Space Science Learning Experience 2

terrestrial planets

4 planets closest to the sun, rocky and solid (Mercury, Venus, Earth, Mars)

jovian/giant planets

much larger and made of lighter ices, liquids, and gases (Jupiter, Saturn, Uranus, Neptune)

asteroids

rocky bodies that orbit the sun like planets

comets 

composed of mainly ice 

meteor

cosmic dust burning up in the sky

Jupiter and Saturn’s chemical makeup

75% hydrogen, 25% helium (very similar to the Sun)

differentiation 

process where gravity helps separate a planet’s interior into layers of compositions and densities (denser materials sinks, lighter material rises to the top)

super earths

planets in size between terrestrial and giant planets

solar nebula 

spinning cloud of dust and gas (supposedly how the solar system formed)

circumstellar disks

flattered, spinning clouds of dust and gas surrounding young stars

planetesimals

smaller objects that are precursors to planets (baby planets)

mass of Earth’s atmosphere

5×10¹⁸ kilograms

troposphere

part of the atmosphere closest to the surface. warm air, heated by the surface (temperature decreases as elevation rises)

stratosphere

about 50 km above the surface, cold and cloud free (temperature increases with altitude). near the top is the layer of ozone 

ozone

protects earth from the sun’s radiation (near the top of the stratosphere)

mesosphere

where meteors enter the atmosphere (temperature decreases with altitude)

ionosphere

100 km above the surface, very very thin

composition of the atmosphere

78% nitrogen, 20% oxygen, 0.03% carbon dioxide, 2% water vapor, and 0.00006% ozone

characteristics of a planet

must orbit the sun, must clear objects from its orbit, and must be large enough to pull itself in a spherical shape

asteroid belt

between the inner planets and outer planets

Kuiper Belt

where comets reside, far beyond Neptune, close to the plane of the ecliptic

Oort Cloud

a sphere of trillions of objects (including comets) that are bound by gravity

why are there different types of planets?

formed at different temperatures and locations (some farther from the sun)

ice giants

Uranus and Neptune

geologic activities

occurs on objects with hot molten interiors and reshapes the surfaces (plate tectonics, volcanos, etc)

impacts 

changes in the surfaces of planets and can bring volatile components 

outgassing

caused by volcanic eruptions and impacts, which releases other compounds into the atmosphere 

climate change 

increasing changes of climate over long periods of time (includes precipitation, temperature, and wind patterns)

global warming

rise in global temperatures due to mainly increasing concentrations of greenhouse gases

examples of greenhouse gases?

CO² (carbon dioxide), NO² (nitrogen dioxide), CH⁴ (methane), water vapor

greenhouse effect

all planets absorb energy from the sun and have equilibrium (amount absorbed = amount reflected) 

Ceres

largest asteroid, has a diameter of 1000 km, dwarf planet

C type asteroids

carbonaceous; changed little chemically since the beginning, composed of silicates mixed with dark, organic compounds

S type asteroids

stony or silicate composition, formed closer to the sun than C type (also brighter)

M type

least common type of asteroid, composed primarily of metals

Vesta

the brightest asteroid, once volcanically active

Spaceguard Survey

goal to discover and track 90% of earth approaching asteroids greater than 1 km in diameter

albedo

a surface’s ability to reflect light 

what absorbs sunlight the best?

land and sea

what reflects sunlight the best?

clouds and ice

how do scientists measure ages of objects in the solar system?

counting carters and sampling radioactive materials in rocks

law of superposition

the bottom layers of rocks are older than the top layers; darker areas are younger, lighter areas are older

half life

the amount of time required for ½ of the original (parent) sample to decay into new daughter atoms 

short period comets

comets with orbits less than a century long

comet’s head or coma

temporary atmosphere of gas and dust illuminated by sunlight (can be as large as Jupiter)

comet’s nucleus

the small, solid comet inside; replenishes the atmosphere; very small and dark

which direction does a comet’s tail point?

always away from the sun

dust tail

brightest part of the comet’s tail

ion tail

fainter, straighter part of comet’s tail made of ionized gas

solar wind

pressure of sunlight, outflow of particles from the sun

meteors 

small objects that move through the atmosphere

meteoroids

meteors that are still in space

meteorites

meteors that have fallen on the surface of earth

meteor showers

from specific comet tails that pass through earth’s orbit (named after the constellation they seem to radiate through) 

Tycho Brahe

last great pre-telescopic observer, accurately built instruments to measure positions of planets, proposed his own hybrid model of the universe

Johannes Kepler

Brahe’s assistant, explained planetary motion by abandoning circular orbits and uniform motion

Kepler’s first law 

all orbits are ellipses

Kepler’s second law

planet’s speed varies as it moves around it’s elliptical orbit (faster when closer to the sun, slower when farther away)

eccentricity 

distance from center to focus / length of semi major axis