EPTAstrophysics blog - Black hole things! - Page 2
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Teoita
Italy12248 Posts
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FFGenerations
7088 Posts
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Teoita
Italy12248 Posts
On July 03 2016 03:04 FFGenerations wrote: sorry i was talking about photos of galaxies in general lol. galaxies are all discs instead of spheres. i thought maybe its coz pictures are easier to understand in a cross section. but i googled it and they said gravity shit makes spheres turn into circles Depends on the kind of galaxy (i wrote about this a bit in my first blog). Elliptical galaxies like M87 are ellipsoids or spheres; the orbits of stars they contain do not have a preferential direction because the total angular momentum of the system is close to null. Spiral galaxies like the Milky Way or M31 have a preferred direction of rotation because to the total angular momentum is greater than zero, so the orbits of stars and gas flatten and the system resembles a disk. | ||
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FFGenerations
7088 Posts
lifepod moon alien/s oblivion approaching the unknown notably i enjoy the aspects of vastness and solitude lol so i like other movies like the quiet earth and eve online where you do nothing but sit in your ship | ||
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Startyr
Scotland188 Posts
Do Elliptical galaxies with almost no angular momentum still have a supermassive black hole at their core and if so is it simply not massive enough to pull enough stars into the kind of orbits of a spiral galaxy? On another note Previously there was a theoretical limit to how massive stars could be, based on the various forces involved in star formation this limit was 150 solar masses. Several years ago a star of up to 300 solar masses was found. http://www.eso.org/public/news/eso1030/ The star would either have to be born that massive breaking the previously thought maximum or several smaller stars collided and merged together. If we use that example for black holes, lets say there has been a highlander-esque story of 'there can only be one' playing out for as long as our universe has existed whereby when black holes meet each other, they merge or one consumes the mass of the other to become supermassive. This could speak to the origins of our universe, if there were clusters of stars where several of them collapsed into black holes which then merged together to form a supermassive black hole whose mass pulled all of the other nearby stars into orbit around themselves which led to the galaxies we know today. The andromeda galaxy is on a collision course with our milky way, what happens if two supermassive black holes collide with one another. As more and more black holes are formed they start to pull all of the galaxies of stars together and all of the black holes are destined to do battle with one another until only one remains which will have consumed the entire universe. This would be followed by the last one standing itself eventually collapsing to ignite the birth of a new universe once again in an endless cycle. Maybe it will be different this time round.. This is mostly speculation on my part, forgive me, I can not help wandering off into science fiction. Also for an astrophysics related game I would recommend universe sandbox 2 | ||
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Teoita
Italy12248 Posts
On July 03 2016 20:31 FFGenerations wrote: do u enjoy space movies like... lifepod moon alien/s oblivion approaching the unknown notably i enjoy the aspects of vastness and solitude lol so i like other movies like the quiet earth and eve online where you do nothing but sit in your ship I guess so yeah, depending on the amount of scientific inaccuracies they contain. I liked Interstellar and fucking hated Gravity for example. My personal favourite is Apollo 13. On July 03 2016 20:50 Startyr wrote: Congratulations on the masters, even more so for the full marks. Do Elliptical galaxies with almost no angular momentum still have a supermassive black hole at their core and if so is it simply not massive enough to pull enough stars into the kind of orbits of a spiral galaxy? Yes, ellipticals actually have the heaviest black holes and tend to host more and more powerful AGN. The black hole's gravitational sphere of influence, where the orbits are dominated by its gravity rather than the gravity of all the stars in the galaxy, is roughly a few parsecs (one parsec is about three light years). For comparison, a fairly large galaxy can have a radius of ~20 kiloparsecs, which is way way more. Either way, the black hole is not capable of changing the stars' angular momentum so they all rotate in the same direction (which is what happens in spirals). As long as you aren't resonably close to a black hole's event horizon (which as i showed is a very, very small radius), objects close to a black hole simply orbit around it, just like the planets in the solar system orbit around the sun. On another note Previously there was a theoretical limit to how massive stars could be, based on the various forces involved in star formation this limit was 150 solar masses. Several years ago a star of up to 300 solar masses was found. http://www.eso.org/public/news/eso1030/ The star would either have to be born that massive breaking the previously thought maximum or several smaller stars collided and merged together. If we use that example for black holes, lets say there has been a highlander-esque story of 'there can only be one' playing out for as long as our universe has existed whereby when black holes meet each other, they merge or one consumes the mass of the other to become supermassive. This could speak to the origins of our universe, if there were clusters of stars where several of them collapsed into black holes which then merged together to form a supermassive black hole whose mass pulled all of the other nearby stars into orbit around themselves which led to the galaxies we know today. The andromeda galaxy is on a collision course with our milky way, what happens if two supermassive black holes collide with one another. As more and more black holes are formed they start to pull all of the galaxies of stars together and all of the black holes are destined to do battle with one another until only one remains which will have consumed the entire universe. This would be followed by the last one standing itself eventually collapsing to ignite the birth of a new universe once again in an endless cycle. Maybe it will be different this time round.. This is mostly speculation on my part, forgive me, I can not help wandering off into science fiction. Also for an astrophysics related game I would recommend universe sandbox 2 When their host galaxies meet, the two supermassive black holes eventually merge into one bigger black hole, although this hasn't been observed directly for supermassive black holes. LIGO observed stellar mass black holes merging, so we do know it's a process that happens in nature, but the dynamics of the merger aren't entirely clear yet. The final mass of the black hole post merger is a bit less than the sum of the original masses, as part of it is emitted as gravitational waves. That said, 1) gravity isn't the only thing regulating the evolution of the entire Universe, which is actually expanding quickly enough that gravity can't pull everything together and 2) it is extremely, extremely unlikely for any individual star in a galaxy to be unlucky enough to be caught close enough for a black hole to devour it. If this happens with a stellar mass black hole, part of the gas of the star can fall onto it and create an X-ray binary. If this happens with a supermassive black hole, an extremely unlikely event called tidal disruption (TDE, tidal disruption event) can happen. In this case, the star is ripped apart by the black hole's gravity and most of its gas is accreted within a few months. A few dozen of these have been observed; we estimate a TDE happens once every million years or so per supermassive black hole, which makes them really really rare. | ||
