At this point of its orbit, any solar satellite such as a comet or a planet is farthest away from the sun.

What is the aphelion?

These small, rocky worlds orbit the sun generally between the orbits of Mars and Jupiter.

What is an asteroid?

This collection of small, rocky bodies are found orbiting the sun, mostly between the orbits of Mars and Jupiter.

What is the asteroid belt?

This type of scientist studies things outside the Earth's atmosphere. she or he  may use telescopes to study the Moon, Sun, planets, stars, or galaxies.

What is an astronomer?

This unit of length is equal to the average distance from the Earth to the Sun; about 150 million kilometers, or 93 million miles.

What is an astronomical unit  
(AU) ?

This organic molecule is found in solid form in the nucleus of comets. On Earth, it is also present as a gas exhaled by humans and most animals.

What is carbon dioxide?

The cloud of hot gas formed when a comet passes close to the sun, causing its ices to sublimate,

What is the coma?

These small bodies are composed of ices and dust and orbit around the sun. They appear as bright, tailed stars when near the Sun.

What is a comet?

This complex organic molecule contains the "pattern" for a living being to reproduce.
*expand the acronym for extra points

What is DNA?

*deoxyribonucleic acid

This type of comet tail is visible because it reflects sunlight, and usually appears curved.

What is the dust tail?


Sometimes called a regular oval, this geometric shape, has two focus points, or foci.

What is an ellipse?

This group of planets contain most of the non-solar mass of the solar system.

*Name them for extra points

What are the giant planets?
*Jupiter, Saturn, Uranus, and Neptune

This spacecraft was launched on July 2, 1985 to study Comet Halley.

What is the Giotto satellite?

This neutral form of carbon is found in interstellar space as well as in pencils.

What is graphite?

This matter fills the spaces between stars, and is composed of gas and interstellar dust.

What is the interstellar medium?


This Dutch astronomer was the first to suggest that many comets come from a large cloud of debris ejected from the early solar system.

Who is Jan Van Oort?

This band of small objects revolves around the sun outside the orbit of Neptune and is believed to be the source of short period comets.

What is the Kuiper Belt?

This unit of length is equal to the distance that light travels in one year, or about nine and a half trillion (9,500,000,000) kilometers.

What is a light year?

These comets come from the Oort Cloud and may take as long as tens of thousands of years to orbit once around the sun. 

What is a long period comet?

Bright streaks in the evening sky, sometimes called shooting stars, and caused by space debris that burns as it falls through Earth's atmosphere.

What is a meteor?


Most of these fragments of debris left behind in the orbits of comets are very tiny.

What is a meteoroid?

This beautiful event occurs when the Earth passes through a trail of debris along a comet's orbit, and the many bits of material burn up in the atmosphere.

What is a meteor shower?

Extraterrestrial debris that reaches the ground before it is completely burned up in the earth's atmosphere.

What is a meteorite?

This relatively small, solid core of a comet is made of ice, dust and rock and is usually hidden from view.

What is the nucleus?

This cloud of early planetesimals forms a comet reservoir around the solar system, and is about 100,000 AU across.

What is the Oort Cloud?


The path that a body in space follows as it revolves around another (for example, the earth around the sun).

What is an orbit?

Compounds made up of the most common substances, or elements in living systems: carbon, oxygen, nitrogen, and hydrogen.

What is organic matter?

At this point of its orbit, any solar satellite such as a comet or a planet is closest to the sun.

What is perihelion?

The time required for a body like a comet or planet to go once around its orbit and return to the same spot.

What is a period?

The planets were formed from these small chunks of dust, rocks and frozen gasses as they collided and stuck together.

What are planetesimals?


A hot gas of charged particles.

What is plasma?

This comet tail glows with its own light and always points straight away from the sun.

What is the plasma tail?

To move around continuously on a closed path, like an orbit.

What does it mean to revolve?

These comets are believed to come from the Kuiper Belt and usually take less than 200 years to revolve once around the sun.

What is a short period comet?

The cloud of gas and interstellar dust from which the sun and eventually the whole solar system were formed.

What is the solar nebula?


The sun and everything that revolves around it, including the planets and their moons, asteroids, comets, and all the objects in the Kuiper Belt and the Oort Cloud. 

What is the solar system?

Hot gases and magnetic fields that stream rapidly out of the sun in all directions at all times.

What is solar wind?

When a solid, such as ice, changes directly into a gas or vapor without becoming a liquid first, it is said to go through this process.

What does it mean to sublimate?

This American astronomer was the first to propose the "dirty snowball" model of comet structure.

Who is Fred Whipple?