7.1 - Naked Eye Astronomy

Question 1

In what direction does the Sun, stars, and the Moon appear to travel across the sky?

Answer 1

East-west

Question 2

Out of the Sun, stars, and the Moon, rank from longest to shortest which travels faster.

Answer 2

1. The Moon (24 hours 49 minutes)
2. The Sun (24 hours)
3. The Stars (23 hours 56 minutes)

Question 3

What is a Sidereal day?

Answer 3

The time taken for the Earth to undergo a complete rotation of 360 degrees.

Question 4

How long is a Sidereal day?

Answer 4

23 hours 56 minutes

Question 5

What is a Solar day?

Answer 5

The time taken for the Sun to appear at the same position in the sky.

Question 6

How long is a Solar day?

Answer 6

24 hours

Question 7

Why is a Solar Day longer than a Sidereal day?

Answer 7

Not only is the Earth rotating on its axis but it is also orbiting the Sun.

In the time it takes the Earth to complete one full rotation, it has moved a bit through its orbit and so needs to rotate a bit further on its axis for the Sun to match the direction faced by the Earth. This takes 4 minutes long.

Question 8

Why can we see the Moon?

Answer 8

The light from the Sun reflects off the Moon.

Question 9

What is a New Moon?

Answer 9

When the Moon is almost directly between the Sun and the Earth. The lit side is facing away from Earth.

Question 10

What is a Full Moon?

Answer 10

When the Earth is almost directly between the Sun and the Moon. The lit side is facing towards Earth.

Question 11

Just after the New Moon, what is the phase called?

Answer 11

Waning Crescent

Question 12

Just after the Waning Crescent, what is the phase called?

Answer 12

Third Quarter (Half Moon)

Question 13

Just after the Third Quarter, what is the phase called?

Answer 13

Waning Gibbous

Question 14

Just after the Waning Gibbous, what is the phase called?

Answer 14

Full Moon

Question 15

Just after the Full Moon, what is the phase called?

Answer 15

Waxing Gibbous

Question 16

Just after the Waxing Gibbous, what is the phase called?

Answer 16

First Quarter (Half Moon)

Question 17

Just after the First Quarter, what is the phase called?

Answer 17

Waxing Crescent

Question 18

How long is one Full Moon cycle? What is this called?

Answer 18

29.5 days - A LUNAR MONTH

Question 19

How do eclipses happen?

Answer 19

When the Earth, Sun and Moon are directly in line.

Thus, the light from the Sun is blocked

Question 20

What are the two types of eclipses?

Answer 20

1. Solar Eclipse

2. Lunar Eclipse

Question 21

How does a Solar Eclipse occur?

Answer 21

When the orbit of the Moon takes it between the Earth and the Sun and the Moon’s shadow falls on the Earth.

Question 22

How does a Lunar Eclipse occurred?

Answer 22

When the Moon’s orbit causes it to pass into the Earth’s shadow.

Question 23

Why do eclipses occur rarely?

Answer 23

The Moon does not orbit the Earth in the same plane as the Earth orbits the Sun.
The Moon must line up perfectly which only occurs about 2-3 times a year.

Question 24

Name all the naked-eye planets (Planets that can be seen with the naked-eye)

Answer 24

Mercury, Venus, Mars, Jupiter and Saturn.

Question 25

Why did the Greeks classify planets as ‘wandering’ ?

Answer 25

The planets APPEAR to wander across the sky (with the stars).

Question 26

As planets move, what appears to happen?

Answer 26

The planets ‘change’ their position relative to the fixed stars.

Question 27

What is the process called when planets appear to move backwards?

Answer 27

Retrograde Motion

Question 28

Why does it seem that planets are overtaking others?

Answer 28

e.g. Planets have different orbital speeds so one planet might overtake another planet. From that perspective, the planet that has been overtaken seems to travel backwards.

Question 29

What is the name of the star that can be seen above the North Pole all year round?

Answer 29

Pole Star (Polaris)

Question 30

Why do the stars that are visible in the night sky change depending on the time of the year?

Answer 30

Due to the position of the Earth in its orbit around the Sun.

Question 31

Why do the stars that we see change as the year progresses?

Answer 31

Our orbit around the Sun changes as we go from season to season.
E.g. During Summer we are on one side of the Sun and we get to see stars that are not blocked by the Sun.

Question 32

What are the two angles we use to describe the position of stars and other astronomical objects?

Answer 32

1. Angle of Declination

2. Angle of Right Ascension

Question 33

What does the Angle of Declination tell you?

Answer 33

How high above the equator to look.

Question 34

What does the Angle of Right Ascension tell you?

Answer 34

Which way to look east-west.

Question 35

What is the Celestial Sphere?

Answer 35

An imaginary dome that stretches over the Earth and has the light from every astronomical object projected onto it.

Question 36

What is within the Celestial Sphere?

Answer 36

1. A north pole (above the North Pole)

2. An equator (above the Equator)

Question 37

Why is the Celestial Sphere used?

Answer 37

Used as a reference point for the coordinate system (Declination, Right Ascension)

Question 38

When talking about the positioning of the Declination, how would it be described?

Answer 38

The angle made between the object and celestial equator directly below, or above, the object.

Question 39

How is the Angle of Right Ascension measured?

Answer 39

From the point where the Sun moves to the Northern Hemisphere.

Question 40

What units does the Angle of Right Ascension use?

Answer 40

Degrees, minutes and seconds.

Question 41

What units does the Angle of Declination use?

Answer 41

Hours, minutes and seconds.

because the Earth and its celestial sphere take 24hrs to rotate 360 degrees and so 1 hour is equivalent to 15 degrees