solar system
: 1 star 8 planets 5 known dwarf
planets, 160+ moons
small solar system objects.
Sun
: 99.85% mass of solar system, 330,000*mass
Earth, 109*diameter Earth.
98%
hydrogen&helium.
Terrestrial planet
: rocky
surface, small, close together, mostly rock&metal.
Mercury: smallest, covered in craters. Venus:
closest planet in size&mass to Earth, thick&toxic
atmos produces greenhouse effect->surface hot.
Mars: frozen desert planet, has seasons, weather,
polar ice caps, volcanoes, canyons.
A planet: 1)in an orbit around a star 2)massive
enough->spherical 3)have cleared its orbit (largest
gravitational pull in the area). Terrestrial planets:
closer together, smaller mass&size, higher density,
solid surface (rock&metal), fewer/no moon, no
ring
.
Jovian planets: bigger, space farther, lower
density, colder temp, made of hydrogen, helium,
ices, no solid surface, rotate faster, have more
moons, all have ring.
Asteroids
: rocky, airless
worlds that orbit Sun. majority orbit within
Asteroid Belt, a ring between the orbits of Mars
and Jupiter. asteroid belt is sparsely populated.
largest asteroid, Ceres, is large enough for its
gravity to make it spheroidal shape, and the only
asteroid classified as dwarf.
The Kuiper Belt and
Oort Cloud:
beyond the orbit of Neptune, icy
bodies, debris left over from the formation of the
solar system. K-belt: disk-shaped region. Pluto
and Eris: largest, best known of these icy worlds.
O-cloud: spherical cloud of small icy bodies,
contain billions of large object.
dwarf planet
:
orbits the Sun, has enough mass to assume a
nearly round shape, not cleared the neighbor
around orbit, not a moon. planets sweep up or
scatter objects near their orbits while dwarf
planets tend to orbit in zones of similar objects.
Dwarf generally smaller than Mercury. five dwarf
planets: Ceres(Asteroid Belt), Pluto,
Haumea, Makemake, and Eris (K-Belt).
Solar
nebula hypothesis
: Sun&planets formed from a
cloud of gas and dust 4.5b years ago.1)
Motion of
Planets
: planets move around Sun in same
direction, counterclock. Sun and most planets
rotate in direction as orbit(venus rotates
backwards, uranus rotates on its side, all moon
orbit counterclock. suggest the planets all formed
from the same flattened disk-like structure,
condensing out of same
material.
3)Asteroids
: small rocky world
.
Comets
: made of “dirty ice”. mostly in orbit
beyond Neptune.
Nebula theory:
1)The solar
system began as a spinning cloud of gas and
dust(nebula). nebula began to contract under the
influence of its own gravity.2)As the spinning
cloud contracted under gravity, most material fell
into protosun at center, rotation rate increase as
physical size decreased, flattened into a spinning
disk(circumstellar disk), temp increased. 3)Within
solar nebula, dust and ice particles collided and
clumped together. Through accretion, these
particles grew into objects (planetesimals).
