Hubble captures galaxy NGC 3156

This dream-like image from the NASA/ESA Hubble Space Telescope features the galaxy known as NGC 3156. It lies about 73 million light-years from Earth, in the minor equatorial constellation Sextans.

Spanish astronomer discovers new active galaxy

By analyzing the images of the Sombrero Galaxy obtained with the Hubble Space Telescope (HST), Elio Quiroga Rodriguez of the Mid Atlantic University in Spain, has identified a peculiar object, which turned out to be a galaxy ...

Galaxy mergers shed light on galactic evolution model

An Australian astronomer has solved a century-old mystery regarding how galaxies evolve from one type to another. The same study shows that the Milky Way, the galaxy we live in, was not always a spiral.

Chemical cartography reveals the Milky Way's spiral arms

Keith Hawkins, assistant professor of astronomy at The University of Texas at Austin, has used chemical cartography—also known as chemical mapping—to identify regions of the Milky Way's spiral arms that have previously ...

Hubble spotlights barred spiral galaxy UGC 678

The barred spiral galaxy UGC 678 takes center stage in this image from the NASA/ESA Hubble Space Telescope. The spectacular galaxy lies around 260 million light-years from Earth in the constellation Pisces and is almost face ...

Hubble spots irregular spiral galaxy NGC 5486

The irregular spiral galaxy NGC 5486 hangs against a background of dim, distant galaxies in this image from the NASA/ESA Hubble Space Telescope. The tenuous disk of the galaxy is threaded through with pink wisps of star formation, ...

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Spiral galaxy

A spiral galaxy is a galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the Nebulae” and, as such, forms part of the Hubble sequence. 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 surrounded by a much fainter halo of stars, many of which reside in globular clusters.

Spiral galaxies are named for the (usually two-armed) spiral structures that extend from the center into the disk. The spiral arms are sites of ongoing star formation and are brighter than the surrounding disk because of the young, hot OB stars that inhabit them. Roughly half of all spirals are observed to have an additional component in the form of a bar-like structure, extending from the central bulge, at the ends of which the spiral arms begin. Our own Milky Way has been recently (in the 1990s) been confirmed to be a barred spiral, although the bar itself is difficult to observe from our position within the Galactic disk. The most convincing evidence for its existence comes from a recent survey, performed by the Spitzer Space Telescope, of stars in the Galactic center.

Together with irregulars, spiral galaxies make up approximately 60% of galaxies in the local Universe. They are mostly found in low-density regions and are rare in the centers of galaxy clusters.

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