Physicists have uncovered some of the very first galaxies that formed in our Universe.
Data collected by academics from the Institute for Computational Cosmology (ICC) at Durham University and Harvard-Smithsonian Center for Astrophysics suggest that a number of known galaxies are more than 13 billion years old.
“Finding some of the very first galaxies that formed in our Universe orbiting the Milky Way’s own backyard is the astronomical equivalent of finding the remains of the first humans that inhabited the Earth,” Carlos Frenk, director of Durham University’s ICC, said in a statement. “It is hugely exciting.
Here’s something they don’t teach you in history class: When the Universe was about 380,000 years old, the first hydrogen atoms formed and collected into clouds that cooled and settled into “halos” of dark matter.
That cooling phase, known as the “cosmic dark ages,” lasted about 100 million years, at which point the halo gas became unstable and formed stars—the first ever galaxies. Among them: Segue-1, Bootes I, Tucana II, and Ursa Major I.
Based on that knowledge, the team identified two populations of satellite galaxies circling the Milky Way. One is very faint, composed of nebulae created during the cosmic dark ages. The other is slightly brighter, made of galaxies formed hundreds of millions of years later.
“A decade ago, the faintest galaxies in the vicinity of the Milky Way would have gone under the radar,” according to Sownak Bose, a former Ph.D. student at the ICC, now a research fellow at the Harvard-Smithsonian Center for Astrophysics.
“With the increasing sensitivity of present and future galaxy censuses,” he continued, “a whole new trove of the tiniest galaxies has come into the light, allowing us to test theoretical models in new regimes.”
The findings are detailed in a paper published this week by The Astrophysical Journal.
The science of space continues to captivate, as astronomers make exciting discoveries about the early Solar System and life beyond Earth. Check out what’s going on in the cosmos here.