A strange but stellar fight

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have spotted a peculiar gas cloud that resulted from a confrontation between two stars. One grew so large it engulfed the other which, in turn, spiralled towards its partner, provoking it into shedding its outer layers.

Like humans, stars change with age and ultimately die. However, says Hans Olofsson from Sweden’s Chalmers University of Technology, the star system HD101584 is special in the sense that this death process “was terminated prematurely and dramatically as a nearby low-mass companion star was engulfed by the giant”.

It was akin to a stellar fight, Olofsson and colleagues suggest. As the main star puffed up into a red giant, it grew large enough to swallow its lower-mass partner. In response, the smaller star spiralled in towards the giant’s core but didn’t collide with it. Rather, this manoeuvre triggered the larger star into an outburst, leaving its gas layers dramatically scattered and its core exposed.

The team says the complex structure of the gas in the HD101584 nebula is due to the smaller star’s spiralling towards the red giant, as well as to the jets of gas that formed in this process. As a deadly blow to the already defeated gas layers, these jets blasted through the previously ejected material, forming the rings of gas and the bright bluish and reddish blobs seen in the nebula.