Chapter 2

Question 1

Nodes

Answer 1

the two points in the Moon’s orbit where it crosses the ecliptic plane

Question 2

Totality

Answer 2

the portion of a total lunar eclipse during which the Moon is fully within Earth’s full shadow or a total solar eclipse during which the Sun’s disk is fully blocked by the Moon

Question 3

Prime meridian

Answer 3

the meridian of longitude that passes through Greenwich, England; defined to be longitude 0 degree

Question 4

Celestial equator

Answer 4

the extension of Earth’s equator onto the celestial sphere

Question 5

Local sky

Answer 5

the sky as viewed from a particular location on earth

Question 6

Angular distance

Answer 6

a measure of the angle formed by extending imaginary lines outward from our eyes to span an object

Question 7

Circumpolar

Answer 7

a star that always remains above the horizon for a particular latitude

Question 8

Stellar parallax

Answer 8

the apparent shift in the position of a nearby star (relative to distant objects) that occurs as we view the star from different positions in Earth’s orbit of the Sun each year

Question 9

June Solstice

Answer 9

both the point on the celestial sphere where the ecliptic is farthest north of the celestial equator and the moment in time when the Sun appears at that point each year

Question 10

Horizon

Answer 10

a boundary that divides what we can see from what we cannot see

Question 11

March equinox

Answer 11

both the point in Pisces on the celestial sphere where the ecliptic crosses the celestial equator and the moment in time where the Sun appears at that point each year

Question 12

Full shadow

Answer 12

the dark central region of a shadow

Question 13

Synchronous rotation

Answer 13

the rotation of an object that always shows the same face to an object that it is orbiting because its rotation period and orbital period are equal

Question 14

Sidereal day

Answer 14

the time of 23 hours 56 minutes 4.09 seconds between successive appearances of any particular star on the meridian; essentially, the true rotation period of Earth

Question 15

Eclipse seasons

Answer 15

periods during which lunar and solar eclipses can occur because the nodes of the Moon’s orbit are aligned with Earth and the Sun

Question 16

Solar eclipse

Answer 16

an event that occurs when the Moon’s shadow falls on Earth, which can happen only at new moon

Question 17

Direction

Answer 17

one of the two coordinates needed to pinpoint an object in the local sky

Question 18

Latitude

Answer 18

the angular north-south distance between Earth’s equator and a location on Earth’s surface

Question 19

Partial shadow

Answer 19

the lighter, outlying regions of a shadow

Question 20

Total solar eclipse

Answer 20

a solar eclipse during which the Sun becomes fully blocked by the disk of the Moon

Question 21

Constellation

Answer 21

a region of the sky covering the celestial sphere

Question 22

Angular size

Answer 22

a measure of the angle formed by extending imaginary lines outward from our eyes to span an object

Question 23

Total lunar eclipse

Answer 23

the Moon becomes fully covered by Earth’s full shadow

Question 24

Zenith

Answer 24

the point directly overhead, which has an altitude of 90 degrees

Question 25

Apparent retrograde motion

Answer 25

the apparent motion of a planet, as viewed from Earth, during the period of a few weeks or months when it moves westward relative to the stars in our sky

Question 26

Solar day

Answer 26

24 hours, which is the average time between appearances of the Sun on the meridian

Question 27

Ecliptic

Answer 27

the Sun’s apparent annual path among the constellation

Question 28

Lunar eclipse

Answer 28

an event that occurs when the Moon passes through Earth’s shadow, which can happen only at a full moon

Question 29

Partial lunar eclipse

Answer 29

a lunar eclipse during which the Moon becomes only partially covered by Earth’s full shaodw

Question 30

Meridian

Answer 30

a half-circle extending from your horizon due South, through your zenith, to your horizon due north

Question 31

Celestial sphere

Answer 31

the imaginary sphere on which objects in the sky appear to reside when observed from Earth

Question 32

North celestial pole

Answer 32

the point on the celestial sphere directly above Earth’s North Pole

Question 33

Penumbral lunar eclipse

Answer 33

a lunar eclipse during which the Moon passes only within Earth’s partial shadow and does not fall within the full shadow

Question 34

Longitude

Answer 34

the angular east-west distance between the prime meridian and a location on Earth’s surface

Question 35

Zodiac

Answer 35

the constellations on the celestial sphere through which the ecliptic passes

Question 36

Saros cycle

Answer 36

the period over which the basic pattern of eclipses repeats, which is about 18 years 11 1/3 days

Question 37

Partial solar eclipse

Answer 37

a solar eclipse during which the Sun becomes only partially blocked by the disk of the Moon

Question 38

December Solstice

Answer 38

both the point on the celestial sphere where the ecliptic is farthest south of the celestial equator and the moment in time when the Sun appears at that point each year

Question 39

Arcminutes

Answer 39

1/60 or 1 degree

Question 40

Altitude

Answer 40

the angular distance between the horizon and an object in the sky

Question 41

Precession

Answer 41

the gradual wobble of the axis of a rotating object around a vertical line

Question 42

September equinox

Answer 42

both the point in Virgo on the celestial sphere where the ecliptic crosses the celestial equator and the moment in time when the Sun appears at that point each year

Question 43

South celestial pole

Answer 43

the point on the celestial sphere directly above Earth’s South Pole