Astronomers using the Planck space telescope have confirmed the presence of a bridge of hot gas bridging the 10 million light-years of intergalactic space between two galaxy clusters.
“Planck is helping to reveal hidden material between galaxy clusters that we couldn’t see clearly before,” said James Bartlett, a member of the U.S. Planck science team at NASA‘s Jet Propulsion Laboratory.
The European Space Agency (ESA) runs the Planck mission, with NASA also participating. The mission’s main goal is to capture light from the cosmic microwave background – the radiation left over from the earliest stages of the universe.
The presence of the hot gas between the clusters Abell 399 and Abel 401 was first detected by the ESA’s XMM-Newton X-ray observatory. Astronomers using the Planck telescope and the Sunyaev-Zel’dovich effect were able to confirm the phenomenon.
The Sunyaev-Zel’dovich effect is the result of the cosmic microwave background radiation interacting with the hot gas that envelops the galaxy clusters, which are huge collections of thousands of galaxies bound together by gravity. As the background radiation encounters the hot gas, its energy distribution is modified in a characteristic way predicted by the Sunyaev-Zel’dovich effect.
Early analysis by astronomers suggests the much of the gas is from gaseous matter that pervaded the early universe. The gas is compressed and heated up by the interacting galaxy clusters, making it easier to spot. By combining the Planck data with X-ray observations from the German satellite Rosat, astronomers have estimated the temperature of the gas to be close to 80 million degrees Celsius (144 million degrees Fahrenheit).
(Image courtesy Sunyaev–Zel’dovich effect: ESA Planck Collaboration; optical image: STScI Digitized Sky Survey)