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New Class of "Hypervelocity Stars" Discovered Escaping the Galaxy
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."
Assuming the observation gets studied and confirmed, this is probably far more common than one might initially expect.
The Milky Way has been on the move billions of years and occasionally meets up with star clusters or even dwarf galaxies.
Many of them probably settle in gravitationally, but some of them aren't going to and continue, largely, about their merry way if the relative speeds are right.
These stars could have been "acquired" 400 million years ago and it can take a long time to traverse a cross-segment of the Milky Way. And these stars would have to be smaller like our sun to have the right lifespan, and we wouldn't notice the really small ones (red dwarfs and such) because they would be hard to see so there is also a mix of observational factors in the equation.
Priest: "Universe from nothing, no laws of physics, sped up time"+ huge discrepancies. Creationism? No. Big Bang Theory
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.
Sig Battery depleted. Reverting to safe mode.
Looking at the trajectories, wouldn't it be a possibility that these stars didn't originate in our galaxy, but rather, could have been tourists flung out in a similar fashion from another supermassive black hole outside of our own galaxy? Just passing through on various trajectories, from potentially various other galaxies. Not much thought put into this - maybe the distance from the nearest supermassive black hole outside of our own galaxy makes this an impossibility, but seems the article doesn't go into any theories at all.
It's not the Puppeteer Homefleet, they aren't flying in formation.
(If you don't know what I'm talking about, look up author Larry Niven.)
I never believed in it, anyway.
You probably don't believe in Monk, Night Court, or All In the Family either.
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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
You're missing the point. These are stars moving at at abnormal speeds and can't be explained by any phenomenon we have observed before.
Every gravity simulation I've ever run has had a few objects flung off at high speed. It doesn't take a lot.
When our name is on the back of your car, we're behind you all the way!
Everybody sing!
Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour,
That's orbiting at nineteen miles a second, so it's reckoned,
A sun that is the source of all our power.
The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour,
Of the galaxy we call the 'Milky Way'.
Our galaxy itself contains a hundred billion stars.
It's a hundred thousand light years side to side.
It bulges in the middle, sixteen thousand light years thick,
But out by us, it's just three thousand light years wide.
We're thirty thousand light years from galactic central point.
We go 'round every two hundred million years,
And our galaxy is only one of millions of billions
In this amazing and expanding universe.
The universe itself keeps on expanding and expanding
In all of the directions it can whizz
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute, and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger all down here on Earth.
When our name is on the back of your car, we're behind you all the way!
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.
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.
Sig Battery depleted. Reverting to safe mode.
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 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.
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. 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.
One of the theories for the origin of these hypervelocity stars is 3-body chaotic gravity assist. When two bodies are entering a gravity assist trajectory around a third, very massive body, their interactions sometimes add up in such a way that one body falls into a tight orbit, and another is ejected at a hypervelocity. Given the number of ternary star systems in the galaxy, this looks like a plausible explanation.
There is even a paper suggesting we could build an interstellar starship from two asteroids (PDF, 10 pages) using this mechanism. It was written by Josef L Breeden and presented at the 100 Year Starship conference.
There is no such thing as "absolute speed"; all movement is relative to other objects in the universe.