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Spiral galaxy or Elliptical galaxy Samenness



 
 
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  #1  
Old November 27th 03, 02:54 PM
G=EMC^2 Glazier
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Default 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

  #2  
Old November 27th 03, 05:21 PM
John Zinni
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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



  #3  
Old November 27th 03, 10:02 PM
Mysak
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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




  #5  
Old November 28th 03, 06:34 AM
David Knisely
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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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  #6  
Old November 29th 03, 12:50 PM
Painius
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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



  #7  
Old November 29th 03, 08:45 PM
David Knisely
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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  
Old November 29th 03, 10:30 PM
Odysseus
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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  
Old November 30th 03, 01:02 AM
Jonathan Silverlight
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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  
Old November 30th 03, 07:32 AM
David Knisely
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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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