Does a galaxy move?

Hi Passero Everything in the universe is in motion. Galaxies on the
deep space scale are being pushed apart by the intrinsic force of space.
Adromeda galaxy is said to be coming towards the Milky way. Both are
spinning spiral galaxies,and that makes measuring the red or blue shifts
tricky. We have to use our planet Earth as a reference point,same way
the Earth's surface is used as a local reference for objects in motion.
It is safe to say all galaxies are moving away from each other as the
size of space grows bigger. Think of galaxies as dots on a balloon that
you are pumbing air into. Bert

Or, are they both "moving away" from some other point on convergent paths?

"starman" wrote in message
...
"Mark F." wrote:

The sun is in orbit around the galactic center it rotates and us along
with
it, Edwin Hubble found that all the galaxies are moving away from us.

So everything is moving somewhere.

In general the galaxies are moving away from each other because of the
overall expansion of the universe but at least one galaxy in our 'local
group', M31 'Andromeda', is approaching our Milky Way galaxy at a
velocity of about 125-km/s. If this continues we will collide with M31
in about 4.3-billion years but I wouldn't worry about it. :-)

You can read more about the 'local group' at:

http://nedwww.ipac.caltech.edu/level...er/node16.html


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On Wed, 14 Jan 2004 07:11:17 -0800, "Starlord"
wrote:

While a Galaxy's speed is great, the area is so vast that it just craws along.




"E pur si muove"
--GG

Nick

--
Nick Theodorakis

nicholas_theodorakis [at] urmc [dot] rochester [dot] edu

On Wed, 14 Jan 2004 10:05:01 -0500, starman wrote:

In general the galaxies are moving away from each other because of the
overall expansion of the universe but at least one galaxy in our 'local
group', M31 'Andromeda', is approaching our Milky Way galaxy at a velocity
of about 125-km/s. If this continues we will collide with M31 in about
4.3-billion years but I wouldn't worry about it. :-)

What? You don't plan on being around to see the show? :-)

From curiosity, has anyone bothered to calculate/estimate where the solar
system will be in its orbit of the galaxy when the fun begins?

Out of the blue thought: Is it possible that either Andromeda or the
Milky Way originated in another Galactic Cluster & was ejected for
whatever reason & thats why they are now on a collision course?

Haven't you heard of the big bang theory? It is like 4th of july
firework. Imagine each sparkle is a galaxy.



"Passero" wrote in message
...
Perhaps a stupid question but i'm new to astronomy and i would like to
know
if a galaxy moves or not and if it moves, how does it move? I mean, the
planets are moving around a sun so does a galaxy move around something or
does it just move because of the big bang or what?

Dat's Me wrote:

Out of the blue thought: Is it possible that either Andromeda or the
Milky Way originated in another Galactic Cluster & was ejected for
whatever reason & thats why they are now on a collision course?

There's no evidence at all that our Galaxy and M31 are "on a
collision course". We can measure the velocity of approach in the
radial direction, but we have no means of measuring lateral
velocities. So the two galaxies *might* eventually collide, but until
we've had the opportunity to make precise observations for perhaps a
few thousand years more it's anybody's guess as to their true
relative velocity. M31 is believed to be a member of the Local Group;
for it to have come from another group (e.g. the Maffei Group,
perhaps two megaparsecs beyond) it would have to have acquired an
enormous amount of extra energy from somewhere in order to escape the
other members' gravity. Here's a map of the 'neighbourhood' out to
twenty million light-tears:

http://www.anzwers.org/free/universe/galgrps.html.

--
Odysseus

"hbb2102" wrote in message
news:vxlNb.68653$xy6.126920@attbi_s02...
Or, are they both "moving away" from some other point on convergent paths?

The local galactic cluster, of which both the Andromeda and
Milky Way are members, are gravitationally bound. That is,
they all orbit each other. This is not to say that these
orbits cannot involve collisions... n-body orbits can be
quite complex and chaotic (in the mathematical sense).

In message , Odysseus
writes
Dat's Me wrote:

Out of the blue thought: Is it possible that either Andromeda or the
Milky Way originated in another Galactic Cluster & was ejected for
whatever reason & thats why they are now on a collision course?

There's no evidence at all that our Galaxy and M31 are "on a
collision course". We can measure the velocity of approach in the
radial direction, but we have no means of measuring lateral
velocities. So the two galaxies *might* eventually collide, but until
we've had the opportunity to make precise observations for perhaps a
few thousand years more it's anybody's guess as to their true
relative velocity.

