Expert: Jayendra Upadhye - 4/14/2007

Question
Hi!

I recently saw the Ultra Deep Field images taken by Hubble Space Telescope in 2004. It certainly is a very impressive portrait of the oldest galaxies in the universe! I've read that some of those galaxies are about 13 billion light-years away. I have also read that the age of the universe is considered to be of about 13.7 billion years. So I wonder how possibly can it take such a short time for a galaxy to be formed. Considering that our own Earth didn't form until 4.5 billion years ago, how can such a massive object as a galaxy containing so many earths and suns, be formed only 0.7 billion years after the big bang?

Thanks in advance for the answer.

Answer
Rafa,
how do you consider that most stars should be as old as the earth?
Our earth comes out of a star that was the nth generation since the bang!
The elements beyond hydrogen  that you find on the periodic table, such as carbon, alluminum, mangansese, sodium, silver, gold, nickel, cobalt, and so on, were all made in the supernova that triggered the formation of the sun. These elements are inherited from it and not generated / native to the solar system.

Even now, the sun is busy converting only hydrogen to helium. Almost all helium made in the sun is still inside the sun.

The sun has not yet reached the helium burning stage even!

So these elements by their abundance on earth prove that the sun is a "next generation" star.

The big bang flashed into existence and in a short time, the universe went dark! because the temperature of the cosmic background radiation went infrared. (below red heat approx. 800 deg centigrade).

Energy and matter decoupled much earlier allowing molecular hydrogen to form.

Vast clouds of elementary hydrogen quickly formed and star formation and galaxy formation started simultanously.

Only, all stars were pure hydrogen.

In a few million years, the first supernova occured, seeding space with the first traces of heavier elements.

the universe as we know it began only then.
But by then vast voids already separated the gravitationally formed "islands" in space, the galaxies.

Remember the initial star formation phase came much more wuickly than the galaxy formation phase.
A star may form in a miilion years but it takes our sun 225 miilion years (hope my memory is right, forgive me), to go once round the milky way galaxy.

As a result, and due to their vast size, galaxies came later. drifting stars quicly formed globular clusters and thsese congregated around galactic centers in roghly spherical ditribution. (the milky way also has them).

Vast majority of late comers soon collapsed into flat discs of the spiral arms.

colliding spiral galaxies settled to form giant elliptical galaxies and show today a predominance of red giants, as they are indeed "older" galaxies.
So do globular clusters.

Meanwhile greater concentration of gas in the arms triggers accelrated rate fo star formation in the spiral arms in spiral galaxies. The sun formed in a stellar nursery (such as the m16 eagle nebula / or the orion nebula) and who knows where its twins are!

There is a theory that one such twin , a brown dwarf orbits it and has a close approach every 65 million years, triggering mass extinctions on the earth. It is the NEMESIS theory.

hope that solves your problem.
Jayen