Record-Breaking Discovery: Scientists Find Faintest Dwarf Galaxy Orbiting the Milky Way

Astronomers have spotted a record-breaking satellite orbiting the Milky Way. While record-breaking might imply that the satellite was bright and huge, the recently discovered satellite was rather the faintest satellite galaxy yet found.

The extremely faint dwarf satellite was spotted by an international team led by astronomers from Tohoku University in Japan using the Subaru telescope, as part of the ongoing Subaru Strategic Survey using Hyper Suprime-Cam.

The faint dwarf named Virgo I, as it was found in the constellation Virgo, has an absolute magnitude of -0.8 in the optical waveband. Absolute magnitude is the brightness of a celestial object from a distance of 10 parsecs away.

"We have carefully examined the early data of the Subaru Strategic Survey with HSC and found an apparent over density of stars in Virgo with very high statistical significance, showing a characteristic pattern of an ancient stellar system in the color-magnitude diagram," Daisuke Homma who found Virgo I said in a press release.

"Surprisingly, this is one of the faintest satellites, with absolute magnitude of -0.8 in the optical waveband. This is indeed a galaxy, because it is spatially extended with a radius of 124 light years - systematically larger than a globular cluster with comparable luminosity."

Science Alert notes that at present, 50 galaxies orbiting our own galaxy had been found already. About 40 of them are faint, which puts them in the category of so-called dwarf spheroidal galaxies.

Earth Sky reported that the discovery of this satellite indicated the presence of a large number of yet-undetected dwarf satellites in the halo of the Milky Way. This would lead to the better understanding of how "dark matter" holds the numerous galaxies together.

Scientists suspect that a whole lot of these satellites are hiding in plain sight. They cannot be found because they might be as faint as Virgo I or even fainter.

The research has been published in the Astrophysical Journal.