The NASA/ESA Hubble Space Telescope has captured this spectacular image of the Pegasus dwarf spheroidal galaxy, a satellite of the Andromeda galaxy.
The Pegasus dwarf spheroidal galaxy resides around 959,000 light-years away from the Andromeda Galaxy. Image credit: NASA / ESA / D. Weisz, University of California – Berkeley / Gladys Kober, NASA & Catholic University of America.
The Pegasus dwarf spheroidal galaxy is located some 2.7 million light-years away in the constellation of Pegasus.
“The Andromeda galaxy, also known as Messier 31, is the Milky Way’s closest grand spiral galaxy neighbor, and is orbited by at least 13 dwarf satellites,” the Hubble astronomers said in a statement.
“The Pegasus dwarf spheroidal galaxy is one of these mini-galaxies.”
“Dwarf spheroidal galaxies are the dimmest and least massive galaxies known,” they explained.
“They tend to have elliptical shapes and relatively smooth distributions of stars.”
“Dwarf spheroidal galaxies are usually devoid of gas and dominated by old and intermediate-age stars, although some have experienced small amounts of recent star formation.”
Also known as Andromeda VI, the Pegasus dwarf spheroidal galaxy was discovered in 1996 in the images from the Second Palomar Observatory Sky Survey (POSS II).
“This galaxy has been characterized as having a small amount of heavy elements and little of the gas needed to form another generation of stars — though more than many of the dwarf spheroidal galaxies within our Local Group of galaxies,” the astronomers said.
“Researchers suspect that Andromeda’s gravitational field may have stripped the star-forming gases from it, leaving a dearth of material to build more than a few generations of stars.”
“In comparison, some of the dwarf spheroidal companion galaxies of the Milky Way found at comparable distances do contain some intermediate-age stars, but this could be because Andromeda is so massive and extended that its gravitational effects extend farther.”
“The jury is still out on how dwarf spheroidal galaxies form,” they noted.
“Theories include collisions between galaxies that break off small fragments, the gravitational influence of larger galaxies on small disk-shaped dwarf galaxies, and processes associated with the birth of small systems among collections of dark matter.”
“Andromeda and the Milky Way are the only galaxies close enough for astronomers to view these dim satellite galaxies, so clues to their formation will have to come from close neighbors like this one.”
“Hubble studied this galaxy as part of an examination of the entire Andromeda system of satellites in order to investigate such critical matters as dark matter, reionization, and the growth of galactic ecosystems across cosmic time.”
Source : Breaking Science News