Epsilon Aurigae system remains mysterious
Epsilon Aurigae. Image Credit: ESO Online Digitized Sky Survey.
Robert Stencel: Epsilon Aurigae has fascinated astronomers for nearly 200 years.
That’s astronomer Robert Stencel. He’s talking about a star system called Epsilon Aurigae, 2,000 light-years away. Astronomers think the main star in this system is eclipsed every 27 years by … something.
Robert Stencel: We can’t seem to pin down what that secondary object really is.
This system gets dimmer for about two years out of every 27. That’s a long eclipse, and astronomers picture a gas cloud as wide as a thousand suns orbiting the main star. When the cloud comes between us and the main star, the whole system gets dimmer.
Stencel and other astronomers are excited about the eclipse of Epsilon Aurigae in 2009. Over the decades, the star has spent more and more time in eclipse, plus the star’s brightness is pulsing more rapidly.
Robert Stencel: If those two trends are extrapolated a couple of decades out, it means that something accelerating in the system now might go ‘bang’ in the night.
The ‘bangs’ might come from a smaller object in the Epsilon Aurigae system. A planetesimal – or chunk of debris within the disk – might be spiraling towards one of its stars. A collision with lots of fireworks could occur by mid-century.
The working hypothesis is that Epsilon Aurigae includes one supergiant star of approximately 15 solar masses, plus about a 12-solar-mass companion in long term binary orbit (27 years). The companion is greatly under-luminous for its mass. As early as 1985, astronomers proposed one way to achieve the high mass with low luminosity is to “hide” a pair of main sequence stars inside an opaque cloud seen edge on from Earth. So there might be three stars in the Epsilon Aurigae system: the main star plus two more hidden in the orbiting cloud.
