Galaxy Definition and 528 Threads

  1. T

    Can Galaxy Lensing Confirm Dark Matter's Presence?

    When we observe galaxy lensing of background objects taking place, is it possible to estimate the total mass of the galaxy carrying out the lensing and from that confirm that dark matter is needed to be present to provide sufficient mass to bend the light by the amount observed? Is there...
  2. liometopum

    Have you explored the incredible galaxies at Galaxy Zoo?

    I have been classifying galaxies at the galaxy zoo site, reachable at https://www.zooniverse.org/ This is a citizen science site, and they need people to help. I have been exclusively at the galaxy zoo site, which you access by clicking on the "Space" link. There are about one million images...
  3. GiantSheeps

    Best way to see Andromeda galaxy

    I just recently got a dobsonian reflector telescope, (Orion SkyQuest XT8 PLUS Dobsonian Reflector Telescope) and I was wondering what the best way to see the andromeda galaxy would be using the telescope? Of these, which would be the best eye piece for that sort of thing?: Orion 2" 28mm...
  4. T

    Massive galaxy cluster could upend theory of universe evolut

    I saw this article and wondered if there is cause for concern? It does seem rather large and well defined so soon after the BB. Massive galaxy cluster could upend theory of universe evolution...
  5. L

    Naive Question regarding Galaxy Rotation Curves

    Many apologies in advance if this question is ridiculous or if it has already been answered on another thread. I've searched and searched through the forums and haven't found the answer - please do direct me accordingly if that's possible. If not - please help! Preamble: We know from...
  6. jedishrfu

    Too Cool Not to Show: Wikipedia as a Galaxy of Articles

    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
  7. M

    Solving Gravitational Lensing Homework for Hubble Constant

    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...
  8. N

    Our galaxy is one of the biggest

    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...
  9. wolram

    How Did Supermassive Black Holes Grow So Massive So Quickly?

    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?
  10. P

    Zero gravity in spiral galaxy center?

    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...
  11. Spinnor

    "Churning galaxy boasts a fiery halo of baby stars"

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

    How is the Rotational Velocity of Galaxies Measured?

    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...
  13. P

    Astronomy iron ratios in galaxy

    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
  14. C

    Oldest part of the galaxy that could have held life?

    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...
  15. wolram

    Galaxy Formation: Searching for Primordial Origins

    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?
  16. ZetaOfThree

    Samsung Galaxy Note: Does it Fit in Your Pocket & Do Math?

    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...
  17. J

    Why does the galaxy LEDA 074886 appear rectangular?

    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) ...
  18. J

    Dark Matter. Space-Time curvature. Galaxy formation

    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...
  19. M

    Exploring the Mystery of Expanding Galaxy Rates

    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...
  20. DennisN

    Unidentified emission line in Galaxy Clusters

    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...
  21. E

    The Effect of Planets Rotation within its Galaxy?

    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...
  22. E

    Data on the Velocity of the Celestial Bodies Orbiting a Galaxy

    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...
  23. S

    Structure of galaxy and the laws behind it

    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.
  24. C

    Trio of Big Black Holes Found in Galaxy Smashup

    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...
  25. B

    How Did Scientists Miscalculate the Distance of UDFj-39546284?

    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 " 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 the...
  26. C

    Five Cepheids Detected on the Other Side of the Galaxy

    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...
  27. D H

    Superkick: Galaxy mergers can eject the central supermasive black hole

    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...
  28. D

    Can we see past from light from nearby galaxy?

    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?
  29. photonkid

    Galaxy separation faster than the speed of light

    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...
  30. junfan02

    Usage of doppler effect to measure speed of a galaxy

    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?
  31. U

    Exploring Galaxy Collisions and Dark Energy's Impact on Galactic Movement

    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?
  32. I

    Could an eliptical galaxy exist with an axis of rotation?

    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...
  33. O

    Find mass of black hole in center of galaxy given eccentricity+

    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 =...
  34. B

    What is the Mass of Dark Matter in a Spiral Galaxy?

    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...
  35. 1

    Are galaxy orbiting around something?

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

    Why space expansion is limited to scales larger than galaxy clusters?

    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...
  37. B

    Most Distant Galaxy EVER Discovered

    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
  38. M

    Is it Reasonable to Assume our Galaxy is in a Steady State?

    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...
  39. T

    Consumption of a galaxy by its central black hole

    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...
  40. D

    Star is expected to be torn apart in the center of our Galaxy

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

    A spring attached to the other side of the galaxy

    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?
  42. A

    Galaxies Rotate Fast: Gravitational Lens Effect

    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 ?
  43. J

    Looking for composite picture of Milky-way from outside galaxy

    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...
  44. F

    The Meissner effect within a galaxy

    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...
  45. F

    How to Generate Initial Conditions for Modeling Galactic Spiral Arms?

    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...
  46. W

    Center of the galaxy and the great attractor

    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...
  47. E

    What is the maximum recessive velocity of a galaxy in the observable universe?

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

    Galaxy rotation curve of higher mass galaxy with same size

    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...
  49. C

    Normal distribution and star density in a Galaxy

    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...
  50. marcus

    Can a Message Travel Faster Than Light to Reach a Distant Galaxy?

    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...
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