ESO Finds Star's Orbit Around Black Hole Confirms Einstein's General Relativity (eso.org) 46
puddingebola shares a report from ESO: Observations made with ESO's Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way moves just as predicted by Einstein's general theory of relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton's theory of gravity. This long-sought-after result was made possible by increasingly precise measurements over nearly 30 years, which have enabled scientists to unlock the mysteries of the behemoth lurking at the heart of our galaxy.
Located 26,000 light-years from the Sun, Sagittarius A* and the dense cluster of stars around it provide a unique laboratory for testing physics in an otherwise unexplored and extreme regime of gravity. One of these stars, S2, sweeps in towards the supermassive black hole to a closest distance less than 20 billion kilometers (one hundred and twenty times the distance between the Sun and Earth), making it one of the closest stars ever found in orbit around the massive giant. [...] Most stars and planets have a non-circular orbit and therefore move closer to and further away from the object they are rotating around. S2's orbit precesses, meaning that the location of its closest point to the supermassive black hole changes with each turn, such that the next orbit is rotated with regard to the previous one, creating a rosette shape. General Relativity provides a precise prediction of how much its orbit changes and the latest measurements from this research exactly match the theory. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole.
Located 26,000 light-years from the Sun, Sagittarius A* and the dense cluster of stars around it provide a unique laboratory for testing physics in an otherwise unexplored and extreme regime of gravity. One of these stars, S2, sweeps in towards the supermassive black hole to a closest distance less than 20 billion kilometers (one hundred and twenty times the distance between the Sun and Earth), making it one of the closest stars ever found in orbit around the massive giant. [...] Most stars and planets have a non-circular orbit and therefore move closer to and further away from the object they are rotating around. S2's orbit precesses, meaning that the location of its closest point to the supermassive black hole changes with each turn, such that the next orbit is rotated with regard to the previous one, creating a rosette shape. General Relativity provides a precise prediction of how much its orbit changes and the latest measurements from this research exactly match the theory. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole.
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This occurrence of confirmation of GR is a byproduct of observing Sagittarius A* and its surroundings.
Why is this news? Because it's science. (Score:5, Insightful)
Re:Why is this news?
Because confirmation by observation is what science is all about.
If you don't understand that, you shouldn't be reading a site called "news for nerds".
It seems unlikely that General Relativity would fail in this particular regime, when it's been verified at lower mass ( like: the sun) and lower gravitational fields... but testing it in a higher mass and stronger field regime is still worthwhile.
Confirmed ~100 years ago! (Score:2)
Because confirmation by observation is what science is all about.
True, but this particular effect was observed in the precession of Mercury [wikipedia.org] and explaining this observation was one of the first successful tests of General Relativity. So, since this precise effect was confirmed about ~100 years ago it's still a valid question to ask why this is news.
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First, the magnitude of the curvature of spacetime, and velocity of the orbiting object aren't remotely in the same vicinity as Mercury and Sol.
Second, Sag. A* is very far away.
This confirms that the law holds both far away, and in very different energy regimes.
It's expected, of course- but confirmation is good.
Re: Why is this news? (Score:4, Funny)
Name checks out.
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Re:Why is this news? (Score:4, Insightful)
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It is news because we know that somewhere in physics, general relativity does not hold. It isn't compatible with quantum mechanics.
More specifically, we know that somewhere in physics, general relativity or quantum mechanics doesn't hold (or at least, needs to be modified).
Basically, general relativity is a theory of massive objects (that becomes indistinguishable from Newtonian mechanics for low mass objects), and quantum mechanics is a theory of small objects (that becomes indistinguishable from Newtonian mechanics for large objects), but there's no theory that covers small, massive objects.
My bet is that we'll end up reinterpreting
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Not a fan of science I see. It matters how *well* the star confirms GR's validity. It isn't a yes or no question.
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What does that do to a star? (Score:2)
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At .3c, do you think it affects the shape of the star? Can it still be basically spherical, or does the black hole and spacetime bending velocity reshape it?
In the star's frame, it doesn't know it's moving.
The star does get subjected to tidal forces, however, which distort it from spherical.
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At [.03c], do you think it affects the shape of the star? Can it still be basically spherical, or does the black hole and spacetime bending velocity reshape it?
The SPEED doesn't do squat. That's the whole POINT of relativity, general or special. As viewed from its own coordinate system it's not going anywhere (but the surrounding light show and cosmic game of bumper-cars is fanTAStic).
The TIDES from orbiting that close to that big a black hole are another matter. But it's still far outside the roche limi
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If you're also asking about frame dragging - exactly what makes the orbit precess: That amounts to the coordinate system ("metric") rotating slightly with the black hole.
It also falls off with distance, so it also results in a tide. But it's smaller than the tide from the Newtonian approximation of gravitational orbital forces by a factor of trillions. The little bit of precession compared to the big ellipse of the orbit. (And the illustrations that make it look lik
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I was thinking that since there are enormous masses and velocities involved, to outside observers like us the space at the star's 'front' might appear compressed. But I am clearly not an astrophysicist.
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Sorry for the nitpicking, but muons travelling at 99% speed of light has been shown to have a longer decay rate than stationary muons due to time dilation. So, it is not the fastest object used to test relativity.
