Astronomers have constructed a model of what the very first galaxies in the universe may have looked like and what they look like today. In doing so, the astronomers discovered that some of the Milky Way's neighbors match the present-day description of the galaxies.
As reported in the Astrophysical Journal, astronomers from Durham University and the Harvard-Smithsonian Center for Astrophysics suggest that dwarf galaxies such as Segue-1, Bootes I, Tucana II, and Ursa Major I are some of the first galaxies ever formed. These tiny satellites of the Milky Way already had stars in place over 13 billion years ago.
“Finding some of the very first galaxies that formed in our universe orbiting in the Milky Way’s own backyard is the astronomical equivalent of finding the remains of the first humans that inhabited the Earth. It is hugely exciting,” Professor Carlos Frenk, director of Durham University’s Institute for Computational Cosmology, said in a statement.
The team’s model aims to predict what went down in the first 100 million years of the Big Bang, an epoch known as the Cosmic Dark Ages. The first atom formed when the universe was roughly 380,000 years old. The first elements then began to slowly clump up in the regions of space that have a bit more gravity, where dark matter was a little denser.
In those “haloes”, galaxies formed over hundreds of millions of years. The team, in particular, was interested in how the satellites of the Milky Way came to form. The model implied that some faint, small satellites formed very early in the history of the universe, while others came afterward. Observations confirmed their results.
“A nice aspect of this work is that it highlights the complementarity between the predictions of a theoretical model and real data,” Dr Sownak Bose, from the Harvard-Smithsonian Center for Astrophysics, added. “A decade ago, the faintest galaxies in the vicinity of the Milky Way would have gone under the radar. With the increasing sensitivity of present and future galaxy censuses, a whole new trove of the tiniest galaxies has come into the light, allowing us to test theoretical models in new regimes.”
The Cosmic Dark Ages are still full of mysteries. We are yet to observe the first population of stars, for example. Work like this highlights the complexity in finding answers about the Universe’s youth.