A sparkling galactic neighbour

The galaxy ESO 300-16 looms over this image from the NASA/ESA Hubble Space Telescope. This galaxy, which lies 28.7 million light-years from Earth in the constellation Eridanus, is a ghostly assemblage of stars which resembles a sparkling cloud. A rogue’s gallery of distant galaxies and foreground stars complete this astronomical portrait, which was captured by the Advanced Camera for Surveys. 

This observation is one of a series which aims to get to know our galactic neighbours; around three quarters of the known galaxies suspected to lie within 10 megaparsecs of Earth have 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 acquaint ourselves with the remaining quarter of the nearby galaxies.

The megaparsec — meaning one million parsecs — is a unit 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 kilometres. The closest exoplanet to the Sun is Proxima Centauri b, which lies 1.3 parsecs away.

[Image Description: An irregular galaxy that resembles the shape of a cloud. It is made of many tiny stars all clumped together, surrounded in a diffuse light. In the central, brightest part there is a bubble of blue gas. The galaxy is surrounded by mostly very small and faint objects, though there are bright stars above and to the left of it, and a string of galaxies nearby.]