Structure of the Universe Flashcards

Flashcards reviewing the structure and composition of the universe based on lecture notes.

What is a light-year?

An astronomical distance unit; the distance light travels in one year

What are galaxies?

Organized structures containing celestial bodies; clusters of stars, dust, gas, and matter.

What is a planetary system?

Planets that are gravitationally bound in orbit around a star or stars.

What is ordinary matter composed of?

Protons, neutrons, and electrons that combine to form atoms.

What is dark matter?

A hypothetical substance that exerts gravity, affecting the path of starlight and the size/shape of galaxies. It does not reflect, emit, or obstruct light.

What is dark energy?

A hypothetical substance that fills the spaces in the universe

What is a celestial object?

Any natural object found in space.

How do most celestial objects form?

When gravity causes gas and/or dust to clump together.

What are the three major types of celestial bodies?

Stars, planets, and moons.

Describe a planet

A round and massive object that orbits or revolves around a star.

What is a moon?

An object that orbits a planet; a natural satellite.

What is the solar system?

A planetary system that includes the Sun, eight planets, and many moons.

How did the solar system form?

From a molecular cloud of gas and dust approximately 4.6 billion years ago, through gravitational collapse and the formation of a protoplanetary disk.

What separates the inner and outer planets?

The Asteroid belt.

What is the Kuiper belt?

A region of asteroids located beyond the last planet.

What are the terrestrial planets?

rocky planets closest to the sun.

What are the Jovian planets?

gas planets furthest from the sun.

List some trends of planets within our solar system.

Why is Earth unique?

Earth is at the perfect distance from the sun for liquid water to exist, because the position is within the Goldilocks zone.

How is color used to categorize stars?

Color indicates the surface temperature of a star.

Which color are cooler stars?

Red

Which color are hotter stars?

Blue

What is a main sequence star?

A normal star that has an average brightness and size.

What is a red giant?

A large, bright, red star that is relatively old.

What is a supergiant?

The largest known type of star that is massive, warm and very bright.

What is a white dwarf?

A very small, dense and hot star that is white to blue and nearly dead.

What is a neutron star?

A very hot, small and super dense star that is mostly made of neutrons.

What is a pulsar?

A spinning neutron star.

How are stars born?

From a dense cloud of gas known as a stellar nebula.

What is the fuel for a star?

Hydrogen

What happens when an average-sized star runs out of helium?

The outer layers of the star drift away from the core, forming a planetary nebula, and the remaining core becomes a white dwarf.

What are extraterrestrial objects?

Objects in space much smaller than stars and planets, including asteroids, comets, and meteoroids.

What is an asteroid?

A small, rocky object that orbits the Sun.

What is a comet?

An icy object made of frozen gases, rock, and dust that heats up and spews off gas and dust when passing close to the Sun.

What is a meteoroid?

A very small, rocky object that travels in space.

What is a meteor?

A meteoroid that penetrates the Earth's atmosphere and is also called a shooting star.

What is a meteorite?

A meteoroid that reaches and impacts Earth's surface.

How long ago did the universe form?

14 billion years ago.

What is cosmic background radiation?

Low-energy radiation in every direction throughout the universe; the afterglow of the Big Bang.

What is spectroscopy?

A technique that helps determine the chemical makeup of a substance by studying the light it emits when it burns.