Astro Terms Chapter 1

Front 1

solar system

Back 1

Sun and all obj. that orbit it, planets, moons and infinite other thins like asteroids and comets

Front 2

Galaxy

Back 2

A great island of stars in space containing a few hundred million-1 trillion stars.

Front 3

Big Bang

Back 3

The beginning of expansion. 14 billion years ago. Universe has continued expanding since.

Front 4

Star life

Back 4

1. gravity compresses the material in a could to the point where the center becomes dense enough and hot enough to generate energy. 2. (Nuclear fision) lightweight atomic nuclei smash together and stick to make heavier nuclei.
3. When energy runs out star throws the material into space

Front 5

origins of other elements

Back 5

STARS, through nuclear fision

Front 6

One light-year

Back 6

about ten trillion kilometers or about 6 million miles. This explains: THE FARTHER WE LOOK IN THE DISTANCE THE FARTHER WE LOOK IN TIME

Front 7

observable universe

Back 7

14 billion light years because that is when the universe was created.

Front 8

FINDING SCALE

Back 8

ex: find how big the sun is: 1/10 billion
1. Divide actual radius by 10 billion
2. do unit conversion

Front 9

Number of stars in the universe comparison

Back 9

counting grains of sand

Front 10

One Astronomical Unit (AU)

Back 10

150 million kilometers (earths path around the sun)

Front 11

ecliptic plane

Back 11

The earth's orbital path. 23.5 degree tilt. The tilt

Front 12

Trends of the universe

Back 12

1. virtually every galaxy outside the local group is moving away from us
2. more distant galaxies appear to be moving faster

Front 13

Singularity

Back 13

A point of infinitely small volume and infinitely large density. M=universe

Front 14

Scaling

Back 14

converting different amounts in the same unit

Front 15

constellation

Back 15

a region of the sky with well defined borders

Front 16

celestial sphere

Back 16

an illusion observed by the ancient greeks that the starts lie on a circular

Front 17

north celestial pole

Back 17

point directly over earth's north pole

Front 18

south celestial pole

Back 18

point directly over earths south pole

Front 19

celestial equator

Back 19

projection of earth's equator into space, makes a complete circle around the celestial sphere.

Front 20

ecliptic

Back 20

is the path the sun follows as it appears to circle around the celestial sphere once each year. Crosses the celestial equator at 23.5 degrees

Front 21

local sky

Back 21

sky scene from where you happen to be standing

Front 22

zenith

Back 22

the point directly overhead

Front 23

meridian

Back 23

imaginary half circle starting at the equator and due south.

Front 24

direction

Back 24

A tactic to locate a star. Sometimes states as azinmuth...horizontal angle from direction from horizon (Ex: SE) altitude is position above horizon (60 deg)

Front 25

angular size

Back 25

the angle an object in the sky appears to span in your field of view. ex: moon is about .5 deg.

Front 26

angular distance

Back 26

the angle that apperas to separate two objects in the sky. (distance between 2 pointer stars in big dipper bowl about 5 deg.)

Front 27

arcminutes

Back 27

sixty arcminutes in one degree

Front 28

arcseconds

Back 28

60 arc seconds in an arcminute

Front 29

circumpolar stars

Back 29

stars relatively near the north celestial pole. Never rise nor set. Make daily counterclockwise circles around north celestial pole.

Front 30

summer solstice

Back 30

around nune 21, northern hemisphere is tipped most directly toward the sun

Front 31

winter solsitce

Back 31

december, northern hemisphere is tipped most directly away from the sun

Front 32

spring equinox

Back 32

march, when north. hemi. goes from being tipped slightly away from the usn to being tipped slightly towrads

Front 33

fall equinox

Back 33

northern hemisphere first starts to be tipped away from sun

Front 34

moon's pattersn

Back 34

apperears to move eastward from night to night through the constellations of the zodiac. around the earth in 27 1/3 days.

Front 35

Lunar eclipse

Back 35

occurs when the earth casts a shadow on the moon. order: Sun, earth, moon. Moon must be full

Front 36

nodes

Back 36

the tow points in each orbit at which the moon crosses the surface

Front 37

solar eclipse

Back 37

moon lies directly between the sun and eath so that the moon's shadow falls on earth. order Sun, Moon, Earth. moon must be new

Front 38

umbra

Back 38

shadow of moon/earth when light is completely blocked

Front 39

prenumbra

Back 39

sunlight is only partially blocked

Front 40

total lunar eclipse

Back 40

moon passes through earth's umbra

Front 41

partial lunar eclipse

Back 41

alignment is somewhat less perfect, only part of full moon passes through the umbra

Front 42

penumbral lunar eclipse

Back 42

moon passes only thorugh earth's penumbral

Front 43

total solar eclipse

Back 43

when moon is relatively close to earth in its orbit, moon's umbra touches a small area of earth's surface

Front 44

partial solar eclipse

Back 44

only part of the sun is blocked from view