‘First of its kind’ triple star system likely swallowed up 4th star

An artist’s interpretation of the quadruple star system HD 98800. The newly discovered triple star system, known as TIC 470710327, has a very similar structure, except that the outer pair of stars orbiting the central binary pair have merged into a single star. (Image credit: NASA/JPL-Caltech/UCLA)

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Astronomers have discovered a triple star system that is unlike any seen before. The unusual trio of stars is much more massive and closely compressed with each other than a typical triple system, which may be due to the fact that star triples used to have a fourth brother before one of the others swallowed it up.

The triple, or tertiary, star system is known as TIC 470710327 and was discovered by researchers using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) observatory, which is in orbit. Earth. The trio has a hierarchical structure, which means that a pair of binary stars orbit each other at the center of the system, while a third star orbits the central pair.

Triple star systems are not uncommon: according to scientists, up to 10% of star systems in the universe can be tertiary. NASA (will open in a new tab). In September 2021, astronomers discovered the only exoplanet orbiting a tertiary system for the first time, suggesting that life could potentially exist in these systems.

However, TIC 470710327 stands apart from all other known tertiary systems due to its size and shape. The stars are much more massive than typical tertiary stars, which also means the trio is much more compact as they all have a stronger impact. gravitational pull than usual.

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“To the best of our knowledge, this is the first of its kind detection,” said study lead author Alejandro Viña-Gómez, an astrophysicist at the Niels Bohr Institute at the University of Copenhagen in Denmark. said in a statement (will open in a new tab).

The binary pair of stars at the center of TIC 470710327 has a combined mass of about 12 times sun, and it takes two stars just over a day to complete one revolution around each other. The larger outer star is even more massive, weighing about the size of 16 suns, and it orbits the binary in 52 days, which is “pretty fast considering their size,” Viña-Gomez said.

The new system was originally discovered by a citizen scientist who was browsing the TESS database looking for anomalies. The star system stood out to the amateur astronomer for its high luminosity, which was a consequence of the fact that three stars shone brightly, and not one. However, it wasn’t until the researchers later evaluated the data that they realized it was a tertiary system. After learning how massive the stars were, the team began trying to figure out how the unusual system could have formed.

An artist's conception of a binary star system, similar to the pair of stars at the heart of a new tertiary system.

An artist’s conception of a binary star system, similar to the pair of stars at the heart of a new tertiary system. (Image credit: Shutterstock)

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There are three possible explanations for how TIC 470710327 was created. The first possibility is that the large outer star formed first and the smaller stars formed later. This is perhaps the most unlikely explanation, the researchers said, as the massive star likely expelled or absorbed the gas needed to form new stars. The second option is that all three stars formed separately and gradually attracted to each other until they began to rotate around each other. This is also unlikely because a massive outer star would likely be at the center of the system.

A third explanation is that the system originally consisted of two binary pairs – one at the center of the system we see today, and another pair orbiting where the more massive outer star currently resides. The researchers suspect that the outer binary pair then underwent a stellar merger to create a single, more massive star.

Based on extensive computer simulations, the team found that this third explanation best explains the stars’ massive size and compactness.

Researchers want to continue the search for similarly massive and compact tertiary systems. “What we really want to know is whether such a system is common in our universe,” study co-author Bing Liu, an astrophysicist at the Niels Bohr Institute, said in a statement. “Perhaps there are more compact systems hidden in the data.”

The study was published online on June 29 in the journal Royal Astronomical Society Monthly Notices (will open in a new tab).