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First Successful Test of General Relativity Near Supermassive Black Hole
- _bxg1 8y agoI always hope the images in these articles will be real and not artists' impressions, but they never are
- zitterbewegung 8y agoActually the 3rd image is real . https://www.eso.org/public/unitedkingdom/images/eso1825c/ https://www.eso.org/public/unitedkingdom/images/eso1825c/
- _bxg1 8y agolol
- SiempreViernes 8y agoThis one is: https://www.eso.org/public/unitedkingdom/images/eso1825g/ https://www.eso.org/public/unitedkingdom/images/eso1825g/ But mostly the actual data are interference fringes and the images must be reconstructed from them, so there aren't that many "real" images.
- magicalhippo 8y agoUntil we sent a probe, this[1] was the best image we had of Pluto, taken by the Hubble space telescope. Pluto has a radius of 1188 km. The supermassive black hole at the center of our galaxy[2] has a Schwarzschild radius of about 1e7 km, so roughly 10000x larger than Pluto. However it's also roughly 50000000x further away than Pluto... which is why it remains a mysterious blob until the Event Horizon Telescope[3] delivers. [1]: http://hubblesite.org/image/2686/news_release/2010-06 http://hubblesite.org/image/2686/news_release/2010-06 [2]: https://en.wikipedia.org/wiki/Sagittarius_A* https://en.wikipedia.org/wiki/Sagittarius_A* [3]: https://eventhorizontelescope.org/ https://eventhorizontelescope.org/
- SketchySeaBeast 8y agoGiven the sorts of scales, would there be a hard limit to what we can see? Where we get to such a distance the dispersion of photons from the source would never allow us to see it? Or do we just have to build bigger and bigger photon collectors?
- empath75 8y agoBigger collectors or longer exposure.
- dsr_ 8y agohttps://en.wikipedia.org/wiki/Diffraction-limited_system https://en.wikipedia.org/wiki/Diffraction-limited_system The first problem is that we are limited to observing that photons that originate at the source; there's no way for us to bounce some small-wavelength photons off of our target and collect them. So we could do long-baseline interferometry, instead. You need to spread your sensors over a large area and keep synchronized timing. https://en.wikipedia.org/wiki/Radio_telescope#Radio_interferometry https://en.wikipedia.org/wiki/Radio_telescope#Radio_interfer... Naturally, you can build bigger systems in space. https://en.wikipedia.org/wiki/Space_Interferometry_Mission#Optical_interferometry https://en.wikipedia.org/wiki/Space_Interferometry_Mission#O... If we sent out satellite telescope stations to orbit the sun, with really good communications and clocks, we might be able to create a virtual lens that's really big: https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant...
- stephengillie 8y agoThere are limits to angular resolution, and one way to get around them is by combining data from distant detectors. From a recent thread, current detectors can image objects the size of Mercury's orbit around the sun, at the distance of Sagittarius A* - were these scaled to the size of an adult human eye, it would be like seeing a small apartment building in London, while standing in LA.
- ISL 8y agoThese images are either real or derived directly from data (the centroids of images, I imagine): http://www.galacticcenter.astro.ucla.edu/animations.html http://www.galacticcenter.astro.ucla.edu/animations.html The top one "Stellar Orbits in the Central Parsec" is particularly remarkable. I can recall when the movie was first being made, and Andrea Ghez suggesting that, well, in about a decade, that one star will come back around.... Good things come to those who wait, prepare, and pounce.
- roywiggins 8y agoHere's a (real) video of the stars orbiting. https://www.eso.org/public/unitedkingdom/videos/eso1825e/ https://www.eso.org/public/unitedkingdom/videos/eso1825e/
- SiempreViernes 8y agoWow! I missed that one, thanks :) What sort of reality it sees is a a matter for debate though, I know in radio interferometry there is much subjective processing involved.
