Nebula
Topic: Origin and Evolution of the Earth and the Solar System · NCERT: Class 11, Ch 2 "The Origin and Evolution of the Earth"
Meaning
A nebula is a very large cloud of gas, mainly hydrogen, and dust in space. In the early universe, gravity pulled hydrogen together into such clouds. Clumps inside a nebula then grew denser and collapsed to form stars. So a nebula is a birthplace of stars, and it is the first step in building a galaxy.
Example
The Orion Nebula is a nebula in the "sword" of the Orion constellation. It can be seen as a faint, fuzzy patch with binoculars, and new stars are forming inside it today.
Don't confuse with
- Galaxy: a galaxy is a huge system of stars, gas and dust, 80,000 to 150,000 light years across. A nebula is a single cloud inside a galaxy.
- Solar nebula: this was the particular cloud of gas and dust around the young Sun, from which our planets formed.