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Fall 23 > Astro 7N Unit 1 > Flashcards

Astro 7N Unit 1 Flashcards

1
Q

What is Newton’s First Law?

A

An object at rest, or in motion in a straight line at a constant speed, will remain in that state unless acted upon by a force.

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2
Q

What is Newton’s Second Law?

A

acceleration due to a force will be in the same direction as the force, with a magnitude inversely proportional to its mass

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3
Q

What is Newton’s Third Law?

A

For every action, there is an equal and opposite reaction

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4
Q

What is an example of Newton’s First Law?

A

If the Sun suddenly disappeared, the Earth would continue in the
direction that it was traveling in its orbit at that time

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5
Q

What is the equation for Newton’s Second Law?

A

Force = mass x acceleration

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6
Q

What is an example of Newton’s First Law?

A

A smaller mass will move faster, if the same force is applied to it

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7
Q

What is an example of Newton’s Third Law?

A

The Sun exerts force on planets, and they orbit it — the planets exert equal force on Sun, but it only moves slightly because of its very large mass relative to the planets

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8
Q

What is the gravity strength equation?

A

g = M / R^2, m is mass and r is radius

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9
Q

What is the correlation between mass and gravity?

A

More mass = more gravity.
If the mass of a planet were twice that of another, but they had the same radius, the gravity felt on the surface of the more-massive one would be twice as strong

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10
Q

What is the correlation between separation and gravity?

A

Larger separation = less gravity.
If the radius of a planet were twice that of another, the gravity is 1 / (2) 2 = 1/4 as strong

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11
Q

What is the surface gravity of Mars relative to Earth?

A

Mars has 1/10 the mass of the Earth and 1/2 the radius of Earth.
So for Mars, g = (1/10) / (1/2)^2 = (1/10) / (1/4) = 4/10

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12
Q

What is Newton’s Universal Law of Gravitation?

A

force of gravity between any two objects in the Universe. force of gravity is proportional to (mass of object 1) × (mass of object 2) divided by the distance between the two objects squared:
F = M1 x M2 / d^2

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13
Q

Based off the Universal Law of Gravitation, what would the force be if objects were moved two times closer?

A

F = M1 x M2 / (1/2)^2 = M1 x M2 / (1/4) = 4 (M1 x M2 )
… so, the gravitational attraction would become 4 times as great

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14
Q

What causes day and night?

A

Rotation of the Earth on its axis.

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15
Q

How does the Sun appear to move in the sky in the course of a day?

A

East to West, because of Earth’s rotation. The stars and planets move in the same way from our point of view, also, because of Earth’s rotation.

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16
Q

What happens to the Earth in one year?

A

It orbits the Sun, once (also referred to as one complete revolution about the Sun).

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17
Q

Why do we have seasons?

A

The tilt of the Earth’s axis of rotation, with respect to the plane of its orbit around the Sun (and not because of changing distance from Sun).
The Earth’s tilt is about 23 degrees.

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18
Q

How is the Earth’s axis tilted when we have summer in the Northern hemisphere?

A

With the North pole toward the Sun.

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19
Q

What season is it in the Southern hemisphere when it is summer in the Northern hemisphere?

A

Winter

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20
Q

Winter begins on or about Dec. 2, which is when

A

in the Northern hemisphere, the
nights are longer than days

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21
Q

Spring begins on or about March 21, which is when

A

days and nights have equal length

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22
Q

Summer begins on or about June 21, which is when

A

days longer than nights in the North

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23
Q

Fall begins on or about Sept. 21, which is when

A

days and nights have equal length

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24
Q

Would seasons happen even if the Earth’s axis was not tilted?

A

the distance between the Earth and the Sun does not change very much over the course of a year, so the temperature does not change much for that reason. Without the tilt of Earth’s axis there would be no seasons on Earth. Mars has a similar tilt to its rotation axis as Earth does

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25
Q

What happens to the moon in 1 month?

A

It moves once around the Earth

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26
Q

What causes the phases of the Moon?

A

The Sun is lighting up different fractions of the part of the Moon we see from Earth

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27
Q

What is the order of the phases of the Moon?

A
  1. New
  2. Waxing Crescent
  3. First Quarter
  4. Waxing Gibbous
  5. Full
  6. Waning Gibbous
  7. Third Quarter
  8. Waning Crescent
  9. New (repeating)
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28
Q

When is the full moon visible?

A

Only at night. It transits (is highest in the sky, or overhead) at midnight;
the full moon rises 6 hours earlier (at sunset), and sets 6 hours later (at sunrise)

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29
Q

When is the new moon visible?

A

The new moon is visible during the day. It transits at noon; it rises 6 hours earlier (at sunrise), and sets 6 hours later (at sunset)

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30
Q

How are the Sun, Earth, and Moon positioned when it is new Moon?

A

in a straight line: Sun — Moon — Earth

31
Q

How are the Sun, Earth, and Moon positioned when it is full Moon?

A

Sun — Earth — Moon

32
Q

What is a solar eclipse?

A

The Moon is blocking the Sun’s light, or a location on the Earth’s surface is passing under the Moon’s shadow

33
Q

How are the Sun, Earth, and Moon positioned when it is a solar eclipse?

A

Sun — Moon — Earth (as in a new Moon)

34
Q

What is a lunar eclipse?

A

Earth’s shadow passes across the Moon

35
Q

How are the Sun, Earth, and Moon positioned when it is a lunar eclipse, and what phase is the Moon in?

