Lecture Notes: Solar System Formation, Orbits, and Kepler's Laws (Vocabulary)

Vocabulary flashcards covering barycenter, universe age, solar system formation, inner/outer planets, orbital elements, and Kepler's laws.

Barycenter

Center of mass around which two or more bodies orbit; may lie outside the larger body (e.g., Sun–Jupiter).

Age of the Universe

Approximately 13.8 billion years old; inferred from cosmic background radiation and expansion measurements (Hubble's Law).

Nebula

Giant cloud of gas and dust that collapses to form a solar system.

Proto-Sun

Early Sun formed at the center of the collapsing nebula.

Protoplanetary Disk

Disk of gas and dust surrounding the proto-Sun from which planets form.

Protoplanets

Larger bodies formed from planetesimals that grow into planets.

Terrestrial Planets

Inner planets (Mercury, Venus, Earth, Mars); small, rocky worlds with thin atmospheres.

Jovian Planets

Outer planets (Jupiter, Saturn, Uranus, Neptune); large gas/ice giants with many moons and rings.

Elliptical Orbit

An oval-shaped orbit; common for planets, with the Sun at one focus.

Eccentricity

Measure of how stretched an orbit is; e=0 is a circle; higher e means a more elongated orbit (Earth ≈ 0.0167).

Semi-major Axis

Half the longest diameter of an ellipse; a measure of orbit size; used in Kepler's laws (units often in AU).

Orbital Period

Time required to complete one full orbit around the Sun.

Kepler's Law of Ellipses

Planets move in elliptical orbits with the Sun at one focus.

Kepler's Law of Equal Areas

A line from a planet to the Sun sweeps out equal areas in equal times; planets move faster near the Sun.

Kepler's Law of Harmonies

P^2 = a^3, where P is the orbital period in years and a is the semi-major axis in AU.

Astronomical Unit (AU)

Average Earth–Sun distance; a standard unit for measuring planetary distances (1 AU ≈ 149.6 million km).