Vocabulary Flashcards for ASTR 104: Elementary Astronomy

This set of flashcards covers key terms and concepts from the ASTR 104 Elementary Astronomy course to aid in exam preparation.

Elliptical Orbit

The path that one body in space takes around another body, shaped like an ellipse.

Saturn

A planet in the solar system known for having the most moons, with 146 confirmed moons as of 2025.

Black Hole

A region in space where gravity is so strong that nothing, even light, can escape from it.

Meteor

A small body of matter from outer space that enters the Earth's atmosphere, appearing as a streak of light.

Scientific Method

A systematic method involving observation, hypothesis formulation, testing, and modification.

Scientific Law

Rules that govern how natural systems behave, believed to hold true universally.

Light-Year

The distance that light travels in one year.

Speed of Light

The speed at which light travels in a vacuum, approximately 300,000 kilometers per second.

Time Delay

The phenomenon that observing distant objects means seeing them as they were when the light left.

Astronomical Unit (AU)

A standard unit of measurement equal to approximately 150 million kilometers, or the average distance from the Earth to the Sun.

Cosmic Time Capsule

How light travel time allows astronomers to study the universe's past.

Planetary Nebula

A type of astronomical object that consists of an expanding shell of gas ejected from red giant stars.

Supernova

A powerful and luminous explosion of a star marking the death of a large star.

Exoplanets

Planets that exist outside of our solar system.

Galaxy

A system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity.

Gravitational Lensing

The bending of light from a distant object around a massive object, allowing the distant object to be seen.

Cosmic Background Radiation

The afterglow radiation from the Big Bang, filling the universe.

Nebula

A giant cloud of dust and gas in space, often the birthplace of stars.

Zodiac Light

A faint glow in the night sky caused by sunlight scattered by interplanetary dust.

Auroras

Natural light displays in the Earth's sky, predominantly seen in high-latitude regions.

Dwarf Planet

A celestial body that orbits the Sun and is massive enough for its gravity to make it round, but has not cleared its orbital path.

Star Clusters

Groups of stars that are physically associated with one another in space.

Globular Cluster

A spherical collection of stars orbiting a galactic core.

Terrestrial Planets

Earth-like planets that are rocky rather than gaseous; includes Mercury, Venus, Earth, and Mars.

Gas Giants

Large planets primarily composed of hydrogen and helium; includes Jupiter and Saturn.

Meteor Showers

Events where numerous meteors are observed to radiate from one point in the night sky.

Comets

Small celestial bodies made of ice, dust, and rocky material that, when close to the Sun, display a visible coma and tail.

Milky Way

The galaxy that contains our solar system.

Magellanic Clouds

Two irregular dwarf galaxies that orbit the Milky Way.

Space Observation

The practice of observing astronomical objects and phenomena using telescopes and other instruments.

Observational Science

A scientific discipline that involves observation as the primary method of data collection.

Historical Science

A science that investigates the past using scientific methods, often dealing with historical phenomena.

Celestial Object

Any natural object outside of the Earth's atmosphere.

Astronomical Observations

The act of observing celestial objects to gather data using telescopes and other instruments.

Cosmic Evolution

The study of the development of the universe from the Big Bang to its current state.

Nature of Science

The understanding of how scientific knowledge is gathered, tested, and revised.

Astrophysics

The branch of astronomy that deals with the physics of celestial objects and phenomena.

Astrobiology

The study of the origin, evolution, distribution, and future of life in the universe.

Planetary Science

The study of planets, moons, and planetary systems, especially those within our solar system.

Lunar Eclipse

An event that occurs when the Earth passes between the Sun and the Moon, causing the Earth's shadow to cover the Moon.

Solar Eclipse

An event that occurs when the Moon passes between the Earth and the Sun, obscuring the Sun’s light.

Total Solar Eclipse

A type of solar eclipse that completely covers the Sun, resulting in a darkening of the sky.

Partial Solar Eclipse

A type of solar eclipse where only part of the Sun is obscured by the Moon.

Annular Solar Eclipse

A type of solar eclipse where the Moon covers the Sun's center, leaving a ring-like appearance.

Galaxies

Large systems of stars and other celestial bodies bound together by gravity.

Supermassive Black Hole

A type of black hole with a mass that is millions to billions of times greater than the Sun's.