Galaxy Definition and 510 Threads

If Wikipedia were a galaxy and each article a star Each section a planet leaving each word to remind us Remind us who we are. http://phys.org/news/2014-12-wikigalaxy-wikipedia-galaxy-stars.html

Homework Statement A quasar at redshift 0.3 is gravitationally lensed into two images by an elliptical galaxy at redshift 0.18. The two images of the quasar are separated from the center of the galaxy by 1.1 and 1.6 arcseconds, on opposite sides. One of the quasar images flares up in intensity...

Heard that line on one of those science channel shows. Forget who they were interviewing. But my question is what is the mathematics behind discovering this fact? How could we possibly know that our galaxy is one of the biggest in the Universe unless we counted all or most of them, how could we...

What is the origin of the M-sigma relation between supermassive black hole mass and galaxy velocity dispersion?] How did the most distant quasars grow their supermassive black holes up to 109 solar masses so early in the history of the Universe?

In many vortex's, the center has low pressure, from the center of a stirring cup of tea to the centere of a hurricane or storm system. I'm trying to crudely model how this might apply to the center of a spiral galaxy. If the behavior is similar, and the center has a low pressure void...

From, http://www.newscientist.com/article/dn26438-churning-galaxy-boasts-a-fiery-halo-of-baby-stars.html#.VEmn2iJ4pcQ

I was wondering, how can we measure the rotational velocity of a galaxy? In practice knowing the mass distributions and so on, we could calculate it by classical mechanics (or maybe GR). However people measured the rotational velocity of the galaxies and found that it doesn't correspond to the...

Homework Statement I understand that [Fe/H] ratios can be used to describe metallicity in a galaxy... but I'm having trouble understanding what [element/Fe] ratios should tell you. Anyone have an idea? Homework EquationsThe Attempt at a Solution

What is the oldest part of our galaxy that theoretically could have held life some millions - billions of years before earth? I'm asking purely out science fictionic curiosity. This may sound like an even dumber question, but is there any region on the "map" of the galaxy that contains these...

When trying to work out how galaxies formed, there must have been some seed; some perturbations that started the ball rolling, These perturbations which collapsed gravitationaly to form seed galaxies must have been primordial in origin, where did they come from?

My old phone broke and it's time for me to get a new one. I'm considering the Samsung Galaxy Note 4 as my top pick. I think it'd be really cool to have a phone you could do by-hand calculations on. For example, instead of looking at Facebook, etc. on my phone while waiting for the bus, I could...

[SIZE="4"]LEDA 074886, also known as PGC 74886, is a dwarf galaxy with a rare rectangular shape, located at a distance of about 70,000,000 light-years ( 21,000,000 pc) ...

1. Gravity is the geometric curvature of space-time caused by massive objects. 2. Dark Matter surrounds galaxies. 3. Dark Matter is thought to be critical in galaxy formation. 4. The mass of Dark Matter creates curvatures in space-time around baryonic matter which forms galaxies. What roles...

We know that distant galaxies (which are expanding) are sometimes expanding at rates that do not conform with our known theories and formulas developed by our own observations of gravity. Einstein's theory is of course at the forefront of this conundrum. To explain it some believe that we...

I could not find a thread about this (and I hope I don't start a duplicate one :smile:). I got a mail from a friend today about this: Detection of An Unidentified Emission Line in the Stacked X-ray spectrum of Galaxy Clusters Esra Bulbul, Maxim Markevitch, Adam Foster, Randall K. Smith...

Hello All, A curious person here would like to know if a planet gains gravitational force as it rotates around the center of its galaxy. From what I understand this speed is quite impressive (the speed at which we travel around the center of our galaxy) so I'm wondering if the sheer mass of...

I am currently researching about the behavior of dark matter and their possible characteristics, and I am needing the individual velocities of the bodies orbiting a center of a galaxy. The collection of data where physicists hypothesized the existence of Dark Matter. Where can I find these data...

dear sir, i want to know the structure of the galaxies. the process that caused it happen.and finally some peculiar and intersting about galaxy.

by Dr. Ken Croswell Astronomers staring across the universe have spotted a startling scene: three supermassive black holes orbiting close to one another, two of them just a few hundred light-years apart. The trio, housed in a pair of colliding galaxies, may help scientists hunting for ripples...

I have read that when UDFj-39546284 was discovered its z was thought to be 10.3 but now is 11.9. It was a "[SIZE="1"] blue stars that existed as we see it 13.42 billion years ago, around "380 million years"[2] after the Big Bang (estimated at 13.8 billion years ago)" I suppose the frequency of...

A Stellar Discovery on the Milky Way's Far Side Five remarkable stars on the other side of our galaxy promise new insight into the outer reaches of our home turf By Dr. Ken Croswell A single Hubble Space Telescope image can capture scores of distant galaxies, but the one galaxy we'll...

Imagine a spinning skater. She pulls her arms in a little and spins faster. She brings her arms all the way into her chest, and spins really fast, and then bam! she rockets up into the sky. Seven years ago, computer simulations revealed a configuration of two spinning black holes that merged in...

sir please tellme if light is reflected from near by galaxy can we see our past from that light? if two light strikes our eyes same time which will be deteced?

If two galaxies are separated by a large distance such that radiation transmitted from the mid-point between the two galaxies never reaches either galaxy due to the expansion of space, how can the expansion of space at the mid-point ever affect the distance between the two galaxies. i.e. how...

I have read that, the light from a distant moving object is tested for doppler shift to calculate its velocity. My question is, we can only lay our hands on the modified frequency, not the original frequency. So how to calculate the doppler shift from that?

