Four new galaxy clusters discovered

Scientists have discovered four new galaxy clusters, each potentially containing thousands of individual galaxies, some 10 billion light years from Earth.
An international team of astronomers, led by Imperial College London, used a new way of combining data from the two European Space Agency satellites, Planck and Herschel, to identify more distant galaxy clusters than has previously been possible.
The researchers believe up to 2,000 further clusters could be identified using this technique, helping to build a more detailed timeline of how clusters are formed.
Galaxy clusters are the most massive objects in the universe, containing hundreds to thousands of galaxies, bound together by gravity.

The light from the most distant of the four new clusters identified by the team has taken over 10 billion years to reach us. This means the researchers are seeing what the cluster looked like when the universe was just three billion years old.
"Although we're able to see individual galaxies that go further back in time, up to now, the most distant clusters found by astronomers date back to when the universe was 4.5 billion years old. This equates to around nine billion light years away," said lead researcher Dr David Clements, from the Department of Physics at Imperial College London.

"Our new approach has already found a cluster in existence much earlier than that, and we believe it has the potential to go even further," Clements said.

"What we believe we are seeing in these distant clusters are giant elliptical galaxies in the process of being formed," said Clements.
Elliptical galaxies have many stars, but little dust and gas. Most clusters in the universe today are dominated by giant elliptical galaxies in which the dust and gas has already been formed into stars.
The researchers are among the first to combine data from two satellites that ended their operations last year: the Planck, which scanned the whole sky, and the Herschel, which surveyed certain sections in greater detail.

The researchers used Planck data to find sources of far-infrared emission in areas covered by the Herschel satellite, then cross referenced with Herschel data to look at these sources more closely.
Of sixteen sources identified by the researchers, most were confirmed as single, nearby galaxies that were already known. However, four were shown by Herschel to be formed of multiple, fainter sources, indicating previously unknown galaxy clusters.
They used additional existing data and new observations to estimate the distance of these clusters from Earth and to determine which galaxies within them were forming stars.
The study is published in the journal Monthly Notices of the Royal Astronomical Society.