Galaxy Definition and 528 Threads

Since our galaxy and the andromeda galaxy are drifting towards each other. How long will it take to look as big as the moon today in the night sky?

heya all, i need some help on a homework question. Here is the question-- We are located about 28000 light-years from the galactic center and we orbit the center once every 230 million years. How fast are we traveling around the galaxy? Give your answer in both km/hr and mi/hr. Okay, i know...

A question. Has there ever been an instance where a single galaxy split into two separate gallaxies or a recorded view where that would seem to be the case. Thank you. Sunblock

http://physicsweb.org/articles/news/10/6/3/1?rss=2.0 ===sample quote=== Levine and colleagues took previously obtained data from the hydrogen "21-cm emission lines" and applied a technique called unsharp masking to increase the contrast between high and low signal regions. They found that the...

Some time ago i post this topic, but i think my explanation was not very clear , i hope now could be better understood My new argument is this: suppose that much billions years ago existed in what now is our Solar System an alien civilization, suppose they have developed the videorecording...

The typed question and attempt at it are below: Question: The Sun orbits the black hole in the center of the Milky Way galaxy. It takes approximately 225 million years for the sun to make one revolution, and the sun is approximately 26,000 light-years away. Using this information and...

Hello. I'm plowing through Linda Sparke's "Galaxies in the Universe: An Introduction". I'm enjoying it quite well and learning a lot. But then I get to Equation 1.18 in the book and am a little confused because it uses variables not previously introduced. Not sure if I can do it here but...

two exiled stars are leaving our galaxy forever They are surely traveling fast!

After the discovery of galaxy HUDF-JD2 is the big bang theory to be revised?

Dark Galaxy found!? You know, I've always been secretly hoping that dark matter was an aberration of our observations or calculations, some value to be tweaked or some normalizing factor to be applied thing that was making galaxies turn faster than formulae predicted. I just couldn't believe...

The Andromeda glaxaxy is two million light-years from earth, measured in the common rest frame of the Earth and Andromeda. Suppose you took a fast spaceship to Andromeda, so it got you there in 50 years measured on the ship. If you sent a radio message home as soon as you reached Andromeda, how...

I decided to post a new thread to distinguish from my other post The paradox is as this: suppose that 10 billions years ago a guy was born ( let's call him "Universeguy"), in a place near the Earth (because obviously Earth doesn't exist yet), first, he was a lucky guy , he discover how to...

Why are the planets in our solar system spread out in a plane instead of being more randomly spread around the Sun? And why is our galaxy in the shape of a plane instead of all the stars in our galaxy being more randomly spread around the middle of our galaxy? Thanks,

The post that held the link to this paper has been moved. I would like to see comments on this paper, including impressions of the mechanism responsible for the interaction of the quasar and the associated galaxy. http://arxiv.org/ftp/astro-ph/papers/0509/0509433.pdf I objected to the...

This topic brings up the Fermi Paradox, once again. I just want to hear the boards opinion on this...should the galaxy have been colonized by now? and a decent portion of it has been colonized would we able to "see" it?

New pics. These are a month old, but I forgot to upload them. They are from Sept 29. That was the first night it got really cold and I drove to the Poconos to set up shop, so while the sky was very clear and very dark, it was also very windy. First is another shot at the Andromeda Galaxy...

for the following question: In its own frame of reference, a proton takes 5min to cross the Milky Way galaxy, which is about 10^5 light-years in diameter. What is the approximate energy of the proton in electronvolts? my problem: v*5*60=(10^5)*3*(10^8)*[1-(v^2/c^2)] however, i can't...

This time the news is that on 21 September this paper was accepted for publication in Astrophysical Journal. It will appear in January. http://www.arxiv.org/abs/astro-ph/0506370 Galaxy Rotation Curves Without Non-Baryonic Dark Matter J. R. Brownstein, J. W. Moffat 43 pages, 7 figures, 4...

Claims universe not expanding: http://www.arxiv.org/abs/astro-ph/0509611 Another recent article about redshifts being apparently wrong: Research on candidates for non-cosmological redshifts "The paradox of apparent optical associations of galaxies with very different redshifts, the...

I know that the velocity of our galaxy towards Andromeda is approximately 300,000km/s, but how quickly does this velocity change? Or can we tell given our relatively short time observing the sky?

Is it possible for a galaxy too fall back into its self?(even if they don't) What would happen?

Hi, i have a question, if we imaging that the universe is static and not expanding, what observation would be made in regards to red shifts in galaxy spectra?

Something important to think about: If it takes us between 225 and 240 millions years to make one Galaxy orbit wouldn’t it be prudent to associate magnetic polar shift, global warming, and ice-ages to where the sun was located when these events occurred? Were we close to or farther away...

a supernova can out light a entire galaxy. I've read it can give out about 10^44J of energy is there anyone of you who now the amount of energy released mor exacly or even better know how to calculate it? i love calculating stuff.

