Content of the Universe

The Universe is not perfectly the same everywhere in space – even when the Universe was just a few hundred thousand years old, some regions were more dense and some were less dense. The more dense regions eventually collapsed under their own weight, via gravity, and formed galaxies, stars, and planets. These fluctuations are not just interesting for galaxy formation, they are also useful for measuring the curvature of space. Density fluctuations on the smaller scales (up to about 1 Mpc, a few million light-years) collapsed gravitationally, forming galaxy clusters and galaxies in which stars and planets formed. Comparing observations of galaxies and galaxy clusters to the cosmic microwave background and separating the two effects is a major theme of the observational aspects of the OCRA program using our 32m radio telescope.