Binary Star EF Eridanus Baffles Astronomers

baldinux writes "Reuters is reporting the finding of a new stellar object in the Eridanus constellation that may require the astronomical community to create a new category of stellar entities -- that is, dead ones. In the binary system, one of the stars 'gave too much' (Reuters) of its own resources to its partner white dwarf star, resulting in a breakdown of nuclear fusion, thus producing this 'dead' entity. Researchers at Gemini North (click here for images) and Keck II observatories at Mauna Kea, Hawaii, have been analyzing this unique system."

Comments

In human terms...

[Anonymous Coward]

In human terms this is known as marriage.

They should name binary pair...

[bobdotorg]

They meet, they accrete, and then dance for years as they happily twirl about. But as time goes by her ass grows more massive as she sucks out his soul and he becomes a shadow of his former self.

So I propose the name: Succubus and the Bitter Old Man.

Probly Classified as an L or a T dwarf

[aws4y]

Though it may have lost its hydrogen and helium burning capeability I would hypothesise that the thing is now an L or T dwarf that is to say it might be Duterium or Lithium burning, or its spectral profile might be very dusty or contain methane. In otherwords we might have just seen an L or T dwarf being made but I highly doubt this is a new class of star.

Re:Probly Classified as an L or a T dwarf

[DLWormwood]

In otherwords we might have just seen an L or T dwarf being made but I highly doubt this is a new class of star.

From the article...

"Now the donor star has reached a dead end -- it is far too massive to be considered a super-planet, its composition does not match known brown dwarfs, and it is far too low in mass to be a star... There's no true category for an object in such limbo"

The unstar appears to fall between the cracks of current astronomical classification...

Re:Probly Classified as an L or a T dwarf

[barawn]

If there's no nuclear fusion in its core, it's not a star.

Actually, this object is incredibly interesting. Composition-wise, it's a star frozen in time, and without all the nasty chemical-changing properties of nuclear fusion going on. There's a lot that could be learned from objects like that.

Re:Probly Classified as an L or a T dwarf

[Christopher Thomas]

Though it may have lost its hydrogen and helium burning capeability I would hypothesise that the thing is now an L or T dwarf that is to say it might be Duterium or Lithium burning,

This seems unlikely, as both D and Li burn a lot more readily than p, if I understand correctly. Thus, the star should have used these up very early in its life. If it started life as something larger than a red dwarf, you could argue that there would be deuterium and lithium in its outer layers that wouldn't have mixed with the core material, but a) the outer layers were mostly what was stripped off by the companion star, and b) the star would have passed through a red dwarf stage as it lost mass, resulting in more thorough mixing during that time period.

So, I'm not sure it's a good bet to say that there would still be D or Li left. What do the spectrographs say, for this object?

or its spectral profile might be very dusty or contain methane. In otherwords we might have just seen an L or T dwarf being made but I highly doubt this is a new class of star.

I'm not sure "star" is the correct term any more, as there's no fusion happening (in all likelihood). A few classifications I can think of:

• Stellar remnant.
  Pretty broad category, so probably not specific enough. Also tends to refer to things like planetary nebula and not stars (we haven't seen anything star-like that's been around long enough to cool down past "white dwarf" levels).
  
  
• Black dwarf.
  It's a stellar core that can no longer sustain fusion. But this term usually refers to the (as yet unobserved) cooled ashes of a burned-out stellar core (cold white dwarf).
  
  
• Brown dwarf.
  It's a sub-stellar mass that's still massive enough that it probably could sustain deuterium fusion, if it had any deuterium to fuse. That probably makes it a brown dwarf on a technicality, even though it's of a bizzare spectral type compared to other brown dwarfs (as you point out).
  
  
• MACHO.
  This is another category that's probably too broad to be useful. If it's stripped to below the point where deuterium fusion can occur, but is not a planet (i.e. condensed from a nebula directly as opposed to from another star's protoplanetary disk), it probably counts as a MAssive Compact Halo Object, on a technicality.
  

I'm voting for "brown dwarf" or "black dwarf", but those are still on technicalities.

See: altruism is evil.

[Chemisor]

> In the binary system, one of the stars 'gave too
> much' (Reuters) of its own resources to its
> partner white dwarf star, resulting in a breakdown
> of nuclear fusion, thus producing this 'dead' entity.

A good example to illustrate the evil of altruism.

Re:See: altruism is evil.

[iggymanz]

No, it shows how the evil objectivist capitalist white dwarf exploited the poor downtrodden proletariat worker-class star

Dead star

[mknewman]

I think this sort of star has been postulated for quite a while, especially with black holes and neutron stars sucking material out of companion stars, but this is the first observation of the result of that process, a star that is no longer fusing. It's a dead husk. I think that makes it a supergiant planet or an ex-star, but I doubt it's fusing anything anymore. It's been sucked dry.

Could this "re-ignite" the dwarf star?

[MobyDisk]

IANAC (I am not a cosmologist)
AINAA (I am not an astrophysicist)
IAAAJ (I am an average joe)

Could the dwarf star absorb enough mass that fusion could start again? That would be awesome!

Re:Could this "re-ignite" the dwarf star?

[barawn]

Could the dwarf star absorb enough mass that fusion could start again? That would be awesome!

This is what novae are (not supernovae, which are different). When a white dwarf star accretes matter, it builds up on its outer shell. Since the white dwarf is incredibly dense, its gravity is incredibly strong, so the layer of matter (hydrogen) is incredibly hot. Eventually the density of hydrogen grows enough that fusion can occur again, and it does - and the star burns off (very quickly - ~few days) what took it several years to build up.

This causes a white dwarf to go from barely visible to extremely bright. In the night sky, it looks like a new star comes out of nowhere, then disappears - hence the word "nova", meaning 'new'.

New category not possible

[rts008]

Naming a new category is not possible anymore...I foresaw this and patented the process of developing AND implementing new categories. This new career RULES!!! since I've been too STUPID in the past to develop a REAL business plan! Mod this: -16 for OFFTOPIC -10 for FUNNY -pi for INFORMATIVE

What I'd like to know is

[$RANDOMLUSER]

OK, the donor "star" no longer has enough mass to maintain fusion, but it's still a big compressed ball of (mostly) hydrogen and helium, held together by gravity. The white dwarf "vampire" star is still sitting right there.

So what caused the process to stop? Why isn't the vampire still sucking on the donor?

Maybe it is, and we can't see it, (even though I suspect we'd see something as the matter was gravitationally accelerated into the vamp star.

Or maybe the two are farther apart than they used to be, even though this doesn't make much sense for a binary star.

Either way, I'm puzzled.

Re:What I'd like to know is

[cjameshuff]

It's not fusing internally any more, so it's cooling down and shrinking. Its "surface" is deeper in its gravity well and colder, so it's not getting stripped away as quickly. The vampirism probably hasn't stopped, just become too small to detect.

Also, the thing probably has much higher concentrations of "metals" than typical brown dwarfs or gas giants...for a while, it was fusing, and it probably lost lighter elements to the white dwarf more easily.