Introduction to Astronomy

A comprehensive set of flashcards covering key concepts from the Introduction to Astronomy lecture.

What is the definition of the Universe?

Everything that exists, including all matter and energy everywhere.

What is Astronomy?

The study of what is beyond Earth (including planets, stars, galaxies, black holes, etc.).

What are constellations?

Groups of stars that appear to form shapes or patterns.

What is the solar system?

The Sun and all the planets (and their moons) that revolve around it.

What is gravitational pull?

A force of attraction between two large moving objects.

How does the gravitational pull of the Sun affect the planets?

It keeps the planets orbiting around the Sun.

What is a star?

A ball-shaped mass of superheated gases that emits huge amounts of light.

What distinguishes a planet from a star?

Planets are generally smaller than stars, do not emit their own light, and revolve around a star.

What is a galaxy?

A collection of billions of stars held together by gravity.

What is the difference between non-luminous and luminous objects?

Non-luminous objects do not emit light, while luminous objects, such as stars, give off light.

What is the definition of an astronomical unit (AU)?

The average distance between the Earth and the Sun, approximately 150 million kilometers.

How long does it take for the Earth to complete one rotation?

24 hours (one day).

What is Earth's revolution around the Sun?

It takes approximately 365.25 days to complete a single orbit around the Sun.

What is a solstice?

An event that happens twice a year when the Sun reaches its highest or lowest point in the sky at noon.

What is an equinox?

An event occurring twice a year when day and night are of equal length.

What is the Big Bang Theory?

A theory stating that the universe formed in a single moment from a dense point that rapidly expanded, creating all matter and energy.

What is cosmic microwave background radiation?

Energy left over from the Big Bang that is detectable today.

What is red shift?

A phenomenon where light from galaxies appears red, indicating they are moving away from us.

What are the two possible futures for the Universe, according to astronomers?

Open Universe and Closed Universe.

What characterizes an Open Universe?

Galaxies will continue to expand outward, and all stars will eventually die off.

What characterizes a Closed Universe?

Galaxies will slow down and eventually stop moving away, leading to a gravitational pull back to the center.