c3rberUs
Japan11776 Posts
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thePunGun
598 Posts
 The idea, that you could travel through time if you were able to get close enough and escape is fascinating! I really love Hawkins theory, that they could even be a portal to another universe, unfortunately we will probably never know for sure. T.T | ||
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endy
Switzerland8970 Posts
As gas is accreted, it needs to dissipate its energy in some way, otherwise its orbit will never approach the Schwarzchild radius Could you explain this better please? I don't see the relation between dissipated energy and orbit. | ||
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Teoita
Italy12248 Posts
On July 04 2016 07:16 endy wrote: I love astrophysics, I should have followed your path! Could you explain this better please? I don't see the relation between dissipated energy and orbit. Sure, i'll try not to use equations. An object orbiting around anything, either a black hole, star or planet, has a given gravitational binding energy, which is what keeps the object on a stable orbit rather than falling onto whatever it is orbiting around. In order for the orbiting object to get closer and closer to the black hole/star/planet at the center, some this binding energy needs to be dissipated and turned into something else. In the case of a typical accretion disk, that something else is electromagnetic energy, ie light. On July 03 2016 22:40 c3rberUs wrote: Is it bad that I understood all the words except for the equations? I always have fun reading theoretical and astrophysics (especially black holes and quantum particles) so major thanks teo! Np, glad this blog is well received! | ||
micronesia
United States24799 Posts
edit: I think I'm incorrectly thinking of binding energy as potential energy, when in fact the binding energy is already taking kinetic energy into account. | ||
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Silvana
3713 Posts
I always liked astrophysics. When I was a child I found a book about the Solar System on my grandpa's library, and became a fan of space related things since then, reading whatever I could find about the subject (unfortunately no internet for me then). Idk if that was the cause, but from my primary school days until my teens I had this recurrent nightmare about our Earth falling into a black hole... The first times I woke up really scared but with time I ended up learning to love my dreams (I dream crazy things all the time), and I particularly thought that the black hole dream was among the coolest I had :D Idk why I choose Computer Science over Physics when I entered the Uni, sometimes I regret the decision when I read about these things and I am not able to understand them :/ | ||
lichter
1001 YEARS KESPAJAIL22272 Posts
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Teoita
Italy12248 Posts
On July 04 2016 08:50 micronesia wrote: edit: I think I'm incorrectly thinking of binding energy as potential energy, when in fact the binding energy is already taking kinetic energy into account. Yeah pretty much. That said, saying that gravitational energy is converted into radiation is a huge oversimplification that is mostly only useful to broadly understand what's going on. The actual equations for the dynamics of an accretion disk are really complex, and to be honest i can't for the life of me understand some of their solutions. On July 04 2016 17:11 lichter wrote: teo ur a black hole no u | ||
TheEmulator
28103 Posts
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endy
Switzerland8970 Posts
On July 04 2016 07:40 Teoita wrote: Sure, i'll try not to use equations. An object orbiting around anything, either a black hole, star or planet, has a given gravitational binding energy, which is what keeps the object on a stable orbit rather than falling onto whatever it is orbiting around. In order for the orbiting object to get closer and closer to the black hole/star/planet at the center, some this binding energy needs to be dissipated and turned into something else. In the case of a typical accretion disk, that something else is electromagnetic energy, ie light. Np, glad this blog is well received! Thanks! | ||
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lossboss
4 Posts
Most people believe: A) infinity is not actually a number B) infinity is not even a terminal point of a sequence or series C) infinity is not a legitimate upper bound D) asia E) quantum physics is scary F) delete '2' G) there is a larger possible quantity than infinity like the integral of infinity from x to y don't you get creative these guys were just lazy. ![[image loading]](http://i.imgur.com/HdNsxO4.jpg) only zapdos, and only zapdos can innervate the universe at a universal level. if only zapdos is unable to do this alone then he will succeed with the help of physics. feel no anxiety. fear no evil gentle peasants. | ||
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Impervious
Canada4222 Posts
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a_flayer
Netherlands2826 Posts
On July 01 2016 09:03 Impervious wrote: This is pretty fascinating stuff. Is there any "light" reading you would recommend for people wanting to learn more about it? Reminds me of this: | ||
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Teoita
Italy12248 Posts
On July 05 2016 10:10 Impervious wrote: I know there aren't any solid theories on where those supermassive black holes came from, but of the theories that are out there, what are your favourites/which do you think are more likely? The main idea is that in the early universe, the black hole "seeds" that eventually became supermassive black holes through a bunch of mechanisms have between a few hundreds and a few tends of thousands the mass of the Sun; this could happen either if a huge cloud of gas collapses on itself, or if somehow the very first stars to be formed are immensly massive (10^4-10^6 times the mass of the Sun), which is actually sort of allowed by the equations of stellar structure in particular conditions. I don't really have a favourite one or one i think is more likely, and i haven't studied them much. They all haven't produced enough testable predictions yet, because these objects are all too far and too faint to be observed with current or next generation instruments. | ||
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