Astronomers have discovered a new dwarf galaxy only 30 million light years away. This was a surprise finding made while studying the globular cluster NGC 6752.
The astronomers used the NASA/ESA Hubble Space Telescope. While studying some of the faintest and oldest stars in the NGC 6752 globular cluster, they unexpectedly found the new dwarf galaxy, which they have called the equivalent in astronomy of a living fossil from the early Universe.
The new discovery has been reported in the journal Monthly Notices of the Royal Astronomical Society: Letters.
How did astronomers discover the new dwarf galaxy?
The aim of their observations was to use the stars to measure the age of the globular cluster, but they also found the dwarf galaxy. By measuring the brightness and temperatures of some visible stars the astronomers concluded that these stars did not belong to the globular cluster as part of the milky way, but actually are millions of light-years more distant than this.
The galaxy has been called Bedin 1 by the astronomers. It is a modest size and is elongated. It measures around 3000 light-years which is only a tiny fraction of the size of the Milky Way, and it is very faint. This means that astronomers have classified it as a dwarf spheroidal galaxy.
The ESA/Hubble information centre commented: “The discovery of Bedin 1 was a truly serendipitous find. Very few Hubble images allow such faint objects to be seen, and they cover only a small area of the sky. Future telescopes with a large field of view, such as the WFIRST telescope, will have cameras covering a much larger area of the sky and may find many more of these galactic neighbours.”
A living fossil from the early Universe
The ESA/Hubble information centre added: “From the properties of its stars, astronomers were able to infer that the galaxy is around 13 billion years old — nearly as old as the Universe itself. Because of its isolation — which resulted in hardly any interaction with other galaxies — and its age, Bedin 1 is the astronomical equivalent of a living fossil from the early Universe.”