How many other galaxies, have a similar trajectory of being on a crash course path with a neighboring galaxy. Is it a consensus that most galaxies are moving away from one another due to dark energy, if so is there a ball park figure of those like the Milky Way and Andromeda?

I was wondering if a galaxy could be perfectly orbiting to create a sort of axis of rotation, with a period being like 50 million years, or is it impossible because of some property that elliptical galaxies have? If it is possible, what is the probability that it exists in our observable...

Homework Statement Astronomers believe that there is a massive black hole at the center of the Milky Way galaxy. What evidence is there for that? A group of astronomers have observed a star "S2" in a 15.2-year orbit around the center of the galaxy. They measured the period of revolution T =...

Homework Statement Suppose that a sprial galaxy has the mass profile: ##M_{disk}(r)=M_d[1-(1+\frac{r}{r_{rd}})e^{-\frac{r}{r_{rd}}}]## Where rrd=3Kpc. and Md is unknown. Like all galaxies, this galaxy also contains dark matter as well as its luminous matter. Using the rotational...

I know some galaxy orbite around other galaxy but are they orbiting only around each other?

Hello everyone, I have a question about metric expansion of space. According to Wikipedia (ok probably is not the best source, but I have only a qualitative understanding of physics) the expansion occurs only at scales larger than galaxy clusters...

Scientists have discovered the most distant galaxy on record EVER, showing a redshift of 7.51 and showing it existed only 700 million years after the big bang. I don't know about you, but I wish my eyesight was this good :P http://www.nature.com/nature/journal/v502/n7472/full/nature12657.html

How can we make the assumption that the Galaxy is approximately in a steady state at the present time? I read this from the textbook: "the time required to complete one orbit at 10kpc is 3×108yr... a typical disk star has completed over thirty revolutions, and hence it is reasonable to assume...

I was thinking about the supermassive black hole that is theorized to be at the center of our galaxy, and indeed, at the center of most galaxies. If that black hole is continuously consuming the stars, planets and gas around it, given enough time, will it not consume the entire galaxy that...

Based on http://en.wikipedia.org/wiki/Sagittarius_A* So "mid to late 2013" - almost the time, are there any new observations yet?

If you had a spring attached to the other side of the galaxy and pulled on it from one end, it can't instantly stretch on the other side, right? Even though that's what springs do? So what would happen?

Hypothesis: Galaxies appear to rotate too fast because their own gravitational lens let's them appear bigger than they really are. Just an idea, do you think it could work ?

Hi, I recall some years ago seeing a composite picture of what our galaxy would look like from outside the galaxy, for example from Andromeda but was not able to find one or even how to search for it on the web. I was wondering if anyone here is familiar with it and perhaps even if we've...

Is it possible that a black hole is so tightly compacted, that its individual particles are unable to move? If this is the case then wouldn't it be extremely cold; close to, or even at absolute zero? Any significant heat would be on the surface caused by friction of attracted matter. With such a...

I need to generate initial conditions for modeling galactic spiral arms. I start with the following polar equation: rho = a. / (log (b * tanh (theta / (2 * n))) with a, b ​​and n are parameters to choose from. to give a thickness along the curve for the generated points, I did the...

I want to know about the center of our galaxy, and every other galaxy by the way, I heard that the condensed matter and light comes from a Super massive black hole that 'aspires' everything around it & I want to know if it's true ( If we have proved it ) or is it just a suposition, & by the way...

The farthest galaxies are receding from us the fastest. Which one holds the speed record? And how fast is it going compared to c?

How would a galaxy rotation curve look if every matter simply had a 6 times larger mass than the visible? (please neglect how that could be) Wouldn't a same size galaxy then reside in a 6 times larger gravitational well so that the spiral arms would still be in the steep part of the well...

Hey all. I'm working on a personal programming project where I'm attempting to simulate (to a small degree) a galaxy. And I have come across a decent 2D density map for a spiral galaxy. This map (array actually) defines a 128x128 grid of values between 0 and 255 representing the frequency of...

I tried out the new version of Lightcone today http://www.einsteins-theory-of-relativity-4engineers.com/LightCone3/LightCone.html It brought to mind, basically just with the default settings, an amazing trek. The one thing I did was open "setup" and get check Vnow and Vthen while X-ing out...

Homework Statement Calculate the time taken to colonize the galaxy using an interstellar ark, making very rough approximations and broad assumptions. There are two rules: 1) The propulsion system must be something that already exists, no warp drives etc 2) Once the ark reaches a planet, the...

Homework Statement A traveller with mass m = 66,5 kg travels with a velocity of 0,82 c to the Andromeda galaxy which is a distance of 2,55·106 lightyears away. Light with the wavelength 459,4 nm is emitted from the galaxy. assume the galaxy doesn't move and use the exact speed of light. How...

I was using Starry Night Pro software tonight, and I was just cutting about the universe having a wee look at the galaxies when I came across this lovely spiral galaxy (hopefully attached). It is named in the software "PGC 38077.1", it has an apparent apparent magnitude of -2.01 (yes, that was a...

At what speed do quasars eject matter out the galaxy. I heard, I don't if I'm remembering correctly, that quasars can eject matter faster then the speed of light and I am very sure i got this information from the show "the universe" a couple years ago.

Hi everyone, I signed up just to ask you guys a quick question, as most of you will know infinitely more than I do on this subject. I'm not an astrophysicist, I have a strong interest in the universe and cosmology, but it's more of a hobby for me than a central focus, so I apologise in...