It is a fascinating confirmation though. The speed at periapsis is about 45x the speed of our sun around the galactic center which is impressive. It's like comparing a car at 80 km/h to the SR-71 blackbird at 3500 km/h. Since the kinetic energy increases as the square, the orbital energy is about 2
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GR tested [Re:Why is this news?] (Score:3)
Sorry for the nitpicking, but muons travelling at 99% speed of light has been shown to have a longer decay rate than stationary muons due to time dilation. So, it is not the fastest object used to test relativity.
But muon decay is a test of special relativity. Periapsis precession is a test of General relativity.
This is the fastest object that has been used to test General relativity.
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But aren't the muon decays a test of Special Relativity and the precessing of orbits a test of General Relativity?
Re: Why is this news? (Score:2)
Special Relativity is just a special case of General Relativity. Consequently anything that's a test of Special Relativity is also a test of General Relativity. The special bit is that it only considers frames of reference that are not accelerating. Of course in the real world frames of reference that are not accelerating basically don't exist but it makes the maths a *LOT* harder. So much harder it took Einstein another 10 years to forumlate General Relativity after coming up with Special Relativity.
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Newton's laws of motion were seen to be perfectly adequate for two centuries until Einstein showed that they were not good enough at high speed, etc. Who knows if/when it will be found that GR does not tell the full story.
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ESO (Score:5, Informative)
I must be the only one not knowing since it's not in TFS.
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Well, at least they did explain VLT. That's 50% success rate, above average for a slashdot post...
Re:ESO (Score:4, Funny)
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European Southern Observatory.
I must be the only one not knowing since it's not in TFS.
We can forgive you this time. It's been so long since Slashdot ran an actual tech story that pretty soon we're going to have to start also explaining what iPhone is.
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That's right, fucking EARTH orbits the Sun like a rosette, but the rate of precession is just very very small. It's why we have leap days.
No, we have leap days because the period of the Earth orbiting the Sun (colloquially called "1 year") is no multiplicative of the time it takes for the Earth to rotate around its axis until the same place on Earth is facing the Sun again (colloquially called "1 day"). On average, there are 365.242192 days in a year. As we don't want to remember new dates every year for fixed constellations of Sun and Earth like summer and winter solstice, or spring and autumn equinox, we have to add from time to time a day
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What really is an effect of the precission are the leap seconds introduced from time to time (but they are heavily disputed).
No, leap seconds are because the Earth's rotation isn't quite constant and an exact multiple of the current atomic-clock definition of the second (which originated from earlier measurements of Earth's rotation).
The Earth is slowing down (and the Moon's orbit slowly rising) due to tidal friction - both in the water and the magma and crust. It's a lot of energy dissipated per year - bu
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It's why we have leap days.
We have leap days because the **rotation** of Earth is not synchronized with its orbit, about ~365 1/4 times per orbit. Even that's not exact, which is why we skip leap years every time it lands on the change of the century (we didn't have a leap year in 2000, which was the second Y2K issue and which affected several mainframe databases). Earth is gradually slowing down as the moon moves further away because of tidal effects, but humans will be long gone by the time a year is exactly 365 days.
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we skip leap years every time it lands on the change of the century (we didn't have a leap year in 2000, which was the second Y2K issue and which affected several mainframe databases
Perhaps you were sleeping the whole day on February 29th 2000, having a nightmare about your database servers?
The rule is: every 4 years (except multiples of 100 (except multiples of 400)). Since 2000 is a multiple of 400, it was a leap year despite 2000 being a multiple of 100.
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Yep, that's right, I had forgotten all of the details, as apparently did the writers of the Empress database that ran on our VAX. They ended up changing that CPU on the VAX to 1972 and just changing all the forms since Empress was no longer supported.
"Confirms" (Score:1)
You keep saying that word. I do not think it means what you think it means. This is science, and that means being open to falsification.
Re:"Confirms" (Score:4, Interesting)
Confirms but does not prove (Score:2)
You keep saying that word.
Correct.
I do not think it means what you think it means.
Incorrect.
In this case, the observation confirms the prediction derived from the theory, to the extent the precision and correctness of the observation is able.
Exactly. This observation confirms the theory, but does not prove the theory. (Since other observations could be made of other things.)
Had the article said that the observation "proves" general relativity, the comment would have been on point and accurate, but it didn't, and it's not.
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You keep saying that word. I do not think it means what you think it means. This is science, and that means being open to falsification.
The word "confirmation" is used correctly here. The falsification principle is not a scientific principle, but a philosophical one, introduced by Karl Popper in 1934. However, philosophy of science did not start nor end with Popper. There are other criteria, including confirmation [utm.edu] and verification.
If a theory makes a correct prediction, then that is not a proof that the theory is correct, but it does increase the acceptance of the theory, in this case General Relativity. This is the correct use of confi
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Orbit of Mercury (Score:3)
It is the same orbital perhelion precession effect that puzzled scientists for a century or so, regarding Mercury's orbit.
To solve this, another planet closer to the Sun was proposed (Vulcan).
Only when Einstein's theory of general relativity came out that an explanation for that orbit was found.
Now, it is confirmed to happen far away in a different setting: a star orbiting our galaxy's blackhole.
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was i wrong?
I also confirm (Score:1)