RS Ophiuchi – A Cosmic Lighthouse
Most people are familiar with a supernova – the most violent event in the known universe. Supernova happen when a super-massive star reaches old age and has fused most of its lighter elements into heavier elements and basically runs out of fuel. The gravity of the star pushing inwards overcomes the pressure of the heat from the burning fuel pushing out words and the star collapses on itself. The star explodes so violently that for a short time, it will outshine the rest of the entire galaxy it inhabits! This happens only to a certain type of star and will happen only once in its lifetime.
Another less-well known type of explosion a star can undergo is called a nova. Nova’s can happen over and over again to a star on a surprisingly regular basis. One way a nova can occur is when one star in a binary star system ‘feeds’ on the other star until it gets too full and explodes. Think of a white dwarf star and a red giant star orbiting each other while the white dwarf feeds on the outer layers of the red giant. The heat builds up enough on the white dwarf to cause a thermonuclear explosion blasting the outer layers of the white dwarf off in a great cosmic gas bubble. The explosion isn’t great enough to destroy the star so even after the nova occurs, the star remains and begins feeding again like a glutton who didn’t learn his lesson. A great example of this is RS Ophiuchi, a system where the white dwarf goes nova about every twenty years. The last time it erupted was in 2006. It has exploded like a beacon in the night every twenty years prior to that dating back to its first discovery in 1898; and undoubtedly for eons before that.
Like clockwork, a small beacon – a lighthouse in the night sky – lights up to warn the seafarers in the vast dark ocean of the cosmos. Is the lighthouse keeper lonely out there? The galaxy is a big and lonely place. He can take solace in the fact that countless observers throughout the galaxy notice his beacon. We can see it across this vast ocean and feel safe to know there’s a safe harbor somewhere. And RS Ophiuchi – the Cosmic Lighthouse – points the way.