[HN Gopher] 2M MPH galaxy smash-up seen in unprecedented detail
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2M MPH galaxy smash-up seen in unprecedented detail
Author : wglb
Score : 60 points
Date : 2024-12-01 03:48 UTC (8 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| gnabgib wrote:
| Source paper: _WEAVE First Light Observations: Origin and
| Dynamics of the Shock Front in Stephan's Quintet_
| https://academic.oup.com/mnras/article/535/3/2269/7904663
| captn3m0 wrote:
| 2M mph ~= 0.5 AU/day
| InvaderFizz wrote:
| When put in that context, it seems rather slow.
| taberiand wrote:
| At solar system scale (and bigger), even light is slow.
| troyvit wrote:
| Even at our solar system's scale it can seem slow. Pluto gets
| to about 50AU from the sun, but the Oort cloud is between
| 2,000 and 5,000 AU from the sun. 24 1/2 days until something
| reaches earth vs almost seven years.
| ajross wrote:
| Earth orbits at 2pi AU/year by definition, so it's 29x faster
| than that. In fact it's not even possible for an object bound
| within the solar system to move that fast, as the radius of
| an orbit at that speed would (per the back of my envelope) be
| well inside the sun itself.
| euroderf wrote:
| 2M mph = 900 kps = three one-thousandths of light speed
| GuB-42 wrote:
| So, really fast, but not what we would consider relativistic.
|
| That's may be in the range of speed that is most unfamiliar to
| us. We get speeds up to orbital velocities, in the 10 km/s
| range, as these are the "fast" objects we know (rockets,
| meteorites, ...), and then we get to significant fractions of
| light speed, mostly in the context of communication. But what
| goes at 900 km/s in our day to day life? Is it a number we see
| anywhere besides colliding galaxies?
| perihelions wrote:
| Not really,
|
| https://en.wikipedia.org/wiki/Orders_of_magnitude_(speed)
|
| 440 km/s-- _" Typical speed of the stepped leader of
| lightning (cf. return stroke below).[31]"_
|
| 445 km/s-- _" Max velocity of the remaining shell (mass about
| 0.1 mg) of an inertial confinement fusion capsule driven by
| the National Ignition Facility for the 'Bigfoot' capsule
| campaign.[32] Current fastest macroscopic human-made
| system."_
|
| 1,000 km/s-- _" Typical speed of a Moreton wave across the
| surface of the Sun."_
| GuB-42 wrote:
| > 440 km/s--"Typical speed of the stepped leader of
| lightning (cf. return stroke below).[31]"
|
| Good one, I didn't think about that one. It means that
| galaxies are travelling lightning fast, literally.
| Trellmor wrote:
| It's also cosmology, but for what it's worth, the solar
| system is moving at about 230km/s around the milky way so you
| could say every one of us is moving at such a number.
| snickerbockers wrote:
| If you continue down this train of thought you eventually
| realize that outside of earth, velocity is just a number
| and all that really matters is the relative velocities of
| the two. So it's impossible to definitively state which one
| is moving or if they're both moving and if so how fast each
| one is moving. And then these sorts of things seem far less
| impressive.
|
| And then it gets weirder when you consider that galaxies
| don't actually collide at all because they're so sparse and
| all that really happens is they pass through each other and
| maybe they permanently merge or maybe some of the matter in
| one galaxy joins the other one and they just keep drifting
| apart in slightly different directions.
| FredPret wrote:
| c is just crazy fast. But still slow compared to the size of
| the universe!
| criddell wrote:
| > As the shock moves through pockets of cold gas, it travels at
| hypersonic speeds--several times the speed of sound in the
| intergalactic medium of Stephan's Quintet
|
| What's the speed of sound in space?
| andreareina wrote:
| https://physics.stackexchange.com/questions/162184/what-is-t...
| criddell wrote:
| From that page, it's very low frequency stuff. One comment
| mentions 1 cycle per month.
| robertlagrant wrote:
| This is unambiguous proof that speed limit[0]s don't work.
|
| [0] https://www.amnh.org/exhibitions/einstein/light/cosmic-
| speed...
| mensetmanusman wrote:
| I wonder how well the local intelligence was ready for that
| event.
| Tuna-Fish wrote:
| If there was anyone around, they probably weren't significantly
| affected.
|
| Galaxy collisions have very little impact on the stars in that
| galaxy, or the planets around them. Stars are so far apart that
| the chance of even one direct collision, or a pass so close it
| would disturb planets around a star, is vanishingly small. Only
| thing that is impacted is the dust and gas in the interstellar
| medium.
| songeater wrote:
| Shouldn't the "sonic boom" here provide good data as to the
| existence of dark matter (akin to the Bullet cluster)? Anyone on
| hn with good background care to comment? Don't see anything in
| the article about it, but would think is one of the most
| significant experimental goals from detecting these sorts of
| collisions.
| dotnet00 wrote:
| My understanding is that, yes, the way matter in a galaxy
| merger behaves acts as strong evidence for the existence of
| dark matter and the theory that it's made of something that
| interacts weakly with normal matter.
| jmyeet wrote:
| "Collision" is a bit of a misnomer when we talk about galaxies.
| As large as stars are, the matter in galaxies is still so sparse
| because stars are so far apart. I saw some maths about the coming
| collision between the Milky Way and Andromeda and the number of
| projected collisions is like less than 10 (IIRC).
|
| Now I'm sure it would be highly disruptive and there'd be
| localized catastrophe but it's important to remember how large
| the distances in space really are.
| floxy wrote:
| Galaxy Collision Simulation
|
| https://svs.gsfc.nasa.gov/10687
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