Unit 3

Question 1

lines of longitude

Answer 1

great circles that pass through both the north and south poles

Question 2

meridian

Answer 2

great circles that pass through both the north and south poles

Question 3

parallels

Answer 3

circles in planes parallel to the equator define north-south measurements

Question 4

lines of latitude

Answer 4

circles in planes parallel to the equator define north-south measurements

Question 5

rotation

Answer 5

an object’s spinning motion about its own axis

Question 6

revolution

Answer 6

an object’s orbital motion around another object

Question 7

precession

Answer 7

the slow movement of the axis of a spinning body around another axis due to a torque (such as gravitational influence) acting to change the direction of the first axis. It is seen in the circle slowly traced out by the pole of a spinning gyroscope

Question 8

nutation

Answer 8

a periodic oscillation of the earth’s axis that causes the precession of the poles to follow a wavy rather than a circular path.

Question 9

sidereal day

Answer 9

the time required for one complete rotation of the earth in reference to a star; 23 hours, 56 minutes, and 4.09 seconds

Question 10

solar day

Answer 10

time required for the earth to complete one revolution around its axis compared to the sun

Question 11

celestial sphere

Answer 11

fictitious sphere centered on the Earth upon which all celestial bodies can be projected

Question 12

right ascension

Answer 12

celestial equivalent of longitude; the angular distance of a point celestial sphere, measured east together with declination, define the position of an object in the sky. Measured in hours (max. 24 hours), minutes (max 60 min), seconds (max 60 sec)

Question 13

declination

Answer 13

angular distance north or south from the equatorial plane of the earth measured toward the poles; together with right ascension, define the position of an object in the sky. Measured in degrees

Question 14

zenith

Answer 14

point on the celestial sphere directly overhead for an observer

Question 15

nadir

Answer 15

the direction opposite the zenith

Question 16

ecliptic plane

Answer 16

the plane in which the Earth orbits the sun, 23.4° from the celestial equator

Question 17

equinox

Answer 17

times at which the center of the Sun is directly above the equator, marking the beginning of spring and autumn

Question 18

hour angle

Answer 18

the distance in hours, minutes, and seconds westward along the celestial equator from the observer’s meridian to the object’s RA

Question 19

troposphere

Answer 19

starts at the Earth’s surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the most dense. Almost all weather is in this region

Question 20

stratosphere

Answer 20

starts just above the troposphere and extends to 50 kilometers (31 miles) high. The ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer

Question 21

mesosphere

Answer 21

starts just above the stratosphere and extends to 85 kilometers (53 miles) high. Meteors burn up in this layer

Question 22

thermosphere

Answer 22

starts just above the mesosphere and extends to 600 kilometers (372 miles) high. Aurora and satellites occur in this layer

Question 23

ionosphere

Answer 23

an abundant layer of electrons and ionized atoms and molecules that stretches from about 48 kilometers (30 miles) above the surface to the edge of space at about 965 km (600 mi), overlapping into the mesosphere and thermosphere. This dynamic region grows and shrinks based on solar conditions and divides further into the sub-regions: D, E and F; based on what wavelength of solar radiation is absorbed. The ionosphere is a critical link in the chain of Sun-Earth interactions. This region is what makes radio communications possible

Question 24

exosphere

Answer 24

upper limit of our atmosphere. It extends from the top of the thermosphere up to 10,000 km (6,200 mi

Question 25

greenhouse effect

Answer 25

way in which heat is trapped close to the surface of the Earth by greenhouse gases

Question 26

constellations

Answer 26

one of 88 groups of stars that have been given a name and a design