Free Astronomy Magazine March-April 2018

16 MARCH-APRIL 2018 SPACE CHRONICLES Earliest galaxies spun like the Milky Way by ALMA Observatory A n international team led by Dr Renske Smit from the Kavli Institute of Cosmology at the University of Cambridge used the Atacama Large Millimeter/sub- millimeter Array (ALMA) in Chile to open a new window onto the dis- tant Universe, and have for the first time been able to identify normal star-forming galaxies at a very early stage in cosmic history with this tele- scope. The results are reported in the journal Nature , and were pre- sented at the 231 st meeting of the American Astronomical Society. Light from distant objects takes time to reach Earth, so observing objects that are billions of light years away enables us to look back in time and directly observe the formation of the earliest galaxies. The Universe at that time, however, was filled with an obscuring ‘haze’ of neutral hy- drogen gas, which makes it difficult to see the formation of the very first galaxies with optical telescopes. Smit and her colleagues used ALMA to observe two small newborn gal- axies, as they existed just 800 million years after the Big Bang. By analyz- ing the spectral ‘fin- gerprint’ of the far- infrared light col- lected by ALMA, they were able to estab- lish the distance to the galaxies and, for the first time, see the internal motion of the gas that fueled their growth. “Until ALMA, we’ve never been able to see the formation of galaxies in such de- A video simulation of rotating disc. [R. Crain (LJMU) and J. Geach (U.Herts)]