Star's rosette orbit around our supermassive black hole proves Einstein's Theory of General Relativity correct
- Reference: 1587104225
- News link: https://www.theregister.co.uk/2020/04/17/black_hole_star_einstein/
- Source link:
The international team of researchers known collectively as the GRAVITY collaboration painstakingly mapped the star's position with a variety of instruments at the European Space Observatory's (ESO) Very Large Telescope over 27 years.
"Einstein's General Relativity predicts that bound orbits of one object around another are not closed, as in Newtonian Gravity, but precess forwards in the plane of motion," [1]said Reinhard Genzel, first author of the study [2]published in Astronomy & Astrophysics, and Director at the Max Planck Institute for Extraterrestrial Physics, Germany.
The motion requires a little technical knowledge to understand. As the star – S2 – orbits the supermassive black hole – Sagittarius A* – it passes two points that brings it closest to the void, known as the periapsis, and farthest from it, known as the apoapsis. The [3]line that connects both the periapsis and the apoapsis slowly rotates over time as S2 moves through Sagittarius A*'s massive gravitational field, making its orbit rosette-shaped.
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"This famous effect – first seen in the orbit of the planet Mercury around the Sun – was the first evidence in favour of General Relativity. One hundred years later we have now detected the same effect in the motion of a star orbiting the compact radio source Sagittarius A* at the centre of the Milky Way," Genzel added.
Known as the Schwarzchild precession or the apsidal precession, the motion had never been detected with a star around a black hole before. Although numerous clusters of stars orbit Sagittarius A*, S2 stands out due to its tight orbit that brings it as closer than 20 billion kilometers from the black hole. As it nears its closest approach to the monstrous void, it travels at almost 3 per cent of the speed of light. The small orbit and fast motion means that S2 completes an orbit once every 16 years.
Sagittarius A* is located 26,000 light years away from the Sun, and is estimated to be four million solar masses. The measurements gathered from ESO's VLT don't just confirm Einstein's General Theory of Relativity, however, they will help the GRAVITY collaboration study dark matter and how supermassive black holes like Sagittarius A* evolve over time.
"Because the S2 measurements follow General Relativity so well, we can set stringent limits on how much invisible material, such as distributed dark matter or possible smaller black holes, is present around Sagittarius A*," said Guy Perrin and Karine Perraut, co-authors of the study and researchers from the Paris Observatory and the University of Grenoble, France. ®
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[1] https://www.eso.org/public/news/eso2006/
[2] https://www.aanda.org/articles/aa/full_html/2020/04/aa37813-20/aa37813-20.html
[3] https://en.wikipedia.org/wiki/Apsis
[4] https://www.theregister.co.uk/2020/04/02/medium_black_hole/
[5] https://go.theregister.co.uk/tl/1936/-8554/forrester-build-a-digital-experience-portfolio?td=wptl1936
Re: Theory?
My pet peeve as well. As they say, proof is for math and booze. Evidence is the word the author is looking for.
Re: Theory?
Generally agreed, but on the other (gripping?) hand, 'evidence' hasn't been well verbed yet, as a standalone. Of course, there are perfectly viable ways to recast the sentence.
Re: Theory?
The scientific meaning of the word "theory" differs from the generally accepted use of the word. Specifically, a scientific theory is reliable, rigorous and comprehensive (thanks Wiki!) which means it can be accepted as proven through mathematical rigour and consensus within the community. Physical proof is just another element of that rigour. The more general use of the word is analogous with the scientific use of the word "hypothesis". So Einstein's Hypothesis of General Relativity would require proving, through one of a few different ways, be it mathematical or observational, before it could be accepted (amongst the scientific community at least) as a Theory.
Re: Theory?
There is no proof of a theory, or law, in science, merely evidence that fits predictions which fail to disprove the theory, which in turn bolsters it. Theories and laws are simply the best fit for the available evidence that we have at this given moment and are always open to be disproven or improved upon.
For example Newton's Law of gravitation is an approximation (i.e. limited in scope and accuracy) of Einstein's general relativity which itself is almost definitely an approximation of some yet to be discovered unified theory of everything.
Re: Theory?
After more then one hundred years, and many successful experiments and evidences found, it's probably time to call it the Law of General Relativity, yes... but probably people are too used to its original name.
