New Class of "Hypervelocity Stars" Discovered Escaping the Galaxy 150
Science_afficionado writes "Astronomers have discovered a surprising new class of 'hypervelocity stars' that are moving at more than a million miles per hour, fast enough to escape the gravitational grasp of the Milky Way galaxy. The 20 hyper stars are about the same size as the sun and, other than their extreme speed, have the same composition as the stars in the galactic disk. The big surprise is that they don't seem to come from the galaxy's center. The generally accepted mechanism for producing hypervelocity stars relies on the extreme gravitational field of the supermassive black hole that resides in the galaxy's core."
Re:Maybe they're not stars.... (Score:5, Informative)
A million miles per hour is not all that much.
All the galaxies in our neighborhood are also rushing at a speed of nearly 1,000 kilometers per second (2,236.936 miles per hour) towards a structure called the Great Attractor, a region of space roughly 150 million light-years away.
In addition, our solar system--Earth and all--whirls around the center of our galaxy at some 220 kilometers per second, or 490,000 miles per hour.
The earth is moving toward the Constellation Leo at the dizzying speed of 390 kilometers per second. (872,405 miles per hour).
Lots stuff going places fast.
Now if you find an inhabitable planet orbiting one of these stars let me know. That would be the mothership of all motherships.
Re:This makes me think more about the word "Speed" (Score:5, Informative)
If one considers the rest frame of the microwave background as the rest frame of the universe, then yes, one can answer these questions.
http://en.wikipedia.org/wiki/Cosmic_microwave_background [wikipedia.org]
Re:it's not the star that is moving it's the space (Score:1, Informative)
space is not limited by the speed of light. What is the matter with you people?
Nothing is limited by the speed of light. The galactic constant is a phenomenon, not a limiting force.
Re:This makes me think more about the word "Speed" (Score:2, Informative)
There are plenty of stars in the galaxy that would make our star look like a rock next to jupiter.
Re:This makes me think more about the word "Speed" (Score:4, Informative)
'Relative' is the key. There is no fixed background to say 'This is going absolutely this fast', any observation point in any kind of motion is as viable as any other. It just falls out of a little bit of simple vector maths - so no, your question is not answerable, as it's malformed.
Re:This makes me think more about the word "Speed" (Score:5, Informative)
Due to the Doppler effect, you see the frequency shift if you move relative to the microwave background, which would otherwise be (almost) the same blackbody radiation of temperature 2.725 K from all direction.
Re:interesting (Score:5, Informative)
Nah, I'm not speculating on where they got their energy at all.
Just pointing out that "million miles per hour" is not unusual in this universe, and therefore escape velocity is not that hard to achieve.
All it would take is galaxies spinning at different angles passing each other to spit off a few stars from the fringe edge. In fact the edge is probably ragged precisely because stars are occasionally spun off, like the outside skater roller derby.
Re:Maybe they're not stars.... (Score:2, Informative)
Those are cool lyrics.. did you write that yourself?
Don't be an Apple...
- Galaxy Song Lyrics by Monty Python
Re:Maybe they're not stars.... (Score:5, Informative)
A million miles per hour is not all that much.
All the galaxies in our neighborhood are also rushing at a speed of nearly 1,000 kilometers per second (2,236.936 miles per hour) towards a structure called the Great Attractor, a region of space roughly 150 million light-years away.
I think they're calling them fast based on the relative speed to the galaxy that they're being ejected from / passing though.
The diagram in TFA seems to indicate that these stars are not originating inside the galaxy, which to me raises the question, from whence do they come?
This image [vanderbilt.edu] makes it appear the stars are mostly passing through the disk of the galaxy. I may be reading too much into the length of the coloured lines though.
Re:What's pulling/pushing the stars ? (Score:5, Informative)
Due to inertia, the stars would continue to travel at their current speeds if nothing were pushing and pulling on them. As it is, whatever gravitational forces are acting upon them at the moment might be comparatively insignificant to their current inertia.
So how did they get their current inertia? They might have gotten it from the supermassive black hole at the galaxy's core without setting their vector towards the core. They could do so possibly using a gravity slingshot effect [discovery.com]. So it is surprising they're not coming from the core, as the article states. So what is interesting about these stars is they don't seem to be explained by the slingshot effect.
Further, gravity is a force of attraction and so does no pushing.
Also, I did a knapkin calculation of the speeds involved and it would be 1/700th the speed of light except the article says that this speed is relative to the movement of the galaxy and not an absolute speed like the slashdot summary intimates.
Re:This makes me think more about the word "Speed" (Score:4, Informative)
Re:What's pulling/pushing the stars ? (Score:4, Informative)
There is no such thing as "absolute speed"; all movement is relative to other objects in the universe.