Galaxy Definition and 510 Threads

Homework Statement The Sun rotates about the center of the Milky Way Galaxy at a distance of about 3.00x10^4 light years from the center (1ly= 9.50x10^5 m). If it takes about 200 million years to make one rotation, estimate the mass of our galaxy. Assume the mass distribution of our galaxy...

I was wondering if studies of individual galaxies predict the same amount and distribution of dark matter as do studies of galactic super-clusters.

Can anyone direct me to a good source of graphs of galaxy rotation curves. I need graphs that show both the observed curve data points and the expected curve along with the names of the galaxies and labeled axis. Thanks

Hi Every picture I see on the internet depicts it brighter than the galaxy as a whole. Now I know that when a black hole is feeding and a galaxy is still in the progress of creation, that's true. But is it true for old galaxies as well whose black hole is not feeding anymore? And if it is...

Hubble Ultra Deep Field "baby" galaxy examination It turns out that galaxies from over 12 billion years ago are anything but small and young. http://www.sciencedaily.com/releases/2005/10/051003233710.htm Is it possible that we got the age of the universe wrong, as it doesn't seem very...

Correcting Galaxy Luminosities for Absorption ?? As light from distant galaxies traverses deep space towards Earth, some amount of that light is absorbed by various features lying between that emitting galaxy, and Earth receivers. Those features imprint those galaxies' observed Spectra, with...

I am having trouble understanding how stars orbit around a spiral galaxy. First off, my understanding of the Local Standard of Rest (LSR) is that it is a point which corresponds to the average velocity of all the stars in the defined local neighbourhood. This point moves around the centre of...

Homework Statement The sun rotates around the center of the Milky Way Galaxy at a distance of about 30,000 light-years from the center (1 light year=9.5x10^15 meters). If it takes about 200 million years to make one rotation, estimate the mass of our Galaxy. Assume that the mass distribution...

Homework Statement The sun rotates around the center of the Milky Way Galaxy at a distance of about 30,000 light-years from the center (1 light year=9.5x10^15 meters). If it takes about 200 million years to make one rotation, estimate the mass of our Galaxy. Assume that the mass distribution...

I'm doing an undergraduate research project this term on some modified theories of gravity, and I need some mass/density profiles. Does anyone know any papers that give mass profiles of galaxy clusters determined predominantly through gravitational lensing measurements? The model I'm working...

I was wondering what is at the center of our galaxy? could it possibly be large amounts of nebula's in which we are orbiting around?

Might there somewhere in the galaxy by a star with a giant set of rings, just like those of our own saturn, only much bigger?

How have we taken the picture of our own galaxy? All the milkyway pictures look like taken from outside the galaxy.

Do any of you know which article(s) are used to do the "expected" rotation curve for galaxies, that always seem to be used to compare with data for calculating the distribution of dark matter? I'm just trying to find which authors have worked out a published result for the theoretical...

Is there a relationship between the mass of a bh and its host galaxy or the age of its host galaxy. (the more distance we look the bigger the bh) ?

At scales of galaxies there is obvious rotational motion but I am wondering if there is an example of a rotating galaxy cluster or super cluster? The rotation could be detected by redshifts the same way it's detected for galaxies. Possibly the rotation would lead to squashing the cluster...

So I am defiantly no scientist and I don's know much so if I jump around with my knowledge I am sorry. If I am wrong, correct me for that is why I am here. It has been said that the black holes take in everything and anything which comes to a miniature 'ball' for say. If what I know about...

as we know that gravitational force increases as mass increases.Then why galaxies are recessing from each other as per Hubble's Law? Does the gravitational forces between galaxies are not enough to hold each other from this recession since mass of galaxies are much bigger.

Hi all, this is the problem: Homework Statement A galaxy shows a rotation curve with a given velocity v(r) . r is the distance from the center, c is the speed of light and r_{c} = 1 kpc is constant. I have to find: 1) the mass density profile of the galaxy \rho(r) 2) the total mass M...

Help on my thought experiment. We know the further galaxy, the faster it runs apart from us. Let's say there is a galaxy (assuming the laws of physics are the same there) running away from us at 99% of the speed of light. Let's say at the SAME time, the people in that galaxy doing the same...

Can a primitive galaxy nova or supernova? Might the former process be involved with star production or the latter with a quasar?

Is there a rigorous definition for what constitutes a galaxy cluster or a super cluster, or are they just identified in an ad-hoc manner?

This is a bit of a dumb question, so I apologise for the bluntness, but I was wondering. Can we see our own Milky Way out there in space due to gravitational effects? I understand that gravity allows us to view single galaxies in duplicate positions across the sky, it made me question whether...

Hi, I was wondering if somebody could help me to answer any of the following questions about galaxies. 1. Describe the major types of Galaxies, including information about their gas content, morphology and evidence for current star formation. 2. What are the similarities and differences...

I have seen several photos of the our milky way galaxy, other galaxies and some photos of even 100's of galaxies in the same picture. How do they do it? Usually if you see in the sky, all you see is the stars. (naked eyes) I believe to be able to see actual of our milky way galaxy we need to...

Is there a reason the center of the galaxy is along the elipitic (in Sagitarius)? Or is that just a coincidence.

