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AS105 > EXAM 2 > Flashcards

EXAM 2 Flashcards

1
Q

Newton - what is light?

A

Light is particles, like bullets or grains of sand

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2
Q

Why are Prue’s glasses pink?

A

The glasses reflect pink light

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3
Q

Passing light through a prism causes light of a different color to ____ at different angles, creating a rainbow!

A

refract

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4
Q

Light behaves as a

A

particle and wave

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5
Q

_____ represents the wavelength of a photon

A

Color

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6
Q

blue light

A

400nm

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7
Q

green light

A

550nm

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8
Q

red light

A

650nm

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9
Q

light is an ___________ wave

A

electromagnetic

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10
Q

Speed

A

the rate at which the peaks of a wave move

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11
Q

Frequency

A

number of peaks per second that pass by

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12
Q

Speed of light

A

wavelength × frequency

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13
Q

Do all waves need a medium in which to travel?

A

Yes

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14
Q

Wiggling a charge creates

A

electromagnetic radiation: light!

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15
Q

Bluer photons have

A

higher energy, hotter

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16
Q

What kind of detector would be most efficient for observing a 15,000 K star?

A

ultraviolet

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17
Q

Why don’t you glow in the dark?

A

People only emit light with wavelengths our eyes cannot detect

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18
Q

At _____, you generate mostly infrared light that your eyes cannot see

A

300k

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19
Q

Say you see a feature in a spectrum at

656.3 nm. What are you seeing evidence of?

A

H (Hydrogen)

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20
Q

Hot, opaque core of star produces the

A

continuous spectrum

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21
Q

Cool, low-density atmosphere produces the

A

absorption lines

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22
Q

Is it possible to know if the red supergiant star Betelgeuse has more iron than the Sun?

A

Yes

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23
Q

How much iron do you think Betelgeuse has

compared to the Sun?

A

More

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24
Q

What happens to the position of the lines of hydrogen if you heat up a star?

A

They stay the same

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25
Q

What happens to the position of the lines of hydrogen if the star moves towards you?

A

They all move to the blue

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26
Q

Doppler Effect

A

changes the wavelength of a source in motion

27
Q

51 Pegasi B

A

“hot Jupiter,” a gas giant planet orbiting very close to its star

28
Q

What is the minimum amount of time an alien would need to monitor the Sun to find the Earth with the radial-velocity method?

A

1 year

29
Q

Biggest doppler shift

A

smallest distance

30
Q

Light Curve

A

derived from a time-lapse movie of how the brightness of an object changes with time

31
Q

As viewed from Earth, will Venus ever transit in front of the Sun?

A

Yes

32
Q

Kepler 10-b

A

discovered in 2011, was the first confirmed terrestrial (rocky) planet outside our Solar System

33
Q

Depth =

A

((radius of the planet)/(radius of the star))^2

34
Q

Why do astronomers want to look at as many stars as possible with space missions like Kepler or TESS?

A

Transits need special alignment, so are rare to detect

35
Q

Kepler

A

mission aimed at measuring the fraction of Sun-like stars with Earth-like planets.

36
Q

Kepler 16b

A

the first circumbinary planet - two sunsets

37
Q

estimating radius: starquakes

A

The larger the star’s radius, the longer the period of the pulsations.

38
Q

estimating radius: luminosity

A

Amount of energy a star radiates

39
Q

Apparent Brightness

A

Amount of starlight that reaches Earth

40
Q

How would the apparent brightness of Alpha Centauri change if it were the same size but 3 times further away?

A

1/9 as bright

41
Q

Stellar parallax

A

allows us to measure the distance to stars.

42
Q

How would the parallax of Star B, closer to Earth, compare to the parallax of Star A

A

Star B has a greater parallax

43
Q

Luminosity depends only on a star’s

A

radius and temperature

44
Q

A star’s intrinsic brightness is sensitive to

A

T^4

45
Q

How to measure star’s radius:

A

1) Measure its distance (parallax) 2) Measure its apparent
brightness to work out ( Count how many photons
we get compared to other stars) its luminosity 3) Measure its temperature (Measure how blue or red the star is)

46
Q

What do we learn from the transit method?

A

The planet’s orbital period, the planet’s radius, the planet’s orbital inclination

47
Q

Would you see transits if i = 0°?

A

No (orbits on plane so it never is moving towards Earth)

48
Q

What will happen to the transit if i = 89°?

A

The shape will always change

49
Q

Would you detect radial-velocity changes if i = 0°?

A

No

50
Q

What do we learn from the Doppler method?

A

Planet’s orbital period, planet’s eccentricity, planet’s minimum mass

51
Q

Kepler-10b transits its host star every

A

20.2 hour

52
Q

Kepler 10b was detected with the

A

radial velocity method and transit method

53
Q

What causes the dips in the Earth’s spectrum?

A

Molecules

54
Q

Can we directly take a spectrum of an exoplanet at any given time?

A

No, need a transit because it is very bright

55
Q

Visible light

A

400-700 nm

56
Q

Light travels through space at a speed that does not exceed

A

300,000 km/s

57
Q

Stars much hotter than the Sun give off most light in the

A

ultraviolet

58
Q

At 300k

A

you generate mostly infrared light that your eyes cannot see

59
Q

Electrons in atoms

A

are restricted to certain energy levels (quantized)

60
Q

How electrons in atoms emit photons

A

An electron is excited to an upper energy level with energy E3. It drops to a lower energy level with energy E2. A photon carries away the difference in energy, E3 – E2

61
Q

Kepler mission

A

stared at 150,000 stars for 4 years - transits are rare (we need to see the shadow), so need a big sample.
on average every star has at least 1 planet orbiting <300 days.

62
Q

Kepler findings

A

15 ± 13% of Sun-like stars host potentially habitable planets, stars with systems of at least 6 planets, exoplanets orbiting a star at least 10 billion years old, first Tatooine-like planet with two sunsets (orbiting 2 stars)

63
Q

From transit method, we get ____, from Doppler method, we get ______

A

radius, mass

64
Q

Search for molecules like _______ or ______ as biosignatures in exoplanet atmospheres

A

O2, Methane

AS105 (3 decks)

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