Hale–Bopp

Alan Hale and Thomas Bopp independently discovered Hale–Bopp in 1995.

Hale–Bopp's official designation is C/1995 O1.

Hale–Bopp passed perihelion in 1997, becoming a celebrated bright comet.

Hale–Bopp was already notably active while still far from the Sun.

Hale–Bopp is a long-period comet whose return takes thousands of years.

Hale–Bopp's nucleus is estimated to span tens of kilometers, much larger than many familiar comets.

Hale–Bopp displayed both a bright dust tail and a straighter ion tail.

Hale–Bopp's highly inclined orbit carries it far from the main planetary orbital plane.

Hale–Bopp's aphelion lies far beyond Neptune's orbit.

Adding a fixed period to 1997 is not enough to predict Hale–Bopp's next return precisely.

The nucleus is a comet's solid body, made mainly of ice, dust, and rock mixed together.

Near the Sun, cometary ice can sublimate directly to gas and carry dust with it.

The diffuse envelope of gas and dust around the nucleus is the coma.

The solar wind influences the ion tail, directing it roughly away from the Sun.

Dust-tail particles have their own orbits, often producing a curved tail.

A comet's tail can point ahead as it moves away from the Sun; it is not exhaust trailing its motion.

A coma can be many times larger than its nucleus; a photo's bright cloud is not the solid body's size.

Meteor showers can occur when Earth crosses debris left by a comet.

A meteor is light produced when a small particle enters the atmosphere, not a falling star.

Most returning comets still require a telescope to observe.

Comet brightness depends on activity, not just distance from Earth.

Short-period comets generally have orbital periods under 200 years.

Many long-period comet orbits suggest origins in the distant Oort Cloud.

Comets preserve early Solar System material and help us study planetary formation.

Comets generally move faster at perihelion and slower at aphelion.

Planetary gravity, especially Jupiter's, can change comet orbits and sometimes disrupt their nuclei.

Cometary gas jets exert small reaction forces that precise predictions must include.

Orbital elements refer to an epoch; neglected perturbations can accumulate over time.

P in a comet designation means periodic; C is commonly used for comets that are not short-period.

Dark dust often coats comet nuclei; containing ice does not make their surfaces snow-white.