Special Sub-Topic: Twenty Questions About Comets
|What are comets believed to be made of?|
Mixture of ice, rock and dust. Comets are sometimes referred to as dirty snowballs.
|Who was the first person to predict the return of a comet?|
Edmund Halley. In 1705 Edmund Halley predicted that the comets of 1531, 1607 and 1682 were the same comet and that it would return in 1758. The comet returned as predicted and was named after Halley. Charles Messier discovered 19 comets, Catherine Herschel found 8. SOHO is a satellite that has discovered more comets than any person (over 500 to date).
|A long period comet is a comet with a period of 200 years or more.|
t. Long period comets are believed to originate from the theoritical Oort Cloud and short period comets are believed to come from the Kuiper belt. Further spacecraft missions could change this.
|What is the most prominent part of a naked eye comet to the unaided eye?|
Dust Tail. The dust tail of a comet can be up to 10 million kilometers or longer.
|What did the ancient Greeks call comets?|
hairy stars. Aster kometes meaning hairy stars.
|How are most comets named?|
After their discoverer. The only exception was Comet Halley, which was predicted to return by Edmund Halley. See the interesting information after question 2.
|What was the name of the ESA mission that went to Halley's Comet?|
Giotto. The mission was named after Giotto di Bondone (1266-1337). He was impressed by the reappearance of Comet Halley in 1301. In his 1304 fresco painting of the Adoration of the Maji he transformed the Star of Bethlehem into a golden comet. The Rosetta mission is an ESA mission to Comet Wirtanen. Sakigake was the Japanese mission to Comet Halley.
|What country backed out of the mission to Halley's comet, which was originally a joint mission with ESA?|
United States. The United States backed out due to financial concerns.
|The Giotto mission to Comet Halley was not ESA's first space mission.|
f. Yes it was. It was also the first spacecraft to take close-up images of a comet nucleus, and the first to encounter two comets. The other comet was Comet Grigg-Skjellerup.
|The Perseid meteor shower is associated with what comet?|
Swift-Tuttle. The peak date is August 12 of each year. A new Moon can make for an impressive display of these meteors.
|What comet was visible to the unaided eye from Earth in 1996-7?|
Comet Hale-Bopp. Comet Hale-Bopp got as bright as -0.8 magnitude. Magnitude is a logarithmic scale used by astronomers. Most people can see down to 6th magnitude in a very dark sky site. Magnitude 1 is 2.512 times brighter than magnitude 2. Magnitude 2 is 2.512 times brighter than magnitude 3, etc. Comet Shoemaker-Levy 9 crashed into Jupiter in July of 1994. Comet West graced our skies in 1976, and Giacobini-Zinner is a short period comet of six and a half years.
|In what year were comets correctly recognized as members of the Solar System?|
1577. Tycho Brahe observations of the comet of 1577 helped to establish that comets were beyond the orbit of the Moon.
|Which comet has the shortest known orbital period?|
Comet Encke. Comet Encke orbits the Sun in about 3.5 years, Comet Halley in 76 years, Comet Schwassmann-Wachmann 1 in about 6.4 years and Comet Borrelly in just under 7 years.
|Who gave Charles Messier his nickname of the Comet Ferret?|
King Louis XV of France. Although Charles Messier discovered 13 comets independently and 6 other comets with co-discoverers, he is more famous for the catalog of objects he made. This catalog contains objects that resembled comets but did not move against the night sky. Amateur astronomers search out these objects and even do what is called a Messier marathon in March. This is when all 110 objects are possible to see in one night. This list of objects include galaxies, clusters, nebulae and even a supernova remnant.
|Who proposed the "dirty snowball" theory about comets?|
Fred Whipple. Fred Whipple proposed this theory in 1950, it was confirmed by the Giotto mission to Comet Halley in 1986. He was the director of the Smithsonian Astrophysical Observatory from 1955 to 1973.
|What comet graced Earth's skies in 1965?|
Comet Ikeya-Seki. Comet Ikeya-Seki was classified as a sun grazing comet since it approached the Sun so closely. Comet Mrkos visited in 1957 as did Comet Arend-Roland, Comet Kohoutek visited in 1974.
|What was the brightest comet in the 20th Century?|
Comet Ikeya-Seki. Comet Ikeya-Seki was visible in the daytime, being brighter than Venus. According to some Japanese observers they estimated the magnitude at -15, which is brighter than the Moon.
|In what year is Halley's comet scheduled to return?|
2061. Halley's nucleus was found to be very dark, it is darker than coal and one of the darkest objects in the solar system.
|Is Comet Halley's orbit retrograde around the Sun?|
y. The Comet is also inclined 18 degrees to the ecliptic.
|Has Comet Halley always appeared every 76 years since it was first seen?|
n. The average is 76 years but there are variances due to the gravitional pull of the planets as the Comet passes by them. It has varied up to about 79 years.
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