A pair of new record-breaking binary stars has been discovered in the Milky Way, about 10,000 light-years from Earth. The two stars are part of an eclipsing binary system, with one periodically hidden from our view.
The system, with the catchy name TYC 2505-672-1, has the longest period between eclipses in a binary system and the longest duration of a stellar eclipse we have ever observed. Details of the discovery can be found in a paper accepted for publication by the Astrophysical Journal.
The discovery was possible thanks to observations by the American Association of Variable Star Observers network and the Digital Access to a Sky Century @ Harvard (DASCH) program. DASCH is a survey based on thousands of photographic plates taken by astronomers from Harvard between 1890 and 1989.
Having data spanning decades allowed the astronomers to characterize the system in detail. The two stars orbit each other every 69 years, they are about 24 astronomical units (3.5 billion kilometers, 2.2 billion miles) apart, and the eclipsing one covers the companion from our point of view for over three and a half years. To explain this, one of the stars may have a large cloud of dust and gas surrounding it.
“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,” lead author Joey Rodriguez said in a statement.
According to the research, the extended disk could be as large as 1 billion kilometers (600 million miles) in diameter. The star within the obscuring disk is very hot (about 7000 kelvins, 12,000°F) and it is possibly a red giant. These stars have a large, swollen atmosphere that can often be disrupted into a large cloud. Although this is the main hypothesis, the astronomers can’t be certain as the system is very distant.
“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.”
1