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Spiral galaxy or Elliptical galaxy Samenness
We read that spiral galaxies have blackholes at their cores. I don't
hear that elliptical galaxies have blackholes at their cores. I read that elliptical galaxies are created when two spiral galaxies collide(come to gether) That means they can have two blackholes revolving around each other. This could create a very bright core. I saw a picture of elliptical galaxy NGC 147 and that is how I came up with this thinking. Bert |
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"G=EMC^2 Glazier" wrote in message
... We read that spiral galaxies have blackholes at their cores. I don't hear that elliptical galaxies have blackholes at their cores. "What evil lurks in the hearts of galaxies? This Hubble Space Telescope picture of the center of the nearby elliptical galaxy NGC 4261 tells one dramatic tale. The gas and dust in this disk are swirling into what is almost certainly a massive black hole." http://antwrp.gsfc.nasa.gov/apod/ap971019.html I read that elliptical galaxies are created when two spiral galaxies collide(come to gether) That means they can have two blackholes revolving around each other. This could create a very bright core. I saw a picture of elliptical galaxy NGC 147 and that is how I came up with this thinking. Bert |
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We read that spiral galaxies have blackholes at their cores. I don't
hear that elliptical galaxies have blackholes at their cores. just take o look on matter burst from galaxy M87 - it's huge elliptical galaxy and that burst is from supermassive black hole in its core. Not all of spiral galaxies have its own supermassive BH in its core. M31 yes, our Galaxy propably yes but M33 not and so on I read that elliptical galaxies are created when two spiral galaxies collide(come to gether) That means they can have two blackholes revolving around each other. This could create a very bright core. NOT TRUE. Astronomers don't know how the evolution goes at galaxies, but it seems, that spiral galaxies are envolving through time from some elliptical galaxies (and some elliptical galaxies stayed elliptical). By the way - BH in center of a galaxy is no reason for some 'bright core' I saw a picture of elliptical galaxy NGC 147 and that is how I came up with this thinking. elliptical galaxy NGC 147 is no good example. This is one of many and many dwarf galaxies, these are to small to evolve to any galaxy with spiral structure. There is a huge difference between 'normal' elliptical galaxies (like M87) and dwarf elliptical galaxies (like these two 147 and 185). By the way, these two a actually satelites of our Galaxy and it's gonna swallow them both in time. Mysak |
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#5
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Mysak wrote:
NOT TRUE. Astronomers don't know how the evolution goes at galaxies, but it seems, that spiral galaxies are envolving through time from some elliptical galaxies (and some elliptical galaxies stayed elliptical). By the way - BH in center of a galaxy is no reason for some 'bright core' Actually, detailed computer simulations and long-exposure imaging have shown clear evidence that many of the giant elliptical galaxies in large galaxy clusters were created from the merger of other galaxies (including spirals) in the very distant past. Some giant ellipticals show very faint indications of residual spiral structure, plumes, odd dust lanes, or outer ring structure, while a few others show double nucleii (ie: nucleii of two colliding galaxies achieving a rough orbit around each other). There is a huge difference between 'normal' elliptical galaxies (like M87) and dwarf elliptical galaxies (like these two 147 and 185). By the way, these two a actually satelites of our Galaxy and it's gonna swallow them both in time. NGC 147 and 185 are distant companions of the more massive galaxy M31 and not of our Galaxy. Although M31 shows a negative radial velocity, it is by no means certain that it will collide with us in the distant future, as there is no way to accurately gage its proper motion and transverse velocity. Clear skies to you. -- David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 11th Annual NEBRASKA STAR PARTY * * July 18-23, 2004, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** |
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"David Knisely" wrote...
