The Milky Way

Professor - The Milky Way is the galaxy that contains the Earth. This name derives from its appearance as a dim milky glowing band stretching across the night sky, in which the naked eye cannot distinguish individual stars. The term Milky Way is a translation of classical Latin ____ from the Hellinistic Greek, Milky Circle. The Milky Way appears like a band disk-shaped structure being viewed from inside. The fact that this faint band of light is made up of stars in 1610 when Galileo Galilei used his telescope to resolve it into individual stars. Do any of you know the name of the astronomer who proved that the Milky Way is just one of many galaxies?

Student - Um, Hubble something... Hubble Edward?

Professor - Almost, Mary. Astronomer Edwin
Hubble showed that the Milky Way is just one of many galaxies in the year 1920. The Milky Way is a spiral galaxy 100,000 to 120,000 light years in diameter containing 200-400 billion stars. It may contain at least as many planets with an estimated 10 billion of those orbiting in the habital zone of their parent stars. The solar system is located within the disk around 2/3 of the way out from the galactic center on the spiral edge shaped concentration of gas and dust called The Orion __. The stars in the inner 10,000 light years are organized in a bulge and one or more bars. The very center is marked by an intense source named Sagittarius A a super massive black hole. The galaxy rotates differentially, faster towards the center and slower towards the outer edge. The rotational period is about 200 million years at the position of the sun. The galaxy as a whole is moving at a velocity at 552 to 630 kilometers per second, depending on the relative frame of reference. It is estimated to be about 30.2 billion years old, nearby as old as the universe. Surrounded by several smaller satellite galaxies, the Milky Way is part of the group of galaxies which forms a subcomponent of the Virgo supercluster.
When observing the night sky, the term "Milky Way" is limited to the hazy band of white light some 30 degrees wide arching across the sky. from unresolved stars and other materials that lie within the galactic plane. Dark regions within the band such as the __ and the __ correspond to areas where light from distant areas is blocked by interstellar dust. The Milky Way has a relatively low surface brightness. It's visibility can be reduced by background light such as light pollution or stray light from the Moon. It is visible when __ or better, while showing a great deal of detail at +6.1. This makes the Milky Way difficult to see from any brightly lit urban or suburban location, though very prominent when ruled from a rural area when the Moon is below the horizon. The Milk Way passes through parts of roughly 30 constellations. The center of the galaxy lies in the direction of the constellation, Sagitarrius. It is here that the Milky Way is the brightest. From __ the hazy band of white light appears to pass westward to the __ in __. The band then continues westward the rest of the way around the sky black to __.
The fact that the band divides the night sky into two roughly equal hemispheres indicates that the Solar System lies close to the galactic plain. The __ is inclined by about 60 degrees to the __. apsses and is far south as the constellation of crooks, indicating the __ and the plain of the ecryptic relative to the galactic plain. 12 hours and 49 meters declination +27.4 degrees, near ___, and the south galactic pole is near __. Because of this high inclination, depending on time of night and the year, the Milk Way can appear relatively low and relatively high in the sky. Observers from about 65 degrees north to 65 degrees south of the Earth's surface, the Milky Way appears directly overhead twice a day.