Chapter 12.3 Comets

Stardust

2004, NASA spacecraft used a material called aerogel to capture dust particles from Comet Wild 2 aerogel was sealed in a re-entry capsule and provided our first direct sample of comet dust

Deep Impact

2005 NASA's spacecraft released a 370-kilogram impactor that slammed into Comet Tempel 1 blast created a plume of hot gas composed of material vaporized from deep within the comet this material contained many complex organic molecules also includes huge amount of dust, telling us that the comet's surface must be covered by dust to a depth of tens of meters

Giotto

European Space Agency first clear view of a comet nucleus came from this spacecraft flew past halley's comet during its 1986 visit to the inner solar system showed the nucleus to be surprisingly dark halley's nucleus is considerably less than water, suggesting that the nucleus is part ice and part empty space release of gas can be quite violent

oort cloud

a collection of many individual comets that don't orbit the sun in the same direction as the planets comets come from far beyond the orbits of planets and orbits seem random must contain about a trillion comets consists of leftover planetesimals that were flung outward after forming between the jovian planets

coma

as the comet accelerates toward the Sun, its surface temperature increases, and ices begin to vaporize into gas that easily escapes the comet's weak gravity some of the escaping gas drags away dust particles from the nucleus, and the gas and dust create a huge, dusty atmosphere called...

comets

basically chunks of ice mixed with rocky dust and some more complex chemicals

third tails

comets eject sand-to-pebble size particles ejected particles are concentrated along the orbits of comets

dust tail

consists of dust-size particles that are unaffected by the solar wind and instead are pushed outward by the much weaker pressure of sunlight itself (radiation pressure) tail points generally away from the sun, but has a slight curve back in the direction the comet came from

plasma tail

consists of gas that is ionized by ultraviolet light from the Sun and pushed outward by the solar wind extends almost directly away from the sun at all times

Rosetta

european space agency mission entered orbit of comet 67p/comet c-g when it was still almost fully frozen in 2014 and stuck with it as it approached and passed perihelion (closest point to the sun) observed the changes that occured also sent a lander to philae--provided key data water ice that drives cometary activity near the Sun is hidden under a substantial crust of dust material that is composed of rock and carbon-bearing molecules other comets also have high proportions of deuterium, suggesting that comets were not the primary source of water delivered to the early earth through comets

nucleus

for a comet plunging inward, this is the frozen center of the comet

comet tails

generally point away from the Sun

particles

responsible for most meteors and meteor shows enter the atmosphere at such high speeds that they make the surrounding air glow with heat its the glow we see as the brief flash of a meteor

kuiper belt

smaller number of comets that visit the inner solar system and have a pattern to their orbits travel around the sun in the same direction and in nearly the same plane as the planets lies beyond the orbit of neptune comets can be nudged by gravity of the jovian planets through their orbital resonances consists of leftover planetesimals that formed and still remain in the outskirts of the planetary realm beyond the orbit of neptune, icy planetesimals were much less likely to be cast off by gravitational encounters; instead they remained here

meteor showers

when our planet is crossing a comet's orbit