One of the problem is anybody accepts an apple falls (although they usually miss the other essential part - the Apple attracts the Earth too....) - Relativity describes phenomena most people aren't used to - so it looks much more like a theory than a law.
Re: Theory?
> Apple attracts the Earth too....
I know, right? In happier times I've seen almost half of it queuing outside the store for the latest iBling.
Re: Theory?
This is the original meaning of the words "proof" and "prove", meaning "test".
Still used with this meaning when referring to proof-mark, proving guns, and proving ground.
If something passes a specific test or tests, it has been proven.
Proven has never meant that something is true, only that it has passed the tests.
Spirograph
Who remembers playing with a Spirograph?
Re: Spirograph
God?
Re: Spirograph
No, s/he just plays dice. (and the occasional very good hand of poker)
Spanish Train & Other Stories
And far away in some recess
The Lord and the Devil are now playing chess
The Devil still cheats and wins more souls
And as for the Lord, well, he's just doing his best
Re: Spirograph
Most gods roll dice, but Fate plays chess, and you don't find out until too late that he's been using two queens all along.
But then there's The Lady, and she has Rincewind.
Is it just me?
Or does everyone else go off vainly hunting for a footnote every time they see mention of Sagittarius A* ?
(* - not a footnote marker)
Re: Is it just me?
I feel your pain
Re: hunting for a footnote
For myself, I just wonder why it's the complex conjugate of Sagittarius A.
And no doubt there are theorists working on quantum black holes who attempt to describe Sagittarius A^{\dagger}.
Re: Is it just me?
I don't understand the use of the marker either. It's not a star, it's a black hole.
Re: Is it just me?
Don't, whatever you do, follow this link.
https://xkcd.com/859/
Re: Is it just me?
It's a pointer.
A rosette round a black hole
Whats not to like?
really fast
"The small orbit and fast motion means that S2 completes an orbit once every 16 years."
Ouch, so the star around the black hole has more or less periods of rotations the same as normally planets around stars ???
If there are any planet around S2, anyone in there should really feel some acceleration !
Re: really fast
If I recall correctly what I've read, the environment at the center of the galaxy is so full of dangerous radiation that life has virtually no chance of existing on any planet in there, unless there is a really thick atmosphere.
Even then, the concentration of stars (and some large ones) means lots of gamma rays, and those guys don't care about atmosphere.
So no, I don't think that there's anything feeling the acceleration. However, I imagine how mind-blowing it is to think of so much mass gaining so much acceleration. If I could understand the equation for inertia and comprehend the result, my head would probably explode.
Wow
3 percent of the speed of light! Holy shit. That must look awesome from up close*
If we ever want unlimited free energy, we really need to harness gravity - it just doesn't seem to run out, certainly not on the scale that we can use it.
Our current technology is still -->
*Say, 6 trillion miles, with suitable radiation shields
Re: Wow
If we ever want unlimited free energy, we really need to harness gravity
No, it doesn't work like that. The only way to harness gravity is things like Hydroelectric where gravity is used to get the potential energy out.
Getting energy directly from gravity is the same as getting energy from a stationary permanent magnet; perpetual motion and the universe does not allow that.
However (in physics there's always a "however") should we ever work out how to do anti-gravity then all bets are off.
Re: Wow
Tidal lagoon hydro-electricity is using gravity. When you hold back the tide, the moon experiences that little bit more drag, and orbits a tiny fraction more slowly and further out.
Re: Wow
What do you think hydro-electric is?
Re: Wow
Hydro-electric is a steam engine powered by the Sun. Sun warms ocean, creates water vapour which then descends as rain and is used to exert pressure on the blades of a turbine. Gravity is just part of the means of transmission.
Proven genius
I'm sure that Einstein himself would insist on his work still being called a theory, not a law, for all the reasons so clearly and concisely outlined above. That said, I wonder how many other theories have had so many data collected which all say if not, "he was right", then very loudly say "he was not wrong". Given the difference between what is known now and what was known when he formulated his theories, the fact that "proves Relativity" type headlines (however imprecise/inaccurate) continue to be written is an impressive legacy and a testament to his genius.
Theory?
Um, if this *proves* Einstein’s theory of General Relativity, shouldn’t we call it a law?
Or not call it a proof.