A recently discovered binary star system has entered the record books for both the longest duration stellar eclipse and the longest period between eclipses in a binary system.
The unnamed binary star system, which is nearly 10,000 light years from Earth, now holds the record for the longest near-total eclipse that lasts for three and a half years, and happens every 69 years.
The discovery of the extraordinary properties of the system, known only by its astronomical catalog number TYC 2505-672-1, was made by astronomers from Vanderbilt and Harvard. Colleagues from Lehigh, Ohio State and Pennsylvania State universities, Las Cumbres Observatory Global Telescope Network, and the American Association of Variable Star Observers also assisted.
Vanderbilt doctoral student, Joey Rodriguez, who is also the paper’s first author, said:
“It’s the longest duration stellar eclipse, and the longest orbit for an eclipsing binary ever found… by far.”
The former record holder was a giant star called Epsilon Aurigae, its companion eclipsed by it every 27 years for periods ranging from 640 to 730 days.
Vanderbilt University says the leading explanation is that Epsilon Aurigae consists of a yellow giant star orbited by a normal star slightly bigger than the sun, embedded in a thick disk of dust and gas oriented nearly edge on when viewed from Earth.
Rodriguez adds that:
“Epsilon Aurigae is much closer — about 2,200 light years from Earth — and brighter, which has allowed astronomers to study it extensively.”
Keivan Stassun, professor of physics and astronomy at Vanderbilt, and co-author, said:
“One of the great challenges in astronomy is that some of the most important phenomena occur on astronomical timescales, yet astronomers are generally limited to much shorter human timescales.
“Here we have a rare opportunity to study a phenomenon that plays out over many decades and provides a window into the types of environments around stars that could represent planetary building blocks at the very end of a star system’s life.”
After analyzing thousands of images of TYC 2505-672-1 it was revealed to be a system similar to the one at Epsilon Aurigae, however there were some important differences.
The system seems to have a pair of red giant stars, with one appearing to have been stripped down to a small core. It is also surrounded by an extremely large disk of material which produces the extended eclipse. Rodriguez explains:
“About the only way to get these really long eclipse times is with an extended disk of opaque material. Nothing else is big enough to block out a star for months at a time.”
The astronomers did admit that TYC-2505-672-1 was so distant that the data from the images was limited. However, they could estimate the surface temperature of the companion star, and had discovered that it is around 2,000 degrees Celsius hotter than the surface of the sun.
By combining this with the observation, it appears to be less than half the diameter of the sun. The researchers propose that it is a red giant that has had its outer layers stripped away, and that this stripped material may account for the obscuring disk. However, they admit this is just a theory.
In order to produce the 69-year interval between eclipses, the team calculates that they must be orbiting at an extremely large distance, about 20 astronomical units, which is approximately the distance between the sun and Uranus.
“Right now even our most powerful telescopes can’t independently resolve the two objects,” said Rodriguez. “Hopefully, technological advances will make that possible by 2080 when the next eclipse occurs.”
The paper was accepted for publication in the Astronomical Journal.