The bulge located in the center is made up of older, dimmer stars, and is thought to usually contain a supermassive black hole. 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. Originally, Edwin Hubble grouped galaxies into four main categories: spiral galaxies, barred spiral galaxies, elliptical galaxies, and irregular galaxies. In the present day, galaxy classification and morphology are largely done using computational methods and physical morphology. The most famous one is the Hubble sequence, devised by Edwin Hubble, and later expanded by Gerard Vaucouleurs and Allan Sandage. Many schemes are in use in which galaxies are classified according to their morphologies. Most galaxies are between 1.000 to 100.000 parsecs / 3.000 to 300.000 light-years in diameter.Ī system used by astronomers to divide galaxies into groups on their visual appearance is the galaxy morphological classification.It is estimated that the galaxy formed just around 400 million years after the Big Bang. It is 32 billion light-years / 9.8 billion parsecs away from us. The oldest and farthest galaxy ever discovered is an irregular type of galaxy called GN-z11.Curious enough, the smallest galaxies are also the elliptical types.They span as much as one million light-years across – 10 times as much as the Milky Way. The largest galaxies are usually giant elliptical galaxies, containing a trillion or even more stars.They lack a distinct shape or form often having a chaotic appearance. Irregular galaxies are commonly small, and collectively they make up about a quarter of all the galaxies.They are very dim in comparison with the very bright spiral galaxies. They make up around 10-15% of galaxies in the Virgo Supercluster, a supercluster of which we are also part of. Elliptical galaxies are usually comprised of very old stars or stars with low mass.It is sometimes named the Hoag-type galaxy. Estimates suggest that around 0.1% of galaxies are this type. The rarest type of galaxies is the elliptical double-ringed galaxy.Our galaxy, the Milky Way is an example of this type of galaxy. Around two-thirds of all spiral galaxies have a bar-like structure – thus they are classified as barred spiral galaxies.A good example of this type is the Andromeda galaxy. Around 77% of the galaxies observed by man are spiral galaxies. The most common type of galaxy found throughout the universe is the spiral galaxy.These types of galaxies are further divided into subcategories while at the same time other types of galaxies exist based on their size and other unique features. There are four main categories of galaxies: elliptical, spiral, barred spiral, and irregular.
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