THE FIRST GALAXIES

I’ve just been reading about the hunt for the first galaxies in New Scientist magazine. It seems that for the first 300,000 years after the Big Bang all you had was this vast soup of free-floating electrons and nuclei – the temperature was too hot, because the universe was too small (up to a mere 300,000 light years across) for atoms to hold together.

After this point the universe became cool enough for electrons and nuclei to hook up – bit by bit they moved from their 5th House serial romancing to 7th House courtship to the firm commitment of the 8th House, in which they became stable hydrogen atoms. In their joy they released bursts of radiation, which we now know as the Cosmic Background Radiation, which tells us a lot about the early state of the universe.

So now emerged a slightly different and cooler soup, made up of atoms. What came now was known as the Dark Ages, because there was nothing around emitting light. Gradually, bored with their monogamous life, some of them got into wife-swapping and swinging: lumps of matter started to form, attracting yet more free-floating atoms, all radiating joyful energy.

The radiation re-ionised the surrounding hydrogen atoms back into electrons and nuclei. This process swept through the entire universe. (You got it: they all got divorced!) As they were re-ionised, these atoms released what is known as 21cm radiation. It is this radiation (stretched after its long journey through space) that astronomers are starting to look for, because it can tell us a lot about that time in which the first objects were forming. If these objects were stars (and no-one yet knows what they were), they would have been very different to today’s stars. They would have been monstrously large, made almost entirely of hydrogen and helium, and pumping out ultra-violet light. Or these objects might have accreted so much matter that they collapsed and became black holes: this would have released X-rays and gamma rays, and again astronomers are looking for tell-tale signs.

These objects and their surroundings constituted the first galaxies, and were probably very different to today’s galaxies. There are a number of specialised telescopes being created to look for evidence, including Hubble’s replacement, the James Webb space telescope, due to be launched in 2013; and the Mileura Widefield array, which will have 8000 antennae and will be located on a remote sheep farm in Western Australia.