Halley

Definition

Halley refers to Halley's Comet, a periodic comet visible from Earth approximately every 76 years. It is named after Edmond Halley, who used Newton's laws of motion to predict its return.

5 Must Know Facts For Your Next Test

1. Halley's Comet was the first comet whose return was predicted using Newtonian mechanics.
2. Edmond Halley applied Kepler's laws and Newton's theory of gravitation to determine the periodicity of the comet.
3. The comet's orbital period is approximately 76 years, classifying it as a short-period comet.
4. Halley's Comet has been observed and recorded by astronomers since at least 240 BC.
5. The last perihelion (closest approach to the Sun) of Halley's Comet occurred in 1986, and its next expected perihelion is in 2061.

Review Questions

• How did Edmond Halley use Kepler's laws to predict the return of Halley's Comet?
• What is the approximate orbital period of Halley's Comet?
• When is the next expected perihelion of Halley's Comet?

Related terms

Kepler's Laws:

Three scientific laws describing the motion of planets around the Sun.

Newtonian Mechanics: The branch of physics dealing with motion and forces acting on objects using Newton's laws.

Perihelion:

The point in an orbit where a celestial body is closest to the Sun.