PEARLSDG: A Peculiar Dwarf Galaxy Challenges Astronomers’ Understanding of Galaxy Formation and Evolution

The dwarf galaxy PEARLSDG subverts astronomers’ understanding of galaxy formation and evolution. (Arizona State University)

Text/Reporter Chen Juncun

Astronomers have discovered strange dwarf galaxies that do not have the characteristics of general dwarf galaxies. They neither generate new stars nor interact with neighboring galaxies. They just stay alone in space, completely overturning astronomers’ understanding of the formation and evolution of galaxies. Cognition.

Arizona State University recently issued a press release stating that a research team led by Tim Carleton, an assistant research scientist at the school, discovered a peculiar dwarf galaxy, named PEARLSDG.

The research team observed a galaxy cluster through the James Webb Space Telescope, and PEARLSDG happened to appear in the images taken by the telescope. PEARLSDG was not originally an observation target, but it appeared next to the main observation area, and the researchers did not expect to see anything in this area.

Galaxies are made up of stars and planets, bound together by gravity, as well as huge clouds of dust, gas and dark matter. Dwarf galaxies are the most numerous galaxies in the universe. They are defined as galaxies with low mass and low brightness. They usually contain less than 100 million stars, but the Milky Way, which is also classified as a dwarf galaxy, has about 200 billion stars.

PEARLSDG is a dwarf galaxy with very sparse internal stars. It does not have the characteristics of a general dwarf galaxy. It neither generates new stars nor interacts with neighboring galaxies. It is actually an isolated quiescent galaxy.

Carlton said that except in very rare cases, such isolated quiescent dwarf galaxies had not been observed before. “Based on our current understanding of galaxy evolution, we really wouldn’t expect them to exist, so this observation can help us improve our theories of galaxy formation. Generally speaking, dwarf galaxies that exist alone will continue to produce new stars.”

Until now, astronomers’ understanding of galaxy evolution was that galaxies existing alone continue to form new stars or interact with larger neighboring galaxies. But this theory does not apply to PEARLSDG. It has ancient stars, but it doesn’t create new stars or interact with other galaxies.

Astronomers can observe individual stars of PEARLSDG through the Webb Space Telescope. Based on the brightness of these stars, PEARLSDG is estimated to be about 98 million light-years away from Earth.

This discovery changes astronomers’ understanding of galaxy formation and evolution, and means that there may be many isolated quiescent dwarf galaxies waiting for astronomers to identify.

The research results have been published in The Astrophysical Journal Letters. ◇