Free Astronomy Magazine November-December 2016

13 NOVEMBER-DECEMBER 2016 SPACE CHRONICLES T his image shows one of the largest known single objects in the Universe, the Lyman-alpha blob LAB-1. The intense Lyman-alpha ultra- violet radiation from the blob ap- pears green after it has been stretched by the expansion of the Universe during its long journey to Earth. [ESO/M. Hayes] clouds of hydrogen gas that can span hundreds of thousands of light- years and are found at very large cosmic distances. The name reflects the characteristic wavelength of ul- traviolet light that they emit, known as Lyman-alpha radiation. Since their discovery, the processes that give rise to LABs have been an astro- nomical puzzle. New observations with ALMA have now cleared up the mystery. One of the largest Lyman- alpha Blobs known, and the most thoroughly studied, is SSA22- Lyman-alpha blob 1, or LAB-1. Em- bedded in the core of a huge cluster of galaxies in the early stages of for- mation, it was the very first such ob- ject to be discovered — in 2000 — and is located so far away that its light has taken about 11.5 billion years to reach us. A team of astronomers, led by Jim Geach, from the Centre for Astro- physics Research of the University of Hertfordshire, UK, has now used ALMA unparalleled ability to ob- serve light from cool dust clouds in distant galaxies to peer deeply into LAB-1. This allowed them to pin- point and resolve several sources of submillimeter emission. (Resolution is the ability to see that objects are separated. At low resolution, seve-