Talk:Sagittarius A*

From Wikipedia, the free encyclopedia

Contents

[edit] Map?

I like to look up into the sky and recognise stories, myths and cosmologies that the heavens provide. It would be nice if someone provided a constellation map of the Sagittarius that showed which visible stars that approximates the centre of our galaxy. —Preceding unsigned comment added by Xact (talk • contribs) 01:31, 23 January 2008 (UTC)

[edit] Sgr A* vs. Sgr A

The "A*" is probably a matter of notation. The bright stuff at the center has been called "Sagittarius A" for quite some time, and once resolution improved they discovered it had two parts, a hypernova remnant and something else I forget--these are "Sagittarius A East" and "West." Further improved resolution came up with a superpowerful radio point--and, with a point nestled within Sagittarius A, it wouldn't be too much of a stretch to assign it a "*" to indicate this.

This is just conjecture; I'm not an astronomer. --The Centipede

I've reverted the changes, and cleaned up the text to make the distinction between Sagittarius A and Sagittarius A* clearer. This article should probably actually be merged with/redirected to the Sagittarius A article, as there isn't much extra information presented here. --Christopher Thomas 02:00, 13 Apr 2005 (UTC)

[edit] Proposed merge with Sagittarius A

Why exactly is the merge being proposed? I'm not saying that it would be a _bad_ thing, I just don't see what's wrong with the current situation.

If a substantial number of lurkers come forward in favour of the merge, I'll be happy to merge it, but I'd prefer not to bother. --Christopher Thomas 05:10, 27 March 2006 (UTC)

[edit] Nay.

I came to this article look specifically for information on Sagittarius A*. Merging would be confusing and all together pointless Nintenfreak 21:51, 30 March 2006 (UTC)

Agree. They are two different things that have very similar names for historic reasons. Sagittarius A is the central region of our galaxy. Sagittarius A* is the much smaller, detectable shell around the super-massive black hole at its heart. It's like saying we should combine the sun and solar system articles. agr 22:10, 30 March 2006

[edit] Nay2

No merge... above arguments say it all. Sagittarius A* is the ultimate hub of our galaxy, and is deserving of a wikipedia survey peg. NevilleDNZ 09:40, 4 April 2006 (UTC)

[edit] I say Nay

No merge, A* is a more specific feature Zzzzzzzzzzz 00:13, 13 April 2006 (UTC)

I've removed the merge templates, as we've had 3 votes against and one abstention since the merge was proposed. --Christopher Thomas 18:43, 14 April 2006 (UTC)

[edit] Update mass

The page Supermassive black hole seems to be based on newer research and mentions a mass of 3.6 millions times the mass of the Sun. See also the UCLA article linked from there. --Andrei Badea 10:19, 17 April 2006 (UTC)

[edit] What's a supermassive blackhole eruption like?

Is this object going to erupt in 10 million years? Xaxafrad 05:51, 11 December 2006 (UTC)

Nope. Deleted the nonsense. --IanOsgood 02:20, 13 December 2006 (UTC)

[edit] I'd love you to try to justify this statement.

Later observations determined the mass of the object to be about 3.7 million solar masses within a volume with radius no larger than 6.25 light-hours (45 AU) or about 4.2 billion miles. For comparison, Pluto orbits our Sun at a distance of 5.51 light-hours or 3.7 billion miles.

This is compatible with, and strong evidence in support of, the hypothesis that Sagittarius A* is associated with a supermassive black hole. While it is possible for the observed mass within the observed volume limit to be distributed among multiple objects, any such objects would undergo orbital collapse into a single black hole anyway within a few hundred years at most, a negligible amount of time compared with the lifetime of the galaxy.

45 AU is 180 times more radius than is necessary for 3.7 million solar masses to not need to be a black hole. It doesn't matter if it's one body or many. That is enough space so that it could be any number of stable systems which aren't black holes, and which need never become a black hole. The last sentence of this passage is wrong for many reasons. --76.224.88.42 (talk) 18:07, 20 December 2007 (UTC)

You know I thought the same thing when I read this article. I cannot speak for whoever edited this. However, the general concept is SrgA* is a cluster of bosons, a black hole cluster that's going to be a super-massive black hole in about 100 years, or a super-massive black hole. As you may or may not know, super-massive black holes have accretion disks (like our sun?), and it is the X-rays reflected and refracted of the accretion disk that we detect. Note that one is able to figure out the maximum size of really bigs objects due to its angular momentum L, speed of light, and the objects mass. The maximum possible size of the INNER radius of this accretion disk is limited by the black hole's aforementioned spin and two other solutions. I believe these formulas might be the Schwarzschild solution and the Kerr-Newman solution, but I know for sure is that they must be exact solutions in general relativity. Anyways with these to solutions, it turns out that the inner radius is between 6GM/c^2 to GM/c^2 in size depending on the mass of the object. Since the black hole has to fit within this disk, it cannot be bigger than the inner radius. --128.61.72.86 (talk) 21:27, 21 February 2008 (UTC)
Also, I DO realize that there are I alot of holes the explination I gave; therefore, I would like to direct you to someone who can give you to a better explanation http://www.physics.arizona.edu/%7Edrb/ David R. Ballantyne]. He is actually the guy whose lecture Note, that his e-mail link is anti-spam (text). I still am not sure how they got 45 AU. Shouldn't it be around 6 times the orbital radius of Mercury? --128.61.72.86 (talk) 21:27, 21 February 2008 (UTC)
This isn't quite a scientifical text, but since they have completely different figures from those given here I think it'd be worth to check: ec.europa.eu/research/.. --84.56.201.227 (talk) 01:16, 6 March 2008 (UTC)

[edit] Event horizon radius

Anyone know the radius of the event horizon of such a black hole? Just wondering how close S2 (star) comes. --P3d0 (talk) 15:47, 4 April 2008 (UTC)


[edit] Biased Attribution

The first paragraph implies that only in 2002 was it discovered this source is a compact object (ie a black hole). In fact, work has been going on for decades toward this end, this includes work of Genzel, Ghez and other researchers. Sgr A* is in every astronomy textbook as a black hole. As written, the article wrongly attributes full credit for discovery of the black hole to one researcher, and was likely written to promote that researcher's work. Attribution should be secondary to a good description of the object itself. If this is not fleshed out better to include previous research, I will remove the specific attribution, and just say "astronomers have determined" etc. Substar (talk) 15:49, 14 April 2008 (UTC)Substar