Mystery of explosive star solved

space.com ^ | 07/20/06 | Ker Than

[KevinDavis]

(SPACE.com) -- In February, a faint star a few thousand light-years away flared suddenly, beaming so brightly that for a few days it was visible to the naked eye.

The star is a stellar corpse the size of Earth, known as a white dwarf, and it is paired in a binary system with a red giant, a dying, bloated star that once resembled our sun. The red giant has been dumping gas onto the surface of the white dwarf, and every few years, enough matter accumulates to set off a giant thermonuclear explosion.

[KevinDavis]

SG1 at it again..

[KevinDavis]

[rocksblues]

The star is a stellar corpse the size of Earth, known as a white dwarf, and it is paired in a binary system with a red giant, a dying, bloated star that once resembled our sun

Amazing that they don't mention the distance between the corpse and giant.

[King Prout]

from what I gather, the white dwarf's orbit around the common centermass of both bodies is actually entirely within the outer "atmosphere" of the red giant.

[rocksblues]

Would receiving warmth from the Giant be considered within the atmosphere?

[King Prout]

I'm pretty sure that they mean that the orbital radius of the white dwarf is smaller than (and, thus, enveloped by) the radius of the red giant's outermost material layers.

[rocksblues]

If our Sun became a Red Dwarf which has been theorized wouldn't Earth fall within it's outermost layers?

[King Prout]

If our Sun became a Red Dwarf which has been theorized wouldn't Earth fall within it's outermost layers?

iirc, Mars would fall within that radius. Earth would be consumed in the expansion. I don't recall whether the asteroid belt or Jupiter would be outside the star. I'm calling in one who can answer.

[rocksblues]

Earth would be consumed in the expansion

I now remember this part of the theory.

[King Prout]

side note - the sun is expected to become a red giant, not a red dwarf. is there such a thing as a red dwarf (aside from a very short communist)?

[beezdotcom]

The size probably varies according to the assumptions made during the calculations - one hypothesis says that Venus and Earth will be spared (but just barely), Mercury (orbit in dashed line) gets eaten:

[King Prout]

ah, thanks!

[Calvin Locke]

Yeah, I think I saw that on Dr. Who...

[King Prout]

you saw a very short communist on Dr.Who?

[Calvin Locke]

Just guessing, but wouldn't the dwarf have a mass "nearly" the equal to the red giant? I would think
that the center of mass of both stars would be outside the red giant's outer layer.

Unless the orbital speed is really fast.

[Calvin Locke]

Oh, they have all sorts of leftist propaganda on Dr. Who.

Probably called him a vertically challenged labour MP, though.

[King Prout]

also just guessing, but I think the white dwarf will have lost mass during its collapse phase.

as to where the centermass would be, a crude illo:

satellite>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>CM>>primary
o>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>+>>>>>O

RGcirc>>>>>>>>>>>>>>>CM>>>>>>>WD>>RGcirc
(>>>>>>>>>>>>>>>>>>>>>+>>>>>>>>>o>>>>)

[Calvin Locke]

Here are a couple of links.

Mira, x-ray photo on the page:

http://www.astronet.ru:8104/db/xware/msg/1205472


And some diagrams, including a "contact" binary. We're both right. Not sure if the enveloped companion can be
a white dwarf, but could a white dwarf strip off a red giant's gas layer to leave two white dwarfs?

http://www.astro.psu.edu/users/rbc/a1/lec16n.html

[King Prout]

thanks!

could a white dwarf strip off a red giant's gas layer to leave two white dwarfs?

dunno - I'm just an interested dilettante when it comes to stuff like this.

[MonroeDNA]

God invented this 600 years ago.

Or 6000 years ago. Or something.

He invented ear hair on the fifth day.