Free Astronomy Magazine July-August 2020

54 JULY-AUGUST 2020 SPACE CHRONICLES T he Wolfe Disk as seen with ALMA (right – in red), VLA (left – in green) and the Hubble Space Telescope (both images – blue). In radio light, ALMA looked at the galaxy’s movements and mass of atomic gas and dust and the VLA measured the amount of molecular mass. In UV-light, Hubble observed massive stars. The VLA image is made in a lower spatial resolution than the ALMA image, and therefore looks larger and more pixelated. [ALMA (ESO/ NAOJ/NRAO), M. Neeleman; NRAO/AUI/NSF, S. Dagnello; NASA/ESA Hubble] A LMA radio image of the Wolfe Disk, seen when the Universe was only ten percent of its current age. [ALMA (ESO/NAOJ/NRAO), M. Neeleman; NRAO/AUI/NSF, S. Dagnello] The team also used the National Sci- ence Foundation’s Karl G. Jansky Very Large Array (VLA) and the NASA/ESA Hubble Space Telescope to learn more about star formation in the Wolfe Disk. In radio wave- lengths, ALMA looked at the gal- axy’s movements and mass of atomic gas and dust while the VLA measured the amount of molecular mass – the fuel for star formation. In UV-light, Hubble observed mas- sive stars. “The star formation rate in the Wolfe Disk is at least ten times higher than in our own galaxy,” ex- plained Prochaska. “It must be one of the most productive disk galaxies in the early Universe.” The Wolfe Disk was first discovered by ALMA in 2017. Neeleman and his team found the galaxy when they examined the light from a more distant quasar. The light from the quasar was absorbed as it passed – which is how it revealed itself. Rather than looking for direct light from extremely bright, but more rare galaxies, astronomers used this ‘absorption’ method to find fainter, and more ‘normal’ galaxies in the early Universe. “The fact that we found the Wolfe Disk using this method, tells us that it belongs to the normal population of galaxies present at early times,” said Neeleman. “When our newest observations with ALMA surpris- ingly showed that it is rotating, we realized that early rotating disk galaxies are not as rare as we thought and that there should be a lot more of them out there.” “This observation epitomizes how our understanding of the Universe is enhanced with the advanced sen- sitivity that ALMA brings to radio astronomy,” said Joe Pesce, astron- omy program director at the Na- tional Science Foundation, which funds the telescope. “ALMA allows us to make new, unexpected find- ings with almost every observa- tion.” through a massive reservoir of hy- drogen gas surrounding the galaxy !