Chapters 4 and 5

Question 1

1. What is the latitude of the North Pole?
2. The South Pole?
3. Why does longitude have no meaning at the North and South Poles?

Answer 1

1. North Pole Latitude: 90 degrees
2. South Pole Latitude: -90 degrees
3. You can only go north or south at the poles, so longitude has no meaning.

Question 2

Make a list of each main phase of the Moon, describing roughly when the Moon rises and sets for each phase. During which phase can you see the Moon in the middle of the morning? In the middle of the afternoon?

Answer 2

New Moon: rises at sunrise, sets at sunset
1st Quarter: rises at noon, sets at midnight (can see middle of afternoon)
Full Moon: rises at sunset, sets at sunrise
3rd Quarter: rises at midnight, sets at noon (can see middle of morning)

Question 3

What are the two ways that the tilt of Earth’s axis causes the summers in the United States to be warmer than the winters?

Answer 3

Earth’s 23.5 degree tilt and days are longer during the summer.

Question 4

What is the origin of the terms “a.m.” and “p.m.” in our timekeeping?

Answer 4

A.M.: Ante Meridian, stands for before midday
P.M.: Post Meridian, stands for post midday
Originate from Latin

Question 5

Why don’t lunar eclipses happen during every full moon?

Answer 5

The Moon’s orbit is tilted relative to Earth’s orbit around the Sun
For a lunar eclipse to occur, the Moon, Earth, and Sun must be aligned so that Earth’s shadow can fall on the Moon.

Question 6

Explain how tidal forces are causing Earth to slow down.

Answer 6

The tidal forces creates waves in water, so Earth’s rotation has friction between water and land, making Earth slow down

Question 7

Explain how tidal forces are causing the Moon to slowly recede from Earth.

Answer 7

Conservation of angular momentum.

Question 8

Where are you on Earth if you experience each of the following?
1. The stars rise and set perpendicular to the horizon.
2. The stars circle the sky parallel to the horizon.
3. The celestial equator passes through the zenith.
4. In the course of a year, all stars are visible.
5. The Sun rises on March 21 and does not set until September 21 (ideally).

Answer 8

1. Equator
2. North or South Pole
3. Equator
4. Equator
5. North Pole

Question 9

Why is the warmest day of the year in the United States (or in the Northern Hemisphere temperate zone) usually in August rather than on the day of the summer solstice, in late June?

Answer 9

Th Earth warms up from June to August. Water also holds a lot of this heat.

Question 10

A car accident occurs around midnight on the night of a full moon. The driver at fault claims he was blinded momentarily by the Moon rising on the eastern horizon. Should the police believe him?

Answer 10

No, the moon is not in the eastern horizon. It would be high in the sky.

Question 11

What is the right ascension and declination of the vernal equinox?

Answer 11

Vernal equinox: The right ascension and declination is 0 degrees and 0 hours

Question 12

What is the right ascension and declination of the autumnal equinox?

Answer 12

Autumnal equinox: Asc and Dec is 0 degrees and 12 hours

Question 13

What is the right ascension and declination of the Sun at noon on the summer solstice in the Northern Hemisphere?

Answer 13

d: 23.5 degrees and a: 6 hours

Question 14

In a part of Earth’s orbit where Earth is moving faster than usual around the Sun, would the length of the solar day change? If so, how? Explain.

Answer 14

The solar day will become longer due to the degree becoming larger then 1

Question 15

If Sirius rises at 8:00 p.m. tonight, at what time will it rise tomorrow night, to the nearest minute? Explain.

Answer 15

7:56pm, the sidereal day is 4 minutes lower then a solar day

Question 16

Explain why some solar eclipses are total and some are annular.

Answer 16

Total solar eclipses happen when the full moon is perigee, meaning it can fully block the sun.
Annular solar eclipses happen when the full moon is apogee, meaning it can’t fully block the sun.

