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A Black Hole Threw a Star Out of the Milky Way Galaxy
- neonate 7y agohttp://archive.is/6KYjo http://archive.is/6KYjo
- deleted 7y ago[deleted]
- RandomInteger4 7y agoYeet
- greglindahl 7y agoThe headline ("A Black Hole Threw a Star Out of the Milky Way Galaxy") isn't very accurate. The black hole in question is the super-massive black hole in the middle of our galaxy, and like most galaxies, there's only one of them. The article does go on to explain that, which is great, but it would be nice if the headline writer hadn't dropped that essential fact.
- Simon_says 7y agoWhat’s not accurate? When I read “a black hole”, I don’t assume we’re talking about Sagittarius A*, just a black hole.
- greglindahl 7y ago... that's exactly what's inaccurate. It's not just some ordinary black hole, it's the unique one in the Milky Way galaxy.
- Simon_says 7y agoI also don’t read it as not Sagittarius A*. I wouldn’t even expect a lay audience to know that name.
- deleted 7y ago[deleted]
- StuffedParrot 7y ago...all definite articles can also be indefinite. The title is absolutely correct.
- shele 7y agoRemind me when you "see a sun rising in the morning" next time. Using an indefinite article here is noticed by the reader and will pose the question "Oh, is there one more?". In language rules are sometimes not as absolute as "all definite articles can also be indefinite".
- afiori 7y agoThis is not a proper comparison, as the relevant property is not of something being the only member of a category, but of being the already mentioned one. For the sun we suppose the person speaking knows of THE Sun. For the supermassive black hole at the center of the galaxy we don't. This can be easily shown as "The Black Hole Threw a Star Out of the Milky Way Galaxy" is clearly misusing the definite article.
- ncallaway 7y ago"The Black Hole at the Center of the Milky Way Threw a Star Out of the Galaxy" would probably be an alternate way to write the headline using the definite article. Agree that _just_ an article swap leaves the headline worse off.
- vehementi 7y agoSo when you say "not very accurate" you're refering solely to how it's not specifying that it's our black hole? As in, the headline is perfectly accurate except it should say "the black hole" instead of "a black hole", and that moves it to "not very accurate" for you?
- remcob 7y agoBut we are talking about Sagittarius A*.
- mberning 7y agoThat ended abruptly. And on a bit of a grim tone. How many college students leave home and never return, not even once. Oh well, at least it wasn’t written in the New Yorker where it would have required a 10k word “slice of life” preamble before even discussing the star. “Dr. Li always enjoyed feeding pigs on the weekend...” As for the star, I wonder what type of relativistic effect a person orbiting it might experience. I assume 4 million miles per hour is an appreciable fraction of C.
- minblaster 7y agoIt's less than 1% of c unfortunately [1111 miles per second]. (https://www.google.com/search?q=4m+mph+in+miles+per+second https://www.google.com/search?q=4m+mph+in+miles+per+second)
- mirimir 7y agoIt's 0.6% c.
- simonh 7y agoWow, that’s actually really moving! I wonder how close the star got to being shredded in the process. The gravitational forces must have been pretty powerful.
- gsaga 7y agoIt's just freefalling. So there won't be any significant forces on it unless it gets very close.
- simonh 7y agoWell that's the questions really isn't it, how close did it have to get and what was the gravity gradient? Too close and tidal forces would strip off the star's upper layers, or tear the whole star apart. We detected that happening not long ago. https://www.sciencealert.com/we-ve-just-caught-the-immediate-aftermath-of-a-black-hole-tearing-apart-a-star https://www.sciencealert.com/we-ve-just-caught-the-immediate...
- zzzeek 7y agowhen they say "it's currently 29000 light years away from earth", doesn't that mean that was its position 29000 years ago ?
- deleted 7y ago[deleted]
- chubbyrabbit 7y agoYes. However, it's like pointing at the sun and say "That's not the sun, the sun was there 8 minutes ago".
- likeliv 7y agoSince the sun isn't turning around the earth, I believe the sun is still where you point at.
- manigandham 7y agoTechnically the Sun is moving as part of the arms of the Milky Way galaxy, which itself is moving through space on a collision course with Andromeda, so where you point at will be off.
