An artist's impression of the newly discovered star system, Gaia14aae, in which a small white dwarf is stealing the gas of a larger giant. (Marisa Grove/Institute of Astronomy)

Astronomers stumbled upon an extremely rare star system about 730 light years away in the Draco constellation, but the scene's a bit unnerving.

It's a binary star system in a bit of a David and Goliath situation. One star, a tiny white dwarf the size of Earth, is "cannibalizing" its massive companion, about 125 times the volume of our sun. The scientists, led by the University of Cambridge, have compared the system to a marble devouring a hot air balloon.

It's a strange system for a couple reasons. First and foremost, it's the only known case of a binary system in which one star completely eclipses the other. Because the two stars are orbiting around each other so tightly, the larger star blocks the other from view every 50 minutes — faster than the minute hand of a clock.

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It's also made up of large amounts of helium, but not hydrogen, according to a spectroscopy analysis from the William Herschel Telescope in the Canary Islands. That's highly unusual, because hydrogen is the most common element in the universe.

The system, named Gaia14aae, was discovered by the European Space Agency's Gaia satellite back in August 2014 when an amateur astronomer alerted the agency that it suddenly became five times brighter during a single day.

"This really highlights the vital contribution that amateur astronomers make to cutting-edge scientific research," said Heather Campbell of Cambridge's Institute of Astronomy, in a statement.

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The white dwarf has such powerful gravitational effects on the bigger star because it's so dense — scientists say one teaspoon of material from it would weigh as much as an elephant. That's caused the companion star, which has only 1 percent of the white dwarf's mass, to swell up like a balloon and move closer.

Astronomers hope Gaia14aae could be the key to the mystery of supernova explosions. This is important because the extreme brightness of the explosions are a tool to measure the expansion of the universe.

"It's a fascinating system — there's a lot to be learned from it," Campbell said.

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The Gaia satellite is a relatively young spacecraft, having launched in December 2013. The craft's mission is to create an enormous three-dimensional map of objects in the Milky Way.

"This is an awesome first catch for Gaia, but we want it to be the first of many," said Simon Hodgkin of the Institute of Astronomy, who is leading the Gaia project.

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