Posted on September 21st, 2012

Phoenix Galaxy Cluster

Astronomers at the National Science Foundation’s South Pole Telescope recently discovered a galaxy that is producing stars at a stellar rate, the Phoenix Galaxy Cluster which appears to be aptly named on two fronts. When it comes to being painfully obvious as NASA naming conventions tend to be, the galaxy cluster falls right in-line due to its location in the Phoenix constellation. Moving toward the mythological, Phoenix defies known conventions of similar central galaxy clusters as instead of warming and dying like every other observed cluster, the galaxy is forming stars at an unheard of rate. Most central galaxies have been dormant for billions of years while the Phoenix galaxy appears to have risen from the ashes with a burst of star formation.


 

Above is an artist’s animation of the Phoenix Cluster star formation. The red area is the hot gas and the elliptical form is the central galaxy that emits large amounts of X-rays which cool over time and cause gases to flow inwards and form stars. (Video Source: NASA/CXC/A. Hobart)

Other observed galaxy clusters are similar to each other in that they have a super-massive black hole in their center; and scientists believe that these black holes emit high amounts of energy into the system which prevents the gas from cooling and star formation from occurring. The central galaxy in these clusters emit X-rays that cool quickly and then gas flows inward along filaments to create stars. The black hole in the Phoenix Cluster is not emitting enough energy to prevent gases from cooling; and this causes Phoenix to create stars 20 times faster than other known clusters. This newly observed phenomenon has made scientist reconsider how galaxy clusters grow and the importance of the cooling gas in the central part of the clusters.


phoenix_pullout

This is a composite image of the central region of the Phoenix Cluster using optical, UV and X-ray data. (Image Credit: X-ray, NASA/CXC/MIT/M.McDonald; UV, NASA/JPL-Caltech/M.McDonald; Optical, AURA/NOAO/CTIO/MIT/M.McDonald)

The X-rays that are emitted in abundance can only be seen and measured by the Chandra space-based telescope; and the Galaxy Evolution Explorer (GALEX) was among a number of space-based telescopes used to count the rate of star formation. You can read about the GALEX telescope in an article I wrote last month here. The number of instruments and telescopes it takes to measure and observe these amazing cosmic structures is rather astounding.

Another very interesting characteristic of some clusters, like the Perseus Cluster, is the burst of powerful jets from their black hole that prevents the gas from cooling. These powerful jets also create giant cavities and produce sound waves with a deep B-flat note. It was believed that this musical anomaly is apparent in all galaxy clusters, however it is absent in the Phoenix cluster.


perseus_xray

Cavities and sound waves in the Perseus Cluster. (Image Credit: NASA/CXC/IoA/A.Fabian et al.)

The black hole at the center of the Phoenix Cluster is expanding rapidly but this expansion isn’t believed to be sustainable. Scientists believe that if it continues to grow, the galaxy and black hole will become larger than their nearby equivalents which seems unlikely. The black hole is already 20-billion times the mass of our Sun. If the current stellar models hold true, the Phoenix Cluster will eventually start emitting powerful jets that will keep gases from cooling and then create the same melodies as the Perseus Cluster. This would also end the cluster’s phenomenal pace of star formation; that said, Phoenix has already broken multiple ‘rules’ so who knows what will happen in the future!

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Above is an image of the South Pole Telescope, a beautiful and frigid world in which to study the cosmos. (Photo Source: NASA)

Katie Nelson

Geospatial Ninja

(303) 718-7163

Katie@apollomapping.com

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