Hey Guys !Welcome to another blog , Today we gonna talk about some intresting facts on Black Hole .
What is a Galaxy?
A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems, all held together by gravity. The word galaxy is derived from the Greek “galaxias” literally “milky”.
The observable universe is estimated to contain 200 billion to 400 billion galaxies. Each light speck in the universe is a galaxy, some of which are as old as 13 billion years.
Etymology
The word galaxy was borrowed via French and Medieval Latin from the Greek term for the Milky Way, galaxias (kuklos), “milky (circle)”, named after its appearance as a milky band of light in the sky. In Greek mythology, Zeus places his son born by a mortal woman, the infant Heracles, on Hera’s breast while she is asleep so the baby will drink her divine milk and thus become immortal. Hera wakes up while breastfeeding and then realizes she is nursing an unknown baby: she pushes the baby away, some of her milk spills, and it produces the band of light known as the Milky Way.
Milky Way
The planet earth that we live on is a part of our solar system and our solar system is part of a galaxy which we known by the name of milky Way.
The Greek philosopher Democritus proposed that the bright band on the night sky known as the Milky Way might consist of distant stars. Aristotle however, believed the Milky Way to be caused by, ”the ignition if the fiery exhalation of some stars that were large, numerous and close together” and that the ignition takes place in the upper part of the atmosphere.
Types and Morphology
Galaxies come in three main types: ellipticals, spirals (our Milky Way is one of the spiral galaxy), and irregulars.
A slightly extensive description of galaxy types based on the appearance is given by the Hubble sequence. Since the Hubble sequence is entirely based upon visual morphological type(shape), it may miss certain important characteristics of galaxies such as star formation.
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