Ch. 30 Galaxies and the Universe

Front

What does a redshift in the light of a star observed from Earth indicate?

Back

The star is moving away from the Earth.

Front

What is the study of the origin, structure, and future of the universe called?

Back

Cosmology.

Front

What is a spiral galaxy?

Back

A type of galaxy characterized by its spiral structure, often containing a central bulge and arms that spiral outward.

Front

What are the two most abundant elements in the universe?

Back

Hydrogen and helium.

Front

What is a galaxy?

Back

A large grouping of stars, dust, and gas bound together by gravity.

Front

What is the difference between a spiral galaxy and an elliptical galaxy?

Back

Spiral galaxies have a flat, rotating disk with stars, gas, and dust, while elliptical galaxies are more rounded and contain older stars with little gas and dust.

Front

What is dark matter?

Back

A form of matter that does not emit light or energy, making it invisible, but it exerts gravitational effects on visible matter.

Front

What is the Big Bang Theory?

Back

The leading explanation for the origin of the universe, proposing that it began as a singularity approximately 13.8 billion years ago and has been expanding ever since.

Front

What is a light-year?

Back

The distance that light travels in one year, approximately 5.88 trillion miles (9.46 trillion kilometers).

Front

What is the observable universe?

Back

The portion of the universe that can be seen from Earth, limited by the speed of light and the age of the universe.