in message news:1069997748.51585@rh9cache... . . . Although M31 shows a negative radial velocity, it is by no means certain that it will collide with us in the distant future, as there is no way to accurately gage its proper motion and transverse velocity. Clear skies to you. This is the first time that i've heard an astronomer say this. Most scientists still seem to believe that Andromeda will collide with the Milky Way in about 5 billion years. And i've been saying all along that the blue shift can only show radial velocity, that Andromeda could be coming in our general direction at an angle that would cause it to miss us by a country megaparsec. That the chances of it actually colliding with us could be slim to none. Thanks, David, for this bit of validation. Do you know if there are other astronomers out there who are warming up to this view? And how do you feel about the possibility that our Milky Way, the Andromeda and the Triangulum are revolving around a common CG that might even consist of a huge mass of dark matter? -- David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 11th Annual NEBRASKA STAR PARTY * * July 18-23, 2004, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** happy days and... starry starry nights! -- a Secret of the Universe... so please don't breathe a word of this-- the Moon above will smile perverse whene'er it sees two lovers kiss; (breathe not a single word of this!) Paine Ellsworth |
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Panius wrote:
This is the first time that i've heard an astronomer say this. Most scientists still seem to believe that Andromeda will collide with the Milky Way in about 5 billion years. And i've been saying all along that the blue shift can only show radial velocity, that Andromeda could be coming in our general direction at an angle that would cause it to miss us by a country megaparsec. That the chances of it actually colliding with us could be slim to none. Thanks, David, for this bit of validation. Do you know if there are other astronomers out there who are warming up to this view? The only astronomers who are saying that M31 will (ie: with certainty) collide with us are either those who are not very well versed in the subject, or those who are trying for some headlines (I suspect the latter). The radial velocity component of M31 (corrected for our solar-system's rotation about the Milky-Way's galactic core) has been known for at least several decades, so when I heard about someone trumpeting about a "collision", I said to myself, "Its probably grant-renewal time again", as you see these sort of news releases put forward by groups hoping to get enough publicity to justify the continuation of funding. I saw this a few years ago when some group claimed that the Earth had a "companion" body, when it was nothing of the sort (merely an asteroid that happened to have an orbital period of about one year). Indeed, the corrected value of the approach speed component is only on the order of *100 kilometers per second*. I have seen values up to as high as 110 km per second in approach, but again, this is only the radial velocity and not the true space velocity. M31's companion galaxy M32 has a corrected radial velocity of 86 kilometers per second *in recession*, so obviously its orbital motion about M31 is a significant factor in that figure. I still see claims on the internet of outrageous velocity figures for M31, all because some yo-yo forgot to subtract out the rotational speed component of our solar system about the galactic core (you would think someone who is supposedly well-versed in Astronomy would have mastered simple freshman-level vector mechanics by now). And how do you feel about the possibility that our Milky Way, the Andromeda and the Triangulum are revolving around a common CG that might even consist of a huge mass of dark matter? There is no evidence of this, so as far as I am concerned, its merely speculative. Clear skies to you. -- David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 11th Annual NEBRASKA STAR PARTY * * July 18-23, 2004, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** |
#8
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David Knisely wrote:
Indeed, the corrected value of the approach speed component is only on the order of *100 kilometers per second*. I have seen values up to as high as 110 km per second in approach, but again, this is only the radial velocity and not the true space velocity. M31's companion galaxy M32 has a corrected radial velocity of 86 kilometers per second *in recession*, so obviously its orbital motion about M31 is a significant factor in that figure. I still see claims on the internet of outrageous velocity figures for M31, all because some yo-yo forgot to subtract out the rotational speed component of our solar system about the galactic core (you would think someone who is supposedly well-versed in Astronomy would have mastered simple freshman-level vector mechanics by now). What is the currently accepted value for the sun's velocity vector WRT the centre of the galaxy? Can you recommend a reference that provides some detail on how the true speed and direction are determined? According to Burnham the solar system is heading in the general direction of Vega (IIRC his position for the Solar Apex is actually in Hercules); the derivation seems to have been accomplished by surveys of stellar motions. But he doesn't go into much detail; I'm left wondering in particular how astronomers compensate for the likelihood that most of the stars surveyed (at least those of Population I) are part of a great 'stream', roughly comoving with the sun as components of the Orion Arm. How is the 'net' motion of the solar system relative to visible stars translated into an 'absolute' frame of reference? -- Odysseus |
#9
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In message , David Knisely
writes Panius wrote: This is the first time that i've heard an astronomer say this. Most scientists still seem to believe that Andromeda will collide with the Milky Way in about 5 billion years. And i've been saying all along that the blue shift can only show radial velocity, that Andromeda could be coming in our general direction at an angle that would cause it to miss us by a country megaparsec. That the chances of it actually colliding with us could be slim to none. Thanks, David, for this bit of validation. Do you know if there are other astronomers out there who are warming up to this view? The only astronomers who are saying that M31 will (ie: with certainty) collide with us are either those who are not very well versed in the subject, or those who are trying for some headlines (I suspect the latter). The radial velocity component of M31 (corrected for our solar-system's rotation about the Milky-Way's galactic core) has been known for at least several decades, so when I heard about someone trumpeting about a "collision", I said to myself, "Its probably grant-renewal time again", as you see these sort of news releases put forward by groups hoping to get enough publicity to justify the continuation of funding. Isn't the point that the transverse velocity is unknown? How big would it have to be before we can be certain that M31 will miss us (bearing in mind that M31's radial velocity is well below "our" galaxy's escape speed?) And is there any chance of measuring the transverse velocity, for instance by measuring the position of the centre of M31 relative to distant objects such as quasars? -- Rabbit arithmetic - 1 plus 1 equals 10 Remove spam and invalid from address to reply. |
#10
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Jonathan Silverlight wrote:
Isn't the point that the transverse velocity is unknown? Yes, it is, but unfortunately, that isn't what many of the quotations from press releases said. More than a few used the words "will collide", instead of "may collide". Again, the idea of a possible "head-on" collision gets the most attention (and maybe the most bucks depending on the researchers). The most likely scenario is that M31 and our Milky Way galaxy will pass each other, perhaps becoming slightly distorted due to tidal interactions, as M51 and its large companion galaxy NGC 5195 are doing. It is just too soon to tell. How big would it have to be before we can be certain that M31 will miss us Oh, I imagine 300 to 800 years would probably be enough, although with extended baseline radio interferometry (and suitable reference radio "noisy" quasars along or close to a visual line close to that of M31's nucleus), this number range could easily be cut in half. Clear skies to you. -- David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 11th Annual NEBRASKA STAR PARTY * * July 18-23, 2004, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** |
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