A total eclipse of the Sun lasts about 12 minutes here on Earth, but if you live in the binary star system TYC 2505-672-1, one sun disappears for three-and-a-half years as it is eclipsed by its companion.
Writing in the Astronomical Journal, researchers from Vanderbilt and Harvard universities say these long eclipses happen every 69 years in the system that is nearly 10,000 light-years away. They say that sets records for both “longest duration stellar eclipse and the longest period between eclipses in a binary system.”
Binary systems contain two stars that orbit each other.
"It's the longest duration stellar eclipse and the longest orbit for an eclipsing binary ever found …by far," said lead author and Vanderbilt doctoral student Joey Rodriguez.
The researchers said the previous record holder was Epsilon Aurigae, which is eclipsed by its fellow star every 27 years for between 640 and 730 days.
The researchers made the discovery using two resources.
First, they accessed the American Association of Variable Star Observers (AAVSO), a non-profit group of amateur and professional astronomers who study variable stars. The group provided the paper’s authors with “a few hundred” observations of TYC 2505-672-1's latest eclipse.
The researchers also used the Digital Access to a Sky Century @ Harvard (DASCH), which contains thousands of photographic plates made by Harvard astronomers from 1890 and 1989.
Using the available observations, the team believes the system is made up of two red giant stars. One of these stars, they say, has been “stripped down to a relatively small core,” creating a large disc of debris that causes the long eclipses.
"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," Rodriguez said.