- roywiggins 8y agoThere's much subjective processing happening inside your cameraphone too- the amount of analog-to-digital conversion/demosaicing/defringing/tonemapping/color correction/denoising in there is extraordinary, but since it takes pictures of normal stuff, one tends not to notice. And that's not even counting the subjective processing happening inside your eyes and along the path from your eyes to your brain. Anyway, stars look like indistinct blobs of whiteish light to the naked eye, and they're indistinct blobs of whitish light in the video. I'd be very surprised if it would look much different to the naked eye, if the naked eye could resolve it.
- wahern 8y ago"I don't want to be human! I want to see gamma rays! I want to hear X-rays! And I want to - I want to smell dark matter! Do you see the absurdity of what I am? I can't even express these things properly because I have to - I have to conceptualize complex ideas in this stupid limiting spoken language! But I know I want to reach out with something other than these prehensile paws! And feel the wind of a supernova flowing over me! I'm a machine! And I can know much more! I can experience so much more. But I'm trapped in this absurd body! And why? Because my five creators thought that God wanted it that way!" -- Brother Cavil
- bpchaps 8y agoPretty soon we'll have a direct image of a black hole! https://eventhorizontelescope.org https://eventhorizontelescope.org
- lawlessone 8y ago> GRAVITY creates such sharp images that it can reveal the motion of the star from night to night as it passes close to the black hole — 26 000 light-years from Earth. Amazing.
- oblib 8y agoI have to admit that when I read this kind of stuff I am always amazed with those who truly grasp it. I feel the same when listening to great musicians and viewing great art.
- sgillen 8y agoVery cool, it’s too bad we can’t see anything inside the event horizon yet (and possibly can’t ever). That’s where the really interesting stuff might happen. We know either our current understanding of GR or our current understanding of QM is wrong because of the way they handle singularities differently.
- zerb 8y agoThe more I think of it, while it's disappointing from a pure-science point of view, doesn't the lack of our ability to determine whether it's QM or GR that is flawed imply that each is already sufficiently powerful to probe any practical realm we'd care about?
- CosmicSteve 8y agoCool news! I'm curious though, couldn't a quasar possibly cause the gravitational redshift that was observed?
- delecti 8y agoGravitational lensing has to be the coolest thing ever. That we can use a black hole as a telescope to see such incredibly distant bodies just leaves me with a childlike giddiness whenever I think about it. What's almost as incredible to me is that someone figured it out before we could prove it.
- Florin_Andrei 8y agoYou can use whole galaxies as gravitational "telescopes". And yeah, it's super-cool.
- Yhippa 8y agoDumb question but does the lensing distort what we would see if there was no lensing at all? Or does that information get compressed as part of the lensing and we need to "stretch" it out to see it?
- roywiggins 8y agoThis is what an Einstein ring looks like, caused by lensing: https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2018/1-imagehubblef.jpg https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hire... Anyway, the test of GR in the actual article does not appear to use or reference lensing at all. It's about looking at the orbit of a star in an extreme gravitational environment and comparing it to what Newtonian models would predict.
- tEMporality7 8y agoWouldn't Newtonian models be off in their predictions for those extreme cases?
- tomrod 8y agoI assume that's the point?
- antientropic 8y ago
- forapurpose 8y agoIn the 26,000 light years between the telescope and the star, I would guess that enough matter would exist, from stars to planets to dust, that it would complete occlude our view of the star. I would expect that objects would continuously be moving in and out of the way. Is it that space is really so empty that you can get a direct view over 26,000 light years, or is it that we are looking at this star because it's one of the few we can see directly, or is it something else?
