December 25, 2014
After observing a galaxy cluster known as Gioiello (Italian for “jewel”) for more than four days, astronomers have determined its mass and it turns out to have 400 trillion solar masses. This is surprising given the relatively young age of the cluster, which could make theorists reevaluate current models that predict such clusters are highly unlikely to exist.
Gioiello galaxy cluster, officially known as XDCP J0044.0-2033, is 9.6 billion light-years away. It's mass is 400 trillion solar masses. Credit: X-ray: NASA/CXC/INAF/P. Tozzi, et al; Optical: NAOJ/Subaru a
Originally discovered by ESA’s XMM-Newton observatory, Gioiello was then observed with NASA’s Chandra X-ray Observatory and resulting discovery of its mass and other properties will be valuable for understanding how the Universe itself evolved.
The Gioiello cluster is only 800 million years old, which means that it is the most massive known cluster at this age or younger. For comparison, El Gordo galaxy cluster is over 7 times heavier, with 3 million billion solar masses, but it is also about 10 times older. Both these clusters are larger than current models predict is possible given their distance and age. Gioiello is 9.6 billion light-years away.
When looking into deep space, we aren’t only looking into distance, but also into the past, because the light takes time to reach us. This means that large galaxy clusters in our neighbourhood are also older and unsurprisingly huge, since they had time to form. Distant galaxy clusters like El Gordo and especially Gioiello were much younger when their light began to travel toward us. This is why they were expected to be less massive than they actually are. If more such galaxy clusters are found at even younger age, the whole theory about how galaxy clusters in the early Universe evolved will need to be reevaluated.
"Finding this enormous galaxy cluster at this early epoch means that there could be more out there," said leader of the new study, Paolo Tozzi of the National Institute for Astrophysics (INAF) in Florence, Italy. "This kind of information could have an impact on our understanding of how the large scale structure of the Universe formed and evolved."
The Gioiello cluster’s galaxies are very young, producing stars at a higher rate compared to galaxies in our proximity. Also, the hot gas in the cluster is structured unevenly which is probably the result of collisions and mergers with smaller galaxy clusters, which would explain how the Gioiello got so big so fast.
"Unlike the galaxy clusters that are close to us, this cluster still has lots of stars forming within its galaxies," said co-author Joana Santos, also from INAF in Florence. "This gives us a unique window into what galaxy clusters are like when they are very young."
The cluster is officially named XDCP J0044.0-2033, but since it has so many star-forming galaxies and hot gas both emitting X-rays, it was named Gioiello, which stands for “jewel” in Italian. Also, the research team first meeting to discuss the data took place in Villa il Gioiello, last residence of Galileo Galilei. It was built in 15th century near Observatory of Arcetri in Florence, Italy.