Astronomy & telescopes glossary - N

Astronomy & Telescopes Glossary - N

Nadir - The point directly below an observer.

NEA - Abbreviation for Near-Earth Asteroid. Asteroids whose orbits bring them within 1.3 AU of the Sun. Also called Earth-Approaching asteroids. NEAs probably came from the main asteroid belt.

Neap tides - Neap tides occur when the gravitational forces of the Moon and the Sun are perpendicular to one another and occur during quarter moons.

NEAT - Abbreviation for Near-Earth Asteroid Tracking, which is a joint NASAJPL program that tracks near-earth asteroids (NEAs).

Nebula - A large, deep-space object comprised of gas and dust. A nebula that glows with its own light is called an emission nebula while one lit from nearby stars is called a reflection nebula. A nebula that blocks light is called a dark nebula.

NEO - Abbreviation for Near-Earth Object, which is any comet or asteroid that is close to the Earth's orbit.

New General Catalog - A classification system that lists over 13,000 deep-sky celestial objects. Abbreviated as NGC.

Newtonian telescope - A reflector telescope that uses a a mirror set in the lower end of a tube. A small, secondary mirror near the upper end of the tube reflects the beam to the eyepiece.

Northern lights - Another name for auroras that appear in the Northern Hemisphere.

North Star - The star, also called the Pole star, located almost due north used for navigation and telescope alignment. Polaris is currently the pole star of the Northern Hemisphere.