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Milestones in Astronomy: 1839 to 1923

During the 1800s, there was still a planet to be discovered and by the 1900s, a classification system was put in place to identify different kinds of stars. Some of the players mentioned include Albert Einstein, Johann Galle and Urbain Le Verrier. In this article, you will learn who discovered the eighth planet and information behind one of the oldest observatories in the world.

1839 , Around 1839, the first photographs of the Moon are taken.

1846 , Johann Galle and Urbain Le Verrier discover the eighth planet. It is named Neptune. Galle is a German astronomer attached to the Berlin Observatory, who first saw the planet along with his student Heinrich Louis d’ Arrest. He knew what he was looking at because he relied on the calculations of French mathematician Le Verrier whose specialty was celestial mechanics. Galle also studied comets and published a list of 414 comet in 1894 with the help of his son, Andreas. In less than a year, Galle had discovered three of the comets himself.

1894 , In Arizona, the Flagstaff Observatory (now known as Lowell Observatory) is founded. This site is one of the oldest observatories in the United States. In 1965, it was given the distinction of being a National Historic Landmark. With guided tours in the daytime, about 70,000 visitors make it to the observatory each year.

1905 , Albert Einstein makes his initial proposals regarding his “Special Theory of Relativity.”

1908 , The description of giant and dwarf stars is made. A giant star possess a much larger radius and luminosity than other stars with the same surface temperature. Usually, giant stars possess radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. They are not the most luminous stars in the sky, as supergiants and hypergiants have them beat.

A dwarf star includes various classes of stars that are identified by different colors. A red dwarf is a low-mass main sequence star. A main sequence star with masses comparable to the Sun is called a yellow dwarf. The Sun is actually categorized as a yellow dwarf. A blue dwarf is a low-mass star which is believed to be the post-main sequence form of a red dwarf.

A white dwarf is thought to be the last stage in the evolution of stars that are not large enough to become part of a supernova. These stars are made up of electron-degenerate matter. A black dwarf is a white dwarf that has cooled down enough that it no longer gives off any visible light. A brown dwarf is characterized as a sub-stellar object that is not large enough to combine hydrogen and helium.

1923 , It is proven that there are galaxies located beyond the Milky Way, which is the galaxy that contains the Solar System that we know. The origin of its name comes from the appearance of the night sky that seemed to have a ‘milky’ glow to it.