A collaboration of professional and amateur astronomers, alongside artificial intelligence, has led to the discovery of a remarkable trio of stars known as TIC 290061484, identified through cosmic “strobe lights” observed by NASA’s TESS (Transiting Exoplanet Survey Satellite).
This stellar system features two stars that orbit each other every 1.8 days, complemented by a third star that orbits the pair in just 25 days. This finding breaks the previous record for the shortest outer orbital period in such systems, which was established in 1956 with an outer star completing its orbit in 33 days.
“Due to the close, edge-on layout of this system, we can accurately assess the orbits, masses, sizes, and temperatures of its stars,” explained Veselin Kostov, a NASA research scientist based at Goddard Space Flight Center in Greenbelt, Maryland, and the SETI Institute in Mountain View, California. “This also allows us to investigate the system’s formation and forecast its future evolution.”
Kostov led a study that was published in The Astrophysical Journal on October 2.
The faint changes in starlight revealed the tight trio located in the constellation Cygnus. The system is almost flat from our viewpoint, meaning that the stars eclipse each other during their orbits, with the nearer star blocking some light from the one further away.
To identify these eclipses, scientists employed machine learning to sift through vast amounts of TESS starlight data to detect dimming patterns. A smaller team of citizen scientists then conducted further analysis, leveraging years of informal training and experience to spot particularly intriguing cases.
These amateur astronomers, who co-authored the new study, initially connected through an online citizen science initiative called Planet Hunters, which operated from 2010 to 2013. They eventually collaborated with professional astronomers to form the Visual Survey Group, which has been active together for more than ten years.
“Our main focus is on detecting signatures of compact multi-star systems, unusual pulsating stars in binary systems, and other unusual objects,” said Saul Rappaport, an emeritus physics professor at MIT in Cambridge. Rappaport, who co-authored the paper, has led the Visual Survey Group for over a decade. “Discovering a system like this is thrilling, as they are infrequently found, but they may actually be more common than current estimates indicate.” Many more such systems probably exist within our galaxy, waiting to be uncovered.
Because the stars in this new system orbit nearly in the same plane, scientists believe it is very stable, despite the close proximity of the three stars (the orbits are smaller than that of Mercury around the Sun). The gravitational interactions among the stars are minimal and do not significantly disrupt each other’s orbits, which could be a concern if their paths were tilted differently.
While their orbits are expected to remain stable for millions of years, “there are no living conditions here,” cautioned Rappaport. “We theorize that these stars formed together through the same developmental process, which would have hindered the formation of planets around any of the stars.” However, there could be a distant planet that orbits the trio as if they are a single entity.
As the inner stars age, they will eventually swell and merge, leading to a supernova explosion within about 20 to 40 million years.
Meanwhile, astronomers are on the lookout for triple star systems with even shorter orbital periods. This task proves challenging with current technologies, but new advancements are on the horizon.
The forthcoming Nancy Grace Roman Space Telescope from NASA will produce images that are much more detailed than those from TESS. The area of the sky covered by one TESS pixel can accommodate over 36,000 Roman pixels. Unlike TESS, which provided a broad and shallow overview of the entire sky, Roman will delve deeper into the densely packed regions at the center of our galaxy, yielding more detailed insights.
“Most of the stars at the galaxy’s center are either unknown or only the brightest are identified,” stated Brian Powell, a co-author and data scientist at Goddard. “Roman’s high-resolution capabilities will enable us to measure light from stars that typically blend together, giving us the best look yet into the nature of star systems in our galaxy.”
Furthermore, Roman’s extensive monitoring of light from hundreds of millions of stars as part of its main survey will enhance the ability of astronomers to discover additional triple star systems where all stars eclipse each other.
“We’re curious why we haven’t encountered star systems with even shorter outer orbital periods,” commented Powell. “Roman should assist in finding them, thus bringing us closer to understanding their potential limits.”
The Roman telescope may also uncover eclipsing stars that are part of even larger groups—potentially counts of half a dozen or more orbiting each other like bees around a hive.
“Prior to the discovery of triply eclipsing triple star systems, we didn’t suspect they existed,” remarked co-author Tamás Borkovits, a senior research fellow at the Baja Observatory of The University of Szeged in Hungary. “However, once we discovered them, we thought, why not? Roman could likewise reveal previously unseen categories of systems and objects that will astonish astronomers.”
