Hubble Space Telescope has photographed such lumps, which may be the precursors to modern galaxies.Īccording to this theory, most of the early large galaxies were spirals. One hypothesis states that galaxies were born when vast clouds of gas and dust collapsed under their own gravitational pull, allowing stars to form.Ī second hypothesis claims that the young universe contained many small 'lumps' of matter, which clumped together to form galaxies. Galaxies are thought to have been formed roughly 13 to 14 billion years ago. For example, our Milky Way, like many other spiral galaxies, has a linear, starry bar at its center. This usually can cause matter in the disk to take on a distinctive spiral shape, like a cosmic pinwheel. The spinning motion reaches speeds of up to hundreds of kilometers/miles per second. They have a flat, spinning disk with a central bulge surrounded by spiral arms. Observations revealed that spiral galaxies were the most common type of galaxies found throughout the universe. He grouped them into four main categories: spiral galaxies, lenticular galaxies, elliptical galaxies, and irregular galaxies. With this revelation further studies were conducted, many other galaxies were discovered and in 1936, Hubble debuted a way to classify galaxies. All of this changed in 1920 when astronomer Edwin Hubble demonstrated that the Andromeda nebula was, in fact, a galaxy. Galaxies were first classified as nebulae since they looked like fuzzy clouds. In fact, we didn’t even know that other galaxies existed, other than the Milky Way for a long time. The discovery of other types of galaxies is fairly recent. Spiral galaxies tend to be the brightest galaxies in the universe.Most spiral galaxies contain a supermassive black hole in the center of the central bulge.Spiral galaxies are mostly found in low-density regions, and very rarely at the center of galaxy clusters.Around 60% of the observable universe is comprised out of spiral galaxies.

Spiral galaxies are the most common type of galaxies found throughout the Universe.Our Milky Way, for example, is a barred spiral galaxy.This bar extends from the central bulge at the ends of which spiral arms begin.Around two-thirds of all spiral galaxies have an additional component in the form of a bar-like structure.They have spiral arms – sites of ongoing star formation that are brighter than the surrounding disk due to the presence of young OB stars that inhabit them.As such, Spiral galaxies are named after their spiral structures that extend from the center into a galactic disk.These bulges are often surrounded by a faint halo of stars, many of which reside in globular clusters – a spherical collection of stars that orbits a galactic core.Spiral galaxies usually consist of a rotating disk that contains stars, dust, gas, and a concentration of stars known as the bulge in the center.They are part of the Hubble sequence a morphological classification scheme for galaxies.

Spiral galaxies are a class of galaxies originally described by astronomer Edwin Hubble in his 1936 work The Realm of the Nebulae.

Spiral galaxy labeled