Galaxies: Big, bright and really hard to miss. However, not all galaxies fit into this stereotype – some are somewhat lower, hidden or simply simple, which explains why the Hubble Space Telescope found the whole galaxy going to our cosmic threshold, which is just 30 million light years away. Of course, it may sound far, but across intergalactic scales, it's like finding a tree in your yard that you didn't understand.
Though it might be difficult to imagine, astronomers got into this galaxy by accident. By studying the ancient white dwarf stars in the bright global cluster NGC 6752, trying to get an accurate cluster age measurement, they noticed something wrong in the background. The cluster is just 13,000 light-years away in our Milky Way galaxy in the direction of Pavo constellation, but when checking the cluster, astronomers noted a dense, weaker star collection over NGC 6752. And after careful measurement of the brightness and background star temperature, they realized they had found something something special – the whole galaxy hidden by the reflection of NGC 6752.
Astronomers, called Bedin 1, and their study were published in the monthly announcements of the Royal Astronomical Society "Letter".
So what do we know about our new galaxy neighbor? For starters it is small. When giving, the galaxies are not "small", but compared to our absolute galactic unit, Bedin 1 is the weight of the feathers. Measuring just 3,000 light years, Bedin 1 is part of the Milky Way (our galaxy is at least 100,000 light years). Needless to say, Bedin 1 is also quite weak, as a result of which astronomers classified it as a dwarf spherical galaxy. Dwarf spheroids are retired galaxies; the star formation party is over and the stars they have are old and dark. They are also quite common in our local galaxy group – we know about 36 of these galaxies and 22 of them are in orbit around our galaxy!
Although it is a common form of tiny galaxy, according to a study Bedin 1 has some special qualities. For starters it is lonely. It is 30 million light-years away from the Milky Way and at least 2 million light-years away from the nearest large galaxy, NGC 6744. Bedin 1 is believed to be the most isolated dwarf galaxy. Its stars are also old really old, discovering that the galaxy is as old as the universe itself – about 13 billion years old. Hubble's statement compares Bedin 1 with the "astronomical equivalent of the early universe living fossil".
Accidentally stumbling across a nearby galaxy gives astronomers a hint that there may be many more of this kind of galaxy, just waiting to be behind the closest star cluster. As the telescopes on the ground and in space become increasingly complex, it seems very likely that this is just a matter of time before the closer cosmic fossils are excavated.