Galaxy Definition and 528 Threads

Hi... Just wondering... Will the Andromeda galaxy really collide with the Milky Way in 3-5 billion years? I've seen a supercomputer-generated video, but is there any actual proof other than the theories of various scientists? Even though it was NASA who came up with it...

Three questions, all related. Firstly, I'm wondering what sort of modifications to Newtonian gravity were tried to explain the flatness of various galaxy rotation curves. (References, and especially a review, would be much appreciated. I haven't been able to find anything appropriate.)...

1. A: Homework Statement If the Earth and Mercury happened to be pulled out of the solar system by the gravitational force of a passing neutron star, and then left in orbit about each other in an otherwise empty region of the galaxy, our lovely planet would probably get very cold. But...

than why center is the brightest part of galaxy? shouldn't black hole suck all the light in? and if so, the more close to center of galaxy, the more time flow slower right? ...... English is not my native language, forgive me If I'm wrong in spelling or gamma

In this picture I took of M33, the Triangulum galaxy, what are the small red areas scattered about in the galaxy? Some sort of star clusters? [PLAIN]http://img708.imageshack.us/img708/4899/m33c.jpg

Hi, I am wondering how to describe a position of our solar system to some other extraterrestrial intelligence in some distant galaxy to find us? Is it possible or not? i mean if such guidance exist for any galaxy or they have to track back movement of your probe or spaceship etc. and some...

The new supernova is in the "pinwheel galaxy", M101, near the edge of a spiral arm. The galaxy is in Ursa Major, roughly where the tip of the bear's tail would be if it flicked upward! It has reached magnitude 10.2, so not a naked-eye object, but visible with binoculars. For a map, see...

In reference to M101 and the Type 1a supernova SN 2011 fe. Distances that I have found for M101 vary from 21 million light-years to 28 mly. The value for the measured redshift of M101 is 0.000804. Will the emissions from the supernova create any changes to the redshift measurement? And if so...

https://www.youtube.com/watch?v=VQBzdcFkB7w Reference: http://www.ibtimes.com/articles/206146/20110830/milky-way-galaxy-model-eris-supercomputer-spiral-galaxy-simulation.htm"

"Infinity" at the Center of the Galaxy http://www.sciencedaily.com/releases/2011/07/110719151234.htm http://www.wired.com/wiredscience/2011/07/milky-way-ribbon/ New observations from the Herschel Space Observatory show a bizarre, twisted ring of dense gas at the center of our Milky Way...

This question has been nagging at me: How are we able to get a clear picture of a galaxy if the light from the far side of a galaxy is arriving 100,000 years or so after the light coming from the near side. With a 100,000 year difference the stars that we are seeing in the far side wouldn't even...

Homework Statement Calculate the comobile distance of a galaxy with z=7.3, H_{0}=72 km/s/Mpc, universe with \Omega_{0}=\Omega_{0,m}=1 Calculate the scale factor when the galaxy emitted the light we receive today. Homework Equations Friedmann equation (\frac{\dot{a}}{a})^{2}=(H_{0})^{2}[...

Hi! I want to estimate the distance and mass of a galaxy by given values. The center of an inclined galaxy sends out light of a certain wavelength (f.ex. the HI line) out to a certain radius r. At the outer edges of the galaxy the emitted line has a wavelength of l +/- dl At first, I...

If I know the diameter of a galaxy in the sky is 150 arcseconds, how do I find the angular diameter?

Hi, Is there a fairly even star (or galaxy) density in every direction we look, ignoring our own galaxy? Or are there some directions where our OU seem denser than others?

How many gamma photons are in the galaxy, and what can we know about the distribution? Which kind of process can absorb them?

Are there any observations or estimations about asteorids outside our solar system?

Observations of distant supernova suggests we live in a deSitter Universe, with cold dark matter invoked to explain galaxy rotation curve. Since direct DM detection experiments have come up null, could the presence of matter in the vacuum cause spacetime around it to become Anti de Sitter, one...

http://1.bp.blogspot.com/_U5OmWgNVk8k/RzZIYQNbhDI/AAAAAAAAAJo/WeH9PPdPrUk/s400/Empire+Strikes+Back+finale.jpg what one was that? i used to wonder why exactly they put that in there at the end (beyond the fact it looks pretty) i mean you never see any other stuff like that in star wars beyond...

Homework Statement My solution isn't working out for this question. Radio waves of wavelength 125 m from a galaxy reach a radio telescope by two separate paths. One is a direct path to the receiver, which is situated on the edge of a tall cliff by the ocean, and the second is by...

Usually spectral lines of spiral arms are corrected for the angle of the galaxy plane with respect to our line of sight to give a velocity curve. I guess this works except in the case when the galaxy is exactly "face-on" from our view (at 90 degrees angle from our line of sight) where no Doppler...

The equation for the isotropic velocity dispersion of the stars, sigma(r), is the Jeans equation, GM(< r)/r^2 = −(1/p*)d/dr(p*sigma^2) Assume that the stellar density p*(r) = 0.8ptot(r), where ptot(r)~1/r^2, as derived earlier. Show that a constant velocity dispersion, sigma(r) = sigma0, is...

Hi, I'm trying to get my head around theories of the universe, and am wondering if Hubbles Law has been mis-understood. I know that light from far away galaxies has been redshifted i.e. has lost energy. But I'm not convinced that this means those galaxies are moving away from us...

Homework Statement Suppose the number density of bright F dwarf stars at the Sun's radial distance from the Galactic center, varied with height above the galactic plane as: n(z)=n0 exp(-z/h) where h = 250 pc. Also suppose that the velocity dispersion of these dwarfs varies with z as...