If there is a black hole at the center of our galaxy, why does the center of our galaxy looks so bright?

Is it possible that the very high concentration of mass at the centers of galaxies is causing a significant enough time dilation to explain a non-negligible part of the rotational curve problem? i.e. time is traveling more slowly in the super-massive, black hole rich cores of galaxies and faster...

I was reading a text which gives (without derivation/reference) the effective grammage along the line of sight through the disk of the galaxy as about 10^-3 g/cm^2. Is this the proper order of magnitude for the accepted value? By my calculation, I claim the galaxy has 1 proton/cm^3 ~ 2 x...

arXiv:0902.0229 [ps, pdf, other] Title: Large-scale fluctuations in the distribution of galaxies from the Two Degree Field Galaxy Redshift Survey Authors: Francesco Sylos Labini, Nikolay L. Vasilyev, Yurij V. Baryshev Comments: 20 pages, 31 figures, to be published on Astronomy and...

1.The radius of our galaxy is approx. 3x10^20 m. A spaceship sets out to cross the galaxy in 25 years, as measured on board the ship. With what uniform speed does the spaceship need to travel? How long wold the trip take, as measured by a timepiece stationed on Earth? 2. v=d/t 3. So far I have...

Homework Statement The Sun orbits the black hole in the center of the Milky Way galaxy. It takes approx 225million years for the Sun to make one revolution, and the Sun is approx 26,000 light-years away. Estimate the mass of the galaxy contained inside the Sun's orbit. If there is roughly 5...

1. What are some specifics about black holes? 2. I've heard there's a supermassive one at the center of our galaxy--FACT or FICTION? Relevant websites, articles, etc. highly welcome! (I'm really interested in cosmology, obviously.)

http://www.sciencedaily.com/releases/2008/09/080923104410.htm ScienceDaily (Sep. 24, 2008) — Using data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), scientists have identified an unexpected motion in distant galaxy clusters. The cause, they suggest, is the gravitational attraction...

Hello, Reading a news on Yahoo, I was asking myself a little question. I assume there are today extensive data about galaxies rotation as well as light bending by the same galaxies. The question is: how consistent are these data? The rotation curve of a galaxy is known to be flatter than...

Homework Statement You wish to travel to another galaxy, which is 1,000,000 light years away. You'd like to be still alive when you get there. How fast must you travel? Given enough fuel, can you do this? Homework Equations t/t(proper)=gamma v=v'+u/1+(uv'/c^2) The Attempt at a...

Why is the closing velocity of Andromeda and our galaxy so high? 100-140 kms^-1 http://en.wikipedia.org/wiki/Andromeda_(astronomy)"

Homework Statement You want to count all the galaxies out to a certain distance R(naught). If the universe were not expanding, then N (number of galaxies) would be proportional to R^3. Justify/derive. For an expanding universe, take into account the finite time that light takes to reach...

In January, a Vanderbilt University astronomer (I forget her name) found that there were probably hundreds of 'rogue' black holes flying about our galaxy. She surmised that the risk to the Earth from these RBH's was infinitesimal. She said that the only possible risk would be that one goes...

GRB's occur once per day. over 10 billion years that's 3650 billion bursts (in the observable universe?). I think there are said to be around 100 billion galaxies in the observable universe so does that mean that 36 bursts occur in each galaxy...

Structure formation is arguably the central problem in cosmology. How did the dilute gas manage to coagulate. On what timetable did stars and galaxies form? What explains the distribution of galaxy sizes and composition--clustering--the wispy cobwebby structure with its various size voids...

http://blackholes.stardate.org/resources/articles/article.php?id=9 This presupposes that dark matter and dark energy interactions play no role?

Very cool image. Does anyone know, is anything in the information we got from this so far at all surprising? Is it likely we will learn anything about gamma ray bursts from this or is more information

When things are kept at the simplest, I've heard that galaxies were formed because gravity pulls stuff together, but there's some things that are not fully making sense. If two objects are far away, and they get attracted by gravity, what happens is that they merely pass each others with some...

According to Kepler third law, the ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. If I can apply this to the rotaion of galaxy, meaning stars in inner part will orbit much faster than the outer ones. But it...

I have been reading this interesting article http://www.subarutelescope.org/Pressrelease/2006/09/13/index.html on one of the earliest galaxies that has ever been observed (z=6.96), that existed when the universe was just 760+/-15 million years old or about 6% of its current age. See also...

Traversing the milky way galaxy! when? Traversing our own galaxy is a lifelong quest for me and I am actually pondering it and long for it all the time, except when I am sleeping. Maybe it's just a fantasy, though I am not into science-fiction version of it, but many of us want to eventually...

This paper http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=AJPIAS000074000008000745000001&idtype=cvips&gifs=yes published in the american Journal of Physics seems to be very relevant to some of the recent threads in this forum. The abstract is quoted below...

Lets suppose I live in a planet that is located in the tip of a galaxy that is ubicated at the most distant point from our universe. What would I see if I look up to the sky at night(looking away from the center of my galaxy)? Manuel.

Now suppose for simplicity that the galaxy,and that its physical diameter was w at the time it emitted the light.find the apparent angular size of the galaxy as it would be observed from Earth today. the answer given by Mr.Guth seems imply that the galaxy itself is also expanding and point out...