Giant superhot blobs of gas fired from hidden star
The Hubble Space Telescope detected these 'cannonballs' flying from the red giant V Hydrae, but other telescopes traced previous blasts back centuries. Belinda Smith reports.
Hot balls of gas twice the size of Mars are blasted from a bloated star near the end of its life – but instead of coming from the dying giant, astronomers think they’re pumped out by a younger hidden stellar companion.
It's certainly an intriguing theory, one put forward by a trio from NASA’s Jet Propulsion Laboratory at Caltech. the University of California, Los Angeles and the State University of New York at Stony Brook in the US.
They used the Hubble Space Telescope to detect huge “cannonballs” barrelling from the red giant star V Hydrae, 1,200 light-years away.
But those projectiles could not have come from V Hydrae because it’s exhausted the nuclear fuel that makes stars shine. The best explanation, they present in The Astrophysical Journal, is another, more active star, which orbits V Hydrae, is that culprit.
Lead author Raghvendra Sahai said it was the first time the process had been captured in action.
Gazing at V Hydrae and its surrounds for a total of 11 years, Hubble showed a string of blobs, each twice as hot as the surface of the sun, flying from the red giant.
Sahai and colleagues compiled a map of the blobs’ location and, using the Submillimetre Array in Hawaii, found cooler, fuzzy structures that may have been hot blobs 400 years ago.
The unseen companion star, calculations suggest, is in an elliptical orbit that carries it close to the red giant's puffed-up atmosphere every 8.5 years.
As it nears the atmosphere, the companion gobbles up material which settles into a disc and serves as the launching pad for blobs of plasma, which travel at around 800,000 kilometres per hour.
The star system may explain why Hubble has found such a wide array of planetary nebulae – the glowing gas clouds that sheath dying stars, with some found riddled with strange knots of material.
A hidden stellar companion may be behind these nebulae.