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 its inexplicably strange orbital location.
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 exoplanet candidate was set aside. in favor of easier goals. Not a terrible decision, given that during his glorious nine-year career, Kepler spotted 4,760 exoplanet candidates.s, of which approximately half have yet to be confirmed.
“The KOI-5Ab was abandoned because it was complex and we had thousands of candidates,” said David Chiardi, chief scientist at NASA’s Exoplanet Science Institute at NASA. statement. “There were easier choices than the KOI-5Ab, and we learned something new from Kepler every day, so the KOI-5 was mostly forgotten.”
Ciardi, along with colleagues, have now looked at the KOI-5Ab with new eyes, namely NASA’s transient exoplanetary satellite and several ground-based telescopes, including the Keck Observatory in Hawaii. The team was finally able to confirm KOI-5Ab as a bona fide exoplanet and in the process uncover some fascinating – if not completely confusing – aspects around its stellar environment. Ciardi, a research astronomer at Caltech, recently presented his team’s findings in virtual meeting of the American Astronomical Society.
The confirmation of KOI-5Ab was done with a tried and true transit method, in which an orbital planet passes in front of its star from our perspective, causing a brief eclipse. Confirmation was further confirmed by another technique, the method of oscillation, in which the slight gravitational attraction of an orbital planet causes a noticeable stagger in its host star. TESS was used for the transit method, while Keck was used to detect the wobble. The combined data allowed the researchers to rule out other possibilities, such as a 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 little strange, the overall environment is less chaotic than it may sound.
Although it has three stellar satellites, KOI-5Ab orbits one star, KOI-5A, once every five days. This host star is caught in orbit with a nearby star called KOI-5B, and the two rotate around each other once every 30 years. A more distant star, KOI-5C, orbits this pair once every 400 years.
The question is related to the orbital alignment of KOI-5Ab 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 protostar disk.
“We don’t know of many planets that exist in triple-star systems, and this one is extremely special because its orbit is distorted,” Ciardi said. “We still have many questions about how and when planets can form in multi-star systems and how their properties are compared to planets in one-star systems. By studying this system in more detail, we may be able to get an idea of how the universe makes planets. “
Ciardi and his colleagues do not know the reason for the discrepancy, but their working theory is that KOI-5B exerts gravitational contraction during system development, disrupting the orbit of KOI-5Ba and causing it to migrate inward to its host star.
About 10% of all star systems include three stars, according to NASA. The planets have been spotted in triple star systems before, and also in binary star systems, but such discoveries remain rare. Many star systems do not seem to be willing to accept many planets. This may mean that the conditions for planet formation are not ideal in these conditions, but this may be the result of an observational effect of selection, as it may be more difficult for astronomers to observe planets in multi-star systems than single ones. star systems.
The answer to this question is important because it has serious consequences in the search for extraterrestrial life. Multi-star systems represent up 85% of all star systems in the Milky Way galaxy. Should we confirm that multi-star systems tend to contain far fewer planets and, consequently, fewer life-planet planets, astrobiologists and SETI scientists should turn their attention to one-star systems.
This list could be further reduced. The vast three-quarters of all stars in the Milky Way are red dwarfs who, because of their propensity to explosion nearby planets with solar flares can also be poor candidates in the search for extraterrestrial life.
Given these factors, it is easy to feel that life must be extremely rare in the galaxy. This may be so, but it is important to remember that the Milky Way has about 100 billion stars. This still leaves us much to choose from, a handful of which can accept civilizations asking exactly the same questions as these.