Comets

nucleus

A block of ice and gasses or a "dirty snowball" roughly 10 km across and containing most of the comet's mass. Nucleus is odd shaped, extremely dark (dust and carbon-rich material coating the surface), and emits gas in jets

fluorescence

A process that makes light directly from electricity. (when one wavelength is converted to light at another wavelength)

kuiper belt

A region of the solar system that is just beyond the orbit of Neptune and that contains small bodies made mostly of ice

solar wind

A stream of electrically charged particles that emanate from the sun's corona.

temperature of comets

Comets in the Oort cloud are a frigid 3 K and only warm up enough to emit gas when they enter Solar System, especially as they pass Jupiter

giant meteor impacts

Every few thousand years, Earth is hit by a huge meteoroid, a body tens of meters or more in size. 65 mil. years ago, an asteroid or comet hit earth and caused mass extinction. Evidence for an extraterrestrial cause of the extinction is the high abundance of the otherwise rare element iridium in the sediments of the time

short period comets

Most comets seen on Earth are "one-time" visitors, having periods of thousands and millions of years. but a small number of comets have periods of less than 200 years. Repeated passages around the Sun eventually deplete the comet of its icy material and only a small amount of dust remains

origin of short period comets

Short-period comets are now believed to be icy nuclei from the Kuiper belt

composition of comets

Spectra of coma and tail shows comets are rich in water, carbon dioxide, carbon monoxide, and small amounts of other gases. Evaporating water is broken up by solar UV radiation creating a large hydrogen cloud around the comet.

radiant

The point in the sky from which the meteors seem to emerge

coma

a gaseous atmosphere that may reach a diameter of 100,000 km. the gas is matter that the suns heat has boiled off of the nucleus

comets and meteor showers

as a comet orbits the sun it leaves behind dust and grit. when we cross through or approach the dust, it rains into our atmosphere and burns up. A meteor shower is the result of a comet filling its orbit with emitted dust and the Earth passing through the dust-filled orbit

what is a comet

comets are made of icy dust particles and frozen gases orbiting the sun

dust tail

dust grains in the coma respond to radiation pressure and are pushed away from the sun

tail

longest part of comet, a narrow column of gas and dust, it may stretch over 100 million kilometers. the tails always point away from the sun no matter what direction the comet moves

origin of comets

most comets come from the oort cloud, a spherical shell of icy bodies believed to lie far beyond Pluto's orbit to a distance of about 150,000 AU. Originally orbiting among the giant planets as planetesimals, comets were tossed into the Oort cloud by those planets

comet density

nucleus has a low density so it is probably more like a snowball than a block of ice

radiation pressure

photons in sunlight exert a pressure on matter

structure of comets

tail, coma, nucleus

ion tail

the gas evaporating off the nucleus is ionized by UV light from sun. it is then caught in the solar wind and it blows in a trail. blows directly away from the sun. has bluish color