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."
Maybe they're not stars.... (Score:1)
Maybe they're motherships :D
Re:Maybe they're not stars.... (Score:4, Funny)
What's pulling/pushing the stars ? (Score:1, Troll)
Maybe those starts just didn't like the neighbourhood they were in and decided to move house
TFA only says that the stars are travelling at a speed high enough that they can escape the pull of the galaxy, but doesn't give any explanation of WHAT is pushing or pulling the stars.
From TFA:
"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"
If it's the "supermassive black hole in the Galaxy core" that's doing the pulling, the stars should have travelling towards the core.
But they are travelling instead away from the core !
Instead of a "pull", it is as if there's something that's "PUSHING" them instead, and I do not think it's the supermassive blackhol
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: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.
Re: (Score:2)
That's right, you can do that, but we don't have an origin for the universe, so we keep setting our origin points for some arbitrary point, like the centre of Sol or the centre of the Milky Way galaxy. Which is another way of saying it's a relative reference point.
Re: (Score:2)
They travel towards it on a trajectory that takes them close to, but not lethally close to, the black hole. They gain so much velocity that they continue out never to return again. If ISON (the comet) had not burned up, the sun would have done the same thing to it.
It's the same general idea as the gravity assist maneuvers that are usually required to send probes to the outer solar system in a reasonable time frame.
Re: (Score:2)
Close, but no cigar.
You need three bodies to interact : a massive central body ("primary") and two "light" (relatively small, but not zero mass) "secondary" objects. All three orbit around their mutual barycentre ("centre of gravity", but it moves as the positions of the three objects change in relation to each other) and the two
Re: (Score:2)
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: (Score:3)
"1,000 kilometers per second (2,236.936 miles per hour)"
Either kilometers are a lot shorter than I remember, or you got your periods and commas mixed up somewhere.
Re: (Score:3)
Should have been all commas. Doh.
At least for those of us on this side of the pond.
Re: (Score:2)
Well, for some of you on whichever side of whichever Pond you're on.
Re:Maybe they're not stars.... (Score:4, Insightful)
Now if you find an inhabitable planet orbiting one of these stars let me know. That would be the mothership of all motherships.
Or really bad luck. Leaving the galactic plane would pretty much assure your species would never branch out beyond your own solar system.
Re: (Score:2)
Maybe they already did that.
Like the GP suggested: Motherships.
What better space ship can you conceive of than traveling with an entire solar system?
Who knows how many worlds they might have seeded.
Some seem to be passing by our neighborhood. Mom? Where are you going?
Re: (Score:3)
yea, but they are headed in the wrong direction, and are moving REALLY slow. If we saw stars moving around at a few percent the speed of light, then maybe. But a million miles per hour? That's 0.0014% the speed of light. Our closest neighbor is 25.8 trillion miles away. So it would take them nearly 3 thousand years just to get there. Not much of a mother ship.
Re: (Score:2)
Who says that 70 years is the maximum average lifespan for sentient beings? We may be abnormally short-lived, and 3000 years might not be an unreasonable time for an explorer to spend on an epic voyage. Yeah, not really applicable here, but it's an objection that I always hear as to why interstellar flight is impossible.
Re: (Score:2)
We may be abnormally short-lived, and 3000 years might not be an unreasonable time for an explorer to spend on an epic voyage
Yep, just ask the Dwellers. (Iain Banks)
Re: (Score:2)
My point is, if they have the power to move a star, they sure as hell have a faster/better way to get where they're going without the star.
Re: (Score:1)
Why not carry around with you a significant power source, that will last potentially billions of years? Sure there could be better or faster ways, but I'd think the star itself would be a precious asset while going out of galaxy!
Re: (Score:2)
Re: (Score:1)
Well... Stars are fusion power plants
Re: (Score:2)
You need a "statistics grammar" filter before posting. I can work out what you probably mean, but what you've typed is incoherent.
