit strange, the environment in general is less chaotic than it may sound.
Despite having three stellar companions, KOI-5Ab orbits a single star, KOI-5A, every five days. This host star is trapped in a reciprocal orbit with a nearby star called KOI-5B, and the two turn on each other every 30 years. A farther star, KOI-5C orbits this pair every 400 years.
The problem is related to 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 calls into question conventional theories of planetary formation, such as how such objects are thought to be. form from a single protostellar disk.
“We don’t know many planets that exist in three-star systems, and this one is very special because its orbit is tilted,” Ciardi said. “We still have many 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, we can gain insight into how the universe produces planets. ”
Ciardi and his colleagues do not know the reason for the misalignment, but their working theory is that KOI-5B exerted a gravitational lift during the development of the system, disrupting the orbit of KOI-5Ba and causing it to migrate to the host star.
About 10% of all star systems involve three stars, according to NASA. The planets were observed in three-star systems beforeand also in binary star systems, but such discoveries remain rare. It seems that many star systems do not tend to host a lot of planets. This could mean that the conditions for planet formation are not ideal in these settings, but could be the result of an observational selection effect, meaning that it may be more difficult for astronomers to observe planets in multi-star systems compared to a single stellar system.
The answer to this question is important because it has serious implications for the search for extraterrestrial life. Multi-star systems represent over 85% of all the star systems in the Milky Way galaxy. We should confirm that multi-star systems tend to have far fewer planets and, as a result, fewer life-bearing planets, astrobiologists and SETI scientists should focus on single-star systems.
This list can be further reduced. A large quarter of three-quarters of all Milky Way stars are red dwarfs, which, due to their propensity to explosion nearby planets with solar flares could also be poor candidates in search of an alien life.
Given these factors, it is easy to feel that life must be exceptionally rare in the galaxy. This may be the case, but it is important to remember that the Milky Way has about 100 billion stars. That leaves us with many more to choose from, a handful of which could host civilizations that ask exactly the same questions as these.