Free Astronomy Magazine September-October 2021

41 SEPTEMBER-OCTOBER 2021 ASTRO PUBLISHING “There are many mysteries we want to unravel,” says Kathryn Kreckel from the University of Heidelberg in Germany and PHANGS team member. “Are stars more often born in specific regions of their host galaxies — and, if so, why? And after stars are born how does their evolution influence the formation of new generations of stars?” Astronomers will now be able to answer these questions thanks to the wealth of MUSE and ALMA data the PHANGS team have ob- tained. MUSE collects spectra — the “bar codes” astronomers scan to unveil the properties and nature of cosmic objects — at every single lo- cation within its field of view, thus providing much richer information than traditional instruments. For the PHANGS project, MUSE ob- served 30,000 nebulae of warm gas and collected about 15 million spec- tra of different galactic regions. The ALMA observations, on the other hand, allowed astronomers to map around 100,000 cold-gas re- gions across 90 nearby galaxies, producing an unprecedentedly sharp atlas of stellar nurseries in the close Universe. N GC 4254 is a grand-design spiral galaxy located approximately 45 million light-years from Earth in the constellation Coma Berenices. Instrumentation and technical features of the image similar to those of NGC 4303. [ESO/ALMA (ESO/NAOJ/NRAO)/PHANGS] N GC 3627 is a spiral galaxy located approximately 31 million light-years from Earth in the constellation Leo. Instrumentation and technical features of the image similar to those of NGC 4303. [ESO/ALMA(ESO/NAOJ/NRAO)/PHANGS] Emsellem, who is also affiliated with the University of Lyon, France, and his team have now released their latest set of galactic scans, taken with the Multi-Unit Spectro- scopic Explorer (MUSE) instrument on ESO’s VLT in the Atacama Desert in Chile. They used MUSE to trace newborn stars and the warm gas around them, which is illuminated and heated up by the stars and acts as a smoking gun of ongoing star formation. The new MUSE images are now being combined with observations of the same galaxies taken with ALMA and released. ALMA, which is also located in Chile, is especially well suited to mapping cold gas clouds — the parts of galaxies that provide the raw material out of which stars form. By combining MUSE and ALMA images astronomers can ex- amine the galactic regions where star formation is happening, com- pared to where it is expected to happen, so as to better understand what triggers, boosts or holds back the birth of new stars. The resulting images are stunning, offering a spectacularly colourful insight into stellar nurseries in our neighbour- ing galaxies.