Astronomers detect a new radio source of unknown origin

During radio continuum observations of a spiral galaxy known as NGC 2082, Australian astronomers have discovered a mysterious bright and compact radio source, which received designation J054149.24–641813.7. The origin and ...

Hubble views an interacting spiral

This image, taken by the Wide Field and Planetary Camera 2 on NASA's Hubble Space Telescope, features the spiral galaxy NGC 3509. Located some 350 million light-years away, NGC 3509 is an interesting galaxy whose sweeping ...

Hubble focuses on large lenticular galaxy 1023

This new NASA Hubble Space Telescope image looks at one of the nearest, massive lenticular galaxies to Earth, NGC 1023 some 36 million light-years away. Lenticular galaxies get their names from their edge-on appearance that ...

A dazzling Hubble collection of supernova host galaxies

Spanning from 2003 to 2021, this collection of images from the NASA/ESA Hubble Space Telescope features galaxies that are all hosts to both Cepheid variables and supernovae. These two celestial phenomena are both crucial ...

Hubble's double take on a spiral galaxy

The magnificent spiral galaxy M99 fills the frame in this image from the NASA/ESA Hubble Space Telescope. M99—which lies roughly 42 million light-years from Earth in the constellation Coma Berenices—is a "grand design" ...

Galactic ballet captured from NSF's NOIRLab in Chile

The barred spiral galaxy NGC 1512 (left) and its diminutive neighbor NGC 1510 were captured in this observation from the Víctor M. Blanco 4-meter Telescope. As well as revealing the intricate internal structure of NGC 1512, ...

Image: Hubble snaps yet another spiral galaxy

The spiral galaxy M91 fills the frame of this Wide Field Camera 3 observation from the NASA/ESA Hubble Space Telescope. M91 lies approximately 55 million light-years from Earth in the constellation Coma Berenices and—as ...

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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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