Compass Image of Bedin 1 in NGC 6752. Credit: NASA, ESA, and L. Bedin (Astronomical Observatory of Padua, Italy)
January 31, 2019, ESA/Hubble Information Centre
Astronomers using the NASA/ESA Hubble Space Telescope to study some of the oldest and faintest stars in the globular cluster NGC 6752 have made an unexpected finding. They discovered a dwarf galaxy in our cosmic backyard, only 30 million light-years away. The finding is reported in the journal Monthly Notices of the Royal Astronomical Society: Letters.
An international team of astronomers recently used the NASA/ESA Hubble Space Telescope to study white dwarf stars within the globular cluster NGC 6752. The aim of their observations was to use these stars to measure the age of the globular cluster, but in the process they made an unexpected discovery.
In the outer fringes of the area observed with Hubble’s Advanced Camera for Surveys a compact collection of stars was visible. After a careful analysis of their brightnesses and temperatures, the astronomers concluded that these stars did not belong to the cluster—which is part of the Milky Way—but rather they are millions of light-years more distant.
Our newly discovered cosmic neighbour, nicknamed Bedin 1 by the astronomers, is a modestly sized, elongated galaxy. It measures only around 3000 light-years at its greatest extent—a fraction of the size of the Milky Way. Not only is it tiny, but it is also incredibly faint. These properties led astronomers to classify it as a dwarf spheroidal galaxy.
Dwarf spheroidal galaxies are defined by their small size, low-luminosity, lack of dust and old stellar populations. 36 galaxies of this type are already known to exist in the Local Group of Galaxies, 22 of which are satellite galaxies of the Milky Way.
For the full original article read more at: https://phys.org/news/2019-01-hubble-fortuitously-galaxy-cosmic-neighbourhood.html#jCp