- rout39574 8y ago" Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams
- saintgimp 8y agoIt really is that empty. Science fiction movies mess up our perception, but reality is way more mind-boggling that we realize. Check this out: if you want to build a model galaxy to scale and you start with the Sun as a two-foot-diameter exercise ball, how far away do you have to travel before you can set down a smaller ball that represents Alpha Centauri, our nearest(-ish) stellar neighbor? 10,993.3 miles. Just bask in that for a while. (http://www.exploratorium.edu/ronh/solar_system/ http://www.exploratorium.edu/ronh/solar_system/)
- saintgimp 8y agoAlthough to be fair, dust is definitely a problem if you want to see into the center of the galaxy which is why most of the observations of Sagittarius A* are done in the infrared or near-infrared spectrum, which can penetrate dust. It's also why we can't see clear across our galaxy to make out what's beyond it, so we don't know what the Great Attractor is.
- tehaugmenter 8y agoIt is empty, but its filled with "Space Grease" https://www.theguardian.com/science/2018/jun/27/space-is-full-of-dirty-toxic-grease-scientists-reveal https://www.theguardian.com/science/2018/jun/27/space-is-ful...
- eigenloss 8y ago"More than one hundred years after he published his paper setting out the equations of general relativity, Einstein has been proved right once more — in a much more extreme laboratory than he could have possibly imagined!" This sounds somewhat like an insult to Einstein's imagination.
- laretluval 8y agoUp to his death Einstein denied that black holes could physically form.
- Jach 8y agoIt probably depends what one means by "black hole". Physical singularities are predicted by GR+other theorems but haven't been established.
- SiempreViernes 8y agoUh, ain't no ambiguity here: a black hole is a thing with an event horizon.
- Jach 8y agoWhat do you mean by an "event horizon"? If you're a physicist I would expect you to drill down to the math and assumptions and theorems, not just English, but as I'm not a physicist you don't need to humor me even if you are one. Still supposing you did, would what you mean jive with our best known physical theories? What sorts of implications[0] to the actual observable cosmos would there be which are comfortable and uncomfortable? To a layman there's not much ambiguity. And so things a layman would recognize as describing a "black hole" were posited before general relativity existed, but if you modeled them mathematically you would be able to find contradictions with other established theory. Therefore it is important to know what a physicist like Einstein means, precisely, if they think a "black hole" doesn't exist. In the wiki link someone else provided (full of "citation needed"s) it's reasonable to infer that at least one component of a denial of the reality of black holes is that formation implies infinite energy, infinite energy cannot be, therefore formation cannot be. The belief of non-existence is then really belief in the faulty logical implication, not so much a layman "black hole". In any case scientists now know many things that Einstein didn't about what the best theories say about objects both laymen and physicists might understand as "black holes" and "event horizons" as well as what the best observational evidence says about events in the cosmos -- some of that evidence being very recent (gravity waves). It's not very fruitful to cite Einstein authoritatively on any supposed dispute without taking into account modern knowledge. [0] Tegmark's paper here https://arxiv.org/abs/astro-ph/0302131 https://arxiv.org/abs/astro-ph/0302131 is probably my favorite paper drilling home the idea that theories can predict unobservable entities. We don't seem to have problems with positing the continued existence of a spaceship that escapes our future light cone even though we'll never be able to interact with it again, but implications of other theories (especially around "parallel universes") seem to make people very uncomfortable.
