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en.wikipedia.org/wiki/Spiral_galaxy

Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, form part of the Hubble sequence. Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are often ...

cas.sdss.org/dr6/en/proj/basic/galaxies/spirals.asp

The most common type of galaxy is called a "spiral galaxy." Not surprisingly, spiral galaxies look like spirals, with long arms winding toward a bright bulge at the center. But be careful - if you looked at a spiral galaxy from the side, you could mistake its shape for a circle, and so you'd have to use other criteria to learn it was a ...

www.space.com/22382-spiral-galaxy.html

Aug 15, 2013 ... A spiral galaxy has a distinct winding shape. Most of the galaxies observed by astronomers are spiral galaxies.

coolcosmos.ipac.caltech.edu/ask/217-What-is-a-spiral-galaxy-

Spiral galaxies get their name from the shape of their disks. In a spiral galaxy, the stars, gas and dust are gathered in spiral arms that spread outward from the galaxy's center. Spiral galaxys are divided into three main types depending on how tightly wound their spiral arms are: Sa, Sb and Sc. Sa galaxies have very tightly ...

www.nasa.gov/multimedia/imagegallery/image_feature_2132.html

Dec 16, 2011 ... Resembling festive lights on a holiday wreath, this NASA/ESA Hubble Space Telescope image of the nearby spiral galaxy M74 is an iconic reminder of the impending season. Bright knots of glowing gas light up the spiral arms, indicating a rich environment of star formation.

astronomy.swin.edu.au/cosmos/S/Spiral+Galaxy

When Hubble developed his classification system for galaxies based on their appearance in optical light, he divided the spirals into those in which the spiral arm radiated from a central bulge (classic spirals), and those where the arms radiated from a central bar (barred spirals). Classic or barred notwithstanding, all spiral ...

www.softschools.com/facts/space/spiral_galaxy_facts/438

Spiral galaxies get their name by the fact that they have a spiral or whirl shape. The "arms" of the spiral are the areas where stars are formed. These arms appear as waves. The galaxy we live in, the Milky Way, is a spiral galaxy. Our planet and Sun lie in the arms of the Milky Way.

www.windows2universe.org/the_universe/Spirals.html

Spiral galaxies may remind you of a pinwheel. They are rotating disks of mostly hydrogen gas, dust and stars. Through a telescope or binoculars, the bright nucleus of the galaxy may be visible but the spiral arms are dimmer and difficult to see. Spiral galaxies are complex objects and have several components: a disk,  ...

www.scientificamerican.com/article/what-process-creates-and

Before delving into an answer, it is important to note that the spiral arms of galaxies are not fixed, solid objects; rather, they are patterns of bright stars and gas clouds within the overall form of the galaxy. The space between the spiral arms is not empty, and stars can move in and out of the arms as they orbit through the ...