Month: July 2025

ELLIPSE – An elongated circle that defines the shape of planetary orbits.

KEPLER’S THIRD LAW (HARMONIC LAW) – The square of a planet’s orbital period is proportional to the cube of its average distance from the Sun.

KEPLER’S SECOND LAW (LAW OF EQUAL AREAS) – A line connecting a planet to the Sun sweeps out equal areas in equal time intervals.

KEPLER’S FIRST LAW (LAW OF ELLIPSES) – Planets orbit the Sun in elliptical paths with the Sun at one focus.

ANGULAR DIAMETER DISTANCE
A method using an object’s apparent size to estimate distance.

GAIA SPACE OBSERVATORY
A European satellite measuring precise stellar parallaxes.

SPECTROSCOPIC PARALLAX
Estimating a star’s distance based on its spectral classification.

COSMIC DISTANCE LADDER
A series of techniques used to measure increasing cosmic distances.

TELESCOPE RESOLUTION
The ability of a telescope to detect small parallax shifts.