TIC 290061484 contains a pair of stars orbiting each other every 1.8 days, and a third star that circles the pair in just 25 days. The discovery smashes the record for shortest outer orbital period for this type of system, set by Lambda Tauri in 1956, which had a third star orbiting an inner pair in 33 days.
This artist’s concept illustrates how tightly the three stars in the TIC 290061484 system orbit each other. If they were placed at the center of our solar system, all the stars’ orbits would be contained a space smaller than Mercury’s orbit around the Sun. The sizes of the triplet stars and the Sun are also to scale. Image credit: NASA’s Goddard Space Flight Center.
Double stars are ubiquitous in the Milky Way, with more than half of the Sun-like stars having a stellar companion, in many cases more than one.
In fact, the nearest star to the Sun — Proxima Centauri — is part of the Alpha Centauri triple system.
This system is rather wide, and all three components are visually resolved. The inner binary, composed of Alpha Centauri A and B, has an orbital period of nearly 80 years, while Proxima takes about 550,000 years to complete one orbit around the common center of mass.
Triple-star systems cover an enormous range of physical parameters, stellar types, and orbital configurations.
The long-period ones, like Alpha Centauri, represent one end of the spectrum where the interactions between the individual components occur on such colossal timescales that a human observer is unlikely to witness an exciting event.
By contrast, compact, short-period systems that reside at the other end of the spectrum of stellar triples can exhibit a multitude of detectable dynamical interactions, in many cases quite dramatic.
Naturally, the shorter the outer period, the stronger the interactions between the individual components, such that the most interesting systems are usually those with outer orbital periods of less than 1,000 days — typically referred to as compact hierarchical triples.
Despite the large leap in the state of current knowledge of compact hierarchical triples enabled by these discoveries, one thing had remained unchanged since the 1950s.
For more than 68 years, Lambda Tauri has reigned supreme as the compact hierarchical triple with the shortest outer period — 33.02 days.
Now, thanks to NASA’s TESS (Transiting Exoplanet Survey Satellite) mission, astronomers were able to do so with the discovery and confirmation of TIC 290061484, a triply eclipsing compact hierarchical triple star with an outer period of only 24.5 days, nearly 9 days shorter than that of Lambda Tauri.
Also known as Gaia 2169382208774963072, TIC 290061484 is located 1,519 parsecs (4,954 light-years) away in the constellation of Cygnus.
“Thanks to the compact, edge-on configuration of the system, we can measure the orbits, masses, sizes, and temperatures of its stars,” said Dr. Veselin Kostov, an astronomer at NASA’s Goddard Space Flight Center and the SETI Institute.
“And we can study how the system formed and predict how it may evolve.”
PanSTARRS image centered on the TIC 290061492 system. Image credit: Kostov et al., doi: 10.3847/1538-4357/ad7368.
Using machine learning, Dr. Kostov and colleagues filtered through enormous sets of starlight data from TESS to identify patterns of dimming that reveal eclipses.
Then, a small team of citizen scientists filtered further, relying on years of experience and informal training to find particularly interesting cases.
These amateur astronomers met as participants in an online citizen science project called Planet Hunters, which was active from 2010 to 2013.
The volunteers later teamed up with professional astronomers to create a new collaboration called the Visual Survey Group, which has been active for over a decade.
“We’re mainly looking for signatures of compact multi-star systems, unusual pulsating stars in binary systems, and weird objects,” said MIT Professor Saul Rappaport.
“It’s exciting to identify a system like this because they’re rarely found, but they may be more common than current tallies suggest.”
“Many more likely speckle our Galaxy, waiting to be discovered.”
Partly because the stars in the TIC 290061484 system orbit in nearly the same plane, it’s likely very stable despite their tight configuration.
Each star’s gravity doesn’t perturb the others too much, like they could if their orbits were tilted in different directions.
“But while their orbits will likely remain stable for millions of years, no one lives here,” Professor Rappaport said.
“We think the stars formed together from the same growth process, which would have disrupted planets from forming very closely around any of the stars.”
“The exception could be a distant planet orbiting the three stars as if they were one.”
“As the inner stars age, they will expand and ultimately merge, triggering a supernova explosion in around 20 to 40 million years.”
In the meantime, astronomers are hunting for triple stars with even shorter orbits.
“We don’t know much about a lot of the stars in the center of our Galaxy except for the brightest ones,” said Dr. Brian Powell, a data scientist at NASA’s Goddard Space Flight Center.
“The high-resolution view of NASA’s upcoming Nancy Grace Roman Space Telescope will help us measure light from stars that usually blur together, providing the best look yet at the nature of star systems in our Galaxy.”
The discovery is reported in a paper in the Astrophysical Journal.
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V.B. Kostov et al. 2024. TIC 290061484: A Triply Eclipsing Triple System with the Shortest Known Outer Period of 24.5 Days. ApJ 974, 25; doi: 10.3847/1538-4357/ad7368
Source : Breaking Science News