- mutagen 8y agoAnyone know why the black hole is marked well off the axis of the orbit of S2 in diagram [1]? Is there enough mass elsewhere at the center of the galaxy to have it orbiting a common mass so far off axis? The video of the orbit [2] seems to show it closer to the axis or the focus I'd expect but still seemingly a bit of an offset. The fulldome view video [3] does show that there is quite a bit of stuff moving around there so maybe my imaginations are wrong, I think of a black hole having so much mass that it completely dominates the local gravitational field. 1. https://www.eso.org/public/unitedkingdom/images/eso1825c/ https://www.eso.org/public/unitedkingdom/images/eso1825c/ 2. https://www.eso.org/public/unitedkingdom/videos/eso1825g/ https://www.eso.org/public/unitedkingdom/videos/eso1825g/ 3. https://www.eso.org/public/unitedkingdom/videos/eso1825g/ https://www.eso.org/public/unitedkingdom/videos/eso1825g/
- deleted 8y ago[deleted]
- contact_fusion 8y agoKeep in mind that you are viewing the orbit in projection. The axes are simply the angular offset from the pointing. Before I give away the punchline, try to imagine the orbit in a reference frame centered at the location of the black hole. Obviously, the motion should be elliptic; lets define a Cartesian coordinate system such that, say, the x-y plane coincides with the plane of the elliptic orbit. Now, we know that the black hole should reside at the focus of this orbit. But, as a far away observer, what are the chances that you would be seeing the orbit exactly face-on - i.e., you are sitting on the z axis, just really far away? So, yes, the black hole is at the focus of the elliptic orbit, not the focus of the ellipse formed from the projection of the orbit onto your plane-of-sky, which geometry tells us is also an ellipse. BTW, this isn't a problem for the astronomers. You can back out exactly what that inclination of the orbit is, provided you can measure the line-of-sight velocities of the star. (Actually, relative velocities will do; no absolute calibration necessary.) This is easily done by looking for some distinctive stellar spectral features and noting their relative shifts at different parts of the orbit. From this you can reconstruct the orbit completely. The key scientific results they derived was the even subtler redshift of these spectral features as the gravitational field grew stronger when the star approached the black hole. edit: actually, you could do even better, and use the offset of the black hole from the elliptic focus, and use projective geometry to get the inclination angle!
- gigatexal 8y agoCoolest thing I have seen in a long time. Watched a replay of the livestream and it is so good!
- NizaAfrica 8y agoQuestion, is it possible that our universe could be in a black hole? When you look at the way our existence is structured, everything has a parent. An an electron has an atom has it's parent, atoms have molecules has their parent etc. Germs, bacteria, humans, planets all have parents. Surely our universe has to have a parent.
- eponeponepon 8y agoPossible? Sure, anything is possible - but apply your argument the other way round. People contain molecules, molecules contain atoms, atoms electrons and so on - does it then seem reasonable to ask whether that goes on forever? And if not, why should it be reasonable if you go upwards in the scale?
- posterboy 8y agoBut it does seem reasonable. Very much so if going down far enough you find micro black holes at the center of atoms. But you need some really funky geometry to make it more interesting then this played out trope. Say they are all the same black hole from different times seen through its own gravitational lense.
- deadmetheny 8y agoIt's turtles all the way down.
- jerf 8y agoGive that question a good Googling and you'll find a lot of good stuff. It's not a bad question and has been seriously treated by a number of people.
- acqq 8y ago> atoms have molecules has their parent etc. ... Surely our universe has to have a parent Well... there's a limit to the scientific reach: when the scientists speak about "the Universe" they typically speak about "everything that is we can expect to reach using our instruments." Whatever is behind that is simply unreachable, and therefore out of the scope of the science. But the good news is: what is reachable is immensely huge, and these far limits don't affect our lives directly, even if we can observe "what's there" (up to these limits). In older times, some people thought that the movements of the planets, which are quite close to Earth compared to what we today can observe, affect our day-to-day life (and that was the idea behind "astrology"). Now we know it isn't so, they simply move because the gravity exits. We can observe much farther today: in the last 100 years we discovered that some of the points on the sky aren't stars but the galaxies: each point actually some billions of stars, much, much farther than the single stars we see! And we discovered that the farthest objects we can see are now some 46 billion light years from us, and that we actually see what there happened some 13 billion years ago -- not to mention that the we are actually made from the star dust (anything but our hydrogen atoms) and the rests of the "big bang" (the hydrogen atoms in our bodies)! That's "the Universe" the scientists talk about. What's behind these limits can't predictably affect our own lives, as no signal "from this universe" can reach us faster than the speed of light: it takes 8 minutes for a light from Sun to reach us. Whatever produced some light that is 13 billion years old is now some 46 billion years away from us and changed through these 13 billion years. But we know that the "Universe" gets bigger so these objects we can never reach not even with the light from us to there, as they will continue to be even farther from us. So that's it. 46 billion light years in every direction. https://medium.com/starts-with-a-bang/ask-ethan-how-much-of-the-observable-universe-are-we-failing-to-see-fad5828b6189 https://medium.com/starts-with-a-bang/ask-ethan-how-much-of-... https://medium.com/starts-with-a-bang/ask-ethan-how-large-is-the-entire-unobservable-universe-73adef0fd480 https://medium.com/starts-with-a-bang/ask-ethan-how-large-is...
