“Vampire star” devouring its companion

ASTRONOMERS HAVE OBTAINED the best images ever of a star that has lost most of its material to a vampire companion.

By combining the light captured by four telescopes at the European Southern Observatory’s (ESO) Paranal Observatory (Chile), they created a virtual telescope 130 metres across with vision 50 times sharper than the Hubble Space Telescope.

Surprisingly, the new results show that the transfer of gas from one star to the other in this double system is gentler than expected.

The video above shows a “zoom in”, through several different images of different resolution, ending with what looks like two blobs—a blue one and a orangeish one. These are the real images of the two stars, with the red giant being the bigger one. Images taken on different dates show how the stars have moved in their mutual orbit around each other.

The astronomers observed the unusual system SS Leporis in the constellation of Lepus (The Hare), which contains two stars that circle around each other in 260 days.

The stars are very close together…separated by only a little more than the distance between the Sun and the Earth. In terms of size, the larger and cooler of the two stars (a red giant) is big enough to extend out to one quarter of this distance — corresponding roughly to the orbit of Mercury.

Because of this closeness, the hot companion star has already cannibalised about half of the mass of the larger star.

The new observations are sharp enough to show that the giant star is smaller than previously thought, making it much more difficult to explain how it lost matter to its companion.

The astronomers now think that, rather than streaming from one star to the other, the gas must be expelled from the giant star as a stellar wind and then captured by the hotter companion.

Adapted from information issued by ESO / Digitised Sky Survey 2 / Nick Risinger (skysurvey.org) / PIONIER / IPAG; music: John Dyson (from the album Moonwind).

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