Timeline for Does the Milky Way orbit around anything?
Current License: CC BY-SA 4.0
22 events
| when toggle format | what | by | license | comment | |
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| Oct 21 at 16:44 | comment | added | Florin Andrei | @WBT "the Milky Way and any other galaxy orbit [...] around the center of mass of all the galaxies in the universe" No such thing, so no. | |
| Sep 30 at 6:49 | comment | added | PM 2Ring | Here's an update to my first comment in this thread. The Solar System barycentre (SSB) is usually outside of the Sun. That is, over the long term, the mean distance from the centre of the Sun to the SSB is greater than the Sun's radius of 695,700 km. See astronomy.stackexchange.com/a/44903/16685 for details and various diagrams. | |
| Sep 30 at 6:45 | comment | added | PM 2Ring | @WBT No, it does not. | |
| Jul 8, 2019 at 18:50 | comment | added | WBT | This answer suggests, but does not explicitly state, that the Milky Way and any other galaxy orbit (perhaps as part of a group or supergroup) around the center of mass of all the galaxies in the universe. | |
| Jul 5, 2019 at 0:28 | comment | added | Chappo Hasn't Forgotten | @FlorinAndrei given the vast majority of Local Group galaxies are simply satellites of the 2 large spirals (ours and Andromeda), at a simplistic level one would expect the 2 large galaxies to orbit around their common barycentre, similar to binary stars - but instead, the 2 spirals are on a collision course. Is this because the evolution of galaxies is fundamentally different from the evolution of binary stars? I'm thinking (much handwaving): stars form out of swirling molecular clouds with angular momentum, but galaxies independently "condense" around lumpy distributions of dark matter? | |
| Jul 4, 2019 at 13:13 | comment | added | N. Virgo | From this simulation of the Milky Way-Andromeda collision, I would guess that the two objects are moving slowly enough relative to each other that they would orbit if they didn't collide. It certainly looks like the Triangulum galaxy ends up in an orbit around the new galaxy that forms during the collision. | |
| Jul 4, 2019 at 13:11 | comment | added | N. Virgo | Hmm. I interpreted the question differently. You seem to be answering the question of "is every object in the Milky Way orbiting around an object in the centre of the Milky Way?", whereas I read the question as "is the Milky Way itself orbiting around the centre of mass of some larger object, in the same way that the Earth-Moon system orbits around the barycentre of the Solar system?" That's actually quite an interesting question, because it depends on the scale at which the expansion of the universe takes over from local gravitational interactions. | |
| Jul 4, 2019 at 9:42 | comment | added | AnoE | So it's basically the ratio of mass to distance that's too small here, @FlorinAndrei? Would be nice if you added that to the answer, it would round it up nicely. | |
| Jul 4, 2019 at 9:13 | comment | added | Florin Andrei | @AnoE Put simply - it's literally too loose, not compact enough; it would be bound gravitationally if its components were located closer together. As to its origin, I do not know the answer. | |
| Jul 4, 2019 at 8:19 | comment | added | AnoE |
Great answer, however However, the Virgo Supercluster is more "loose" - it is not gravitationally bound together. is like a hard TV series cliff-hanger. Why is it not bound? Why does it stick together anyway (does it in fact stick together, or is everything just there coincidentally?
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| Jul 4, 2019 at 0:02 | comment | added | Barmar | @Mazura I think much of the large-scale structure of the universe is remnants of fluctuations in matter/energy density in the nascent universe, which then turned into these clusters when the universe expanded. | |
| Jul 3, 2019 at 15:47 | comment | added | Mazura | If the Virgo Supercluster isn't gravitationally bound together, then why is it where it is? I'd tried to answer with 'dark [stuff]' but failed miserably.... isn't there something about that stuff being a scaffold for the distribution of matter in the universe? | |
| Jul 3, 2019 at 14:24 | comment | added | PM 2Ring | @Mast Saittarius A*, the black hole at the centre of the Milky Way, has a mass close to 4 million solar masses, which can be calculated from the orbits of the stars that are close to it. But that's only about 0.25% of the mass of the whole galaxy. | |
| Jul 3, 2019 at 14:03 | comment | added | chepner | @PM2Ring Thanks, happy to be corrected. | |
| Jul 3, 2019 at 10:11 | comment | added | Mast | "There is no super-heavy thing at the center" Is that something we know (measured) or do we simply have no reason to assume there is? | |
| Jul 3, 2019 at 8:53 | comment | added | dotancohen | @PM2Ring: I believe that the diagram linked is the inferred barycenter, not the measured barycenter. Discovering e.g. a large planet at 80+ AU may alter that diagram. | |
| Jul 3, 2019 at 7:54 | comment | added | Ferrybig | One of the best examples of the orbit around center of mass that I found online is labs.minutelabs.io/Chaotic-Planets | |
| Jul 3, 2019 at 6:16 | vote | accept | Zeeshan Ahmad Khalil | ||
| Jul 3, 2019 at 0:19 | comment | added | PM 2Ring | @chepner Wikipedia has diagrams of the solar system barycentre relative to the Sun here, for 1945-1995 and 2000-2050. It's hard to tell from those diagrams, but I think the barycentre is outside of the Sun at least 50% of the time. It's been outside since mid 2016 and will remain so until early 2027. | |
| Jul 2, 2019 at 23:34 | comment | added | chepner | It's probably worth pointing out that the barycenter of the solar system, due to the usual mass distribution of the planets and everything else, is typically inside the sun. | |
| Jul 2, 2019 at 18:55 | history | edited | Florin Andrei | CC BY-SA 4.0 |
added 15 characters in body
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| Jul 2, 2019 at 18:47 | history | answered | Florin Andrei | CC BY-SA 4.0 |
