Cal Poly - ASTR 102 Exam 1

Q 2.2 - Why canty we see a galaxy 15 billion light-years away?

a. Because no galaxies exist at such a greatdistance.

B. Galaxies may exist at that distance, but

their light would be too faint for our

telescopes to see.

C. Because the light has not had the time to reach us yet.

C.

Light Travels at a finite speed, the farther away we look in distance, the further back we look in time.

The Astronomical Unit (AU)

Average distance between sun and earth - what we use to describe distance in our solar system

Light Year

Distance light travels in one year - what we use to describe distances in the milky way galaxy

Constellations

Regions in the sky

Q 3.1 The Brightest stars in a constellation

A. all belong to the same star cluster.

B. all lie at about the same distance from Earth.

C. may actually be quite far away from each other.

C.

Think about an inverted standard mixing bowl. That is what appears to us, whereas in actuality, stars lie in completely different distances.

Altitiude

location above horizon/zenith(directly above observer)

Cardinal direction

location along horizon/azimuth

Q 3.2 If you walk out of this building and

face directly south, which direction is east?

A. Slightly to the right

B. Slightly to the left

C. Directly right

D. Directly left

E. Behind you

D.

If you are facing directly south, east will be exactly 90 degrees to the left of you

Q 4.1

Imagine that from your current location

you observe a star rising directly in the east. When this star reaches its highest position above the horizon, where will it be?

A. High in the northern sky

B. High in the eastern sky

C. High in the southern sky

D. High in the western sky

E. Directly overhead

C.

Position 1 - is the horizon shown a real phsycial horizon or an imaginary plane that extends from your observing location on earth out to the celestial sphere?

Imaginary

Position 2 - can the observer shown see a star when it is located below the horizon? Why or why not?

no because it is below the horizon, which is the line of sight for the observer.

Position 4 - When a star travels from a position below the observer's horizon to a position above the observer's horizon, is that star rising or setting?

rising/ going up in the east

Position 5 - When a star travels from a position above the observer's horizon to a position below the observer's horizon, is that star rising or setting?

setting/ going down in the west

what is a star called that never rises or sets?

a circumpolar star

True or false: Rising and setting is defined relative to the observers horizon

true

How often does earth rotate around its AXIS?

Daily/once every ~24 hours

How often does earth orbit around the sun?

Yearly/once every ~365 days

Do the stars appear to move clockwise or counterclockwise around the north star?

counter-clockwise

By how much does the sun move through the zodiac?

a. 365 degrees

b. 12 degrees

c.~30 degrees

d. 1 degree

D. one degree

Motion 9 - two student are discussing the direct motion of a star rising directly in the east. which one is right?

Student A: Stars move east to west so any star rising directly in the east must be moving straight up so that it can later set in the west. if the arrow were angled, the star would not travel so that it would set in the west

Student 1: say a given star starts in the east at the horizon. As time progresses, this star will go up and will later be high in the southern sky, and then it will set in the west. To do this it has to move toward the south as it rises, so i drew my arrow angled up and to the right.

Student 1 is right because the star has to go to the east at the highest point to go to the west

Is this comment correct or incorrect:

The amount of time that all stars are above the horizon is 12 hours because it takes 12 hours for a star to rise in the east and then set in the west

incorrect - some stars are always visible because of their location in relations to the earths rotation. the correct statement would be. - the amount of time that it takes all stars to rotate through have of their particular rotation is 12 hours

how quickly do constellations move through the sky?

a. they rotate every 24 hours

b. the move every 2 hours

c. they move very slowly, one visible from ground circle once a month

d. they do not move

a. they rotate every 24 hours like every other star.

they shift from the sun roughly every month, but because they do not have special orbits that defy laws of gravity or polar pulls, they move through the sky once every 24 hours

Q 5.4

Say on a given day, The Sun is near the stars of the constellation Gemini. Near which constellation would you have expected the Sun to be located at sunrise on this day?

A. Leo

B. Cancer

C. Gemini

D. Taurus

E. Aries

C. Gemini

on any given day, the sun will move with the stars

Within a given day, the Earth moves very little in its orbit, so the Sun moves with the Stars (due to Earth rotation around its axis), so the Sun will be in the same constellation all day. your options for answers are 'rise', 'set', or 'highest in the sky'.

