Even today, scientists don’t know what dark matter is nor what it’s made of. However, they have the right tools in order to say for sure that it exists and that it consists of 27% of the Universe’s mass. Dark energy, on the other hand, accounts for 68% of our Cosmos. Only about 5% of the Universe’s mass consists of the usual matter we see and interact with every day.
According to VOA, scientists led by researchers from the Nagoya University (Japan) collected enough data to determine when the oldest dark matter existed: roughly 12 billion years ago, meaning “only” about 1.7 billion years after the Big Bang. In other words, dark matter existed shortly after our Universe’s birth.
Taking advantage of the CMB
In order to determine the existence of dark matter, scientists decided to exploit the opportunities that the cosmic microwave background (CMB) gives, meaning the leftover radiation that comes from the Big Bang itself. They also used data from observations performed using Subaru Telescope’s Subaru Hyper Suprime-Cam Survey instrument.
Yuichi Harikane, an Assistant Professor of the University of Tokyo’s Institute for Cosmic Ray Research, explains:
Most researchers use source galaxies to measure dark matter distribution from the present to eight billion years ago
However, we could look further back into the past because we used the more distant CMB to measure dark matter. For the first time, we were measuring dark matter from almost the earliest moments of the universe.
Twelve billion years surely means a lot of time both for the Universe itself and for us. This aspect is also emphasized well in the following statement:
I was happy that we opened a new window into that era,
12 billion years ago, things were very different. You see more galaxies that are in the process of formation than at the present; the first galaxy clusters are starting to form as well.
Researchers from the University of Tokyo, America’s Princeton University., and the National Astronomical Observatory of Japan were also involved in the new work.