Superfast spinning stars

This article makes me wonder:

SPACE.com -- Fast-Spinning Star on Verge of Breaking Apart
""Alpha Arae is very close to its breakup velocity, and the matter
may freely escape the equatorial regions, 'launched' by the centrifugal
force, as if you were on a crazy merry-go-round," lead researcher
Philippe Stee of the Observatory of Côte d'Azur in France, told
SPACE.com."
http://www.space.com/scienceastronom...star_spin.html

So if there are stars spinning so fast that they are on the verge of
breaking up, it would stand to reason that there were stars that spun
so fast that they went over that critical limit. My question would be,
so what happened to those stars? Did those stars spin away enough of
their outer layers to the point where they became much smaller-diameter
stars, at which point they could exist in equilibrium again because
they were no longer at critical speed? Or did they just completely
fling their gas away until they became just a big cloud of gas again?

Yousuf Khan

"bbbl67" wrote in message
oups.com...
This article makes me wonder:

SPACE.com -- Fast-Spinning Star on Verge of Breaking Apart
""Alpha Arae is very close to its breakup velocity, and the matter
may freely escape the equatorial regions, 'launched' by the centrifugal
force, as if you were on a crazy merry-go-round," lead researcher
Philippe Stee of the Observatory of Côte d'Azur in France, told
SPACE.com."
http://www.space.com/scienceastronom...star_spin.html

So if there are stars spinning so fast that they are on the verge of
breaking up, it would stand to reason that there were stars that spun
so fast that they went over that critical limit. My question would be,
so what happened to those stars? Did those stars spin away enough of
their outer layers to the point where they became much smaller-diameter
stars, at which point they could exist in equilibrium again because
they were no longer at critical speed? Or did they just completely
fling their gas away until they became just a big cloud of gas again?

Yousuf Khan

http://www.androcles01.pwp.blueyonde...lgol/Algol.htm

Androcles

In article .com,
"bbbl67" writes:
http://www.space.com/scienceastronom...star_spin.html

The preprint is at http://xxx.lanl.gov/abs/astro-ph/0606404

So if there are stars spinning so fast that they are on the verge of
breaking up, it would stand to reason that there were stars that spun
so fast that they went over that critical limit.

How could they form? An accretion disk spinning at breakup isn't
going to let matter drop down onto a stellar surface.

Did those stars spin away enough of their outer layers to the point
where they became much smaller-diameter stars

If some external force "spins up" a star, it starts losing mass from
its equator. If the ejected mass couples to the star, either through
viscosity or magnetic fields, angular momentum can be transported
outwards, and the star will slow down. If there is no coupling, then
mass loss continues until the star's radius falls below the critical
value.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

Steve Willner wrote:
So if there are stars spinning so fast that they are on the verge of
breaking up, it would stand to reason that there were stars that spun
so fast that they went over that critical limit.

How could they form? An accretion disk spinning at breakup isn't
going to let matter drop down onto a stellar surface.

Perhaps a momentum boost from another passing star?


Did those stars spin away enough of their outer layers to the point
where they became much smaller-diameter stars

If some external force "spins up" a star, it starts losing mass from
its equator. If the ejected mass couples to the star, either through
viscosity or magnetic fields, angular momentum can be transported
outwards, and the star will slow down. If there is no coupling, then
mass loss continues until the star's radius falls below the critical
value.

Okay, so it sounds like the star simply gets smaller in diameter.

Yousuf Khan

So if there are stars spinning so fast that they are on the verge of
breaking up,...

SW How could they form?

In article ,
Yousuf Khan writes:
Perhaps a momentum boost from another passing star?

I don't think a mere close passage will work. It's very difficult
for one star to apply a torque to the other. A binary merger might
do it, though.

SW If some external force "spins up" a star, it starts losing mass from
SW its equator. If the ejected mass couples to the star, either through
SW viscosity or magnetic fields, angular momentum can be transported
SW outwards, and the star will slow down. If there is no coupling, then
SW mass loss continues until the star's radius falls below the critical
SW value.

Okay, so it sounds like the star simply gets smaller in diameter.