Re: (Score:2)
yea, but they are headed in the wrong direction, and are moving REALLY slow. If we saw stars moving around at a few percent the speed of light, then maybe. But a million miles per hour? That's 0.0014% the speed of light. Our closest neighbor is 25.8 trillion miles away. So it would take them nearly 3 thousand years just to get there. Not much of a mother ship.
3000 years wouldn't be much of a journey if you are taking your planet with you. For instance if we knew our sun was going
to die in 5000 years and we wanted to relocate our planet to a new sun and we didn't want to be cramped in small spaceships
or abandon our home then moving our solar system to a new solar system and then "swapping suns" would seem like a reasonable
option assuming we had the capability of doing it. It also eliminates the need of having to find a suitable planet to teraform.
Re: (Score:3)
Re: (Score:2)
Or really bad luck. Leaving the galactic plane would pretty much assure your species would never branch out beyond your own solar system.
But the view of the Milky Way would be gorgeous!
Re:Maybe they're not stars.... (Score:5, Funny)
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.
Re: (Score:2, Informative)
Those are cool lyrics.. did you write that yourself?
Don't be an Apple...
- Galaxy Song Lyrics by Monty Python
Re: (Score:2)
Catchy tune - we used to square dance to it :-)
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:Maybe they're not stars.... (Score:4, Interesting)
They are likely wandering stars from another galaxy. Wasn't it estimated that we already had one galaxy pass through the Milky Way and sometime in the future we may pass through Andromeda?
So perhaps there are three mechanisms for high speed stars;
1) ejected by a super massive black hole.
2) remnant of non-colliding stars from Galactic collisions (and actually, most stars don't hit each other in these situations).
3) L3 advanced civilization finding that solar tourism is more fun if you can take all your stuff with you.
3-body chaotic gravity assist (Score:5, Insightful)
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 [prescientmodels.com] (PDF, 10 pages) using this mechanism. It was written by Josef L Breeden and presented at the 100 Year Starship conference.
Re: (Score:2)
For a sun-like star, that's around a diameter per hour.
Hardly speedy.
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: (Score:2)
All it would take is galaxies spinning at different angles passing each other to spit off a few stars from the fringe edge.
Isn't it known whether galaxies are close enough for that to be a factor? TFA doesn't say "and it's right next to the closest galaxy, so that's probably the reason." Furthermore, galaxies are mostly empty space, so it seems like how individual stars would interact to spin each other out would still be an interesting observation problem.
Re: (Score:2)
Re: (Score:2)
In general, far as I can tell, galaxies don't really 'pass' each other. Big ones gobble up small ones as the Milky Way has undoubtedly done to many dwarf galaxies in the area. Big ones merge with other big ones, as we shall do with Andromeda in a couple of billion years. Those interactions will definitely send some stars hurtling through intergalactic space, but we won't have a disk galaxy after that. Sadly more of an amorphous blob.
I'm not prepared to argue that point, although I've seen some reference in passing to galaxies passing right through other galaxies [al.com].
But I'm not sure it matters, because any interaction between galaxies, might leave remnants of one traveling at odd angles
and speeds within the other. I write code for a living, and therefore, I'm totally guessing here.
Re: (Score:2)
Re: (Score:2)
Oh, I also found some info about random non-galaxy stars that theoretically might be "picked up" by a galaxy.
http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question29.html [nasa.gov]
http://www.astronomycafe.net/qadir/q2486.html [astronomycafe.net]
Re:Maybe they're not stars.... (Score:5, Funny)
(If you don't know what I'm talking about, look up author Larry Niven.)
Re: (Score:2)
It was reminding me of the Fast Protosun. Of course, there's a big gap between 10^6 mph and 0.8c. Not to mention a number of other likely differences (not least because they would be spoilers).
OMG! Marshall Applewhite! (Score:2)
Friederich Pohl was right all along... (Score:3)
This is obviously 'Wan-to' up to his old tricks again.