That's what I thought until recently, but in fact it will apparently be
possible to measure the transverse velocity with missions such as GAIA.
The topic came up recently on alt.astronomy (thread "'Round 'n 'Round
the Darkmatter Bush (was - Spiral...)") and here's what I posted then.
Typing "transverse velocity of M31" into Google gives two hits, one of
which assumes it's zero http://arxiv.org/pdf/astro-ph/0210255 and the
other http://arxiv.org/pdf/astro-ph/0010480 says the velocities of
nearby galaxies are on the order of 100 km s-1, large enough to be
detected and tested by the proposed SIM and GAIA satellite missions.

RADIAL AND TRANSVERSE VELOCITIES OF NEARBY GALAXIES
P. J. E. Peebles 1, S. D. Phelps 1, Edward. J. Shaya 2,3, and R. Brent
Tully 4
1 Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544
2 Raytheon ITSS, Goddard SFC, Greenbelt MD 20771
3 U. of Maryland, Physics Dept., College Park MD, 20743
4 Institute for Astronomy, University of Hawaii, Honolulu, HI 96822
--
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nightbat wrote

Odysseus wrote:

Dat's Me wrote:

Out of the blue thought: Is it possible that either Andromeda or the
Milky Way originated in another Galactic Cluster & was ejected for
whatever reason & thats why they are now on a collision course?

Odysseus
it would have to have acquired an
enormous amount of extra energy from somewhere in order to escape the
other members' gravity. Here's a map of the 'neighbourhood' out to
twenty million light-tears:

http://www.anzwers.org/free/universe/galgrps.html.

--
Odysseus

nightbat

True, very true, that you understand this Odysseus, ha, ha, but
I wasn't aware that the collective new mini galaxy cosmos shed
"light-tears" when being ejected so far out...(:~(

The newly formed galaxy ( after only a few millions years ) was ejected
due the collective energy/mass acquired by the collapsed neutron star
turned strong gravity singularity " Black Comet ". However, as the
subsequent mass and energy reached a critical upper limit itself, she
over comes and free fall travels out beyond the center of mass of the
originating mother galaxy to start a new life of its own. Ok, I have to
admit my profound model for galactic formation dynamics under the
nighbat " Continuing Universe Rule " is so sweet and logical, that it
can bring tears to your eyes.

And to answer Dat"s Me's question, yes, two galaxies can collide, just
like any other space body in gravitational outer space free fall. Thank
your lucky stars that the cosmos is as big as it is otherwise it
wouldn't be just called chaotic but there goes the neighborhood again!

My model is so unifying that apparently even lurking aliens (Darla and
Company) on this news group are apparently tracking its unique
fundamental development due to its far reaching implications. Now they
want to know the meaning of life and how it was made, give me a break,
isn't the TOE premise enough? I thought I was done and now they want to
know what makes nightbat tick? Hello, buy the book coming soon to your
local book stores on nightbat's " Continuing Universe Rule ", you might
get a clue.


the nightbat

Jonathan Silverlight wrote:

That's what I thought until recently, but in fact it will apparently be
possible to measure the transverse velocity with missions such as GAIA.
The topic came up recently on alt.astronomy (thread "'Round 'n 'Round
the Darkmatter Bush (was - Spiral...)") and here's what I posted then.
Typing "transverse velocity of M31" into Google gives two hits, one of
which assumes it's zero http://arxiv.org/pdf/astro-ph/0210255 and the
other http://arxiv.org/pdf/astro-ph/0010480 says the velocities of
nearby galaxies are on the order of 100 km s-1, large enough to be
detected and tested by the proposed SIM and GAIA satellite missions.

Thanks for the links, although much of their content is beyond me ...
but it's my impression that in the first one a zero transverse
velocity is just being used as a simplifying assumption for analysis
of the M31 system's internal dynamics. Concerning the second paper,
note that M31's blue-shift indicates an approach velocity of somewhat
over 100 km/s, so if its transverse velocity is nearly the same its
net direction would be something like 40° from the lign of sight,
implying that it will miss us by well over a million light-years. I
hadn't heard of either proposed satellite before; apparently SIM will
use interferometry to make astrometric observations of unprecedented
precision, while GAIA seems to be a 'Hipparcos on steroids' that may
be capable of determining the proper motions of nearby galaxies. So
we may only have to wait for a couple of decades, rather than
millennia, to acquire more information about the dynamics of the
Local Group.

--
Odysseus