Skip to content

Galaxies begin to form

13 200 million years – 13.2 kilometres

Ancient galaxies seen with the Hubble space telescope. (G. Illingworth et al. / R. Bouwens / HUDF09 Team / NASA / ESA)

The second generation (Population II) star, HE 1523-0901, is born. The amount of iron in this star is only one-thousandth of the amount of iron in the Sun. This means that it cannot form planets around it. The formation of galaxies starts. The sparse interstellar material begins to reionize into plasma.

Image: The Hubble Ultra Deep Field image shows very old galaxies. G. Illingworth et al. | R. Bouwens | HUDF09 Team | NASA | ESA

The funny names of stars

The HE in the name of the star HE 1523-0901 signifies the Hamburg-ESO survey, and the number indicates where the star is on the sky. The star is also known as 2MASS J15260106-0911388. These names for the same star indicate that it appears to have moved slightly, and that the 2MASS-catalogue uses a slightly more accurate position. The main difference is that the reference system has changed between the two catalogues. The HE survey uses the system from the year 1950, and the 2MASS survey using the system from the year 2000. The star itself has hardly moved on the sky.

Only a few stars are known by names. Most are identified only by a number in a catalogue. Very few of us recognize that HE 1327-2326 is also one of the oldest stars, and contains only one 250000th of the iron that the Sun contains. Or that HIP 11767 is actually a Ursae Minoris, or the North Star.


Plasma, or ionised gas, is the so-called fourth form of matter, the others being: solid, liquid and gaseous. Plasma is made up of free electrons and ions. Ions are the nuclei of atoms without the electrons that normally orbit them.