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The Universe Vocabulary
Universe
All existing matter and space considered as a whole.
Star
A very large ball of burning gas in space that is usually seen from the earth as a point of light in the sky at night. Our sun is a star.
Galaxy
A huge collection of gas, dust, and billions of stars and their solar systems. It is held together by gravity and is classified by its shape.
Spiral Galaxy
In a spiral galaxy, the stars, gas and dust are gathered in spiral arms that spread outward from the galaxy's center (known as a bulge). They can look like a pin-wheel or like a hurricane symbol.
The Milky Way Galaxy is a spiral galaxy.
The Milky Way Galaxy is a spiral galaxy.
Elliptical galaxy
These galaxies are symmetrical and elliptical in shape (circles, ovals). There is little gas and dust which means there are no stars forming, they are the oldest types of galaxies.
Irregular Galaxy
A galaxy that does not have a distinct regular shape, usually looks chaotic. Thought to be the youngest galaxies.
Nebula
A cloud of gas and dust where stars are born and die. Considered a star nursery.
Hertzsprung-Russell diagram
A scatter plot of stars showing the relationship between the stars' absolute magnitudes (luminosity), temperature, color, and classification.
Luminosity
The condition of being bright or having light. A star's luminosity is mostly attributed to it's size.
main sequence star
Stars on the Hertzsprung-Russell diagram which trend from the upper left (hot, bright stars) to the lower right (cool, dim stars).
Our sun is a main sequence star.
Our sun is a main sequence star.