A tiny but terrible dwarf star in a binary system with another star has turned cannibal, devouring its neighbor by sucking up its gas, astronomers say.

In the rare binary star system astronomers classify as a cataclysmic variable, a massively dense and compact white dwarf star has been observed stealing the gas from its stellar companion, they say.

The binary pair dubbed Gaia14aae is around 730 light years from Earth in the constellation Draco.

In August 2014 the Gaia satellite of the European Space Agency detected it when it unexpectedly increased its brightness by five times in a period of just one day, astronomers say. Gaia's work is the ESA's effort to make a 3D map of the galaxy.

That sudden outburst of brightness was evidence the white dwarf -- a star so dense one teaspoonful of its material would weigh many tons -- was making a meal of its circling companion.

The pair is also rare in being what is known as an eclipsing binary, in which one of the stars orbits directly in front of its companion and is large enough to completely block out the view from Earth of the eclipsed star, say study leader Heather Campbell of the Institute of Astronomy at Cambridge University in England.

"It's rare to see a binary system so well-aligned" she says. "Because of this, we can measure the system with great precision in order to figure out what these systems are made of and how they evolved. It's a fascinating system - there's a lot to be learned from it."

Astronomers say they'll be able to gather measurements of the masses and sizes of the two stars with a greater accuracy than in any similar systems discovered do far.

The white dwarf is no larger than the earth while its companion is around 125 times the size of our own sun, the researchers say, noting that they orbit each other so closely and so rapidly that there is an eclipse of the smaller star every 50 minutes.

The discovery could help in understanding what causes supernova explosions, they say, something that could happen if the two stars in the binary system eventually come close enough to collide.

"Every now and then, these sorts of binary systems may explode as supernovae, so studying Gaia14aae helps us understand the brightest explosions in the universe," says Morgan Fraser at the Cambridge institute.

On the other hand, the researchers say, the white dwarf may completely consume its companion before that happens. The unique system was found with help of amateur astronomers who were analyzing Cambridge data.

Details of the new research will be published in the journal Monthly Notices of the Royal Astronomical Society.