The universe is full of oddities and formations that range from magnetars to solar systems with four stars. One of those oddities is the stellar trio, where two stars orbit each other and then a third star orbits the other two. A group of professional and amateur astromers used NASA's TESS satellite and AI to find a stellar trio unlike any of the others observed so far.
The trio of stars, which has been given the catchy name of TIC 290061484, is special because its orbits are extremely fast. Two of the stars orbit each other every 1.8 days while the third member of the trio orbits the other two every 24.5 days. For reference, Earth orbits the sun every 365 days, and Mercury orbits the sun every 88 days. The sun completes its orbit around the center of the Milky Way galaxy once every 225 million Earth years.
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According to The Astrophysical Journal, the fastest stellar trio previously observed involved an outer star orbiting its duo in 33.02 days. That makes TIC 2900061484 the fastest such trio of stars ever observed by humans.
The trio was discovered by astronomers using NASA's TESS satellite, along with AI. Initially, the satellite observed flickers of starlight. Since the system is flat when viewed from TESS, the star with the longer orbit would eclipse the two smaller stars, causing the flickers. Astronomers used machine learning to sift through large sets of starlight data to identify when the eclipses occurred, and a smaller team of citizen astronomers filtered the data further to find the trio.
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NASA uploaded a video of TESS observing the stellar triplets on YouTube. As the stars orbit one another, one passes in front of the other. Creating an eclipse event can help astronomers identify a duo or trio of stars on a flat plane. Notably, from 1:05 to 1:15 in the video, you can watch all three stars eclipse each other as their orbits take them around. That's the type of information the astronomers were looking for when filtering the data.
"Thanks to the compact, edge-on configuration of the system, we can measure the orbits, masses, sizes, and temperatures of its stars," said Veselin Kostov, a research scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the SETI Institute in Mountain View, California. "And we can study how the system formed and predict how it may evolve."
While it is unusual to see a trio of stars with such small orbits—all three orbit each other in a space smaller than Mercury's orbit around the sun—the orbit appears to be stable. All three stars orbit on a flat plane, which signals that their gravitational pulls don't upset the orbits of the other stars. For the time being, all three stars should remain in orbit with each other in perpetuity.
However, as the stars age, that's when the fireworks are set to begin.
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"As the inner stars age, they will expand and ultimately merge, triggering a supernova explosion in around 20 to 40 million years," NASA says.
Currently, this trio has the shortest orbit of any trio of stars observed, but it may not be for long. NASA's Nancy Grace Roman Space Telescope captures more detailed imagery than TESS, which will allow astronomers to see deeper into the Milky Way galaxy with more clarity. This could uncover previously undiscovered trios with even shorter orbits.
"We don't know much about a lot of the stars in the center of the galaxy except for the brightest ones," said Brian Powell, a co-author of the study and Goddard data scientist. "Roman's high-resolution view 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."