Feeds

Red Giant fails to devour Brown Dwarf companion

Saving it for later

Internet Security Threat Report 2014

Astronomers using the European Southern Observatory's Very Large telescope have identified a star system in which a brown dwarf has survived being engulfed by its companion star's Red Giant phase.

Now, both stars are planet sized, and orbit one another very closely, and very fast. The orbital period is around two hours. One is a white dwarf - a star roughly earth-sized, but around half as massive as our sun, and the other is a brown dwarf - a failed star approximately 55 times as massive as Jupiter.

But it wasn't always that way, according to Pierre Maxted, lead author of a paper in this week's Nature

"Such a system must have had a very troubled history", he said. "Its existence proves that the brown dwarf came out almost unaltered from an episode in which it was swallowed by a red giant."

Millions of years ago, the white dwarf was a star very much like our own sun, and was orbited by its then much more distant brown dwarf companion. As its supplies of hydrogen began to run out, it started to collapse. This created a little extra pressure at its core, giving it a little more energy to keep those fires burning by igniting the hydrogen that remained in its shell.

As the hydrogen in the star's shell burnt, so the shell expanded outwards and the star became a red giant and started burning helium, just for fun.

It got so large that it enveloped its companion star. Being inside a star instead of just orbiting one is a disturbing thing, and the brown dwarf was jostled into a new orbit, spiralling closer and closer to the centre of the red giant.

At some point, the Red Giant ran out of helium and collapsed in again. When the core collapsed, it released energy causing the star's envelope to blow off. And so the star shed its outer layers in a planetary nebula (nothing to do with planets), leaving its core intact, and visible to us as a white dwarf.

The brown dwarf is also intact, although orbiting the star much more closely. If it had originally been less than 20 Jupiter masses, it would have evaporated.

Eventually, the two stars will move still closer together, and their orbital period will reduce still further. In about 1.4bn years they will be so close that the white dwarf will begin siphoning material off the brown dwarf. ®

Secure remote control for conventional and virtual desktops

More from The Register

next story
Rosetta probot drilling DENIED: Philae has its 'LEG in the AIR'
NOT best position for scientific fulfillment
'Yes, yes... YES!' Philae lands on COMET 67P
Plucky probot aces landing on high-speed space rock - emotional scenes in Darmstadt
THERE it is! Philae comet lander FOUND in EXISTING Rosetta PICS
Crumb? Pixel? ALIEN? Better, it's a comet-catcher!
SEX BEAST SEALS may be egging each other on to ATTACK PENGUINS
Boffin: 'I think the behaviour is increasing in frequency'
HUMAN DNA 'will be FOUND ON MOON' – rocking boffin Brian Cox
Crowdfund plan to stimulate Blighty's space programme
Post-pub nosh neckfiller: The MIGHTY Scotch egg
Off to the boozer? This delicacy might help mitigate the effects
I'M SO SORRY, sobs Rosetta Brit boffin in 'sexist' sexy shirt storm
'He is just being himself' says proud mum of larger-than-life physicist
NASA launches new climate model at SC14
75 days of supercomputing later ...
prev story

Whitepapers

Choosing cloud Backup services
Demystify how you can address your data protection needs in your small- to medium-sized business and select the best online backup service to meet your needs.
Getting started with customer-focused identity management
Learn why identity is a fundamental requirement to digital growth, and how without it there is no way to identify and engage customers in a meaningful way.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Internet Security Threat Report 2014
An overview and analysis of the year in global threat activity: identify, analyze, and provide commentary on emerging trends in the dynamic threat landscape.
Intelligent flash storage arrays
Tegile Intelligent Storage Arrays with IntelliFlash helps IT boost storage utilization and effciency while delivering unmatched storage savings and performance.