I think coupling by viscous forces is more likely, but I could easily
be wrong. It's not as though there are lots of examples to study.
The real result probably depends on the exact details of the merger.
Come to think of it, this process may be relevant for "blue
stragglers." I bet somebody has tried to calculate models for those,
but I don't know for sure. If not, there's a dandy PhD thesis
waiting to be written.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

"Steve Willner" wrote in message
...
| So if there are stars spinning so fast that they are on the verge of
| breaking up,...
|
| SW How could they form?
|
| In article ,
| Yousuf Khan writes:
| Perhaps a momentum boost from another passing star?
|
| I don't think a mere close passage will work. It's very difficult
| for one star to apply a torque to the other. A binary merger might
| do it, though.
|
| SW If some external force "spins up" a star, it starts losing mass from
| SW its equator. If the ejected mass couples to the star, either through
| SW viscosity or magnetic fields, angular momentum can be transported
| SW outwards, and the star will slow down. If there is no coupling, then
| SW mass loss continues until the star's radius falls below the critical
| SW value.
|
| Okay, so it sounds like the star simply gets smaller in diameter.
|
| I think coupling by viscous forces is more likely, but I could easily
| be wrong. It's not as though there are lots of examples to study.
| The real result probably depends on the exact details of the merger.
| Come to think of it, this process may be relevant for "blue
| stragglers." I bet somebody has tried to calculate models for those,
| but I don't know for sure. If not, there's a dandy PhD thesis
| waiting to be written.


That's all it's about, writing crap nobody can prove or disprove.
You even get Nobel prizes that way.
http://www.androcles01.pwp.blueyonde...lgol/Algol.htm

"Steve Willner" wrote in message
...
So if there are stars spinning so fast that they are on the verge of
breaking up,...

SW How could they form?

In article ,
Yousuf Khan writes:
Perhaps a momentum boost from another passing star?

I don't think a mere close passage will work. It's very difficult
for one star to apply a torque to the other. A binary merger might
do it, though.

SW If some external force "spins up" a star, it starts losing mass from
SW its equator. If the ejected mass couples to the star, either through
SW viscosity or magnetic fields, angular momentum can be transported
SW outwards, and the star will slow down. If there is no coupling, then
SW mass loss continues until the star's radius falls below the critical
SW value.

Okay, so it sounds like the star simply gets smaller in diameter.

I think coupling by viscous forces is more likely, but I could easily
be wrong. It's not as though there are lots of examples to study.
The real result probably depends on the exact details of the merger.
Come to think of it, this process may be relevant for "blue
stragglers." I bet somebody has tried to calculate models for those,
but I don't know for sure. If not, there's a dandy PhD thesis
waiting to be written.

Surely this would be the fate of grazing binaries
and isn't it highly likely they would get tidally
locked before merger? These appear relevant:

http://tinyurl.com/n4xe6

http://tinyurl.com/nm87j

George

"George Dishman" wrote in message
...
|
| "Steve Willner" wrote in message
| ...
| So if there are stars spinning so fast that they are on the verge of
| breaking up,...
|
| SW How could they form?
|
| In article ,
| Yousuf Khan writes:
| Perhaps a momentum boost from another passing star?
|
| I don't think a mere close passage will work. It's very difficult
| for one star to apply a torque to the other. A binary merger might
| do it, though.
|
| SW If some external force "spins up" a star, it starts losing mass from
| SW its equator. If the ejected mass couples to the star, either
through
| SW viscosity or magnetic fields, angular momentum can be transported
| SW outwards, and the star will slow down. If there is no coupling,
then
| SW mass loss continues until the star's radius falls below the critical
| SW value.
|
| Okay, so it sounds like the star simply gets smaller in diameter.
|
| I think coupling by viscous forces is more likely, but I could easily
| be wrong. It's not as though there are lots of examples to study.
| The real result probably depends on the exact details of the merger.
| Come to think of it, this process may be relevant for "blue
| stragglers." I bet somebody has tried to calculate models for those,
| but I don't know for sure. If not, there's a dandy PhD thesis
| waiting to be written.
|
| Surely this would be the fate of grazing binaries
| and isn't it highly likely they would get tidally
| locked before merger? These appear relevant:
|
| http://tinyurl.com/n4xe6

Cookies Required for Access
Your web browser must accept cookies to access this free content.
Please enable cookies before clicking continue. For more information
on cookies, please consult your browser's help index.

|
| http://tinyurl.com/nm87j
|
| George
|
|