This week’s Hubble Space Telescope image shows a galaxy in our backyard, cosmically speaking, taken as part of a project to image nearby galaxies. Galaxy UGCA 307 lies 26 million light-years away in the constellation of Corvus, or The Raven, a small constellation visible from the southern hemisphere that was documented as early as 1,000 years BC.
There is only a small group of stars within this galaxy, as it is a type called a dwarf galaxy. These are defined as galaxies with only a few billion stars, which seems like a lot until you compare it to the hundreds of billions of stars found in our Milky Way galaxy.
UGCA 307 does not have much structure, again unlike our Milky Way with its central bar and clearly defined spiral arms. Instead, this galaxy is dim and hazy with sprinkles of stars.
Still, there are visible features in this galaxy, such as the bright red regions where new stars are forming. When stars are young, they emit ultraviolet radiation, which lights up nearby gas and makes it glow brightly.
The image was taken with Hubble’s Advanced Camera for Surveys (ACS) instrument, which looks in the same part of the electromagnetic spectrum that the human eye can perceive, called visible light, or optical range. It doesn’t see ultraviolet radiation from new stars, but it does see the effect the radiation has on dust clouds around star-forming regions.
“This image is part of a Hubble project to explore all known nearby galaxies, giving astronomers information about our galactic neighborhood,” the Hubble scientists explain.
“Prior to this set of observations, Hubble had investigated nearly three-quarters of the nearby galaxies in enough detail to detect the brightest stars and understand the stars that populate each galaxy. This Hubble project set out to explore the remaining quarter of the nearby galaxies by taking advantage of the short gaps in Hubble’s observing program.”