A newly-discovered binary star experiences a near-total solar eclipse that lasts for three and a half years once every 69 years, setting new records for the longest duration for a stellar eclipse and the longest period between eclipses in a binary system, according to a new study.
In the paper, which has been accepted for publication in the Astronomical Journal, first author and Vanderbilt University doctoral student Joey Rodriguez and his colleagues revealed that the unnamed star resides in a binary system known only by its astronomical catalog number, TYC 2505-672-1, and which is located approximately 10,000 light years away.
“It’s the longest duration stellar eclipse and the longest orbit for an eclipsing binary ever found… by far,” Rodriguez said in a statement. The new star shatters the previous records of 640 to 730 day long eclipses every 27 years, which were held by a giant star called Epsilon Aurigae.
“Epsilon Aurigae is much closer – about 2,200 light years from Earth – and brighter, which has allowed astronomers to study it extensively,” he added. Epsilon Aurigae, a yellow giant star that is orbited by a normal star slighter bigger than the sun, is believed to be enveloped in a thick gas and dust disk that is oriented nearly edge-on when it is viewed from the Earth.
Opaque disk of material believed to be responsible
Rodriguez, Vanderbilt physics and astronomy professor Keivan Stassun, their co-authors used observations made by the American Association of Variable Star Observers (AAVSO) network and the Digital Access to a Sky Century @ Harvard (DASCH) program in discovering the long-lasting eclipse.
It was Sumin Tang from the Harvard-Smithsonian Center for Astrophysics who first noticed the star’s unusual activity while digitizing plates for the DASCH survey, and Rodriguez learned of it while attending a conference where she presented her findings. Afterwards, he and Tang decided to collaborate to learn more about the star through recently-obtained images.
Eventually, Rodriguez took over when Tang became occupied with other projects, and found that the new binary system is similar to the Epsilon Aurigae one in many ways. However, instead of being a yellow giant and a normal star, it appears to be a pair of red giant stars, one of which has been stripped to its relatively small core and surrounded by a very large disk of debris.
It is this disk of material, the authors explained, that is responsible for the prolonged eclipse. As Rodriguez said, “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.”
In order for the 69 year long eclipses to occur, he and his colleagues calculate that the system’s stars must be about 20 astronomical units (AU) apart, or about the same distance separating the Sun and Uranus. Currently, not even the most powerful of telescopes are able to independently resolve the two objects, they added, but they are hopeful that the instruments will have improved enough by the next eclipse in 2080 to make such observations possible.
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