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Astronomy > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What is an AU

A

average distance from the sun to the Earth

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2
Q

What is a light year

A

Distance light travels in one year

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3
Q

Put the following in order from smallest to largest:
human, universe, Galaxy, local group, Earth, Superclusters, and Solar system

A

Human, Earth, Solar system, Galaxy, Local group, Supercluster, and Universe

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4
Q

How did Aristotle know the Earth was round?

A
  • Saw the shape of Earth’s shadow in the eclipse of the moon
  • New stars become visible as you travel South
  • Distant ships disappear at the bottom first
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5
Q

What is parallax?

A

An apparent shift of nearby stars with respect to distant stars as the Earth orbits the Sun

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6
Q

What is the “resolution” of a telescope

A

the smallest angular separation such that two points can be distinguished

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7
Q

What is the difference between heliocentric and geocentric thinking

A

heliocentric thinking is the thought that the planet orbits the sun while geocentric is the thought that the planets orbit Earth

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8
Q

What was Copernicus’ main contribution to astronomy

A

Challenged the Greek’s geocentric thinking

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9
Q

What were Galileo’s main contributions to astronomy

A

Discovered the 4 largest moons of Jupiter and the phases of Venus, further backing up Copernicus’ geocentric thinking

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10
Q

What was Tycho Brahe’s main contributions to astronomy

A

Collected data on the stars by making detailed, naked eye observations

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11
Q

What were Johannes Kepler’s contributions to astronomy

A

Using data collected by Brache, he came to 3 major conclusions

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12
Q

What is Kepler’s 1st Law?

A

Planets move in elliptical orbits with the Sun at one focus of the ellipse

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13
Q

What is Kepler’s 2nd law

A

The orbital speed of a planet varies so that a line joining the Sun and the planet will sweep out equal area in equal time intervals; the closer a planet is to the Sun during its orbit, the faster it moves

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14
Q

What is Kepler’s 3rd law

A

The amount of time a planet take to orbit the Sun is related to the size of its orbit; implies that a planet with a larger distance from the Sun, will take longer to orbit the Sun

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15
Q

What equation came out of Kepler’s 3rd law and what do the variables stand for

A

p^2 = a^3
a is the semimajor axis (half the diameter) and p is the time to complete orbit

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16
Q

What is Newton’s first law

A

Objects at rest tend to stay at rest while objects in motion tend to stay in motion

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17
Q

What are the vectors of velocity

A

Speed and direction

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18
Q

What is acceleration

A

speeding up/down or changing direction of velocity

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19
Q

What is force

A

anything that acts to change the velocity of an object

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20
Q

What is Newton’s second law

A

force = ma

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21
Q

What is Newton’s 3rd law

A

for any force, there is an equal and opposite reaction force

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22
Q

what is the equation for the momentum of an object

A

momentum (p) = M/v (mass divided by velocity)

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23
Q

How were Kepler’s 1st and 2nd law apply to orbiting objects

A

Found that both objects move in ellipses about a common center of mass that could be anywhere between the two objects

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24
Q

When an object is in orbit, what is the relationship between altitude and speed

A

When at higher altitude the object will slow down and vise versa

25
Q

What is escape velocity

A

The needed velocity to escape an object’s orbit

26
Q

What is gravitational potential energy

A

Stored energy when two objects are gravitationally attracted to each other

27
Q

How would escape velocity for an object at the top of Mt. Everest compare to the escape velocity for the same object at sea level

A

Escape velocity would be lower at sea level since there is a larger radius making the denominator of the equation larger

28
Q

How does the force of gravity from the moon affect the Earth

A

Water on the near side is pulled towards the Moon more than average while water on the far side is pulled towards the moon less than average

29
Q

How does the Sun affect the tides on Earth

A

Sun also causes tides on Earth that can augment or partially cancel the tides from the Moon

30
Q

What is a Roche limit

A

When an object get too close to its planet, the tidal forces will pull it apart

31
Q

What is an eclipse

A

When a celestial body can occasionally be interrupted by another celestial body temorarily getting in the way

32
Q

What is amplitude

A

magnitude of a wave

33
Q

What is wavelength

A

distance from crest to crest of a wave

34
Q

What is wave interference

A

When crests from one region combine with the crests of another to cause destructive or constructive interference

35
Q

Is light a wave or particle

A

Both. light acts like a particle on microscopic scales while it acts like a wave on macroscopic scales

36
Q

How does intensity of light change with distance

A

As you get farther out, the light spreads out into more area, so the amount per unit area decreases; gets less intense

37
Q

What causes temperature

A

motion of atoms/molecules

38
Q

Put the following in order of most hottest to least hottest: Orange, yellow, and red

A

Yellow, orange, red

39
Q

What does a high temperature imply

A

Higher energy photons since they are moving more and shorter wavelength since wavelength and energy have an inverse relationship

40
Q

Star Antares appears red while star spica is blue. Which star is hotter?

A

Star spica

41
Q

What is power

A

energy given off per unit of time

42
Q

What is luminosity

A

how many watts a star puts out

43
Q

What is a blueshift

A

As wavelengths decrease, they shift towards the blue end of the spectrum

44
Q

Waht is a redshift

A

When the source move away from you and the wavelength gets longer

45
Q

A green laser has a wavelength of ~510.0 nm. If we see a green laser coming from the Andromeda galaxy, it would have a wavelength of 509.5 nm. How fast is Andromeda moving relative to us?

A

See slide for answer

46
Q

What are the advantages and disadvantages of refractors

A

simple to construct and easy to clean but big lenses are hard to support, are expensive, can’t avoid defect in glass, and they absorb UV light

47
Q

What are the types of radiation wavelenghts in order of lowest to highest frequency

A

Radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma ray

48
Q

What are the benefits of using telescopes

A

Resolution (need an object to make a larger aperature), can only make so many observations with the naked eye, records what is being seen, humans are blind to most of the electromagnetic spectrum

49
Q

Telescope A has a mirrir of a certain diameter. Telescope B has a mirror with a diameter 3 times larger. How many times bigger is the light-gathering capability of telescope B?

A

9 times larger since light gathering capability depends on the area which depends on the square of the size of the mirror

50
Q

What is interferometry

A

Focusing individual mirrors on the same area to increase the aperature of the image

51
Q

What is aperture

A

the diameter of the lens/mirrror the telescope uses to collect light

52
Q

What is the use of infrared telescopes

A

anything that is colder than the sun emits a lot of IR radiation thus, allows us to see a lot more. Newly formed stars also emit in IR

53
Q

What is a PSR

A

Pulsar; extremely hot star near the end of it life cycle

54
Q

In 1996, astronomers discovered an icy object beyond Pluto, which was given the designation 1996 TL 66. It has a semimajor axis of 84 AU. What is its orbital period?

A

See study guide

55
Q

Why might an astronomer decide to install a diffraction grating at the focus of an optical telescope

A

Diffraction grating acts like a prism, it splitsthe light up by wavelength. They are used to identify chemical elements in stars, determine stellar temperature, measure doppler shift…

56
Q

What advantages are there to using a reflector telescope over refractor telescopes

A

no chromatic aberration, UV light is less absorbed in lenses, lenses are heavier than mirrors thus, harder to support since they have to be held by the edges

57
Q

When looking for a photon with the greatest energy what shift do you look for? largest frequency? largest wavelenght?

A

highest to lowest level, largest energy, and wavelength and energy are inverse so lowest energy

58
Q

How much energy an object emits is dependent on what

A

its size and temperature

Astronomy (4 decks)

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