Talk:Galactic halo
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[edit] Galactic disc
Is the galactic disc all on a plane? Is the galactic bulge not part of the disc? Gerry Lynch 11:16, 4 Aug 2004 (UTC)
- Yes, galactic discs are usually pretty thin and planar, although they are often warped - in the Milky Way, the disk is about 15 kpc in radius but much less than 1 kpc thick. And the galactic bulge is not really part of the galactic disc - it has a completely different stellar population for a start, although similar in many respects to the halo - indeed, the bulge is sometimes thought to be a dense inner part of the halo. But the bulge includes a significant quantity of the stars in a spiral galaxy, so I've added a line about it. -- ALoan (Talk) 13:24, 4 Aug 2004 (UTC)
[edit] disambig
i've changed this to a disambig page - in the MW, the galactic spheroid is a totally negligible component from a dynamical point of view relative to the DM halo, the spheroid only constitutes about 0.1% of the total mass - so there's really a big danger in confusing the different components by calling them part of a single "halo". The only thing common to them is that they're more or less spherically symmetric (meaning that their stars/particles travel in a spatial distribution which is roughly spherically symmetric), which is where the word halo comes from, but there's no strong physical link between them.
The word corona was used by at least one galactic structure astronomer to describe the galactic spheroid during the '90s, but now it seems to have been picked up for something more closer, in physical nature, to the Sun's corona - this is relatively new stuff, so i've added a stub galactic corona with 3 astro-ph links for anyone interested in reading/writing further.
- the galactic spheroid component - stars
- the galactic corona - some hot gas (ie. a plasma)
- the dark matter halo
Boud 15:26, 16 March 2006 (UTC)