1. The constellation the Sun is in on that day will ____ at sunrise

2. The constellation the Sun is in on that day will ___ at sunset

3. The constellation the Sun is in on that day will be ____________ at noon

4. The constellation that is highest in the sky at midnight on that day will _____ at sunset

5. The constellation that is highest in the sky at midnight on that day will _____ at sunrise

1. rise

2. set

3. highest in the sky

4. rise

5. set

Q 7.5 One night, you see the star Sirius rise at exaclty 7:36PM. the following night, will it rise

A. slightly earlier

B. at the same time

C. Slightly later

Slightly earlier

Seasonal Stars - 10

imagine last night you saw the star Betelguese just starting to rise on you eastern horizon at 7:15pm. At 7:15pm tonight, will Betelgeuse be above, below, or exaclty at your easter horizon?

Betelgeuse will be above the eastern horizon, but not by much.

since the earth goes around the sun, any constellation rises earlier each month, so betelgeuse must rise a little bit earlier each month too. tonight, Betelgeuse would rise a little before 7:15, so therefore at 7:15, Betelgeuse would be a little above the eastern horizon.

Sidereal day

related to stars. time period for any star to go from highest point in the sky one day to highest point in the sky the next day. approx. 23 hours, 56 minutes, 4.09 seconds

Solar day

related to sun. time period for sun to go from highest point in sky one day to highest point in sky the next day. 24 hours on average.

Q 8.1

You go out tonight and see the brightest star in the constellation Orion just rising above your eastern horizon at 10 PM. One week later at 10 PM this same star will be.

A. Slightly higher in the sky.

B. At the same height as before.

C. Below your horizon.

D. Setting on your western horizon.

A. Slightly higher in the sky, as sidereal days, or days in relation to stars are shorter than what is typically conceived as a day, or a solar day.

Solar V. Sidereal 1

earth orbits the sun in a counterclockwise direction once every 365 days. Approximately how many degrees does earth move along its orbit in one day?

one degree

Solar V. Sidereal 2

As earth orbits the sun, it also rotates in a counterclokcwise direction about its axis as shown in Figure 1. We define 24 hours as the time from when the sun is highest in the sky one day to when it is highest in the sky the next day. How many degrees does earth rotate about its axis in exactly 24 hours:

a. exactly 360 degrees

b slightly less than 360 degrees

c. slightly more that 360 degrees

c. slightly more than 360 degrees

Solar V. Sidereal 3

How long does it take Earth to rotate exactly 360 degrees?

a. slightly less than 24 hours

b. exactly 24 hours

c slightly more than 24 hours

a. slightly less than 24 hours

when does the earth rotate a greater amount, during a solar day, or during a sidereal day?

during a solar day. To complete a solar day, Earth must rotate an additional amount, equal to 1/365 of a full turn. The time required for this extra rotation is 1/365 of a day, or about 4 minutes. So the solar day is about 4 minutes longer than the sidereal day.

since earth must rotate a litte (more/less) during a solar day, it will take (more/less) time ti complete a solar day then a sidereal day

more, more

Q 8.2 What component of Earth's motion causes the stars to rise earlier on successive nights?

A. Its rotation about its axis.

B. Its orbit around the Sun.

C. The tilt of its rotation axis.

B. It's orbit around the sun

Q 8.3

Through how many degrees does Earth rotate in exactly 24 hours?

A. Less than 360.

B. Exactly 360.

C. More than 360.

C. More than 360

Q 8.4 Imagine that Earth begins orbiting the Sun twice as fast while maintaining the same rotation rate. It now orbits once around the Sun every 6 months. In this case, what happens to the length of the solar day?

A. It gets slightly longer.

B. It does not change.

C. It gets slightly shorter.

D. It is cut in half.

E. It doubles

A. It get's slightly longer - It gets 8 minutes longer because instead of moving one degree extra during a solar day, you must move 2 degrees extra.

Q 8.5 Imagine that Earth stops orbiting the

Sun but continues to rotate in place about its own axis at its current rate. In this case, what happens to the length of the solar day?

A. It gets slightly longer.

B. It does not change.

C. It gets slightly shorter.

D. It is cut in half.

E. It doubles.

C. It gets slightly shorter. 361 degrees per solar day to 360 degrees per solar day. 24 hours exactly each rotation, and a solar and sidereal day become exactly the same

Path of the Sun 2

If it is wintertime right now(just after the winter solstice), how does the height of the sun at noon change over the next several months?

A. increases

B. Stays the same

C. Decreases

A. increases

Path of the Sun 3

Is there ever a time of year when the sun is directly overhead at the zenith at noon for an observer in the continental US? If so, on which date does this occur?

No, since we are not located at the equator, there is no time where the sun is directly overhead at noon

Path of the Sun 4a

During which months of the year would the sun rise north of east?

June

Path of the Sun 4b

During which months of the year would the sun rise south of east?

