Expert: Jayendra Upadhye - 7/4/2009

Question
What is the Milky Way?  and how did it happen?

Answer
Hi Gabriella,
Sorry for the delay.
The milky way is quite quite old, and yet not as old as the elliptical galaxies.
Colliding spiral galaxies end up as ellipticals in due course, with a larger proportion of the population consisting of old and red stars.
Immediately after the bang, that is during the dark age after the bang, the first stars began to be formed, in less than a million years after the bang.
These congregated into globular clusters. The clusters soon were found orbiting around a central massive cluster, the galactic hub.
Even today, these are found in a spherical galactic halo, orbiting the central hubs of the spiral galaxies. Cold dark matter had mean while formed accretion disks upto 100,000 light years around the massive hubs of the spiral galaxies. From these disks, emerged the bright new star forming regions such as the Eagle nebula and the Orion Nebula.
The spiral pattern is just a pattern, as each star is actually orbiting in a roughly circular orbit, around the galactic center.
All galaxies are constantly in interaction gravitationally with each other. Our current companions are the local group comprising of about 13 such galaxies large and small.
The most prominent is the Andromeda galaxy with its two tight spiral satellites, 2 million light years away.
Plus we have the large and small magellanic clouds, which as irregular small satellites of the milky way, and have a greater proportion of bright objects such as Tarantula nebula, and SN1987A, that went super nova in 1987, that lies on its edge.
The nebula is so bright that if it were to be near the Orion nebula, it would cast shadows on earth! It has two globular clusters in the making.
refer:- http://upload.wikimedia.org/wikipedia/commons/3/3e/Tarantula_Nebula.jpg
Meanwhile the Andromeda galaxy will coalesce with the milkyway in about 5 billion years time, by which period, the whole local group is expected to merge with the Huge Virgo cluster of galaxies.
(large scale structure of the universe).

regards
Jayen