Researchers Find Star Being Consumed By Its Smaller, Deader Neighbor

The Sun may be a lone star in our solar system, but about half of all other stars in the Milky Way are part of binary systems, in which two orbit each other. These can have incredibly fast orbital periods - scientists have found two white dwarfs that take just 5 minutes and 21 seconds to orbit each other. Another binary system is notable for a different reason: one star feasts on the other.

About 3,000 light-years away, there is a binary system that belongs to a class called "Cataclysmic Variables". That's an amazing term that I'm going to use after my next failed dining experience, by the way. In spatial terms, when a star similar to our sun orbits closely around a white dwarf, it is a cataclysmic variable. As Reuters notes, "variable" refers to how the combined brightness of the two stars changes over time, at least as far as how we see the system from the ground. These light levels can change significantly, which is where the "cataclysmic" part comes in.

The two stars in the system in question, 8 billion years old, revolve around each other every 51 minutes. It is the shortest orbital period known for a cataclysmic variable system. The distance between the stars has shrunk over millions of years and they are now closer to each other than we are to the Moon, researchers at the Massachusetts Institute of Technology and elsewhere have determined. In a paper published in Nature this week, the researchers said the white dwarf keeps matter away from the Sun-like partner.

"It's an old pair of stars, where one of them has moved on - when stars die of old age, they become white dwarfs - but then that remnant started eating its mate" , MIT astrophysicist and lead author of the paper Kevin Burdge told Reuters. "Just before the second could complete its stellar life cycle and become a white dwarf like stars normally do - evolving into a type of star called a red giant - the remaining white dwarf remnant of the first star interrupted the end of the companion's life cycle and began to slowly consume it."

Researchers have found that the largest star has a temperature similar to that of the Sun, but has shrunk to about 10% the diameter of our celestial neighbor. It is now the size of Jupiter. The white dwarf is much smaller, having a diameter about 1.5 times the size of Earth. However, it has a dense core, with a mass about 56% that of our Sun.

The white dwarf has eaten hydrogen from the outer layers of the largest star, leaving the latter exceptionally rich in helium. The larger star also transforms into a teardrop shape due to the white dwarf's gravitational pull. This is one of the reasons for the changes in the brightness levels of the binary system.

MIT notes that the system can emit "huge and variable flashes of light" as a result of the hydrogen-sapping process. He added that long ago, astronomers believed that these flashes were the result of an unknown cataclysm. While we have a better understanding of the situation these days, it's further proof, as if it were needed, that space is both cool and terrifying.

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