What is the structure of most radio galaxies?
926329
Rocks, dust and icy carbon particles and have many carbon Dioxide.
70579
Interesting. I vaguely remember a "great attractor" from chaos theory, but what I find when I look it up now is that it refers to a cluster of galaxies, "in the direction of Centaurus and Hydra" where nobody is sure why they're grouped like that.\n\nHere's a direct quote from another source though which I think directly addresses what you're asking about: The galaxy rotational problem refers to the phenomenon of the descrepency between the observed rotational motion of the matter of the galactic disc from the predictions of Newtonian dynamics. (See links below and search for "12.25.I".)\n\nI think in layman's terms what they're boggling about is the "bar" shape that occurs in most galaxies, our own apparently included. A recent issue of Scientific American had a very good theory on how that occurs and why.\n\nIf I'm getting the gist of it right, they're not sure why clusters of stars occur in a semi-pinwheel pattern, since based on observed mass there simply isn't enough to cause such a structure to form or remain stable.  The theory in SciAm had something to do with a coincidence of travelling wave patterns rather than any deep dark mysteries of physics, filiments, or anything else.\n\nSee http://www.sciam.com/, October 2005 issue, p. 43, "Ripples in a Galactic Pond." Very nice article and they explained it more clearly than anything I could put together.
138345
Just about all astronomers agree that at the center of our Milky Way Galaxy (and probably at the center of most other galaxies) lies a supermassive black hole. It probably has a mass at least 2-million times that of our Sun, and is approximately 96-million miles in diameter.\n\nThese figures come from careful observation and measurment of the motions of other objects near the galactic center.\n\nThis page has more info, plus a photo ---\nhttp://antwrp.gsfc.nasa.gov/apod/ap021018.html
890850
Yes, our galaxy (and the local group) is generally heading in the direction of the virgo cluster of galaxies. All together, we are moving in the direction of a much larger structure called the 'Great Attractor' that is in the direction of the constallation of Centaurus. I'm guessing that this is what you heard about.\n\nhttp://en.wikipedia.org/wiki/Great_Attractor
789137
Galaxies are a collection of billions of star systems (like our solar system) all rotating about one central mass, called the galactic center.   They are the largest "structures" in the universe, and there are as many galaxies out there as there are stars you can see in the night time sky.
663722
The largest galaxies that we know of are giant elliptical galaxies in the centres of clusters of galaxies. They are sometimes called cD galaxies (for giant diffuse galaxies) or BCGs (for brightest cluster galaxies). These galaxies are about 10 times more luminous that a typical galaxy (like the Milky Way) and about 100 times more massive. They can have diameters of more than 6 million light years (compare to about 100 thousand light years for the Milky Way). A good example is the central galaxy in the cluster Abell 2029. \n\ncD galaxies are thought to grow by accreting any galaxy that comes anywhere near them, and in the centre of a cluster this can be a lot of galaxies over the age of the universe - so their mass can grow by a large factor. They usually have an area around them in which no smaller galaxies are found (as they've all been 'eaten') and a diffuse halo of gas and dust which is thought to be the debris of the smaller galaxies.
270562
This has been asked maybe 137 times but instead of researching, please, keep asking.  The latest research shows that it is expanding faster than ever.  So it will probably keep going.  There is no 'edge' to the galaxy and nobody understands why.  I personally think it has a finite size but it is expanding at the speed of light.
425326
The spiral arms and the "halo" in the center, which is thought to be massive amounts of stars and light trapped in an extremly large black hole.\n\nAlso, there is evidence in super nova explosions that show the propable formations of large black holes and, eventually, galaxies.
777198
the Milky Way is a galaxy
529002
The obvious answer is black holes. But other kinds are non reflective nebulae and dark matter.
295233
there are as many as 200 billion galaxies in the observable universe
215166
Let´s say there is a bubble of radio signals moving away from earth at the speed of light. It should have an average radius of about 100 lightyears since radio came into use about 100 years ago (tv about 30 years later). Most of the earliest transmissions didn´t last very long so they would make a coneshaped bubble expanding from earth as earth would block it going in all directions. As more radios came into use the cones would combine to form a highly irregular radio bubble. A radio cloud would be a more accurate description. But let´s just say it is a sphere with an average radius of 100 ly.\n\nI haven´t been able to find a chart with more than 34 of the nearest stars (you may have more luck). They are all within a 13.05 lightyear radius of earth. Let´s say that the density of stars within a 100 lightyear radius from earth is uniform (it isn´t) then there could be as many as 15300 stars within that radio bubble. So if there are any ham radio alien dudes on a planet among those 15300 stars then they would know we are here...
212650
Check your terminology! A spiral galaxy is an immense collection of stars, planets along with huge clouds of dust and gas. Our sun and its planets are inside a spiral galaxy called the Milky Way.\n\nGod is spelled B-I-G B-A-N-G\nPBrax@netscape.com
224500
Wikipedia claims that the observable universe contains about 7 × 1022 stars, organized in about 100 billion galaxies, which themselves form clusters and superclusters. An Ask the Scientist response to this question claimed that there are about 10 billion (10^10) stars in an average galaxy, \nand there are about 10 billion galaxies that we can observe in the universe, so the answer is 100 billion billion or 10^20. I don't think it is an issue that we have a precise answer for as yet.
788068
Almost none. The Andromeda spiral is visible without a telescope or binoculars and the Magellanic clouds are also. There are the only galaxies visible without some optical aid. The previous poster forgot the Magellanic clouds, which are visible from the southern hemisphere.
79909
Some galaxies form in spiral or disk shapes similar to the disks found in star systems.  These are spiral galaxies.  However some, actually the majority, form in sphere like shapes.  These are the called elliptical galaxies.  Do a google image search of "NGC 1316" to see one of these. \n\nGeneral relativity need not be applied to understand the formation mechanism.  Galaxies are believed to form in a similar way that stars form.  You start with a giant spheroidal cloud of material which undergoes gravitational contraction through some kind of induced instability.  The cloud contracts to a smaller size due to gravitational forces and as a result the cloud must spin faster in order to conserve angular momentum (a type of energy conservation).  The last sentence is the real key here. \n\nThe consequence of a contracting cloud spinning faster is to flatten out into a disk shape.  The inward gravitational pull does the "flattening" while the spin-up, so to speak, extends out the disk.  This is analogous to spinning out dough to make a pizza or watching a baseball stretch in the middle as a result of rapidly spinning after a pitch as been fouled off.   \n\nThe motion of the stars and gas in the galaxy does start out random but then is forced into a disk shape as a result of the aforementioned effects.\n\nThere are still a number of mysteries that surround how galaxies form.  Currently we don't know why some galaxies are elliptical while some are spiral?  Can one turn into the other?...among other questions.\n\nI hope that helps.
575553
Nope.  Whoever told you this has been watching too much science fiction.\n\nBlack holes are just collapsed stars, and their gravity is no bigger than any other star (except to things that are very close to it).  There are enormous black holes at the center of galaxies, but these don't pose a threat to the majority of the galaxy ... and the earth is way out near the edge of our galaxy.  And there is no black hole even theorized that is big enough to swallow entire galaxies.