The Milky Way is the galaxy that contains our Solar System. The descriptive “milky” is derived from the appearance from Earth of the galaxy – a band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
What is the Milky Way?
From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. It is a barred spiral galaxy with a diameter between 100,000 light-years and 180,000 light-years. It is estimated to contain 100–400 billion stars. There are likely at least 100 billion planets in it.
The Solar System is located within the disk, about 27,000 light-years from the Galactic Center, on the inner edge of one of the spiral-shaped concentrations of gas and dust called the Orion Arm.The very center is marked by an intense radio source, named Sagittarius A*, which is likely to be a supermassive black hole.
It consists of a bar-shaped core region surrounded by a disk of gas, dust and stars. The mass distribution within the Milky Way closely resembles the type Sbc in the Hubble classification, which represents spiral galaxies with relatively loosely wound arms.
Astronomers began to suspect that it is a barred spiral galaxy, rather than an ordinary spiral galaxy, in the 1990s. Their suspicions were confirmed by the Spitzer Space Telescope observations in 2005 that showed the Milky Way’s central bar to be larger than previously thought.
Text: Wikipedia contributors. “Milky Way.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 20 Jul. 2016. Web. 1 Aug. 2016.