Image: Hubble views a not-so-lonely galaxy

Galaxies may seem lonely, floating alone in the vast, inky blackness of the sparsely populated cosmos—but looks can be deceiving. This image of NGC 1706, taken by the NASA/ESA Hubble Space Telescope, is a good example of ...

Going against the flow around a supermassive black hole

At the center of a galaxy called NGC 1068, a supermassive black hole hides within a thick doughnut-shaped cloud of dust and gas. When astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to study this ...

Hubble snaps spiral's profile

The NASA/ESA Hubble Space Telescope sees galaxies of all shapes, sizes, luminosities and orientations in the cosmos. Sometimes, the telescope gazes at a galaxy oriented sideways—as shown here. The spiral galaxy featured ...

Image: Hubble spots a swarm of stars

This image from the NASA/ESA Hubble Space Telescope shows a dwarf galaxy named UGC 685. Such galaxies are small and contain just a tiny fraction of the number of stars in a galaxy like the Milky Way. Dwarf galaxies often ...

Image: X-raying a galaxy's stellar remnants

This colourful spread of light specks is in fact a record of extremely powerful phenomena taking place in a galaxy known as Messier 83, or M83. Located some 15 million light-years away, M83 is a barred spiral galaxy, not ...

Image: Hubble traces a galaxy's outer reaches

Believe it or not, this long, luminous streak, speckled with bright blisters and pockets of material, is a spiral galaxy like our Milky Way. But how could that be? 

Image: Hubble snaps a galactic potpourri of particles

Every now and then, the NASA/ESA Hubble Space Telescope glimpses a common object—say, a spiral galaxy—in an interesting or unusual way. A sharply angled perspective, such as the one shown in this Hubble image, can make ...

Image: Hubble spots a stunning spiral

Galaxies come in many shapes and sizes. One of the key galaxy types we see in the universe is the spiral galaxy, as demonstrated in an especially beautiful way by the subject of this Hubble Space Telescope image, NGC 2985. ...

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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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