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A rare planet with three suns has a super strange orbit



The artist's vision for the planet KOI-5Ab is to pass in front of its star, with two other star companions in the background.

The artist’s vision for the planet KOI-5Ab is to pass in front of its star, with two other star companions in the background.
illustration: California Institute of Technology/R. Damage (Infrared Processing and Analysis Center, or IPAC)

Astronomers have confirmed the existence of a three-star exoplanet 1,800 light-years from Earth. A planet anchored in a multi-star system is rare, but due to its inexplicable weird orbital arrangement, the object is particularly unusual.

In 2009, NASA’s Kepler Space Telescope found the first trace of KOI-5Ab, but that was in the early days of the mission, so the exoplanet candidate was put aside Support easier goals.Considering that Kepler discovered 4,760 exoplanet candidates during his outstanding 9-year career, this is not a bad decision.s, about half of which still need to be confirmed.

David Ciardi, chief scientist of NASA’s Institute of Exoplanet Science, explained: “KOI-5Ab was abandoned because it is complicated and we have thousands of candidates.” statement. “It is easier to pick than KOI-5Ab, and we learn new things from Kepler every day, so KOI-5 is mostly forgotten.”

Ciardi and his colleagues are now looking at KOI-5Ab with new eyes. They are NASA’s Exoplanet Survey Satellite and some ground-based telescopes, including the Keck Observatory in Hawaii. The team was finally able to confirm that KOI-5Ab is a true exoplanet, and in the process discovered some fascinating (if not completely confusing) aspects of its stellar environment. Ciardi, a research astronomer at the California Institute of Technology, recently presented his team’s findings at a conference. Virtual meeting American Astronomical Society.

This image shows the orbital plane of the exoplanet KOI-5Ab and the orbital plane shared by the stars KOI-5A and KOI-5B (not drawn to scale).

This image shows the orbital plane of the exoplanet KOI-5Ab and the orbital plane shared by the stars KOI-5A and KOI-5B (not drawn to scale).
Graphical: California Institute of Technology/R. Damage (Infrared Processing and Analysis Center, or IPAC)

The confirmation of KOI-5Ab was done through the tried-and-tested real transit method in which, from our perspective, a planet in motion passes in front of its star, causing a brief dimming. This confirmation is further verified by another technique (the rocking method), in which the slight gravitational pull of an orbiting planet causes a detectable tilt of its host star. TESS is used for the transit method, while Keck is used to detect swings. The combined data allowed the researchers to rule out other possibilities, such as the fourth star.

KOI-5Ab may be a gas giant, but in terms of its size, it is similar to Neptune. It is located in a three-star system. Although its track is a bit strange, its overall environment is not as chaotic as it sounds.

Despite having three star companions, KOI-5Ab orbits a star KOI-5A every five days. This host star is in a common orbit with a nearby star called KOI-5B, and the two stars orbit each other once every 30 years. The farther star KOI-5C orbits the pair of planets every 400 years.

This problem is related to the orbital alignment of KOI-5Ab relative to KOI-5B.The two objects do not share the same orbital plane. This is an unexpected result, which raises questions about the traditional theory of planet formation, such as how to believe these objects. form From a single protostar disk.

Giardi said: “We don’t know many planets that exist in the three-star system, and this planet is special because its orbit is inclined.” “About how and when planets form in a multi-star system Compared with planets in a single-star system, we still have many problems with their formation and their properties. By studying the system in more detail, perhaps we can gain insight into how the universe constitutes planets.”

Ciardi and his colleagues do not know the reason for this misalignment, but their working theory is that KOI-5B applied a gravitational shrug during the development of the system, disrupting the orbit of KOI-5Ba and shifting it inward. Its main star.

According to NASA, about 10% of all star systems involve three stars.The planet was found in a three-star system prior to, As well as in binary star systems, but such discoveries are still rare. It seems that multi-star systems do not tend to have many planets. This may mean that the conditions for planet formation in these environments are not ideal, but this may be the result of observation selection effects, because it is more difficult for astronomers to discover planetary star systems in multi-star systems than in single star systems.

The answer to this question is very important, because it has serious significance in the search for alien life.Multi-star system Over 85% All star systems in the Milky Way. If we determine that multi-star systems tend to have far fewer planets, and therefore reduce living planets, then astrobiologists and SETI scientists should focus on single-star systems.

This list can be further narrowed down.In the Milky Way, as many as three-quarters of the stars are red dwarfs due to their inertia blasting Planets with solar flares nearby may not be suitable for finding alien life.

Considering these factors, it is easy to feel that life in the galaxy must be extremely rare. This may indeed be the case, but it is important to remember that the Milky Way has approximately 100 billion stars. This still leaves us with a lot of options to choose from, a few of which can accommodate civilizations that ask exactly the same questions as these.


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