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Galaxy videos
(i.e., Galaxy
videos):
- When galaxies collide! | 1:36:
Good grief.
A computer simulation
from
NASA/ESA.
The Andromeda-Milky Way collision
is an example of
interacting galaxies
and galaxy merger.
The two spiral galaxies
(the Milky Way and the
Andromeda Galaxy (M31)) merge
and become an elliptical galaxy.
The elliptical galaxy
is also a
quenched galaxy
due to
golden-mass quenching
(see Man & Belli 2018, p. 1;
Bower et al 2016).
     
This video is hypothetical.
The Andromeda Galaxy is
in the Local Group of Galaxies
and is the nearest large galaxy to the
Milky Way.
It is approaching us at 266 km/s and
according to recent calculations has ∼ 50 % chance of
galaxy merger
with the
Milky Way
on the time scale of 8
gigayears (Gyr)
(Sawala 2024, "Apocalypse When? No Certainty of
a Milky Way -- Andromeda Collision, p. 4).
If there is NO galaxy merger
on this time scale,
the Andromeda Galaxy and
Milky Way will NOT
merge
(Sawala 2024, "Apocalypse When? No Certainty of
a Milky Way -- Andromeda Collision, p. 4), except by wild extrapolation of
the Λ-CDM model
on the time scale of 10**6 = 10**15 years
(Wikipedia:
Graphical timeline from Big Bang to Heat Death (but note that the left-hand vertical
scale is tricky: for
> 10 years, it is x=100*log(log(t_year)), and so t_year=10**(10**(x/100)) ).
     
Actually, one wonders where does the initial
gravitational potential energy
of the merging galaxies go to.
It becomes kinetic energy
as they fall together, but only a little of this
dissipates
to heat and then
is emitted to infinity as photons
due to colliding
interstellar medium (ISM).
The stars almost never collide
in a body-on-body sense, and so CANNOT
dissipate
kinetic energy that way.
And the dark matter
(whatever kind of particles
it is) do NOT dissipate
kinetic energy via
collisions much either.
Well, much of the
kinetic energy
must become
rotational kinetic energy
of the orbits of the
stars and
dark matter particles.
Also in the complex
galaxy merger process, probably
a lot of
stars and
dark matter particles
get ejected to infinity carrying of
kinetic energy.
The ejection could be in
long tidal tails
or via
gravity assists (AKA gravitational slingshot maneuvers).
The ejected stars are so spread out
they just form a low density
star population
spread through
intergalactic space.
But yours truly needs an authoritative explication.????
     
This version of the video
was prepared by old pal
Phil Plait (1964--).
Good and short enough for the classroom.
- NASA supercomputer simulation of colliding galaxies | 1:38:
Not as good as
When galaxies collide! | 1:36,
but still short enough for the classroom.
"This computer simulation follows
the collision
of two spiral galaxies that harbor
supermassive black holes.
The collision causes a black hole merger
and stirs up gas in both
galaxies.
The merged supermassive black hole
gorges on the feast and lights up, forming an
active galaxy nucleus
called a quasar and creating a "wind" that
blows away much of the galaxy's
gas." (Moderately edited.)
Since a quasar is formed, this
is a relatively early observable universe
event since quasars are extinct in the modern
observable universe.
Authoritative since it comes from
NASA.
Good for the classroom.
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