A

Sun — Earth — Moon (as in a full Moon)

36
Q

Why do eclipses not occur every month on Earth?

A

The Moon orbits the Earth in a slightly different plane than the Earth orbits the Sun

37
Q

Eclipses of the moons of Mars…

A

Mars has two small moons, Phobos and Deimos. Relative to Earth’s Moon, they are tiny, and closer to their planet and orbiting faster — and closer to the orbital plane of Mars around the Sun. This leads to more frequent eclipses visible from Mars

38
Q

How many hours before it is overhead does a moon phase rise?

A

6 hours, and sets 6 hours after it is overhead

39
Q

What are Constellations?

A

large defined areas of the sky, anything visibly within that region is considered “in” that constellation, 88 total

40
Q

Why are different constellations visible during different times of the year?

A

Because as the Earth travels around the Sun, its nighttime side faces different regions of space

41
Q

What is an Ecliptic?

A

the apparent path of the Sun over the course of a year, with respect to the distant stars — also refers to the plane in which the Earth orbits the Sun

42
Q

What are Zodiac Constellations?

A

the 12 (or 13) constellations that lie along the ecliptic

43
Q

What is the significance of Zodiac Constellations and the Ecliptic?

A

The Sun is inside a Zodiac constellation at all times = in each one for about a month, each year.

During that time you cannot see that constellation since it is behind the Sun all day and not on the nighttime side of Earth

44
Q

What are Winter Zodiac Constellations?

A

ones opposite the Sun in the winter

45
Q

What are Summer Zodiac Constellations?

A

ones opposite the Sun in the summer

46
Q

What are Photons?

A

particles of light

47
Q

What are the forms of light, from high-energy to low-energy? (GXU VIMR)

A
  1. gamma ray (most)
  2. X-ray
  3. ultraviolet (UV)
  4. visible
  5. infrared (IR)
  6. microwave
  7. radio (least)
48
Q

How do you get a bluer color?

A

high-energy light = high frequency =short wavelength = a bluer color

49
Q

How do you get a redder color?

A

low-energy light = low frequency = long wavelength = a redder color

50
Q

Do all forms of radiation travel at the speed of light?

A

Yes

51
Q

In what units do you measure the wavelength of radio waves?

A

meters and centimeters

52
Q

In what units do you measure the wavelength of visible light?

A

(hundreds of nanometers)

53
Q

In what units do you measure the wavelength of X-Rays?

A

even smaller (nanometers down to picometers)

54
Q

How do Prisms split light into different colors?

A

bending different wavelengths at different angles

55
Q

What is a Blackbody Spectrum?

A

the spectrum of light produced by anything that is heated, a higher temperature = more light in total,

peak intensity at a shorter wavelength (bluer color)

56
Q

What is the surface temperature of the Sun?

A

5800 Kelvin

57
Q

What color is the Sun?

A

Its spectrum peaks in the visible light region (peak around green — a “green star”!)

58
Q

What is room temperature in Kelvin?

A

about 300 degrees Kelvin

59
Q

What happens to a blackbody at room temperature?

A

peaks in the infrared region of light

60
Q

What kinds of radiation get through the Earth’s atmosphere?

A

visible and radio, to see the other kinds of a light you would need a telescope in space

61
Q

What is the continuum spectrum?

A

light emitted at all wavelengths, like a rainbow

62
Q

What is the absorption spectrum?

A

a spectrum of electromagnetic radiation transmitted through a substance, showing dark lines or bands due to absorption of specific wavelengths — produced by a (less-energetic) gas cloud in front of a light source

63
Q

How is an absorption line produced?

A

electrons in atoms absorb photons and remove light of specific energies from the spectrum. Then the electrons move from a lower to a higher energy level

64
Q

What is the emission spectrum?

A

the pattern of lines formed when light passes through a prism to separate it into the different frequencies of light — bright lines at specific wavelengths, in an otherwise empty (dark) spectrum

due to emission of photons from atoms in gas that have electrons in elevated levels

65
Q

How is an emission line produced?

A

electrons jump from higher to lower energy levels, and emit photons of those specific energies

66
Q

Why does every chemical element have their own “footprint”

A

Different chemical elements have different energy levels that their electrons can occupy

67
Q

What is a Reflecting telescope?

A

use a mirror to collect and focus light

68
Q

What is a Refracting telescopes?

A

use a lens to collect and focus light

69
Q

What are the important qualities of a telescope? (LAQ)

A
  1. light-gathering power
  2. angular resolution
  3. quality of the instruments

(magnification is not that important)

70
Q

What is light gathering power?

A

Telescopes collect light in proportion to the area of their mirror, The area of circle is proportional to its diameter squared.
* example: a 2m-diameter telescope collects 2 x 2 = 4 times as much light as a 1m-diameter telescope (1 x 1 = 1)
* or, a a 2m-diameter telescope collects the same amount of light as a 1m-diameter telescope in 1/4 the time

71
Q

What is angular resolution?

A

the ability to distinguish or separate two nearby light sources

72
Q

How does Earth’s atmosphere limit Angular Resolution?

A

limits angular resolution for ground-based telescopes — makes stars twinkle

73
Q

What is magnification?

A

zooms in on a smaller portion of the sky, to see more detail (but also observes a smaller overall area of the sky)

74
Q

Telescopes above Earth’s atmosphere are better because

A
  • certain kinds of radiation cannot get through atmosphere all the way to the surface (X-ray, gamma-ray, UV, IR)
  • conditions give clearer images without atmospheric blurring; i.e., better seeing

Fall 23 (18 decks)

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