Galaxy Definition and 528 Threads

Since nebular theory states that our solar system formed from the gravitational collapse of a giant gas cloud. Could this giant gas cloud be the remnants of its predecessor’s nova?

So I was reading through a textbook and came across the term 'close encounter' but no definition or explination of what it means. From what I can make out, I would assume it's referring to asteroid interaction with young galaxies and the role in forming galaxies and stars but this is all...

If we pick a target star 1000 light years away, from the point of view of an observer on Earth we will need at least 1000 years to send a ship there even with the ship traveling near the speed of light. But, from the point of view of someone on that ship that travels with near the speed of...

THE CENTER of The Milky Way Galaxy! Supposedly, in the center of our galaxy (and in most galaxies, if I'm not mistaken) there is a super massive black hole. In my mind I've always had the picture of a galaxy where there is a bright light in the center and lots of starts orbiting it... so if...

So it's often said that the Andromeda galaxy is much wider than the moon, if you count all of its outer regions as well. Yet, you can clearly see much of the Andromeda's spiral structure in the small region that the visible-to-naked-eye region occupies. So what do the outer regions of it look...

I read that Andromeda galaxy is moving towards our galaxy at a speed of 200,000 miles per hour. Does it mean that Andromeda galaxy has increased mass and slowed time in comparison to us (or the opposite is true or no effect on its mass or time is there)? No mathematical answers please (I am...

How do I calculate the redshift of a galaxy that is 650 Mpc away if I am only told its spectral lines should show a redshift z=.15?

I just read this in Wikipedia: "The Canis Major dwarf galaxy is classified as an irregular galaxy and is now thought to be the closest neighbouring galaxy to our location in the Milky Way" (emphasis mine). Umm, why thought? What is it that makes us uncertain? Or is this an error in Wikipedia?

How was we able to take the pictures of galaxies?

Homework Statement Most of the galaxies in the universe are observed to be moving away from Earth. Suppose a particular galaxy emits orange light with a frequency of 5e14 Hz. 1) If the galaxy is receding from Earth with a speed of 3325 km/s, what is the frequency of the light when it...

Hello!:wink: May I ask for a little assistance in filling in the gaps of my understanding? :S I understand that the current large scale structure of the Universe is thought to be the result of early fluctuations in density which have been stretched out in the expansion of the Universe. I...

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 folks, I'm supposed to derive the func. form of the rotation curve for the outer parts of our galaxy, in the absence of dark matter. Im assuming that I treat this as a linear curve, since in reality, dark matter flattens out the curve, when it should continue following the linear(?)...

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 want a shirt with a spiral galaxy on both sides. On the front, it's slightly blue, and on the back, it's slightly red. So, when I'm walking toward/away from people.. get it? No one steal it and make a million dollars please.

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?

Homework Statement The galaxy luminosity function  \phi(L) tells us the number density of galaxies as a function of luminosity L. The luminosity density of the universe l is thus given by the expression l = \int^{\infty}_{0}L\phi(L)dl a) For a Schechter luminosity function...

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...

Homework Statement SUppose you have a galaxy with a spherically symmetric mass distribution with the mass density rho(r) = rho0 (r0/r)^5/3, where rho0 and r0 are constants. Derive the expression for M(r) the total mass interior to r, Then derive the rotation curve function. Homework...

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...