- The name comet comes from the Greek word meaning ‘hair of the head’, it came from the Greek philosopher Aristotle who observed comets as ‘stars with hair’.
- The nucleus of a comet is made of ice and can be as small as a few meters across to giant boulders a few kilometres across.
- The closest point in a comet’s orbit to the Sun is called “perihelion”. The most distant point is called “aphelion”.
- As a comet gets closer to the Sun, it begins to experience heat. That causes some of its ices to sublimate (similar to dry ice sizzling in sunlight). If the ice is close to the comet’s surface, it may form a small “jet” of material spewing out from the comet like a mini-geyser.
- Comets are usually made of frozen water and supercold methane, ammonia and carbon dioxide ices. Those are mixed with rock, dust, and other metallic bits of solar system debris.
- Comets have two tails: a dust tail (which you can see with the naked eye) and a plasma tail, which is easily photographed but difficult to see with your eyes.
- Comets are not spaceships or alien bases. They are fascinating bits of solar system material that date back to the formation of the Sun and planets.
- Comet orbits are elliptical. It brings them close to the sun and takes them far away.
- Halley’s Comet is the most well known comet. It is known as a periodic comet (or short term comet) because the time it takes to orbit the Sun is less than 200 years.
- The first comet shown to be periodic was Halley’s Comet, 1P/Halley, in 1705.
- Records of humans observing Halley’s Comet go back thousands of years, with appearances noted by Babylonian, Chinese and European star gazers.
- Comets are thought to originate in one of two theorized regions in the Solar System: the Oort Cloud
of the Kuiper Belt
- The lander, named Philae, has taken over ten years to reach comet known as 67P/Churyumov–Gerasimenko on the space probe Rosetta.
- The assassination of Julius Caesar, the Black Death and King Harold’s defeat at the Battle of Hastings were all blamed on comets.
- Edmond Halley suggested that Noah’s Flood was caused by a comet’s collision with earth