11 ms·
A new Einstein cross is discovered
- Krokku 8y agoand it is not a kvasar, which is unusual
- cdelsolar 8y agowhat is a kvasar
- jbf1001 8y agoI had to look it up too, it's the German word for Quasar. https://en.wikipedia.org/wiki/Quasar https://en.wikipedia.org/wiki/Quasar.
- bhaak 8y agoThat's wrong, Quasar is also the German word for Quasar. But it looks like that the Scandinavian and the Slavic languages use the form "kvasar".
- oska 8y agoWiktionary is good for finding what languages a particular sequence of characters appears in. https://en.wiktionary.org/wiki/kvasar https://en.wiktionary.org/wiki/kvasar According to that entry, it appears in both Swedish and Czech (as an alternate spelling). Given the commenter's username is krokku and the fact that "krok ku" means "(a) step forward/towards" in Czech, I think we can assume that the commenter is Czech.
- bhaak 8y agoTwo entries are not that much. On Wikipedia you can look at the list of articles in other languages. Or go directly to Wikidata https://www.wikidata.org/wiki/Q83373 https://www.wikidata.org/wiki/Q83373
- oska 8y agoAh, interesting. So I see it also appears in Danish, Estonian and Norwegian. But with the additional clue from the username I'm still betting on Czech.
- coinerone 8y ago"Kvasar" is Czech i think.
- ableal 8y agoSometimes I go to google translate to hear words pronounced, e.g. https://translate.google.com/#view=home&op=translate&sl=de&tl=en&text=quelle%0A%0Aquasar%0A%0Aquantum https://translate.google.com/#view=home&op=translate&sl=de&t... (I hear "kvasar" and "cantoom" for quasar and quantum)
- dan_hawkins 8y agoIt's quasar - OP is probably not a native speaker.
- UI_at_80x24 8y agoI can guarantee that OP is infact a native speaker. English however might not be OP's native language. =)
- jamesrcole 8y agoBut given that the rest of the OP's comment was in English, it is natural to interpret the GPs comment as meaning "not a native speaker of the language they wrote the comment in (English)".
- twic 8y agoIt's a type of supermassive object formed in the early universe from the fermentation of rye bread.
- msla 8y ago> It's a type of supermassive object formed in the early universe from the fermentation of rye bread. Stop being kvazy!
- _verandaguy 8y agoAssuming you mean quasar here. It's unusual, but only because there's such a small set of Einstein Crosses -- it's not particularly significant that the lensed object is another galaxy.
- gmm1990 8y agoHow can the further Galaxy be 20 billion light years away?
- McKayDavis 8y agosee my comment here: https://news.ycombinator.com/item?id=19483785 https://news.ycombinator.com/item?id=19483785
- 6nf 8y agoThe universe began 13.8 billion years ago. However the universe is not expanding at the speed of light. It's expanding faster than that, such that the observable universe from earth's perspective is about 47 billion light years in radius.
- okket 8y agoLink to paper on arXiv: https://arxiv.org/pdf/1902.10964.pdf https://arxiv.org/pdf/1902.10964.pdf Abstract: https://arxiv.org/abs/1902.10964 https://arxiv.org/abs/1902.10964
- nvusuvu 8y agoWhy wouldn't it be a halo around the lensing galaxy instead of four distinct points?
- colanderman 8y ago"While gravitationally lensed light sources are often shaped into an Einstein ring, due to the elongated shape of the lensing galaxy and the quasar being off-centre, the images form a peculiar cross-shape instead." [1] [1] https://en.wikipedia.org/wiki/Einstein_Cross https://en.wikipedia.org/wiki/Einstein_Cross
- SiempreViernes 8y agoNot all lenses are good lenses, especially not the ones nature makes by accident. It also matters where the background source is relative the centre to the crappy lens, see third picture here for how the same basic shape can make different images of the same source: http://inspirehep.net/record/850223/plots# http://inspirehep.net/record/850223/plots#
- deleted 8y ago[deleted]
- ycombinateur 8y agoWhy does gravitational lensing produce four copies of the star and not a whole circle of copies? I would have expected the light to bend evenly around the intermediate star, giving a halo-like effect.
- colanderman 8y ago"While gravitationally lensed light sources are often shaped into an Einstein ring, due to the elongated shape of the lensing galaxy and the quasar being off-centre, the images form a peculiar cross-shape instead." [1] [1] https://en.wikipedia.org/wiki/Einstein_Cross https://en.wikipedia.org/wiki/Einstein_Cross
- lainga 8y agoI was also interested. It seems to be a combination of the intermediate galaxy being elliptical, and the star behind it being off-center from our point of view: https://physics.stackexchange.com/questions/14056/how-does-gravitational-lensing-account-for-einsteins-cross/14631#14631 https://physics.stackexchange.com/questions/14056/how-does-g...
