ASTRONOMY 104 Study Guide Key Concepts and Equations

A comprehensive set of flashcards covering key concepts and definitions in astronomy, suitable for exam preparation.

Astronomy

The science that studies celestial objects (stars, planets, galaxies) using physics and observations.

Astrology

The non-science belief that celestial positions influence human behavior, using horoscopes without empirical evidence.

Celestial Sphere

An imaginary sphere surrounding Earth, used to map the positions of stars and celestial objects as if they were fixed on its surface.

Geocentrism

The model where Earth is the center of the universe, with all celestial bodies orbiting it.

Heliocentrism

The model where the Sun is the center of the universe, with Earth and planets orbiting it.

Nicolaus Copernicus

Proposed the heliocentric model in 1543, shifting the understanding from Earth-centered to Sun-centered orbits.

Tycho Brahe

Made precise naked-eye observations of planetary positions, providing accurate data for Kepler.

Johannes Kepler

Formulated the three laws of planetary motion using Brahe’s data.

Galileo Galilei

Used telescopes to observe celestial bodies, providing evidence for heliocentrism.

Isaac Newton

Developed the laws of motion and universal gravitation, explaining planetary orbits.

Earth's Tilt

Earth's axis is tilted approximately 23.5 degrees, causing seasons.

Ecliptic

The apparent path of the Sun across the celestial sphere as seen from Earth.

Circumpolar Stars

Stars near the celestial poles that never set below the horizon.

Kepler's Three Laws of Planetary Motion

(1) Planets orbit in elliptical paths, (2) A line from a planet to the Sun sweeps out equal areas in equal times, (3) The square of a planet's orbital period is proportional to the cube of its semi-major axis.

Newton's Three Laws of Motion

(1) An object remains at rest or in uniform motion unless acted upon, (2) F=ma, (3) For every action, there is an equal and opposite reaction.

Universal Law of Gravitation

Every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.

Centripetal Force

The force that keeps an object moving in a circular path, directed toward the center of the orbit.

Escape Velocity

The minimum speed an object needs to escape a celestial body's gravitational pull without further propulsion.

Orbital Velocity

The speed an object must maintain to stay in a stable orbit around a celestial body.

Properties of an Ellipse

Includes shape, foci, semi-major axis, semi-minor axis, and eccentricity.

Wave–Particle Duality of Light

Light behaves both as a wave and as a particle, depending on how it’s observed or measured.

Electromagnetic Spectrum

The range of all possible wavelengths of electromagnetic radiation.

Resolution of Telescopes

The ability to distinguish fine details, determined by aperture size, wavelength of light, and atmospheric conditions.

Spectra

The distribution of light from a celestial object across different wavelengths, revealing its composition.

Energy of a Photon

Determined by E = h * f, inversely proportional to wavelength and directly proportional to frequency.

Luminosity

The total energy output of a star per unit time, measured in watts.

Stefan–Boltzmann Law

The total energy radiated per unit surface area of a blackbody is proportional to the fourth power of its temperature.

Wien’s Law

The wavelength at which a blackbody emits maximum radiation is inversely proportional to its temperature.

Nebular Hypothesis

A model explaining solar system formation from a rotating cloud of gas and dust.

Habitable Zone

The region around a star where conditions allow liquid water to exist on a planet's surface.

Goldilocks Zone

Another term for the habitable zone.

Radioactive Decay

The process contributing to heating Earth's core.

Constants

Fundamental values such as G, h, and c necessary for astronomical calculations.

Kepler's Third Law

P^2 = A^3, relating a planet's orbital period to its distance from the Sun.