Question 17

1. What distinguishes one type of electromagnetic radiation from another?
2. What are the main categories (or bands) of the electromagnetic spectrum?

Answer 17

1. Wavelength and frequency define the wave
2. Radio waves, microwaves, infrared waves, visible waves, ultraviolet, x-ray, gamma rays

Question 18

What is a wave? Use the terms wavelength and frequency in your definition.

Answer 18

A wave is a disturbance that transfers energy by repeating patterns of crests and troughs, where the distance between two consecutive crests (or troughs) is called the wavelength, and the number of crests that go by a second is called the frequency.

Question 19

Where in an atom would you expect to find electrons? Protons? Neutrons?

Answer 19

You would find electrons orbiting around the nucleus, while protons and neutrons are found within the nucleus

Question 20

Explain how emission lines and absorption lines are formed.

In what sorts of cosmic objects would you expect to see each?

Answer 20

Emission lines form when an electron drops it’s energy level and emits a photon

Absorption lines form when an atom or molecule absorbs energy, and the electron goes to a high energy level

You would expect to see this in gas clouds

Question 21

What kind of motion for a star does not produce a Doppler effect? Explain.

Answer 21

Tangential or across, since there is no motion either toward or away from the observer

Question 22

Which type of wave has a longer wavelength: AM radio waves (with frequencies in the kilohertz range) or FM radio waves (with frequencies in the megahertz range)? Explain.

Answer 22

A.M. has longer wavelength cuz it’s frequency is lower

Question 23

Explain why we have to observe stars and other astronomical objects from above Earth’s atmosphere in order to fully learn about their properties.

Answer 23

The atmosphere blocks many waves, meaning we can’t get a full study on stars and other astronomical objects

Question 24

Explain why hotter objects tend to radiate more energetic photons compared to cooler objects.

Answer 24

A hotter object emits shorter wavelength. Making the frequency higher, which means the energy is higher

Question 25

Explain how we can deduce the temperature of a star by determining its color.

Answer 25

Hotter stars are gonna be blueish and cooler stars will be reddish.

Question 26

Explain how we use spectral absorption and emission lines to determine the composition of a gas.

Answer 26

Every atom has a specific spectral signature, like a “fingerprint”, and you can look for that within stars.

Question 27

Is it possible for two different atoms of carbon to have different numbers of neutrons in their nuclei? Explain.

Answer 27

Yes, but they would be called isotopes.

Question 28

Explain why astronomers use the term “blue shifted” for objects moving toward us and “redshifted” for objects moving away from us.

Answer 28

When objects are shifting towards you, the waves get smaller and shift to the bluer spectrum
And for objects shifting away, the waves get longer, and shift to the redder side of the spectrum

Question 29

Water faucets are often labeled with a red dot for hot water and a blue dot for cold. Given Wien’s law, does this labeling make sense?

Answer 29

No, as in Wien’s law, the higher frequency, which is hotter, is blue and lower frequency, which is cooler, is red

Question 30

What is the frequency of a red laser beam, with a wavelength of 670 nm, which your astronomy instructor might use to point to slides during a lecture on galaxies?

Answer 30

c=λf –> f=c/λ
nm = 10^-9
speed of light: 3 x 10^8
3 x 10^8 / 670 x 10^-9
= 4.5 x 10^14 hz

Question 31

You go to a dance club to forget how hard your astronomy midterm was. What is the frequency of a wave of ultraviolet light coming from a blacklight in the club, if its wavelength is 150 nm?

Answer 31

c=λf –> f=c/λ
nm = 10^-9
c= speed of light: 3 x 10^8
3 x 10^8 / 150 x 10^-9
= 2 x 10^15 Hz

Question 32

What is the temperature of a star whose maximum light is emitted at a wavelength of 290 nm?

Answer 32

λmax= 2.9 x 10^6 / T
T= 2.9 x 10^6 / λmax
2.9 x 10^6 / 290 = 10,000 K