December

Path of the Sun 4c

During which months of the year would the sun rise directly in the east?

March&September

Path of Sun

Does the sun always set in precisely the same location on the horizon throughout the year?

No, the path of the sun moves north and south over the course of a year

Path of Sun

What direction would a shadow of a stick be cast if the sun rises in the southeast?

Northwest

Q 9.1 Which of the following statements is true about the location of the Sun at sunrise during the middle of winter?

A. The sun will rise north of east

B. The sun will rise directly in the east

C. The sun will rise south of East

D. None of the above

C. The sun will rise south of East

Q9.2

Which of the following statements istrue about the location of the Sun at sunset during the middle of summer?

A. The Sun will set north of west.

B. The Sun will set directly in the west.

C. The Sun will set south of west.

D. None of the above.

A. The sun will set north of west

Q9.3: If it is summertime right now, how does the altitude of the noontime sun change (if at all) as winter approaches?

A. It increases.

B. It decreases.

C. It stays the same.

B. It decreases

Q9.5

When does a vertical flagpole not cast a shadow at your current location?

A. Every day at noon

B. Every day at the time when the Sun is highest in the sky

C. When the Sun is highest in the sky on the summer solstice

D. When the Sun is highest in the sky on the winter solstice

E. A vertical flagpole always casts a shadow at our current location.

E. A vertical flagpole always casts a shadow at our current location

True or False:

Temperatures are generally higher during the summer months because...

1. ...the Earth is closer to the Sun during summer.

2. ...our hemisphere is closer to the Sun during summer.

3. ...the Sun gives off more energy during the

summer.

4. ...the Sun passes higher in the sky during

summer.

5. ...the Sun is above the horizon longer in the summer.

1. F

2. F (technically true as a statement but not the reason for the season)

3. F

4. T

5. T

Seasons 1

Is the direction the earths axis is tilted changing as the earth orbits the sun?

no

Seasons 6

Do you think the differences in distance between Earths northern and southern hemispheres are the cause of the seasons?

No, the tilt of the earth changes the amount of time the sun is in the sky for

Seasons 15

During which season is the number of daylight hours the greatest? how many hours?

Summer, 14 hours

Seasons 16

During which season is the sun highest in the sky at noon?

summer

when it is summer, the tilt of the earth causes the sun to be above the horizon for (many/few) hours of the day, and the sun at noon will be (high/low) in the sky, providing (direct/indirect) sunlight to that hemisphere of the earth

many, high, direct

Q 10.1

In the northern hemisphere, when the sun is ___ in the sky at noon, it is summer

A. Highest

B. Lowest

C. For a given location on earth, the sun is always at the same height in the sky at noon.

A. Highest

Q10.2

Complete this statement:In the northern hemisphere, the Sun is up in the sky ... during the winter.

A. More hours

B. Less hours

C. For a given location on earth, the sun is always up in the sky the same amount of hours.

B. Less hours

Q10.3

Imagine that Earth's orbit were changed to be a perfect circle around the Sun so that the distance to the Sun never changed. How would this affect the seasons?

A.We would no longer experience a difference between the seasons.

B.We would continue to experience seasons in essentially the same way we do now.

C.We would still experience seasons, but the difference would be much more noticeable.

D.We would still experience seasons, but the difference would be much less noticeable.

A. We would no longer experience a difference between the seasons

Earth's rotation around axis determines length of ___

day

Earth's orbit around Sun determines length of ____

year

Tilt of Earth's rotational axis with respect to plane of Earth's orbit causes _________

seasons

Moon's orbit around Earth determines length of _______

month

Tropical Year

time it takes Sun to return to same positionin sky as seen from Earth for a full cycle of seasons(e.g., from spring equinox to spring equinox)

A refracting telescope uses a ______ lens toconcentrate incoming starlight

glass

A reflecting telescope uses ________ to concentrate incoming starlight

mirrors

Main functions of a telescope from most to least important

1) to gather more light

2)to see fine detail

3) to magnify

In astronomy, what is the primary source of information?

light

Angular separation

car headlights from .5 mile away versus 100 ft away

A larger lens provides a ______ image

A. Brighter

B. Bigger

A. Brighter

Q11.1

You take an image of a star with a 4m radius telescope and expose for 10 seconds. In order to get the same bright image of the star with a 1m radius telescope, how many seconds will you have to expose for?

A. 10 seconds

B. 20 seconds

C. 40 seconds

D. 80 seconds

E. 160 seconds

E. 160 seconds

Area = piR^2, 4^2 = 16x10, so need exposure 16 times longer

Electromagnetic Spectrum

All of the frequencies or wavelengths of electromagnetic radiation.