Re: (Score:3)
Re: (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.
The Puppeteers Are Leaving! (Score:1)
They've spotted the explosion! Get in your General Products Hull and run for it! Our only salvation will be to find the Ringworld and move it out of the galaxy!
Re: (Score:3)
Moving the Ringworld is not the problem, getting the star to go along with it might be though.
Re: (Score:2)
Assuming ... (Score:5, Interesting)
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.
Re: (Score:3)
Beat me to the hypothesis. Just because a star is in the milky way doesn't mean that it was formed there. It may just be passing by, with its doors locked and hoping to look inconspicuous because it's got a similar composition as the local hot hooligans (how likely is that? that's not specified in TFS)
Re: (Score:2)
Except that if the star was captured by the Milky Way, that already tells you that it was moving at less than the escape velocity, while these are moving faster than the escape velocity.
Still, it would be interesting to see if they share orbital elements with known satellites or streams...
[TMB]
Re: (Score:1)
TFA says that those stars appear to have the same composition as normal disk stars, so they cannot come from dwarf galaxies.
Also, traversing the disk at 'hypervelocity' takes definitely less than 400 million years. Mind that our Sun takes just half that go around the disk at about half its diameter and at a regular velocity.
Re: (Score:2)
slingsot (Score:1)
Re: (Score:3)
Maybe two super-massive black holes passed close to each other and spun these off?
Perhaps. But now instead of explaining why one common star is moving somewhere fast you need to explain why two uncommon black holes are moving somewhere fast, and on top of that why they nearly hit each other and some common star...
Not the only supermassive black hole... (Score:4, Interesting)
Re: (Score:2)
It's possible, I suppose. The Andromeda galaxy is the closest large neighbor to the Milky Way, and it is 2.5 million light years away. At "more than a million miles per hour" (0.0015 c) a star would take only one or two billion years to make the trip across the intergalactic void... a long journey, to be sure, but doable within a stellar lifetime. However, because our galaxy occupies less than 1% of the sky as seen from Andromeda, the odds of randomly flung stars hitting our galaxy from that distance awa
Alien physics experiments (Score:2)
This makes me think more about the word "Speed" (Score:4, Interesting)
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: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: (Score:2)
But why is the background radiation ALREADY Doppler shifted? In other words; our solar system and galaxy are moving at a high rate of speed already -- so there should already be a Doppler effect.
So is there a "relativistic lens" of the space we are in that normalizes the shift we see?
I get that we see a Doppler shift if we quickly moving in a given vector -- I'm just curious why we don't see more effects from the vectors we are already moving in. It suggests that space is a "thing" and in many cases, it is
Re: (Score:2)
It is already Doppler shifted, and the GP either knows too well what he's talking about and simplified it into something unrecognizable, or simply has no idea at all.
In theory, you can calculate a "universal" rest frame from the background radiation if the Universe is planar enough. I have no idea if this is actualy the case.
Re: (Score:2)
IIUC, it doesn't really seem to be planar enough. Perhaps, though, the "axis of evil" is some systematic error.
Re: (Score:2)
And as a second tough, it would also be a quite local "universal" referential. Probably bigger than a galaxy, but not an overall constant.
Re: (Score:1)
Yes, it is already doppler shifted because we are moving relative to it. That is why you see a large dipole in images of the background radiation (google: CMB dipole). It has been removed in many images to show the absolute values.
I am not sure what you mean by "relativistic lens" and "current". Something like a wrap drive we local areas of space carry stuff around? While there are such solutions of general relativity, that is not how our universe looks. It is described by a FLTW metric, which means that it
Re: (Score:3)
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.
Re:This makes me think more about the word "Speed" (Score:5, Interesting)
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.
Re: (Score:3)
Re: (Score:3)
Re: (Score:1)
Re:This makes me think more about the word "Speed" (Score:4, Funny)
Re: (Score:2, Informative)
There are plenty of stars in the galaxy that would make our star look like a rock next to jupiter.