- quakeguy 8y agoNot a Star behind it, but another galaxy!
- sampo 8y agoEinstein rings exist, too. A cross happens when the lensing object has a certain shape and orientation. https://en.wikipedia.org/wiki/Einstein_ring https://en.wikipedia.org/wiki/Einstein_ring https://en.wikipedia.org/wiki/Einstein_Cross https://en.wikipedia.org/wiki/Einstein_Cross
- btilly 8y agoPlease note that these are galaxies, not stars. While stars can do gravitational lensing, due to both the fact that we can see more galaxies, and they have larger mass, it is easier for it to happen with galaxies.
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- McKayDavis 8y agoWMAP measurements put the age of the universe at ~13.77 billion years, so I was initially perplexed by this part of the article: > The object acting as a lens turns out to be an elliptical galaxy located at a distance of approximately 7 billion light years (z = 0.556), while the source is at least 20 billion light years away (z = 3.03). ...but I found this explanation in the Wikipedia article on the most distant known galaxy (GN-z11), which is 32 billion light-years away [1]: > At first glance, the distance of 32 billion light-years (9.8 billion parsecs) might seem impossibly far away in a Universe that is only 13.8 billion (short scale) years old, where a light year is the distance light travels in a year, and where nothing can travel faster than the speed of light. However, because of the expansion of the universe, the distance of 13.4 billion light years traveled by light from GN-z11 to Earth, called the light-travel distance, has expanded to a distance of 32 billion light-years during the 13.4 billion years it took the light to reach us. [1] https://en.wikipedia.org/wiki/GN-z11#Notes https://en.wikipedia.org/wiki/GN-z11#Notes see also: [2] https://en.wikipedia.org/wiki/Expansion_of_the_universe#Measuring_distances_in_expanding_space https://en.wikipedia.org/wiki/Expansion_of_the_universe#Meas...
- teekert 8y agoThank you, went to the comments to learn this. So the universe actually expands pretty fast then! Faster than the speed of light? Strangely...
- jhoechtl 8y agoWhich makes it then effectivelly infinite?
- mirimir 8y agoIANAP, but I think so. I vaguely recall that early inflationary expansion was very fast. Like several times the speed of light.
- knappe 8y agoNo, not really. One theory is that eventually things will slow and then collapse again. https://en.wikipedia.org/wiki/Big_Crunch https://en.wikipedia.org/wiki/Big_Crunch Taken to the extreme, this expansion and collapse has been happening over and over again in a cyclical fashion. https://en.wikipedia.org/wiki/Cyclic_model https://en.wikipedia.org/wiki/Cyclic_model
- panarky 8y ago> This study, which has combined images from the Hubble Space Telescope with spectroscopic observations from the GTC, has confirmed the existence of a new example of a gravitational lens What is the "GTC"? The article doesn't say. It appears to be the Gran Telescopio Canarias. https://en.wikipedia.org/wiki/Gran_Telescopio_Canarias https://en.wikipedia.org/wiki/Gran_Telescopio_Canarias
- happy-go-lucky 8y agoThe article is provided by the Instituto de Astrofísica de Canarias and this institute operates the Roque de los Muchachos Observatory. One of the telescopes at the site is Gran Telescopio Canarias (GranTeCan or GTC). https://en.m.wikipedia.org/wiki/Roque_de_los_Muchachos_Observatory https://en.m.wikipedia.org/wiki/Roque_de_los_Muchachos_Obser...
- btilly 8y agoMy favorite thing about Einstein crosses is that the images do not appear at the same time. So a supernovae will appear at a different time in each image. See https://www.space.com/31418-hubbles-einstein-cross-supernova-strikes-back.html https://www.space.com/31418-hubbles-einstein-cross-supernova... for a case where we actually saw that.
- sandworm101 8y agoWhat is really odd is that we are alive to see both. At billions of light-years even a slight extension of the travel time, say a few hundred years, would exceed human perception and probably go unnoticed. For a short-lived object like a nova, we may only ever have one of the two images visible at any one time.
- btilly 8y agoIt may be surprising, but if you do the math, this is what we should expect. According to http://www.marmet.org/cosmology/einsteincross/ http://www.marmet.org/cosmology/einsteincross/, the distance between images is on the order of 1.6 arcseconds. That's a bit under 10^(-5) radians. The difference in time here is proportional to the difference in cosines of the angles taken. An cos is proportional to the square of the angle in radians. Which means we'd expect a time difference on the order of 10^(-10) of the total time taken. If the distant object is several billion light years away, we would therefore expect time gaps in arrival time that can be measured in no more than months.
- waynecochran 8y agoI don’t understand the geometry and why they occur at these four positions 90 degrees from each other?