I was reading on Space.com about our galaxy and it said that there is a bar of stars, mostly old and red, at the center and at a 45 degree angle from the plane the rest of us are on. In addition to this there is a super-massive black hole. How can the BH be there and the bar of stars, let...

I am reading about galaxy surveys. I want to know what is shot noise ? how we estimate it into real and Fourier space ? I am basically reading astro-ph/0503603 & astro-ph/0503604. I am not able to solve exercise 4, 5, 6. I will be thankful, if anybody can provide me some reference.

"infinite Galaxy" If our "infinite" universe had a beginning, it has an end, right?

The CDM model predicts the existence of lots of dark halos without star formation. These are halos which did not attract enough baryons in order to set some kind of gravitational instability, which could lead to the further collapse of the baryons and to star formation (see, e.g...

To form, is it one of the oldest?

I recently came across an argument that stated that Earth's nighttime view pretty much always faces the outer rim of our galaxy, while the day time view is facing right towards the center, which of course we don't see due to sunlight. There was refrenced a few indian tribes in s.america who trek...

If there a massive black hole at the center of each galaxy then; near the center of our galaxy, stars should be revolving the BH at very high speeds, hence we should be able to note their revolutions around the BH in months, days or even hours. And hence we should also be able to see some of...

A Cepheid variable in a nearby galaxy looks 10^6 times fainter than an identical Cepheid in the Milky Way. The Cepheid in the Milky Way is 1000 parsecs away. How far away is the nearby galaxy? I know this formula v = hd but how does that help me? i'm lost...

Hey guys For those who have seen HHGG, that sweet white Nokia cellphone that Arthur Dent has, does it exist? If so, does anyone know the model #? Thank you Aychamo

For all those that wanted this to be a great movie... http://planetmagrathea.com/shortreview.html

http://movies.yahoo.com/feature/thehitchhikersguidetothegalaxy.html

Orbits What does our galaxy orbit? more questions will follow once previous ones are answered

As you can read in http://pinot.phys.uvic.ca/~jfn/mywebpage/gxform.html, recent simulations show that the accepted model of dissipational collapse for the formation of galaxy disks, leads to an excessive loss of angular momentum in the disk when mergers are considered. What are the current...

I have another exam question, which I'm having some slight problems with... "In a particular galaxy the velocity curve is constant over a large range of radii, and equal 300 km/sec at a particular radius of 10kpc in this range. Estimate the mass inside this radius." Can I use centrifugal...

http://ernie.ecs.soton.ac.uk/opcit/cgi-bin/pdf?id=oai%3AarXiv%2Eorg%3Aastro%2Dph%2F0402319 Reionization seems to be a fundamental process to the formation of our universe, but when did it occur? I have seen papers state z=6, but this seems to be a lowest limit, as this paper suggests a galaxy...

http://www.physicsweb.org/articles/news/9/3/2/1 title: "Galaxies break new records" Last year Roser Pello's team at the Pyrennees Observatory thought they had found a 10 billion year old galaxy IIRC, but this was later challenged [CORRECTION: hellfire reminded me that Roser thought she had...

Why is our galaxy planar? Why isn't it spherical?

Is the Andromeda Galaxy going to collide with the Milky Way? I've heard that the Andromeda Galaxy is going to collide with the Milky Way someday. I understand how its radial velocity relative with respect to the Milky Way is determined through its blueshift, but how do we know its tangental...

The latest figures for baryonic mass etc.

so i heard that a galaxy was headed at us at like 100 times faster than a bullet. so what happens when it gets to us. Earth would be dead by then. mankind with it probably. but what happens to the galaxy?

good day, well the coming fall I'm entering the astronomy faculty and i started from now to study the NGC and M objects... while i was searching for the names and numbers on the web.. i have found several descriptions, which i didn't understand: 1) when they display the distance in LY, is...

Is our galaxy in the centre of the universe? If it is not, how can the age of galaxies be determined? how can data from the CMBR be correct? IF our position in the universe is unknown, (we could be near the event horizon) how would this effect our knowledge of cosmology?

Hi! Let's say that astronomers observe some galaxy or something several million lightyears away and then come to conclusions about that object. But since the light from there has been on the way for millions or even billions of years, then is it correct, that they are actually seeing the...

This is amazing, I haven't heard of any merger of two galaxy clusters until now. http://www.newscientist.com/news/news.jsp?id=ns99996443 "One of the hottest, most energetic mergers of two colossal galaxy clusters has been imaged in exquisite detail by an X-ray observatory in space...

http://www.msfc.nasa.gov/news/news/releases/2004/04-231.html , a Chadra PR, goes on to say: "A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA's Chandra X-ray Observatory. Astronomers...

Good Paper if anyone is interested:http://uk.arxiv.org/abs/gr-qc/0408008 The paper deals with some aspects for Entropy Conservation for Dynamical Blackholes, from the abstract :An effective gravitational-radiation energy tensor is obtained, providing measures of both ingoing and outgoing...