Free Astronomy Magazine September-October 2022

48 SEPTEMBER-OCTOBER 2022 ASTRO PUBLISHING spread out and diffuse, especially in the outer regions of galaxies, where the gas and dust become sparse and thus fainter. For some nearby galax- ies, that meant Herschel missed up to 30% of all the light given off by dust. With such a significant gap, as- tronomers struggled to use the Her- schel data to understand how dust and gas behaved in these environ- ments. To fill out the Herschel dust maps, the new images combine data from three other missions: ESA’s re- tired Planck observatory, along with T he Small Magellanic Cloud is a satellite of the Milky Way, containing about 3 billion stars. This far-infrared and radio view of it shows the cool (green) and warm (blue) dust, as well as the hydrogen gas (red). The image is composed of data from the European Space Agency (ESA) Herschel mission, supplemented with data from ESA’s retired Planck observatory and two retired NASA missions: the Infrared Astronomy Survey and Cosmic Background Explorer, as well as the Parkes, ATCA, and NANTEN radio telescopes. [ESA, NASA, NASA-JPL, Caltech, Christopher Clark (STScI), S. Stanimirovic (UW-Madison), N. Mizuno (Nagoya University)] two retired NASA missions, the In- frared Astronomical Satellite (IRAS) and Cosmic Background Explorer (COBE). The images show the An- dromeda galaxy, also known as M31; the Triangulum galaxy, or M33; and the Large and Small Magellanic Clouds – dwarf galaxies orbiting the Milky Way that do not have the spi- ral structure of the Andromeda and