Galaxy Definition and 510 Threads

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...

How can we see the x-ray emission from the center of our galaxy? I thought that the intersteller dust extinguished practically all of the visible light from that direction, which is why we can't "see" the bulge. How then, can even shorter wavelength photons manage to get through? I thought...

Can anyone work out the probabality of intelligent life at around our current level exisiting within our galaxy.

several months back some PF people were discussing the finding of a z = 10 galaxy by a French team led by Roser Pello Now three Anglo-Saxons at the Imperial College have reluctantly expressed doubts: they have tried to find the reported Lyman Alpha line and did not see it. S. J...

Largest Galaxy: The central galaxy of the Abell 2029 galaxy cluster, 1,070 million light-years from Earth, has a major diameter of 5.6 million light years - 60 times the diameter of the Milky Way Galaxy. Reference: Guinness World Records 2000 - Millennium Edition

why aren't we spending more money on developing nuclear-powered rockets? an interesting article about nuclear rocket propulsion "...Nuclear-reactor rockets, like the ones that would be used in the Bimodal Nuclear Thermal Rocket, conduct nuclear fission reactions -- the same kind employed...

Would you please tell me what is in there ? I mean what substances are existing ? Where can i find out some information about this ? Thank you very much,

Our solar system is in the milky way galaxy. if you are told that in another galaxy a planet p has a circular orbit equal to that of the Earth's (that is they both have the same radius). the masses of the suns in the 2 galaxys are Se and Sp respectively and planet p completes its orbit in half...

thanks to MARCUS. this discussion started in S B and LQG, i thought i had better move to a more appropriate place. the recent discovery of a Z=10 galaxy, if confirmed means it was was formed when our universe was only 500MYs old. this paper discuses the discovery...

i don't understand how dark matter acts upon the rotation of a galaxy. galaxy rotation doesn't work the same way that solar system rotation does in that it's not a simple gradient of further planets rotate slower, right? nor is it further planets rotate faster, like a vinyl record...i take it...

I bought a nexstar 114gt a few months ago, and I have been unable to use the auto align features, which would allow me to use the tracking and goto features on the telescope. I am not certain if the telescope itself is flawed, or if I am simply doing something wrong. I sent two emails to...

Roser Pello and her colleagues at the MidiPyrenees observatory have reported finding a z=10 galaxy this galaxy is currently 31.5 billion light years from us and is receding from us at 2.3 times the speed of light for more details see "the most distant object thread" especially links...

This is my first post, so I am going to get straight into a double barreled question that has been bugging me for a while. (1) How long does it take for stars to conglomerate around a general loci, in order to form a proto-galaxy. ? I ask this in the light of the most recent Hubble images...

Dear Sir, Please Find the story at the link http://www.internationalreporter.net/scripts/headDetails.asp?id=108 which has a story ,also given under. This could be an eye opener to the scientific community. We definitely seek your response regarding this. Thanx.. Arif FARTHEST...

I hadnt heard of GW recoil imparting velocity to a black hole. http://www.arxiv.org/astro-ph/0402056 "How Black Holes Get Their Kicks..." It's an article by three people, from Cornell, MIT, and Chicago. When two black holes spiral in and merge, linear momentum is carried off...

So, this doesn't fit the current model, right? http://heraldsun.news.com.au/common/story_page/0,5478,8344220%255E662,00.html Nasa: http://www.gsfc.nasa.gov/topstory/2004/0107filament.html

A newly released mosaic image from Hubble, with 4 billion pixels, covering a square of sky about 1/2o wide, with an angular resolution of 0.05", and a depth of 24 or 25 mag. "Not only does the GEMS study cover a large area at high resolution; it is also a three-dimensional map. Of the 60,000...

First of all let me say Hello! as this is my first post. I am a biologist, and have been reading over the very basics of SR for a little while and have a lot of questions on the implications of the theory. I had been asking my questions primarily at a different forum, one that wasn't...