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Speeding star set to escape our galaxy

FLO

By FLO
in The Astro Lounge

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FLO

FLO

Posted
Posted

I found this article and thought I'd share it here. 

The Basics: A black-hole at the center of our galaxy with a mass of 3

million suns has catapulted (slingshot style) a heavy metal star out of

the galaxy at a speed of 1.5 million mph and, though it has been

travelling for 80 million years (without hitting anything!), it still has

another 80-100 million years before it enters open space...

Steve :)

Full article here:

http://space.com/scienceastronomy/escaping_star_050208.html

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daz

daz

Posted
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The distances involved really do blow your mind - it has travelled for 1,051,200,000,000,000,000 miles so far and still has between

1,051,200,000,000,000,000 and 1,314,000,000,000,000,000 miles left to go.

Hope there's a service station.....

DJ

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daz

daz

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Question: Is a 3 million solar mass object large, in comparison to other objects in the galaxy?

I was just thinking what would happen if it actually collided with something. If the object hit was larger, there could well be a bit if a bang, but if smaller, then would the resulting explosion get consumed by the star, or would there be a discernable explosion?

Question: Is there a limit to the size of stars?

Question: Where would it put the wrist band?

Daz

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Ant

Ant

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Posted

Just re-read the article - the 3 million solar mass object is the black hole... So I'm guessing that the star is a "normal" size star.

Which means that the wrist band will fit - just.

on a galactic scale is 1.5 million miles per hour actually that fast?

What is the speed in relation to? If our whole galaxy is moving through space at 1 million miles and hour and this star is moving at speed relative to our galaxy then depending on the direction it's going in it could be speeding along at 2.5m mph or having a stroll at only 500k mph.

Some outer parts of spiral galaxies must be moving at speeds similar to that to maintain their shape.

Ant

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Astroman

Astroman

Posted
Posted

Makes a change for a black hole to expel a star like that, rather than to devour it.

It may be unusual for whole stars, but this is not all that uncommon for regular matter.  Matter entering the event horizon can be swallowed or ejected, depending on its initial velocity and trajectory.  Sometimes it gets a gravitational boost in much the same way satellites do when they travel to Mars or Jupiter et al. The "jets" coming from black hole candidates and galaxies such as M81 are examples of matter being expelled at high rates.

What happens (if anything) to a star once it leaves the galaxy?

Most likely, not much.  It should live out its life fusing hydrogen and such until it blows up or evolves into a red giant.  Depends entirely on its mass and composition.  Its life cycle has definitely been altered by the boost in velocity, but shouldn't have all that much effect on the star itself. It may be sweeping up matter, extending its life, or the velocity may be stripping off the outer layers, shortening it. That may be an interesting grant request for some Keck time...?!

It must get one of those little coloured wrist bands to prove that has already paid and left to go outside for a fag or something?

Ant

Don't be silly guys.  Everone knows that stars get a stamp that can only be seen in ultraviolet light.  Sheesh.

Question: Is a 3 million solar mass object large, in comparison to other objects in the galaxy?

I was just thinking what would happen if it actually collided with something. If the object hit was larger, there could well be a bit if a bang, but if smaller, then would the resulting explosion get consumed by the star, or would there be a discernable explosion?

Question: Is there a limit to the size of stars?

Daz

On pretty much any scale you'd choose, yes, 3 million solar masses is big.  Galactic black holes are the largest single entities known.  Though the evidence for their existance is compelling, they are still theoretical of course.

If you were colse to an object of stellar mass that collided with something else of similar mass at this velocity, it'd spoil your day.  I'm fairly sure it'd make a mess of both objects, and radiate anything close beyond recognition.  And yes, I'm sure we could detect it-now.  But maybe not when it happened.  The thing about this particular scenario is, if it was going to hit something, it probably already would have.  The density of matter is much much higher near the galactic center than where it is now, and it only gets thinner the farther you go.

There is no known limit to the size of a star, but large stars tend to be very low density.  Mu Cephei is a red giant that's many times the size and mass of our Sun, but so diffuse as to be barely recognizable as a star at its outer atmosphere.  There is a limit to the mass a star can have and become a white dwarf though.  It's called the Chandrasekhar limit and is roughly 3.8 solar masses.  Stars bigger than this can explode as supernovae and collapse into black holes.

on a galactic scale is 1.5 million miles per hour actually that fast?

What is the speed in relation to? If our whole galaxy is moving through space at 1 million miles and hour and this star is moving at speed relative to our galaxy then depending on the direction it's going in it could be speeding along at 2.5m mph or having a stroll at only 500k mph.

Some outer parts of spiral galaxies must be moving at speeds similar to that to maintain their shape.

Ant

1.5 million mph is not all that fast.  It's only 0.22% light speed ©.  Still, it's moving right along.  Since the article doesn't say, I can only assume it's in relation to us on Earth.  And you're exactly right on your theory of galactic motion, though I'm not sure of the numbers, offhand.

I hope this adds something to the discussion.

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AndyMac

AndyMac

Posted
Posted

As always, appreciate your input Astroman.

I must admit that my thought was that once a star was ejected from our galaxy, it would continue to travel towards whatever galaxy next had the strongest gravitational pull on it (i.e. the star). Clearly this is not necessarily the case.

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Astroman

Astroman

Posted
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As always, appreciate your input Astroman.

I must admit that my thought was that once a star was ejected from our galaxy, it would continue to travel towards whatever galaxy next had the strongest gravitational pull on it (i.e. the star). Clearly this is not necessarily the case.

Did I say that? Sure, it'll keep going toward...whatever. But it'll most likely burn out before it reaches anything.

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