I know that Hubble observed redshift which led to the conclusion that space was expanding. But why did redshift lead to such conclusion? Why didn't they just think that galaxy were "flying" away from each other instead of thinking that it was the space that was actually expanding? What made...

Galaxy gravity ? Which equation must be used to calculate Acceleration due to gravity inside a galaxy I mean it is not the same as to calculate the acceleration towards the Earth GM/r2, - right ?

Is there an exact relationship between the size of a galaxy and the density of its black hole?

Why is the Milky Way a barred galaxy? http://en.wikipedia.org/wiki/Barred_spiral_galaxy http://upload.wikimedia.org/wikipedia/commons/8/89/236084main_MilkyWay-full-annotated.jpg

I was watching a program on dark matter and how galaxy spin was used to deduce the existence of dark matter. The thought occurred to me if the rate of galaxy spin has been measured on many galaxies and how does the spin differ if it does. Another question arose are there any galaxies with...

When I look at the stars in the sky with my undressed eye, they are blue. But pictures of stars taken by scientist always show them as red. Does this mean that the stars in our galaxy are fairly stationary and/or moving closer to earth? Will I find that most red shifts will be seen in stars...

If I suppose number of civilizations at the present time (ignoring light travel time) is 10-4. (drake equation) Where the civilizations lifetime is 1000 years. Then over the history of the galaxy, Number of civilizations over the galactic history=N* Galactic lifeitme (1010)/ Lifetime of...

When we analyze the light coming from a distant galaxy, we find a particular absorption line with a wavelength of 1118 nm. This same absorption line in light from the sun has a wavelength of 625 nm is this galaxy moving towards us or away from us? Calculate the magnitude of the velocity of...

A galaxy is observed to have a significant redshift in all of its spectral lines. The line normally seen at a wavelength of 327 nm is instead observed at 360 nm. How far is this galaxy from the milkyway My approach All I can calculate here is the red shift based on the formula Z=...

Homework Statement The Milk Way galaxy rotates about its center with a period of about 200 million yr. The Sun is 2 X 10^20 m from the center of the galaxy. How fast is the Sun moving with respect to the center of the galaxy?

I was wondering if anyone could indicate me towards recent(and respectable) findings over the number of Earth type planets in the galaxy. examples of exoplanet studies and the like would be great. thanks a lot. And also findings on the number of exoplanets surrounding stars would be most...

Why don't galaxies for giant "solar systems"?

Some of galalxies have bar style center. Very mysterious. The origin? The galaxies are SBa, SBb and SBc style. Spiral galaxies are familiar to us. it seems like hurricane. What kinds of force act on bar centered galaxies?

What features of Andromeda Galaxy can you make out with an Amateur Telescope?? With an amateur telescope, (field of view of 2 degrees) what features can see you see in and around the andromeda galaxy? Just curious.

Sorry if someone already posted this link but did anyone see this in the news? http://www.nasa.gov/home/hqnews/2010/nov/HQ_10-295_FERMI.html What are people's opinions on what this might be?

Homework Statement Hi everyone, I'm a bit stuck and have been staring at my fortran code all day. For my project this year I'm writing a program to model a spiral galaxy in which gas clouds circulate, collide and produce star formation. I've written code for gravitational acceleration due to...

I am trying to calculate the mass of the galaxy within the orbit of the sun. M = Mass of the galaxy = ? r = ‘Distance of sun from galactic centre = 7.6 kpc’ = 2.3 x 1017 km = 2.3 x 1020 m (2 sf) G = Gravitational constant = 6.67 x 10-11 Nm2kg-2 v = ‘Radial velocity of the sun =...

http://arxiv.org/abs/1010.4312 This is the actual paper that was published yesterday in Nature magazine. Good show ESO! Galaxy is now 3.1 billion years old. The baby picture that European Southern took of it is when the universe had been expanding for only 600 million years.

Homework Statement A star is moving in a circular orbit of radius r within a galaxy. What is it's orbital speed v(r) as a function of \rho(r) and radius. The galaxy is spherically symmetric with a mean density \rho(r) and radius R. Homework Equations F =...

Using stellar parallax, it is possible to judge the distance of stars, and therefore given this distance combine with the speed of light, we know how old the images of the stars are the we see (ie, like 1 million light years old). What other methods do we have to confirm how old the images...

Does anyone know if there is an understood correlation between the amount of dark matter we suspect in a galaxy and the age of the galaxy? Basically, I am wondering if older galaxies tend to have more dark matter. But I need references to information on this, not just opinions :) Thanks.

Where there's a query, there's a forum! I'm glad I found this place. So here's my quandary. The Earth is rotating. It's orbiting the sun. Our solar system drifts through the galaxy which galaxy is drifting through the universe. Supposedly, even though I stand still, I'm moving in some strange...

We observe farther galaxies with higher redshifts. How can we be sure that this is due space itself expanding? How do we know that this is not just Doppler shift of galaxies running away from us at higher speeds long time ago, that got lowered (decelerated by gravity of matter in the...

I hope this is the right place to ask this. for a long time I wondered why our galaxy, or all galaxies for that matter, is more or less shaped like a disc. I assume this has something to do with the way gravity works. Yet I also assume that the simplest shape gravity would form is a sphere...

We all know that Galaxies are moving away from each other at a great speed, Is there any specific path through which they are moving? Again we know few things about the Universe like Moons rotate around Planets, Planets around star, stars around the center of galaxy. And it seems all follow a...

I am creating this wavelength chart (attached). I was told to use Compton's formula; I got this: (6.626068 × (10^(-34))) / (1.1542e+42 * 299 792 458) = 1.91493535 × 10-84 Apparently, it is substantially off scale. I was then told to try de Broglie wave. Wikipedia only shows relations...