Free Astronomy Magazine May-June 2015

SPACE CHRONICLES but it proved to be precocious. At this age it would be expected to dis- play a lack of heavier chemical ele- ments — anything heavier than hydrogen and helium, defined in astronomy as metals. These are pro- duced in the bellies of stars and scat- tered far and wide once the stars explode or otherwise perish. This process needs to be repeated for many stellar generations to pro- duce a significant abundance of the heavier elements such as carbon, oxygen and nitrogen. Surprisingly, the galaxy A1689-zD1 seemed to be emitting a lot of radia- tion in the far infrared, indicating that it had already pro- duced many of its stars and significant quanti- ties of metals, and re- vealed that it not only contained dust, but had a dust-to-gas ratio that was similar to that of much more mature gal- axies. “Although the exact ori- gin of galactic dust re- mains obscure,” explains Darach Watson, “our findings indicate that its production occurs very rapidly, within only 500 million years of the be- ginning of star forma- tion in the Universe — a very short cosmological time frame, given that most stars live for bil- lions of years.” The findings suggest A1689-zD1 to have been consistently forming stars at a moderate rate since 560 million years after the Big Bang, or else to have passed through its period of extreme starburst very rapidly before entering a declining state of star formation. Prior to this result, there had been concerns among astronomers that such distant galaxies would not be detectable in this way, but A1689- zD1 was detected using only brief observations with ALMA. Kirsten Knudsen (Chalmers Univer- sity of Technology, Sweden), co-au- thor of the paper, added, “This amazingly dusty galaxy seems to have been in a rush to make its first generations of stars. In the future, ALMA will be able to help us to find more galaxies like this, and learn just what makes them so keen to grow up.” n T his view includes infrared light images from the WFC3 instrument on the NASA/ESA Hubble Space Telescope as well as visible light views. It shows a close up look at part of the rich galaxy cluster Abell 1689. [ESO/J. Richard] surprised the observers with its rich chemical complexity and abundance of interstellar dust. “After confirming the galaxy’s dis- tance using the VLT,” said Darach Watson, “we realised it had pre- viously been observed with ALMA. We didn’t expect to find much, but I can tell you we were all quite excited when we realised that not only had ALMA observed it, but that there was a clear detection. One of the main goals of the ALMA Observato- ry was to find galaxies in the early Universe from their cold gas and dust emissions —and here we had it!” This galaxy was a cosmic infant —