Spiral Arms
Regions of stars and interstellar matter that extend from the center of spiral galaxies, forming a spiral pattern; in the Milky Way, these include the Orion Arm where our Solar System resides.
Source: esa.int
APODs including "Spiral Arms"
NGC 3621: Far Beyond the Local Group
05/06/2002
Far beyond the local group of galaxies lies NGC 3621, some 22 million light-years away. Found in the serpentine southern constellation Hydra, the loose spiral arms of this gorgeous island universe are loaded with luminous young star clusters and dark dust lanes. Still, for earthbound astronomers NGC 3621 is not just another pretty face-on spiral galaxy. Some of its brighter stars have been used as standard candles to establish important estimates of extragalactic distances and the scale of the Universe. This color picture was constructed from astronomical image data recorded with the Very Large Telescope Antu, at Paranal Observatory in Chile. At the original resolution, individual, hot supergiant stars can be identified and studied across NGC 3621.