Free Astronomy Magazine November-December 2016

12 NOVEMBER-DECEMBER 2016 SPACE CHRONICLES Up to now astronomers did not understand what made these huge clouds of gas shine so brightly, but ALMA has now seen two galaxies at the heart of one of these objects and they are under- going a frenzy of star formation that is lighting up their surround- ings. These large galaxies are in turn at the center of a swarm of smaller ones in what appears to be an early phase in the forma- tion of a massive cluster of galaxies. The two AL- MA sources are destined to evolve into a single giant ellip- tical galaxy. LABs are gigantic A n international team using the Atacama Large Millime- ter/submillimeter Array (AL- MA), along with the European South- ern Observatory’s Very Large Tele- scope (VLT) and other telescopes, has discovered the true nature of a rare object in the distant Universe called a Lyman-alpha Blob (LAB). by ALMA Observatory T his rendering shows a snapshot from a cosmological simulation of a Lyman- alpha Blob similar to LAB-1. This simulation tracks the evolution of gas and dark matter using one of the latest models for galaxy formation running on the NASA Pleiades supercomputer. This view shows the distribution of gas within the dark matter halo, color coded so that cold gas (mainly neutral hydrogen) appears red and hot gas appears white. Embedded at the centre of this system are two strongly star-forming galaxies, but these are surrounded by hot gas and many smaller sat- ellite galaxies that appear as small red clumps of gas here. Lyman-alpha photons escape from the central galaxies and scatter off the cold gas associated with these satellites to give rise to an extended Lyman-alpha Blob. [J.Geach/D.Narayanan/R.Crain] ALMA uncovers secrets of giant space blob