Term
| The closest star to earth |
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Definition
| the sun. The largest mass in the solar system. 4.5 billion years old. 150 million km away. 99% of the mass in our solar system in sun. |
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Term
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Definition
| The Pleiades. 430 light years away. |
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Term
| Galaxy closest to the milky way |
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Definition
| The Andromeda Galaxy. 2,200,200 light years away. |
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Term
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Definition
| massive gravitationally bound system-made of stars, dust, matter, that circles around a large mass. |
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Term
| cluster of galaxies closest to us |
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Definition
| The coma cluster. 320 million light years away. 10 million light years across. |
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Term
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Definition
| The lagoon Nebula visible from the northern hemisphere. 4100 light years away. |
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Term
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Definition
| astron=star. nomos=law. The science of stars, clusters of stars, galaxies, clusters of galaxies, dwarf planets. |
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Term
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Definition
a satellite, our moon is 380,000 km away.
a natural satellite is an object that orbits a planet larger than itself.
Satellites=moons |
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Term
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Definition
planets going from closest to farthest from the sun:
mercury
venus
earth
mars
jupiter
saturn
uranus
neptune |
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Term
| Planet, the things that make a planet |
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Definition
1. it orbits around the sun.
2. has enough mass to achieve a round shape
3. it has cleared its neighborhoods path of debree. |
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Term
| A dwarf planet, what makes a dwarf planet |
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Definition
| If it meets 2 of the three requirements for a planet it is a dwarf planet. A dwarf planet close to us-Ceres. |
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Definition
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Term
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Definition
Comet Hale-Boopp
nucleus: 10 km across
tail: 100 million km long
composed of ice-falls off as it travels. |
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Term
| Systematic study of the universe |
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Definition
| Gather facts---guess and explanation---test hypothesis---modify hypothesis---back to beginning(gather facts) |
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Term
| Astronomers unit of measurement for length |
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Definition
length in meters, astronomical units, light years
distance from earth to sun=1 astronomical unit |
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Term
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Definition
1.5 x 10^11
150 million km |
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Term
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Definition
distance traveled by light in one year
9.5 x 10^15
63,000 AU |
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Term
| measurements of time by astronomers |
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Definition
seconds,
Time for earth to go around the sun= 1 yr.
365 1/4 days= 3.2 x 10^7 seconds
Age of earth=4.6 x 10^4 |
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Term
| astronomers measurement for mass |
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Definition
mass in kg
mass=amount of matter
weight=force which gravity tugs on matter
mass=1kg
=35 oz on earth
=6 oz on moon
=13 oz on mars |
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Term
| two most important questions in astronomy |
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Definition
What have astronomers learned?
How have they learned it? |
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Term
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Definition
| Sky is divided into 88 constellations. |
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Term
| Stars are "attached" to the celestial sphere |
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Definition
Distances to stars are hard to measure. We pretend stars are at the same distance from us.
Position on the celestial sphere is known even when the distance is unknown. |
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Term
| what is the celestial sphere? |
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Definition
a large imaginary sphere centered on earth
Special locations:
--North celestial pole=point directly above earths north pole(near star Palaris)
--South celestial pole=point above earths south pole
--celestial equator=circle above earths equator. |
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Term
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Definition
earth's north pole: polaris directly overhead
Earth's equator: polaris is due north on the horizon
Earth's northern hemisphere: Polaris due north height above the horizon
Location on earth--Lat. & longitude
celestial sphere has right ascension(up and down)
Declination(side to side) |
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Term
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Definition
RA=vertical lines-measures entire sphere-360 degrees total.
Line of zero or 360 degrees is called the "first point of Aries"
also measured in hours-24 hrs total.
convert it to decimal
multiply it by 15 degrees |
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Term
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Definition
horizontal lines
measures entire sphere=180 degrees total
celestial equator is equal to 0 degrees
positive 90 degrees for north celestial pole
negative 90 degrees for south celestial pole |
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Term
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Definition
celestial sphere appears to rotate about the celestial poles (1 day cycle)
Stars, sun, moon and planets move in counterclockwise circles around the north celestial pole
objects near celestial equator move east to west when above horizon (sun rises in the east sets in the west)
1-day cycle
starts are stationary; earth rotates about its axis once per day |
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