Re: (Score:2)
Re: (Score:2)
Why should their gender be relevant?
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: (Score:2)
I'm sure there have been some tests, but has anyone conclusively found a "vector" to space? Currently, we use Universal Background Radiation -- allegedly this is the noise left over from the poorly named "Big Bang".
The problem of Relativity is that either their is a universal time or all time is local -- and each object has a relative time displacement to each other. In the simple model of relativity, you have an observer, or someone leaves a planet at high speed and comes back and their clocks have account
Re: (Score:2)
There is no universal time or space frame of reference; there are merely frames of reference that are convenient to use. For some purposes, using the CMB is quite handy.
In the rocket experiment, the difference in experienced time beween rocket and Earth has nothing to do with any absolute reference frame, but rather that the rocket changes reference frames and Earth doesn't. This is experienced as acceleration. For purposes of Special Relativity, if you feel no acceleration you're staying in the same
Re: (Score:1)
Re:This makes me think more about the word "Speed" (Score:4, Informative)
Re: (Score:2)
I think it theory you can use the fact that c is constant to prove your absolute speed. Imagine you send a single photon down both ends of a tube and measure where they meet. You know both photons have travelled at the same speed and so covered the same distance. Imagine your ship travels at 0.5c and the tube is 100cm, in the time it takes the photons to cover 50cm each your ship will have moved 25cm so they actually meet at 75/25cm not 50/50cm as you'd expect. Get a perfect 50/50cm in three axis and you wi
Re: (Score:2)
You're actually fairly close to the Michelson-Morley experiment there, although they were measuring speeds at right angles. The answer is that, given no acceleration, the photons will meet in the middle no matter how the ship moves relative to anything. The failure of Michelson and Morley to find any difference in observed speeds was considered very odd at the time, and led to relativity.
The speed of light in vacuum is the same under all conditions. Once you accept this, and ditch concepts like "at th
I guess (Score:3, Funny)
Astronomers get a clue (Score:1)
Miles per Hour and Inferiority Complexes (Score:1)
Ah -- all those sorry imperia that are reminded of when their deficient units of measurement find
their only shelter in planetary travel and galactic theories.
Is the galaxy Anglosaxon? No, all rejoice -- it is not.
We know what this is. (Score:1)
Puppeteer planets escaping.
Next assignment (Score:3)
It's obvious (Score:3)
These stars were ejected by the polar vortex.
Could just be gravitational sling-shotting... (Score:1)
I'd think an N-body problem with 300 billion stars would almost inevitably produce a few stars that just by chance get a sufficient number of gravitational slingshots from other stars that they get up to escape velocity...
Those aren't stars... (Score:2)
Somebody stop them! (Score:4, Funny)
Re: (Score:2)
I stand for the freedom of those stars to choose a neighborhood.
Questions for people that could do the math (Score:1)
What would happen if one of these beasts passed near the Solar system. For "near" consider the following scenarios: 1. Oort cloud. 2. Kuiper belt (I don't recall which one is closer and I'm too lazy to google it). 3. Just outside the orbit of Neptune. 4. Collision with Jupiter. 5. A passage inside the orbit of Mercury, no planetary collision or collision with Sol.
Finally, assuming none of these scenarios killed us by disruption the relationship between the Earth and Sun or flinging large bodies a
Paul Glister blogged about this today (Score:2)
His take [centauri-dreams.org] on such matters is generally well informed and interesting.
How it would feel living in that solar system? (Score:2)
I wonder how it would have felt for humanity if Earth happened to orbit such a star, and we knew that every moment we were going farther and farther from the galaxy.
I'm no astrophysicist, but (Score:2)
If they really wanted to know how these particular stars got boosted without going through the galactic center,
Re:There goes the Big Bang Theory (Score:5, Funny)
I never believed in it, anyway.
You probably don't believe in Monk, Night Court, or All In the Family either.
Re: (Score:2)