Twinkling

: an effect by the earth's atmosphere

Q12.1

Which of the following wavelengths can be easily observed from the Earth surface?

A. X-ray

B. Ultraviolet

C. Radio

D. All of the above wavelengths

E. None of the above wavelengths

C. Radio

Telescopes and Earth's Atmosphere 1

which of the different wavelengths of light are able to completely penetrate earths atmosphere and reach the surface?

Radio and Visible Light

Telescopes and Earth's Atmosphere 2

which of the different wavelengths of light are able to partially penetrate earths atmosphere and reach the surface?

Ultraviolet and Infrared

Telescopes and Earth's Atmosphere 3

which of the different wavelengths of light are not able to penetrate earths atmosphere and reach the surface at all?

Gamma and X rays

Q12.2

Which is the correct reasoning for why a gamma ray telescope located in Antarctica that is to be used to look for evidence of black holes in the centers of galaxies would not get funded?

A. There is no way to detect the presence of a black hole.

B. Gamma rays are too energetic to detect with a telescope

.C. You cannot build a functioning telescope in Antarctica.

D. Gamma rays do not penetrate Earth's atmosphere .

D. Gamma rays do not penetrate Earth's atmosphere

Q12.3: Imagine you are the head of a funding agencythat can afford to build only one telescope. Which of the four proposed telescopes below would be best to support?

A. A gamma ray telescope in Antarctica

B. A radio telescope in orbit above the Earth

C. A visible telescope located high on a mountain in Peru

D. An ultraviolet telescope located in the Mojave desert

C. A visible telescope located high on a mountain in Peru

For any type of wave: Velocity = wavelength x frequency:v = l x f

Q13.1

High frequency photons...

A. travel faster than low frequency photons.

B. have more energy than low frequency photons.

C. have longer wavelengths than low frequency photons.

D. are smarter than low frequency photons.

B. have more energy than low frequency photons.

Q13.2

Which of the following is not a form of light?

A. Radio waves

B. Microwaves

C. X-rays

D. All of the above are a form of light.

E. None of the above are a form of light.

D. All of the above are a form of light.

Q13.3

Which of the following travels the slowest?

A. Radio waves

B. Visible light

C. X-rays

D. Infrared light

E. They all travel at the same speed (in vacuum).

E. They all travel at the same speed (in vacuum).

EM Spectrum of light 1

Which type of light has the highest frequency?

gamma rays

EM Spectrum of light 2

Which type of light has the longest wavelength?

radio waves

EM Spectrum of light 3

Which type of light moves at the fastest speed?

they all move at the same speed.

EM Spectrum of light 4

Which type of light has the greatest energy?

Gamma rays

EM Spectrum of light 6

The portion of the electromagnetic spectrum of light with the greatest energy has the ______ frequency and the ______ wavelengths

highest, shortest

EM Spectrum of light 7

A)infrared light has _______ energy than UV light

B)X-ray photons have _______ wavelengths than gamma ray photons

C)Visible light has a ________ frequency than radio light

D)Infrared light has a __________ speed than microwave light

A.lesser

B.longer

C.higher

D.same

if the sun were to cool off dramatically and start giving off light at wavelengths longer than visible light, how would frequency energy and speed of this light be different?

Frequency - lower

Energy - lesser

Speed - same speed as always

An electromagnetic wave with a high frequency has a_____ wavelength and ______ energy and travels at______ speed (in vacuum) than/as a low frequency wave

short, high,same

An electromagnetic wave with a low frequency has a_____ wavelength and ______ energy and travels at______ speed (in vacuum) than/as a high frequency wave.

longer, low, same

Q13.4

Which of the following

has the shortest wavelength?

A. A photon of ultraviolet light.

B. Blue electromagnetic radiation.

C. An X-ray.

D. A radio wave.

E. Infrared radiation

C. An X-Ray

Q13.5

Which of the following

is true about comparing gamma rays

and radio waves?

A. The radio waves have a lower energy and

travel slower than gamma rays.

B. The gamma rays have a shorter wavelength and a lower energy than radio waves.

C. The radio waves have a longer wavelength and travel at the same speed as gamma rays.

D. The gamma rays have a higher energy and

travel faster than radio waves.

C. The radio waves have a longer wavelength and travel at the same speed as gamma rays.

Q13.6: Which of the following

has the least energy?

A. Radio waves.

B. Visible light.

C. X-rays.

D. Infrared light.

E. They all have the same energy

A. Radio Waves