People on Earth look forward to sky events such as a solar eclipse, where the moon fully or partially blocks the sun. The solar eclipses experienced here last only for a few minutes and are nothing compared to a stellar eclipse that was discovered by scientists to last for three and a half years.

Every 69 years, in a binary star system about 10,000 light-years from Earth, the sun disappears in a near-total eclipse.

The binary system, referred to as TYC 2505-672-1, is now known for two reasons. Among all known binary systems, it has the longest time between eclipses and the longest duration stellar eclipse.

Past Record Holder

In the past, the title holder was Epsilon Aurigae. This giant binary star is eclipsed by its partner star every 27 years for a period of 640 to 730 days. At 2,200 light-years from Earth, it is nearer than TYC 2505-672-1. Aside from its proximity, its brightness also allows astronomers to study it in greater detail.

The Discovery

An international team of astronomers from Vanderbilt University and Harvard University made the discovery. Scientists from Ohio State University, Lehigh University, Pennsylvania State University, Las Cumbres Observatory Global Telescope Network and the American Association of Variable Star Observers (AAVSO) assisted with the study. Scanned photographic plates from the Digital Access to a Sky Century at Harvard (DASCH) program were also crucial in the discovery of the bizarre properties of the system.

The researchers examined 1,432 images of TYC 2505-672-1 captured by astronomers from Harvard between 1890 and 1989 as well as nearly 9,000 images of the system taken in the last eight years. When the researchers analyzed these together with the AAVSO network's photos of the most recent eclipse, they were able to piece everything together.

The researchers found that TYC 2505-672-1 consists of a pair of red giant stars. One of the stars is surrounded by an "extended disk of opaque material" that causes the eclipse to last for years. As for the 69-year eclipse interval, the researchers' calculations show that the red giants must be orbiting at a great distance.

"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," said Keivan Stassun, professor at Vanderbilt and co-author of the study.

The study has been accepted for publication in the Astronomical Journal. 

What Happens On Earth If A Solar Eclipse Lasts For Years?

On July 16, 2186, people on Earth will experience the longest total solar eclipse in 12,000 years. Scientists predict there will be more than seven minutes of darkness when the moon passes between the planet and the sun.

If the Earth will experience a solar eclipse that will last for three and a half years, it would be enough to kill all life on Earth. The planet will be too cold and dark that everyone and everything that depends on the sun for survival would die.

However, in stars, it's a different story. Years of stellar eclipse are possible in a binary star system.

Photo: NASA Goddard Space Flight Center | Flickr