In 1937, astronomer Harlow Shapley discovered something mind blowing. Located around 300,000 light years away from Earth, was a Dwarf galaxy. The planets that make up a Dwarf galaxy are known as Dwarf planets. A dwarf planet has been described as a celestial body that orbits the sun and has enough mass to make a nearly round shape. But, the size of the planet is too small and it causes the planet to lack gravitational forces that pull in and help accumulate material found in their orbits. In our galaxy, known as the Milky Way, the dwarf planets that exist are smaller than Earth’s Moon!
You might be wondering, why is the Milky Way, a large barred spiral galaxy, not a Dwarf galaxy if it has Dwarf planets. Well, I’ll first explain what a Dwarf galaxy is. Dwarf galaxies are actually the most abundant type of galaxy in all of the universe. However, because of their low mass, small size, and small amount of light, they are hard to detect. They are usually found in galaxy clusters. This means that they are found in the middle of two or more larger galaxies. There are three types of Dwarf galaxies. The first type is Dwarf Elliptical galaxies. They are elliptical in shape, they have small to zero amounts of gas, and have no evidence of any recent stars forming. They have different light distributions than normal elliptical galaxies and despite being similar in looks, they have lower metallicities. The second type is Dwarf Spheroidal galaxies, they exist at the end of the Dwarf Elliptical scale. These galaxies have a different type of shape and are more spherical than elliptical and they tend to be smaller than Dwarf Elliptical galaxies. The third type is Dwarf Irregular galaxies, they have similar properties to the larger irregular galaxies. They contain a large amount of gas and dust which is evidence for ongoing star formation.
Here is a picture of what our galaxy looks like!
