Recently on Cosmically Curious, we touched on the knowns and unknowns about the birth of stars. This week, we’re going for even more drama. If you’re looking for a little more flair in your night sky, look no further than cataclysmic variable stars.
Host Patrick McNamee King sat down with resident NHPR Sky Guy, John Gianforte from the University of New Hampshire, to break down what these stars are and whether they live up to their explosive name.
According to Gianforte, they absolutely do.
Kind of like water spiraling down your drain... this material that's gravitationally pulled off the companion star swirls into [and] falls down upon the white dwarf star.John Gianforte
To understand why, it helps to break the name apart. In astronomy, a variable star is simply any star whose light output changes over time.
Sometimes, this happens because of a simple cosmic eclipse. In a binary system — where two stars orbit one another— one star might be much brighter than its companion. When the dimmer star passes in front of the brighter one, the overall light output dips.
While eclipsing stars are fascinating, they lack the sheer power of the cataclysmic variety.
When you add "cataclysmic" to the mix, things get more dramatic.
"That means there's something really powerful, energetic taking place at that star," Gianforte explains.
These systems always feature a binary pair where one of the stars is usually a white dwarf, the dense, burnt-out core of a dead star. Because the white dwarf is so incredibly dense, it still packs an immense gravitational punch. If it sits close enough to its companion star, it will actively steal its neighbor's matter.
"Kind of like water spiraling down your drain... this material that's gravitationally pulled off the companion star swirls into [and] falls down upon the white dwarf star."
As this stolen material crashes down onto the white dwarf, it creates a massive amount of heat and generates intense light across different wavelengths. This causes the entire system to brilliantly flare up in the night sky.
Eventually, this energy subsides and the light dims, until the white dwarf pulls in enough material to trigger the cycle all over again.
Are you Cosmically Curious? Let us know your questions about the night sky by emailing us at Cosmic@NHPR.org
