The galaxy ESO 300-16 looms over this captivating image from the Hubble Space Telescope. This galaxy, which lies 28.7 million light-years from Earth in the constellation Eridanus, is a ghostly assemblage of stars that resembles a sparkling cloud. A rogue’s gallery of distant galaxies and foreground stars completes this astronomical portrait, which was captured by the Advanced Camera for Surveys (ACS).
Hubble’s In-depth Exploration
This particular observation is one of a series that aims to get to know our galactic neighbors. Remarkably, about three-quarters of the known galaxies suspected to lie within 10 megaparsecs of Earth have already been observed by Hubble in enough detail to resolve their brightest stars and establish the distances to these galaxies. A team of astronomers proposed using small gaps in Hubble’s observing schedule to investigate the remaining quarter of the nearby galaxies.
Grasping Astronomical Distances
The megaparsec — meaning one million parsecs — is a unit of length used by astronomers to chart the mind-bogglingly large distances involved in astronomy. The motion of Earth around the Sun means that stars appear to slightly shift against very distant stars over the course of a year. This small shift is referred to as parallax and is measured in angular units: degrees, minutes, and seconds. One parsec is equivalent to saying a parallax of one arcsecond, and is equivalent to 3.26 light-years or 30.9 trillion kilometers. Proxima Centauri b, the closest exoplanet to our Sun, lies 1.3 parsecs away.