Astronomers have detected a massive, sprawling, churning galaxy cluster – about 1,000 times more massive than our Milky Way galaxy – that formed only 3.8 billion years after the Big Bang. The early universe was a chaotic mess of gas and matter that only began to coalesce into distinct galaxies hundreds of millions of years after the Big Bang. It would take several billion more years for such galaxies to assemble into massive galaxy clusters.

Astronomers at Massachusetts Institute of Technology (MIT), the University of Missouri and the University of Florida have detected IDCS J1426.5+3508 (or IDCS 1426), the most massive cluster of galaxies yet discovered in the first 4 billion years after the Big Bang. Located 10 billion light years from Earth and potentially comprising thousands of individual galaxies, the mega structure is about 250 trillion times more massive than the Sun, or 1,000 times more massive than the Milky Way galaxy.

IDCS 1426 appears to be undergoing a substantial amount of upheaval. The researchers observed a bright knot of X-rays, slightly off-centre in the cluster, indicating that the cluster’s core may have shifted some hundred thousand light years from its centre. Galaxy clusters are conglomerations of hundreds to thousands of galaxies bound together by gravity. They are the most massive structures in the universe, and those located relatively nearby, such as the Virgo cluster, are extremely bright and easy to spot in the sky.

However, finding galaxy clusters that are farther away in space – and further back in time – is a difficult and uncertain exercise, researchers said. In 2012, scientists using NASA’s Spitzer Space Telescope first detected signs of IDCS 1426. To get a more precise estimate of the galaxy cluster’s mass, the researchers used data from the Hubble Space Telescope, the Keck Observatory, and the Chandra X-ray Observatory.