- afiori 7y agoThis would be unnecessarily pedantic but not wrong* if not that the heart rotates on itself, so you are pointing at a 8 minutes old direction. *All these discussion make no sense at all, as neither synchronous remote events nor the concept of what rotates around what are meaningful. This is not to say that we should not have this conversation, but to say that you are being pedantic without bringing anything to the table.
- gdubs 7y agoI’m listening to Carlo Rovelli’s book, “Reality is not what it seems”, and I’m still hung up on the concept of the “extended now”. The way he describes it, everything being relativistic, there’s no such thing as an “objective” point of view. So, if I understand his take on your example, we’re not seeing the sun as it was 8 minutes ago. It simply takes 8 minutes for the sun’s “now” to reach us.
- wruza 7y ago>the seriously blinding speed of four million miles an hour That’s ~600km/s. The Sun's orbital speed around the Galaxy: ~200 km/s. Distance from BH to “suburbans”: 400ly or 3.8x10^15km. Time to escape: 200k years.
- Tepix 7y agoAccording to the paper it's moving at 1700km/s (see also: https://www.wolframalpha.com/input/?i=4+million+miles+per+hour https://www.wolframalpha.com/input/?i=4+million+miles+per+ho... ). I prefer "20.4 light seconds per hour" :-) It's also 0.56% the speed of light. The escape velocity of the Milky Way is 500km/s.
- wruza 7y agoI divided by 1.8 instead of multiplying by 1.6 and messed it all up. Got it only now, thanks for the correction!
- jcims 7y ago(Edit: To get an idea what this would look like if you were to watch this star moving across the sky like a comet) The sun's apparent diameter in the sky is roughly a half a degree. Over the course of an hour, it will move approximately 15 degrees across the sky, or rougly 30 apparent diameters. The actual diameter of the sun is ~860,000 miles, making the 'apparent velocity' of the sun across the sky nearly 26 million miles per hour or ~6 times faster than this beast. I mention that to apply wet socks to any notion of a bullet star flinging across the sky like tracers at the Knob Creek night shoot. It's fast yet, but at that scale, doesn't look it. (for the uninitiated - https://www.youtube.com/watch?v=h11uEvGc7u8 https://www.youtube.com/watch?v=h11uEvGc7u8 )
- fractaled 7y agoA web search says your approach (which I admit I don't follow) is off by a factor of 40 -- the Sun moves approximately 500k mph around the galactic center. A speed 8x slower than the star mentioned in the article.
- nickparker 7y agoThe GP is talking about the sun’s apparent speed in Earth’s sky, which is dominated by Earth’s rotation. Another way of stating it: The sun is 1 AU distant and appears to revolve around Earth once a day from our perspective so it has apparent speed of 6.28 AU / day or 2.4 million mph. Their point is that unless this star was very close to us it wouldn’t appear to move quickly across the sky, because the sun has similar apparent velocity and looks stationary to our eyes.
- jcims 7y agoyep!
- SamBam 7y ago"Quick" being relative to your expectations, of course. If OP is right, and it moves six times faster than the sun, then it would go from one side of the sky to the other in just three nights, right? That's extremely fast for any star gazer. Faster than any planet we can see. Someone who was familiar with the night sky and who could see this star would notice its speed quickly.
- biddlesby 7y agoDid the black hole impart any energy to the leaving star? It sounds more like there were two stars each under the other's influence and the black hole removed one star, freeing the other to go off on an adventure
- raducu 7y agoThe author said on /r/space that was the case -- this was a binary system with the stars orbiting very close to eachother.
- ars 7y agoHe was asking if the velocity was given by the black hole, or if it was already there from the binary star orbit. I can't figure out any way a black hole can give velocity (relative to the black hole) - any increase in velocity would be balanced by a decrease as the object leaves.
- phaedrus 7y agoNot velocity - momentum is what is conserved. So the black hole could have absorbed the equal and opposite momentum, but being more massive, not gained much velocity. Or, a hypothetical scenario in separating the two it could have flung them in opposite directions, in which case it would be net zero momentum. (But I don't know if - and kind of doubt whether - that is a possible outcome of a three-body interaction.)
