Astronomy Exam 1

Order of the planets

Mercury, Venus, Earth, Mars,Jupiter, Saturn, Uranus, and Neptune

open cluster of stars

young

Globular cluster of stars

old

galaxy

large grouping of stars held together by gravity and orbiting a common center of mass

galaxy group

a grouping of a few to several 10’s of galaxiesheld together by gravity

galaxy cluster

a large groupings of galaxies including several dozen up to more than 100 galaxies all held together by gravity

galaxy supercluster

groupings of galaxy clusters

universe

the sum total of all matter and energe, encompassing all superclusters, voids, and everything within them

About how many stars are in teh milky way

100 billion (10^11)

what is the correct ordering from smallest to largest?

planet, star, galaxy, galaxy group, galaxy cluster

How many moons can fit inside of earth

approximately 4

how many times larger is the sun than the earth

110 times larger

Astronomical unit

the distance between the earth and the sun; approximately 93 million miles (150 km)

Light year

the distance that light travels in a year

Scientific method

ask a question, hypothesis, experiment, observation, analyze data, conclusion

earth’s tilt

23.5 degrees

latitude

north-south position from the equator

longitude

east-west position relative to Greenwich England

declination

stars latitude(north/south); position above or elow the celestial equator

right ascension

star’s longitude (east/west); position along the celestial equator

ecliptic

sun’s apparent path through the celestial phase

celestial equator

a projection of our equator into space

zenith

directly overhead

horizon

the half of the sky you can see at your position

circumpolar star

never set or rise below the horizon at your location

precession

the earth’s axis wobbles causing the place it points to change; takes about 26,000 years

earth’s only natural satellite

the moon

Moon’s orbit around the earth completes every

27.3 days

sidereal month

moon complete orbit around the earth

the moon returns to the same position relative to the sun every

29.5 days

lunar month

the moon returning to the same position relative to the sun

lunar cycle phases repeat every

29.5 days

lunar phases

new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third quarter, waning crescent

tidally locked

we see the same side of teh moon all the time

solar eclipse

moons shadow falls on earth

lunar eclipse

earth’s shadow falls on the moon

arcminute

60 per degree

arcsecond

60 per arcminute

constellation

one of the 88 section into which astronomers divide the sky

asterism

a noticeable star pattern within a constellation

Exodus model of the solar system

Earth is the center of the universe

Ptolemaic model

Builds on Exodus model; Earth at center but the outer planets needed to have special extra orbit: “epicycle”-geometric models

heliocentric model

sun is at the center and teh earth and planets rotate around it