Free Astronomy Magazine January-February 2015

SPACE CHRONICLES T he new MUSE instrument on ESO’s Very Large Telescope (VLT) has provided researchers with the best view yet of a spectac- ular cosmic crash. The new observa- tions reveal for the first time the motion of gas as it is ripped out of the galaxy ESO 137-001 as it ploughs at high speed into a vast galaxy clus- ter. The results are the key to the solution of a long-standing mystery — why star formation switches off in galaxy clusters. A team of researchers led by Mi- chele Fumagalli from the Extra- galactic Astronomy Group and the Institute for Computational Cosmol- ogy at Durham University, were among the first to use ESO’s Multi Unit Spectroscopic Explorer (MUSE) instrument on the VLT. Observing ESO 137-001 — a spiral galaxy 200 million light-years away in the southern constellation of Triangu- lum Australe (The Southern Trian- gle) — they were able to get the best view so far of exactly what is happening to the galaxy as it hur- tles into the Norma Cluster. MUSE gives astronomers not just a picture, but provides a spectrum — or a band of colours — for each pixel in the frame. With this instru- ment researchers collect about 90,000 spectra every time they look at an object, and thereby record a staggeringly detailed map of the motions and other properties of the observed objects. (MUSE is the first large integral field spectrograph ever installed at an 8-metre tele- scope. As a comparison, previous studies of ESO 137-001 collected no more than 50 spectra.) ESO 137-001 is being robbed of its raw materials by a process called ram-pressure stripping, which hap- pens when an object moves at high speed through a liquid or gas. This is similar to how air blows a dog’s MUSE reveals true story behind galactic crash T he MUSE instrument on ESO’s Very Large Telescope has provided researchers with the best view yet of a spectacular cosmic crash. Observations reveal for the first time the motion of gas as it is ripped out of the galaxy ESO 137-001 as it ploughs at high speed into a vast galaxy cluster. The results are the key to the solution of a long-standing mystery — why star formation switches off in galaxy clusters. In this picture the colours show the motions of the gas filaments — red means the material is moving away from Earth compared to the galaxy and blue that it is approaching. Note that the upper-left and lower-right parts of this pic- ture have been filled in using the Hubble image of this object. [ESO/M. Fumagalli] by ESO