- glaberficken 7y agorelevant: Factual explanation of the 3 body problem: https://en.wikipedia.org/wiki/Three-body_problem https://en.wikipedia.org/wiki/Three-body_problem And the 1st book of an (excellent) si-fi triology: https://en.wikipedia.org/wiki/The_Three-Body_Problem_(novel) https://en.wikipedia.org/wiki/The_Three-Body_Problem_(novel)
- Tepix 7y agoFascinating. I wonder if any planets survived this "flinging manoeuvre". This star is also covered in the latest episode #159 of the Interplanetary Podcast: https://www.interplanetary.org.uk/post/159-andrew-rader-beyond-the-known https://www.interplanetary.org.uk/post/159-andrew-rader-beyo...
- bloak 7y agoImagine being an astronomer in a society living on a planet orbiting an intergalactic star like that: no proper stars in the sky, just smudges of distant galaxies. It might be difficult to discover the "Copernican principle" in such circumstances.
- SiempreViernes 7y agoThere'll be plenty of quasars to act as stars, the big problem is they will be very hard pressed to measure any exosolar distances at all. This particular star is not that big too, so over its lifetime of 1Gyr it'll make it pretty far in the local group. For fictional purposes you could therefore imagine a solar system being sent from one galaxy into another one, that'll make for some interesting astronomical history!
- samanator 7y agoCheck out The World at the End of Time by Frederik Pohl. This is exactly what this is about!
- small_fish 7y agoAlso _Against a Dark Background_ by Iain M. Banks. It describes a very, very old civilization with no stars close enough to even think about interstellar travel.
- Analemma_ 7y ago> If we were in the center of the void, we would see no stars in the sky with the naked eye. According to astronomer Greg Aldering, the scale of the void is such that "If the Milky Way had been in the center of the Boötes void, we wouldn't have known there were other galaxies until the 1960s." Via https://en.wikipedia.org/wiki/Bo%C3%B6tes_void https://en.wikipedia.org/wiki/Bo%C3%B6tes_void. Pretty eerie to think about.
- notimetorelax 7y agoSorry for the offtopic post. I recently see a high number of posts linking to nytimes.com. Every time I'm not able to read the articles because they are paywalled. I'm accessing them from Europe, is the experience different from the US? Or is the majority of HN have NY Times subscription? As an alternative, I found an article by CCN: https://edition.cnn.com/2019/11/12/world/milky-way-black-hole-star-scn/index.html https://edition.cnn.com/2019/11/12/world/milky-way-black-hol...
- rch 7y agoSomeone here also usually posts a link to the actual research being reported on, e.g.: https://arxiv.org/abs/1907.11725 https://arxiv.org/abs/1907.11725
- skokage 7y agoIt's paywalled everywhere, not just for you. The easiest thing to do for almost any website that is paywalled is to just disable javascript through your browser: https://support.google.com/chrome/forum/AAAAP1KN0B0BYOQskiuGU0/?hl=en&gpf=%23!topic%2Fchrome%2FBYOQskiuGU0 https://support.google.com/chrome/forum/AAAAP1KN0B0BYOQskiuG...
- davesque 7y agoI've had pretty good success by disabling JavaScript.
- bildung 7y agoYou can block Javascript and cookies just for nytimes.com. Suddenly the site is fast, too!
- novaRom 7y agoThey introduced it like a year ago, so I stopped reading NYT since then.
- 300bps 7y agoI use Brave which is a fork of Chromium just like Chrome. Click Settings, Additional Settings, Privacy and Security, Site Settings, Javascript. Then under Block click Add and type www.nytimes.com as the URL and click Add. The site works fine for me then and is sooooo much faster to boot.
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- SiempreViernes 7y agoAs far as I can tell the big deal is they are completely sure it came from Str A*. It is also moving too fast to be easily explainable, but for now I would bet on this simply being a very extreme event. The set of hyper velocity stars is rather small at the moment, something like ~20 in total, so I don't think there is any reason to believe we have an unbiased sample. Amusingly they do use it to measure the position of the _sun_! Preprint at: https://arxiv.org/abs/1907.11725 https://arxiv.org/abs/1907.11725
- pfdietz 7y agoI believe some of the stars very near our galaxy's central black hole have been measured at ~3% of the speed of light, at periapsis. They are gravitationally bound, though, so their total energy (after subtracting out the gravitational potential energy) is less than this star.
- Izmaki 7y agoWhat a mean bully!
- croon 7y agos/ully/ouncer
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- samirillian 7y agoAnybody else think of Lovercraft when you read this? And wonder, but what if?? (it's actually some battle between elder gods)
- novaRom 7y agoLog in or create a free New York Times account to continue reading in private mode.