Our Milky Way galaxy has another neighbor.
The Hubble Space Telescope discovered a dwarf galaxy in our own cosmic backyard, just 30 million light-years away from the Milky Way. (This may sound like a distant piece, but remember: the observable universe is an incredible 93 billion light-years).
The finding was fortuitous. An international team of astronomers was using Hubble's Advanced Camera for Surveys instrument to study white dwarfs – superdense stellar corpses – in the NGC 6752 globular cluster, which is part of the Milky Way. [Gallery: 65 All-Time Great Galaxy Hits]
The Hubble images revealed a strange set of stars. Analyzes of the stars' glows and temperatures indicated that they were beyond NGC 6752 and were, in fact, part of an unknown galaxy.
The researchers determined that this galaxy – dubbed Bedin 1 after the leader of the discovery team L. R. Bedin of the INAF-Osservatorio Astronomico di Padova in Italy – is a "spheroidal dwarf" with only 3,000 light-years wide. (For comparison, the famous spiral disc of the Milky Way has a diameter of about 100,000 light-years.) Spheroidal dwarf galaxies are not uncommon; astronomers already knew more than 20 that are satellites of the Milky Way. But Bedin 1 is special in many ways, according to the Discovery team.
For example, the dwarf is about 2 million light-years away from the nearest large galaxy that could be its host (which is called NCG 6744), the researchers said. Bedin 1 may therefore be the most isolated isolated dwarf galaxy.
And then there is the age of Bedin 1.
"From the properties of their stars, astronomers were able to infer that the galaxy is 13 billion years old – almost as old as the universe itself," Hubble team members wrote in a statement. "Because of its isolation – which resulted in almost no interaction with other galaxies – and its age, Bedin 1 is the astronomical equivalent of a living fossil of the early universe."
The researchers published their findings online today (January 31) in the Monthly Notices magazine of the Royal Astronomical Society: Letters.
The Hubble Space Telescope, a joint project of NASA and the European Space Agency, was launched into Earth orbit in April 1990, aboard the Space Shuttle Discovery. The cosmic views of the oscilloscope were initially blurred – the result of a small flaw in Hubble's primary mirror – but astronauts on the way to space corrected that problem in December 1993.
The astronauts maintained, repaired and upgraded Hubble in four additional maintenance missions, the last of which occurred in May 2009.
Mike Wall's book on the search for alien life, "Out There" (Grand Central Publishing House, 2018; illustrated by Karl Tate), is now available. Follow him on Twitter @michaeldwall. Follow Us @Spacedotcom or Facebook. Originally posted on Space.com.