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Fraser
2004-Aug-06, 06:29 PM
SUMMARY: Astronomers used to believe that dwarf irregular galaxies were leftover building blocks from the beginning of the Universe which somehow avoided getting gobbled up by larger galaxies. New observations using the Subaru Telescope of dwarf galaxy Leo A has challenged this theory, however, as it's clearly been through a lot in its history. Astronomers found that size and structure of Leo A is significantly more complex than previously observed, and it shares many aspects of larger, more complex galaxies like our own Milky Way - it probably went through similar mergings and galactic collisions.

What do you think about this story? Post your comments below.

om@umr.edu
2004-Aug-06, 07:33 PM
Thank, Fraser, for an interesting report.

We continue to learn that we do not know what we thought we knew.

Hopefully Leo A will fulfil its role as the “Rosetta stone” for understanding the process of galaxy formation and evolution.

With kind regards,

Oliver
http://www.umr.edu/~om

Algenon the mouse
2004-Aug-06, 09:14 PM
If they are like their bigger counterparts, then we might be able to learn more about big galaxies by observing the smaller ones.

Any theories about a black hole being in the middle of the smaller galaxies?

sarahnade_me
2004-Aug-07, 12:18 AM
I have a question that was triggered by the last question about there being a Blackhole in the middle of smaller galaxies...Do you think that our galaxy may one day be a lot smaller because of matter taken from the Black hole in the center of our Galaxy? Does the black hole get bigger...and so on...

antoniseb
2004-Aug-07, 10:25 AM
Originally posted by sarahnade_me@Aug 7 2004, 12:18 AM
Do you think that our galaxy may one day be a lot smaller because of matter taken from the Black hole in the center of our Galaxy? Does the black hole get bigger...and so on...
The Black hole in the center of our galaxy will very slowly get bigger, by absorbing material that falls into it. I don't have a paper I can point to that gives hard numbers, but I doubt that Sgr A* has grown more than 10% in mass in the time since our sun was formed.The actual number might be closer to 1%. At some point in the far far distant future , our central black hole may merge with the central black hole from M31. This will hugely increase its size a lot for two reasons:
- the M31 black hole is much larger
- in the process a lot of chaos will interfere with the path of stars and gasses, some of which will suddenly be able to leave orbit and fall into one black hole or the other.

om@umr.edu
2004-Aug-07, 12:52 PM
Sarahnade_me:

Our understanding of Black holes, if Bh's exist, probably does not permit an answer to your question.

Please see the July 15, 2004 news report where Prof Stephen Hawking claims to have solved one of the greatest mysteries of Black holes:

"After nearly 30 years of arguing that a black hole destroys everything that falls into it, Stephen Hawking is saying he was wrong."

http://in.rediff.com/news/2004/jul/15hawking.htm

The concept of Black holes was proposed long before repulsive interactions between neutrons were recognized [J. Fusion Energy 20, 197-201 (2003)]

http://www.umr.edu/~om/abstracts2003/jfe-n...-neutronrep.pdf (http://www.umr.edu/~om/abstracts2003/jfe-neutronrep.pdf)

I.e., the current state of Bh knowledge does not permit an answer to your question.

With kind regards,

Oliver
http://www.umr.edu/~om

antoniseb
2004-Aug-07, 02:20 PM
Originally posted by om@umr.edu@Aug 7 2004, 12:52 PM
the current state of Bh knowledge does not permit an answer to your question.
You post this AFTER I've answered her question.

In fact we do know a great deal about black holes, and can answer her questions. It is true that we do not know for certain the physics of what happens inside the event horizon, be we can be certain that event horizons have formed.

I dispute that the neutron repulsion described in your paper published in the Journal of Fusion Energy is valid, but even if it is, and is relevant to something as massive as Sgr A*, a body of neutron star density that has a mass of three million times the mass of the sun will certainly have an event horizon, and all of the physics associated with the exterior qualities of black holes is valid.

om@umr.edu
2004-Aug-08, 02:37 PM
Sorry, Anton.

I thought Sarahnade_me would be interested in

-1. The recent news report that begins with:

"After nearly 30 years of arguing that a black hole destroys everything that falls into it, Stephen Hawking is saying he was wrong."

http://in.rediff.com/news/2004/jul/15hawking.htm

-2. The recent paper that reports confirmation of repulsive interactions between neutrons [J. Fusion Energy 20, 197-201 (2003)].

http://www.umr.edu/~om/abstracts2003/jfe-n...-neutronrep.pdf

Science is continuously evolving, not a fixed set of truths. Good science always includes a variety of opinions. Measurements dispute or confirm these, hopefully moving science ever closer to truth.

With kind regards,

Oliver
http://www.umr.edu/~om

Algenon the mouse
2004-Aug-08, 06:41 PM
I have always found the event horizon of a black hole fasinating as the laws of our current physics really do not apply to it.

But getting back to my question:

Does anyone know if there is a black hole in the center of these smaller galaxies or is it just confined to the more average or bigger galaxies?

antoniseb
2004-Aug-08, 11:44 PM
Originally posted by Algenon the mouse@Aug 8 2004, 06:41 PM
Does anyone know if there is a black hole in the center of these smaller galaxies or is it just confined to the more average or bigger galaxies?
I've never seen anything mentioning a central balck hole for the Large Magelenic Cloud having been observed [or for any of the other small nearby galaxies], but that doesn't mean it isn't there. There is a good chance that the LMC is debris from the last close encounter between the Milky Way and M31, in which case it wouldn't need to have had a central black hole to form.

Eric Vaxxine
2004-Aug-09, 03:13 PM
Do black holes only form at the center of galaxies? Do they not form elsewhere ie: the edges of galaxies for instance? Are there any hubble pictures of black holes we can look at?

om@umr.edu
2004-Aug-09, 03:30 PM
Eric,

Stephen Hawking is the authority on black holes. Some of us are not yet convinced such exist.

For Hawking's most recent opinions on this matter, see:

http://in.rediff.com/news/2004/jul/15hawking.htm

With kind regards,

Oliver
http://www.umr.edu/~om