Galaxy Definition and 528 Threads

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...

Hello, I'am studying a code (called "starscream") which allows to make initial conditions (positions and velocities) for NBody simulation. They are based on Springel and White (1999) model. I have several problems about the underlying equations used in this code. Firstly, See attachment...

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...

Hello, Whenever I read over net or search over some pictures of galaxies, the Andromeda galaxy pops up in the list as first and some resources mention it to be the nearest galaxy to our Milky Way. Wikipedia suggests Canis Major Dwarf as the nearest: 0.025 mly. It is always in picture or...

This question may be quite trivial but I was wondering if you were observing a galaxy that was say 10 arc seconds in diameter with a telescope whose diffraction limited resolution was 15 arc seconds would the galaxy appear completely unresolved or just "blurry".

In the January 2013 issue of Physics World there is an article by Steve Eales, illustrated with some remarkable images of galaxies obtained with the Herschel observatory. One, on page 31, is very appropriately captioned "Not stars; galaxies", because it looks very like star clouds, say in...

Hello, If I am not wrong, I think that no galaxy can be viewed from Earth with naked eye, right?

http://www.theregister.co.uk/2013/01/08/17_billion_other_Earth's/ "there are 17 billion other Earths in our galaxy, the Milky Way." and that's only this galaxy. How many there are in the entire universe?! Also, does anyone out there know we are here? Are they counting us a part of some...

"A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda Galaxy" Published in Nature 3 days ago. Rodrigo A. Ibata, Geraint F. Lewis, Anthony R. Conn, Michael J. Irwin, Alan W. McConnachie, Scott C. Chapman, Michelle L. Collins, Mark Fardal, Annette M. N. Ferguson, Neil G...

Hello, this is my first topic/question, thanks for reading thus far... It is very easy to find explanations about the general path that the solar system takes when it orbits the center of our galaxy, when viewed in 2D from above, a circle around the center some distance away from that center...

The Milky Way is a Barred Spiral Galaxy 100,00 -120,000 Across. I was wondering if there is a website or list of what Stars of Constellations exist in what Spiral Arm. I there exists: Orion-Cygnus Arm Perseus Arm Scutum-Centaurus Arm Norma and Outer Arm Carina-Sagitarius Arm...

http://arxiv.org/abs/1211.3663 CLASH: Three Strongly Lensed Images of a Candidate z ~ 11 Galaxy Dan Coe et al (Submitted on 15 Nov 2012) We present a candidate for the most distant galaxy known to date with a photometric redshift z = 10.7 +0.6 / -0.4 (95% confidence limits; with z < 9.5 galaxies...

Dear All, If the image we see from a distant galaxy shows how it looked 1 billion year ago, what would that galaxy appear if we are traveling towards it at the speed of light? Do we see the galaxy developing twice as fast? It would be great if someone could explain it with both a simple...

Hope you enjoy the following, http://www.youtube.com/watch?v=_Ssc1GsqHds&feature=player_embedded From, http://planetsave.com/2012/10/20/galaxies-trend-towards-more-ordered-disk-like-forms-over-time-upending-old-assumptions/

MACS 1149-JD is the now the oldest, most distant Galaxy discovered to date. It began forming during the "dark ages" just 300Million years after the BB and was viewed here on Earth as it was when the Universe was 500Million years old...

Hello, I'm trying to simulate disc galaxy dynamics with a nbody code. The main problem is to get good initial values (positions and velocities of each star) in order to reproduce the experimental dynamics. For the positions, I began by generating a gaussian distribution of stars on 0x...

I'm having a bit of trouble wording this particular question, but here goes. Let's say I'm observing a spiral galaxy which is 100,000 lightyears across. The furthermost stars are seen as they were 100,000 years ago (not counting the number of lightyears away from the galaxy I'm positioned). What...

Homework Statement We are not allowed to use any videos from youtube. They have to be a realiable source. We are having difficulty copying the embeded link to the power point presentation. Homework Equations The Attempt at a Solution First, we right click on the video to copy it...

How strong is the influence of dark matter typically at the periphery (50.000 LY away from the center) for example in the Milky Way I mean is the Acceleration Due to Gravity (due to dark matter) (typically) 80% - 85% - 90% - 95 % - or 97% stronger as the Acceleration Due to Gravity caused...

anyone read this article about latest relevation about dark matter? any thoughts? http://arstechnica.com/science/2012/07/dark-matter-is-the-thread-connecting-galaxy-clusters/

How strong is acceleration due to gravity ? For example at the periphery at a galaxy ?

The frequency of supernovas in our galaxy is about one per century. Has there been a supernova in the Andromeda Galaxy in the last 200 years?

Is it possible to see galaxies/clusters/astronomical-objects "outside" our own galaxy without use of a telescope or equipment, other than our eyes? Thanks;)

A HST team measure the sideways motion of Andromeda so they can be definite about the collision.Here is a movie. http://hubblesite.org/newscenter/archive/releases/2012/20/video/a/ Here are the technical papers that the movie and press releases are based on: http://arxiv.org/abs/1205.6865 The...