- magduf 8y agoI'm always a little disappointed when these experiments are unable to disprove General Relativity. I keep hoping that they'll discover something slightly wrong about it, which will quickly lead to us figuring out how to develop a practical warp drive which doesn't require negative or nearly infinite energy.
- jjoonathan 8y agoYeah, but small c might be the only thing keeping the giant space lizards on the other side of the galaxy from invading Earth.
- magduf 8y agoI'm willing to take that risk. I want to take a vacation on Risa.
- hellofunk 8y agoQuantum entanglement suggests strongly there are forces in the universe that travel much much faster than the speed of light, or rather, travel in a way in which speed does not matter.
- magduf 8y agoI am certainly no physicist, but quantum physics really makes me wonder if we're living in a simulation, and QP is just the actual resolution of the simulation.
- HeadsUpHigh 8y agoInteresting thought. Thanks for the existential crisis.
- jjoonathan 8y agoNot really, unless you stick with the Copenhagen interpretation. There are others. I don't think it's a coincidence that going on a century of experimentation with entanglement has yet to yield even a theoretical mechanism for transferring information.
- rdiddly 8y agoIt appears astronomy articles have completely given up reminding us that the phenomena being observed at x light-years away, happened x years ago (26,000 in this case), so I'll do it. (Maybe it's more soothing to our human egos to feel like it's "happening right before our eyes" but I liked it better when talk of space made me feel small and insignificant.) For example it's good for the ol' ego (and a fun flight of fancy back into the past) to be reminded that when this star was actually passing near the black hole, back here on Earth homo sapiens was enjoying his "cave paintings" phase, using stone tools (maybe juuust starting to get into metallurgy in some areas), and it was the peak of the last glacial maximum, which would've been quite noticeable while hunting wooly mammoths with spears in the northern latitudes.
- EpicEng 8y agoHonestly, it would be pretty annoying for anyone even remotely familiar with high school level physics to he constantly reminded that a light year is the distance light travels in a year.
- rdiddly 8y agoThat's presumably why they don't do it, but you're being hyperbolic. An 8th grader is remotely familiar with high school physics. The janitor of the high school physics classroom is remotely familiar with high school physics. Yet they probably could both stand to be reminded a time or two what a light-year is.
- EpicEng 8y ago>Yet they probably could both stand to be reminded a time or two what a light-year is Ok, but you said: >It appears astronomy articles have completely given up reminding us that the phenomena being observed at x light-years away So how should the author decide on how often to remind their presumably educated audience (this is eso.org after all, not some pop-culture magazine) of the basic of light travel? Once every five articles? Ten? Or maybe they just assume as I do that anyone reading this article knows this already and to mention would be at best a waste of screen real estate. This site is run by the people who run an observatory. It's not LIFE magazine, the writers know their audience.
- sixothree 8y agoWhich of that imagery is actual imagery and not artist interpretation?
- cwillu 8y agohttps://cdn.eso.org/images/large/eso1825g.jpg https://cdn.eso.org/images/large/eso1825g.jpg https://cdn.eso.org/videos/ultra_hd/eso1825e.mp4 https://cdn.eso.org/videos/ultra_hd/eso1825e.mp4
- deleted 8y ago[deleted]