- Slides: 25
What are Comets? • Made of ice, rock, and other organic materials. • Has Nucleus, coma, and two tails (dust and ion/plasma tail) • Nucleus is actual body of rock and ice; varies in size, and ranges from. 5 to 25 miles across • Coma is gas and dust that surrounds nucleus like an atmosphere • Ion tail is charged gasses, and dust tail is mixture of dust and gas from nucleus breaking down. Both tails can be many millions of miles long. Ion tail glows fluorescently, and dust tail reflects light from sun. • Usually easier to see dust tail. Both tails always point away from sun. This is due to solar wind.
What is solar wind? • A solar wind is a stream of charged particles (i. e. , a plasma which is an ionized gas) which are ejected from the upper atmosphere of a star. • It is not exactly a “wind” as we know it, but it describes similar actions.
Where do comets come from
Comets are thought to come from one of two places • Long-period comets (those which take more than 200 years to complete an orbit around the Sun) originate from the Oort Cloud. Short-period comets (those which take less than 200 years to complete an orbit around the Sun) originate from the Kuiper Belt.
Oort Cloud • Danish astronomer Jan Oort proposed that comets reside in a huge cloud at the outer reaches of the solar system, far beyond the orbit of Pluto. This has come to be known as the Oort Cloud. • Statistics imply that it may contain nearly a trillion comets and accounts for a significant fraction of the solar system’s mass. However, since individual comets are so small and far away, we lack direct evidence about the actual existence of the Oort Cloud.
Kuiper Belt • The Kuiper Belt is a disk-shaped region past the orbit of Neptune roughly 30 to 100 AU from the Sun. The Belt contains many icy bodies which can becomets. Occasionally the orbit of a Kuiper Belt object will be disturbed by gravitational interactions with the giant planets in such a way as to cause the object to take up an orbit that crosses into the inner solar system.
Halley’s comet nucleus 15 km = almost 10 mi
What are Asteroids? • Rocky or metallic (sometimes a combination) bodies that orbit the Sun. Metals are Iron and nickel. • Sometimes called minor planets or planetoids—doesn’t have an atmosphere • Size can range from a small pebble to hundreds of miles wide • Largest known has a diameter of more than 500 miles— named Ceres discovered by Piazzi in 1801 • Ceres is a dwarf planet • Most found in asteroid belt between Mars and Jupiter • Thought to be left over from formation of universe
What are Meteors? • Fragments of comets, asteroids, moons, or planets that have broken off • Sometimes called shooting stars • Meteor showers usually occur when Earth passes through a comets orbit • Most meteors are about the size of a match head, but they can be as big across as a mile • If a meteor is able to get past the Earth’s atmosphere and impact the Earth it is called a meteorite
LIVE INCOMING METEOR
So could a comet really hit the earth? One hit Jupiter in 1994! But don’t worry too much, we have technology that would give us enough warning to possibly destroy or divert a comet.
Jupiter • Jupiter through a 60 inch telescope
Artist Rendition of Deep Impact Mission 2005
Launch of Deep Impact Mission • Going after Temple 1 Comet • Probe hits comet
Actual Impact in 2005