Halley's Comet

Halley's Comet, named after Edmond Halley, can be seen

from Earth with the naked eye once every 75-76 years.

Fast Facts About Halley's Comet:

• A comet is a celestial body that's made up of gas, rock, ice, water, and dust.

• Comets are much, much smaller than planets or stars.

• Comets are cold and contain solid materials, like rock, dust, and ice, unlike stars which are made up of very hot, burning gasses.

• Comets have 3 parts: a coma, a nucleus, and a tail.

• Halley's Comet is a short-period or periodic comet, because its orbital period (how long it takes to make one whole orbit around the Sun) is less than 200 years.

• Halley's Comet is named after a famous scientist named Edmund Halley, who proved that the comet would reappear every 75-76 years, when it reached the point in its orbital path that passed by Earth.

• The last time Halley's Comet was visible from Earth was in 1986, the year Ms. Coburn was born.

• The next time Halley's Comet will be visible from Earth is expected to be in 2061, when you will be 55 or 56 years old.

All About Halley's Comet

Halley's Comet, officially named 1P/Halley, is the best-known of the short-period comets and is visible from Earth every 75–76 years. Halley's Comet is the only short-period comet that is clearly visible to the naked eye (you can see it without a telescope when you look up at the sky). It's also the only visible comet that can appear twice in a human's lifetime. Halley's Comet last appeared in the inner Solar System (near Earth) in 1986 and it won't appear again until 2061, when you're 55 or 56 years old.

Halley's Comet orbits the Sun, but it has a weird orbital path called a retrograde orbit, meaning that the comet travels around the Sun in the opposite direction of all the planets in our solar system. While Earth and the other seven planets travel counterclockwise around the Sun, Halley's Comet travels clockwise. The Comet's orbital path is gigantic. It takes 75-76 years for the Comet to complete one full orbit around the Sun. The Comet gets very close to the Sun, traveling between the orbital paths of Mercury and Venus, and then it travels all the way to the other end of our Solar System, nearly as far away as the dwarf planet Pluto.

Sightings of Halley's Comet have been recorded by astronomers since at least 240 BC, over 2,254 years ago. Chinese, Babylonian, and medieval Europeans described the comet in writings and illustrations that modern-day scientists found thousands of years later. However, these ancient civilizations didn't realize that all of these sightings were of the same comet. They thought they were seeing different comets, shooting stars, or flying objects. They thought comets traveled in a linear path (a one-way line).

Halley's Comet's periodicity (its reappearance every 75-76 years) wasn't discovered or proven until much more recently in history. A little over 300 years ago, in 1705 a British astronomer named Edmond Halley proved to the world that Halley's Comet traveled in an elliptical orbit (oval-shaped) around the Sun. Because Halley's Comet followed an eliptical orbit, Edmond Halley correctly predicted that the Comet had and would continue to reappear in the night sky every 75-76 years.

During its 1986 appearance, Halley's Comet became the first comet to be observed in detail by spacecraft. Seeing Halley's Comet from so close allowed scientists to learn more about the three parts of a comet: the nucleus, the coma, and the tail. These close-up observations of Halley's Comet proved that Astronomer Fred Whipple's "dirty snowball" comet theory was correct. Just as Whipple had thought, comets are composed (made) of a mixture of dust and ices – such as ice (frozen water), frozen Carbon Dioxide, and frozen Ammonia.

Parts of a Comet

The Nucleus of Halley's Comet

Links:

Learn More About Halley's Comet

Watch this Brainpop Video on Comets

(You will need to ask your teacher for the username and password)

Check Out What NASA Has To Say About Comets

NASA's Comet Photo Gallery

Films About Halley's Comet: