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RXJ080631527 Binary Stellar System with the Shortest Period
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RXJ08063+1527: Binary Stellar System with the Shortest Period Known

April 22, 2005
An amazing stellar binary system

Observations with ESO's Very Large Telescope (VLT) in Chile and the Italian Telescopio Nazionale Galileo (TNG) on the Canary Islands during the past two years have enabled an international group of astronomers [1] to unravel the true nature of an exceptional binary stellar system.

This system, designated RX J0806.3+1527 , was first discovered as an X-ray source of variable brightness - once every five minutes, it "switches off" for a short moment. The new observations have shown beyond doubt that this period reflects the orbital motion of two "white dwarf" stars that revolve around each other at a distance of only 80,000 km . Each of the stars is about as large as the Earth and this is the shortest orbital period known for any binary stellar system.

The VLT spectrum displays lines of ionized helium, indicating that the presence of an exceedingly hot area on one of the stars - a "hot spot" with a temperature of approx. 250,000 degrees. The system is currently in a rarely seen, transitory evolutionary state .

This image shows U and R filter images of the sky field around RX J0806.3+1527 (at centre of circle), obtained with the FORS2 multi-mode instrument on VLT KUEYEN. The object is brightest at the shorter wavelength (U-band) - reflecting its very high temperature.