Hi, I have been trying to understand the nature of rotating objects within a galaxy, but with limited sucess. I am trying to understand if the rotation of objects (for example solar systems / stars / black holes within the Milkyway galaxy) are generally consistent with the rotation of the galaxy...

%area of the universe is galaxy? Hi. I'm trying to determine the approximate percentage of the universe's area that is made up of galaxies for a question I was asked earlier this week. I have been looking everywhere and can not find any information of use. Can someone please help?

Homework Statement The sun mass MS = 2.0 E30 kg revolves around the center of the milky way which has a total extension of 2.2 E20 m. The sun takes 2.5 E8 years to complete one revolution. Estimate the number of star in our galaxy based on this data. Suppose that the distribution is...

I'm becoming more and more convinced that light isn't the only particle that can interfere with itself, and that the behavior may instead be a function of a particle's level of interaction. The multi-galaxy collision we witnessed not long ago may have been the first time we've had the scale...

This seems like it would be fairly complex as any material that is not in the suns would absorb photons and convert part of that energy over to kenetic energy giving a false value for actual luminosity from the stars themselves. Galaxies appear to be very different from one another, is it...

Hello, When you look at the accretion disk around NGC 4261 (see here), you can read that the dark, dusty disk represents a cold outer region which extends inwards to an ultra-hot accretion disk with a few hundred million miles from the suspected black hole. So, from the outside, you have...

Hypothetically speaking of course, if we were to observe a galaxy billions of light years away on the opposite end of the universe through a wormhole, what would the red shift look like compared to other galaxies in the observable universe? For example, I'll set up a thought experiment. We...

are all stars in some galaxy? i now get interested in the universe could anyone recommend some basic textbooks for me? i have a doctor degree in theoretical physics.

A highly magnified candidate for a young galaxy seen when the Universe was 500 Myrs old http://arxiv.org/abs/1204.2305 "... We derive a robust photometric redshift of z = 9.6 ±0.2, corresponding to a cosmic age of 490 ±15Myr (i.e., 3.6% of the age of the Universe). ... The object is the...

From what i know there is this Goldilock Zone of the galaxy where is not too much radiation coming from the Super Massive Black Hole at the center of our galaxy and where our solar system is... but in the future, can we venture closer to the center of the galaxy where is no more the galactic...

Homework Statement I'm trying to understand how the mass of a galaxy at redshift 1 can be estimated by knowing its luminosity in the K-band. I've been told you are able to use the IMF but I'm not sure of the details. I really don't see how you could use the salpeter, or the luminosity...

Im trying to calcuate the energy output of Saigtarius A star if it were to accrete material at the same rate as a typical Seyfert Galaxy which I understand to be about 1 solar mass per year (correct?). I am getting an answer that looks way too low. As I understand it we should get a number...

Hey all. Just finished my best galaxy picture yet, this time of the Whirlpool Galaxy, AKA Messier 51. Enjoy! http://img13.imageshack.us/img13/5875/m51colorfinal.jpg

In another topic, a member dave13214321323 or whatever his name is :p said that the popular opinion is that in the early universe gas contracted into denser spaces forming galaxies and black holes were consequences of galaxy formation, not the other way around; Black holes at centers of galaxies...

It is said that it takes a particle accelerator the size of a milky way to probe the Planck length. But with the resources available in the universe and with other billions year A.D. civilizations out there existing. What if they had created one already. Is there any galaxy out there that look...

Hi Astro forum... I have got something to clarify which came across my mind as I was trying to answer few problems.So without any further delay , let's start : For simplicity we will assume that dark matter doesn't influence the center of mass of galaxy A. Now let's say galaxy A has mass 'M'...

If an observer on the Andromeda galaxy looked back at us, how would the Milky Way galaxy look to him? Edge-on, spiral face on, or in between?

Hello, What do Alfven waves look like? Say you have a spherical galaxy. What would the Alfven waves of the three lowest frequencies look like? I read that they are transverse waves but I can't visualize a spherical transverse wave. Thanks! :)

Is a quasar a one off phenomenon at the inception of a galaxy, or does a super massive black hole produce quasars repeatedly as a by-product when there is too much matter to be absorbed.

Reading through various publications for Luminosity Functions and it mentions completeness a lot without ever explaining what it actually is. Could someone shed light on this please? Thanks

http://www.tecca.com/news/2011/01/26/nasa-announcement-details-hubble-discovery-of-oldest-galaxy-ever-seen/ How is the age of the Universe most accurately estimated and is it possible there is a discrepancy between the Oldest observed Galaxies and the estimated Age of the Universe...

Two thoughts on this. If the Milky Way is one hundred light years in diameter and Andromeda is 2.5 million light years away that means Andromeda is 25 times the diameter of the Milky Way distant from us. That's not much. When will they merge? And I wonder how long it will take for the...

it takes many years to see the change of arms of a galaxy. so how was the rotation of arms measured?