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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

APODs including "Spiral Arms"

Massive Nearby Spiral Galaxy NGC 2841

21 April 2014

Massive Nearby Spiral Galaxy NGC 2841
Image Credit: Robert Gendler / NASA APOD

It is one of the more massive galaxies known. A mere 46 million light-years distant, spiral galaxy NGC 2841 can be found in the northern constellation of Ursa Major. This sharp view of the gorgeous island universe shows off a striking yellow nucleus and galactic disk. Dust lanes, small, pink star-forming regions, and young blue star clusters are embedded in the patchy, tightly wound spiral arms. In contrast, many other spirals exhibit grand, sweeping arms with large star-forming regions. NGC 2841 has a diameter of over 150,000 light-years, even larger than our own Milky Way and captured by this composite image merging exposures from the orbiting 2.4-meter Hubble Space Telescope and the ground-based 8.2-meter Subaru Telescope. X-ray images suggest that resulting winds and stellar explosions create plumes of hot gas extending into a halo around NGC 2841.