To all, Each week in 2023, Astronomy Editor Dave Eicher will bring you the latest and greatest in astronomy, courtesy of our sponsors at Celestron. This week, we’ll talk about dark matter, a strange and invisible type of stuff with huge consequences for the future of our universe. In the 1930s, Dutch astronomer Jan Oort proposed the existence of dark matter after analyzing the movements of stars close to the Sun. If the galaxy was not disintegrating, then there must be enough material in the disk to prevent the stars from spreading outward from the galactic center, he reasoned. According to Oort’s theory, there should be three times as much dark matter as regular matter in the solar neighborhood.
Later, when astronomers studied the rotation curves of galaxies, illuminating their disks and halos, the evidence became more compelling. The study of groups of galaxies provides further evidence for the presence of dark matter. Even further away from Earth, in the Coma cluster of galaxies some 300 million light-years away, American astronomer Fritz Zwicky theorized that considerably greater clouds of dark matter exist. Zwicky determined that there must be 10 times more mass than was observed via visible light in order to keep the galaxies gravitationally bound by analyzing the Doppler shifts of individual galaxies in the cluster.
The composition of dark matter has been the subject of intense investigation in recent years. Numerous theories have been offered by scientists throughout the years to explain astronomers’ observations, and each has its own set of advantages and disadvantages. Massive amounts of standard neutrinos, brown dwarfs, neutron stars, and black holes are all examples of MACHOs, while exotic particles, axions, massive neutrinos, and photinos are all examples of WIMPs. Because it accounts for 26% of the total mass energy in the universe, whatever dark matter is made of has far-reaching consequences for the cosmological structure and its destiny.