Gravity binds a galaxy, a vast collection of gas, dust, billions of stars, and their associated solar systems. Galaxies exhibit an array of sizes, from small dwarf galaxies with modest populations of a few billion stars to large elliptical galaxies with trillions of stars. While most galaxies have elliptical shapes, some have unique shapes, such as toothpicks or rings. One of the most amazing forms of galaxies in existence is the spiral galaxy.
A NASA astronomy image of a spiral galaxy named Arp 78. It is a massive galaxy that spans about 200,000 light-years and is about 100 million light-years away in the constellation Aries. Arp 78 is also known as NGC 772. Along with Arp 78, another faint galaxy can be seen, which is NGC 770. This picture was taken by astronomer Joseph Druids.
What is a spiral galaxy?
According to NASA, spiral galaxies are actively forming stars that make up the bulk of all galaxies in our nearby universe. They can be further divided into two groups: normal spirals and interrupted spirals. In barred spirals, a bar of stars passes through the central bulge of the galaxy.
NASA image description
The strange spiral galaxy Arp 78 is found within the boundaries of the strong constellation Aries. Some 100 million light years from our stars and nebula The Milky Way Galaxy, the island universe spans 200,000 light years. Also known as NGC 772, it sports a prominent, outer spiral arm in this detailed cosmic portrait.
Tracking along sweeping dust lanes and lined with clusters of young blue stars, Arp 78’s more advanced spiral arm is pumped by galactic-scale gravitational waves. Interactions with its brightest companion galaxy, visible above and to the right of the more compact NGC 770 large spiral, are likely responsible. Included among the faint star streams visible in deep binocular exposures, NGC 770’s fuzzy, elliptical shape contrasts well with the corresponding bright yellow foreground Milky Way stars.
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