- btilly 8y agoThere is a long explanation at https://physics.stackexchange.com/questions/14056/how-does-gravitational-lensing-account-for-einsteins-cross https://physics.stackexchange.com/questions/14056/how-does-g... that gives all of the details. Here is a simplified version. First you need to understand Fermat's principle. Light will follow a particular path from A to B when all nearby paths take approximately the same time as that one. Distant paths may be faster or shorter - consider a straight line vs a mirror. But if nearby paths are different lengths there is destructive interference and no light travels. Now suppose that we have a spiral galaxy between us and the distant source, but tipped on its side. And that galaxy is most of the way to us. From our view it is somewhat elliptical. There are five paths from there to here that meet the description of Fermat's principle. They are a straight line through that galaxy, a bent line to either side of the galaxy, and a bent line over the edges of the galaxy. At all other angles and directions, you don't meet Fermat's principle, and therefore light doesn't reach us that way. However the central image gets blocked out by the lensing galaxy. Therefore you only see the other four. Somewhat counterintuitively, the short side of the ellipse represents a greater gravity gradient, which bends the light more. Therefore those two images are farther apart and we don't get a perfect cross. Also the lensing object is never perfectly lined up. This will also affect the size and placement of the images. Plus the length of time that light takes to get here. Your understanding matches mine if you follow the following explanation. In the 2015 supernova, the lensing object was slightly off center. This meant that light that passed to the side of the lensing galaxy more or less straight to us had a fairly short route. Likewise light that passed by the long ends of the ellipse were bent less (because less gravitational gradient) so were also short. Therefore the light of the supernova came fairly close in time along those three routes. The fourth image, which went on the far side of the center of the lensing galaxy, bends the most and therefore had a longer route. Which is why it arrived with a significant delay from the other three.
- amelius 8y ago> With GTC it was possible to isolate and disperse the light of objects ABC, demonstrating that they belong to the same light source. That's pretty amazing.
- samstave 8y agoELI5: How can the universe be "infinitely big" yet have a measurable "finite age" and the velocity arc of the 'expanding' universe not be some known rate? Such that we can estimate the actual farthest distance. And WHAT THE HECK is the universe 'expanding into'? The answers to these questions make me dubious on tiny-human understanding of the nature of reality. Mechanical Elves, anyone?
- nwallin 8y agoThe entire universe is infinitely large, (we think) but the observable universe is finite, limited by the age of the universe, the speed of light, and the portion of the early universe when space was opaque. (which is what the cosmic microwave background, or CMB is) (note that terminology is confusing; when people use the word "universe" you have to determine base on context whether they're talking about the infinite entire universe, or the finite observable universe) Imagine an RTS game on an infinitely large map with fog of war. Sure, there's something out there beyond the fog of war, but we can't see it. (don't try to go too far with this analogy though) The universe isn't expanding into anything. It just is. This is the key to your misunderstanding I think; the universe isn't expanding through or into some other, extra-dimensional medium. The universe itself is expanding.
- mcguire 8y agoInfinitely large? My understanding was that the universe originated as a point, inflated a great deal, then began expanding at a rate that has changed over time. As a result, the universe would be significantly larger than the visible universe, but would have a finite size. (A finite size, but no boundaries. The universe is a sphere whose circumference is everywhere but whose center is nowhere. Cue Borges music.)
- rough-sea 8y agoIt’s a common misunderstanding of the Big Bang. There is not a point where the universe originated. Rather everything was just closer together. Imagine traveling back in time - you would see galaxies move closer and closer - until everything was super dense and hot - like the center of the sun but everywhere.
- deleted 8y ago[deleted]
- Causality1 8y agoWhy does the lense effect produce four separate images instead of a single image in the middle or a smeared ring all the way around the outside?
- sizzzzlerz 8y agoSpace is 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's, but that's just peanuts to space. 20 billion light-years! Truly mind-boggling.
- BenMorganIO 8y ago> in four separate images in the form of a cross, the light of another galaxy located 20,000 million light years away. So that's 20 billion light years away.... Interesting. I think something's wrong here given the universe is 13 billion years old.
- BenMorganIO 8y agoAh, see McKayDavis for the explanation.
- acct1771 8y agoUniverse is expanding faster than the speed of light? Convenient. Simulation.
- Grue3 8y ago>One of the most striking conclusions of Albert Einstein's theory of general relativity is that the trajectory of light curves in the presence of matter. A good example of "garden path sentence" [1]. "The trajectory of light curves in the presence of matter is what?". It took me a while to realize that curves is supposed to be a verb and not a noun. [1] https://en.wikipedia.org/wiki/Garden-path_sentence https://en.wikipedia.org/wiki/Garden-path_sentence