Hubble spots a strangely organized satellite galaxy

Aug. 30 () –

Andromeda III is one of at least 13 dwarf satellite galaxies orbiting the Andromeda galaxy, or Messier 31, the closest spiral galactic neighbor to the Milky Way.

It is a faint spheroidal collection of old, reddish stars that appears devoid of new star formation and younger stars. In fact, Andromeda III appears to be only about 3 billion years younger than most globular clusters, dense knots of stars that are thought to have been born mostly at the same time and contain some of the oldest known stars in the universe.

Astronomers suspect that dwarf spheroidal galaxies may be remnants of the type of cosmic objects that were shredded and merged by gravitational interactions to form the halos of large galaxies. Interestingly, studies have found that several of the Andromeda dwarf galaxies, including Andromeda III, orbit in a plane around the galaxyas the planets in our solar system orbit the sun.

According to NASAthe alignment is puzzling because galaxy formation models do not show dwarf galaxies being arranged in such orderly formations, but instead moving around the galaxy randomly in all directions. As they slowly lose energy, Dwarf galaxies merge to form the larger galaxy.

The strange alignment could be due to the fact that many of the Andromeda dwarf galaxies They fell into orbit around her as a single groupor that dwarf galaxies are remnants left over from the merger of two larger galaxies. Either theory, which is being investigated using NASA’s James Webb Space Telescope, would complicate theories of galaxy formation but also help guide and refine future models.

The Hubble Space Telescope took this image of Andromeda III as part of an investigation into the star formation and chemical enrichment histories of a sample of dwarf spheroidal galaxies M31 who compared their first episodes of star formation with those of the satellite galaxies of the Milky Way.