The outskirts of the galaxy NGC 4603 are packed with a sea of stars as imaged by the Hubble Space Telescope. NGC 4603 was one of 18 galaxies studied in detail for one of Hubble’s first major projects, a search for Cepheid variable stars at greater distances than previously resolved to help pin down the Hubble constant and thus the age of the universe. The “key project” found some 800 Cepheids in far-flung galaxies, allowing astronomers to determine, with an uncertainty of 10 percent, that the universe was approximately 12 billion years old. Subsequent research pushed the age back to 13.8 billion years with an uncertainty of just 20 million years or so. NGC 4603 is about 108 million light years from Earth in the constellation Centaurus.
Many galaxies are chock-full of dust, while others have occasional dark streaks of opaque cosmic soot swirling in amongst their gas and stars. However, the irregular dwarf galaxy IC 1613 contains very little cosmic dust, allowing astronomers to explore its contents with great clarity. This is not just a matter of appearances; the galaxy’s cleanliness is vital to our understanding of the universe around us.