Galaxies are sociable and like to group together, just like people. Scientists have wondered if this was always true or if it was something that happened recently.
Astronomers have found a group of very old galaxies in the early stages of forming a galaxy cluster. This collection of 12 galaxies is the oldest ever found - they existed roughly 13 billion years ago! This is only a short time after the birth of the Universe.
To find this special early galaxy cluster in the making, astronomers studied a giant map of the Universe taken by the Subaru Telescope in Hawai‘i, USA. They noticed an area that was very crowded. This turned out to be a group of very old galaxies that were beginning to group together under the force of gravity.
This discovery is exciting for scientists because it means that galaxies were beginning to come together even as the first stars were still forming. There is still much to find out about galaxy clusters and how the universe developed soon after the Big Bang.
Image credit: NAOJ/Harikane et al.
Galaxy clusters can contain up to one thousand galaxies. That makes for many billions of stars in each galaxy cluster!