Feeds

Red Giant fails to devour Brown Dwarf companion

Saving it for later

Intelligent flash storage arrays

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. ®

Providing a secure and efficient Helpdesk

More from The Register

next story
MARS NEEDS WOMEN, claims NASA pseudo 'naut: They eat less
'Some might find this idea offensive' boffin admits
SECRET U.S. 'SPACE WARPLANE' set to return from SPY MISSION
Robot minishuttle X-37B returns after almost 2 years in orbit
LOHAN crash lands on CNN
Overflies Die Welt en route to lively US news vid
Experts brand LOHAN's squeaky-clean box
Phytosanitary treatment renders Vulture 2 crate fit for export
You can crunch it all you like, but the answer is NOT always in the data
Hear that, 'data journalists'? Our analytics prof holds forth
No sail: NASA spikes Sunjammer
'Solar sail' demonstrator project binned
America's super-secret X-37B plane returns to Earth after nearly TWO YEARS aloft
674 days in space for US Air Force's mystery orbital vehicle
Carry On Cosmonaut: Willful Child is a poor taste Star Trek parody
Cringeworthy, crude and crass jokes abound in Steven Erikson’s sci-fi debut
Origins of SEXUAL INTERCOURSE fished out of SCOTTISH LAKE
Fossil find proves it first happened 385 million years ago
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Cloud and hybrid-cloud data protection for VMware
Learn how quick and easy it is to configure backups and perform restores for VMware environments.
Three 1TB solid state scorchers up for grabs
Big SSDs can be expensive but think big and think free because you could be the lucky winner of one of three 1TB Samsung SSD 840 EVO drives that we’re giving away worth over £300 apiece.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.