Lecture 5 - Comets and asteroids

what is a comet

object composed mostly of ice and dust that
comes from the outer Solar system towards the Sun,
creating a tailcreating a tail

what is an asteroid

small rocky body in solar system

what is a metworid

small particle from an asteroid or comet orbiting the sun

what is a meteor

a meteorid that is observed as it burns up in earth’s atmosphere

what is a meteroite

a meteroid that survives its passage through earth’s atmosphere and impacts the surface

what is the oort cloud

a spherical shell around the sun at a distance of 50000 AU extending to 1 light year

what is the kuiper belt

a ring of icy objects beyond the orbit of neptune

what is the typical sise of comts

they are small ranging from a few miles to tens of miles wide in their frozen states

how to comets travel through space

they remain in the oort cloud/kuiper belt until a gravitational pertubation by a nearby star causes some of them to change their orbits suffieciently that they pass through the solar system

what happens once a comet breaks free from the orrt cloud

they either have an eliptical orbit or a hyperbolic orbit

what is an elliptical comet orbit around the sun

• the tail increases with dereasing distance to the sun

• points away from the sun

• two tails: ion tail (blue) and dust tail (curved)

what is a hyperbolic orbit of a comet

it takes the comet flying though the solar system just once and then flings them back out

why are comets frequently referred to as dirty snowballs

• a rocky core surrounded by water ice

• with an added blend of other frozen gases and complex compounds

why are comets important to life on earth

• they are very dangereous to life (damage it)

• they could have brought life to earth

what is comet shoemaker-levy 9

• the greatest collision ever seen in the solar system occuring in july 1994 when it impacted Jupiter

why was SL9 more dramatic

because of the prior fragmentation of the comet into a dozen pieces by a previous encounter to Jupiter two years earlier

how long is a day on Jupiter

9 hours 55 min

what was the impacts of Jupiter of the SL9

• the energy and destructive force was impressive

how did fragment G impact jupiter

• was a mile-wide object weighing a few tones

• the temperature of the fragment reached 20,000K before it disintergrated into a fireball of 10-100km in size

• It threw a plume of debris 3000 km up into the sky before raining molten debris down over a region around 20,000 km in sizehun

what is the range in size of asteroids

hundreds of km to millions smaller than 1 km across

what were asteroids though to represent

the remains of a would be planet that was prevented from forming by Jupiters gravitational force

what are the three main types of meteorites

• carbonaceous chondrite (c-type)

• silicaceous (s-type)

• metallic (m-type)

what twp metals do almost all meteroites containe

nickel and iron

what % of meteroites do c-type make up

75%

what % of meteroites do s-type make up

17%

what % of meteroites do m-type make up

8%

what is needed to observe c-type

need a small telescope to observe them

what is the colour of c-type

dark carbonaceous chondrites

what is needed to observe s-type

binoculars

what is the make up of s-type

bright metallic nickel-iron mixed with magnesium and iron silicates (stony composition)

what is the make up of m-type

Bright, pure (some, not all) nickBright, pure (some, not all) nickel-iron material.
Iron content of approx. 90-95%. Very heavy.

what is needed to observe m-type

only detected by telescopes as so far away

how have asteroides affected the moon

they have created massive craters

when were most of the creators produced on the moon

3.5 billion years ago

what is the Ceres asteroid and its diameter

discovered in 1801, 975 km in diameter

what is EROS 433

an s-class asteroid discovered in 1898. it is the second largest near earth asteroid

what is the dinasaur killer

cicxulub crater around 180 km in diameter. occured 66 million years ago

what is chelyabinsk

a 17m meteor moving at 65,000 km/h exploted into our atmsphere in 2013