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Astronomy 💫 > Chap 1 > Flashcards

Chap 1 Flashcards

1
Q

Smallest to largest units?

A
  1. Kilometer (~.6 miles) (meter ~ yard) (1,000 meters)
  2. Astronomical Unit (Earth to Sun)
  3. Light Year (Distance light will travel in a year)
  4. Parsec (3.3 Ly Distance to star with a parallax of 1 arcsecond)
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2
Q

Order of planets in our galaxy?

A

Mercury, Venus, Earth, Mars, (asteroid belt), Jupiter, Saturn, Uranus, Neptune

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3
Q

Smallest to largest planets?

A

Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn, Jupiter

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4
Q

Prefixes?

A

10^3 kilo, 10^6 mega (1 million), 10^9 giga, 10^12 tera

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5
Q

1,000,000 Ly in sci notation? Prefix?

A

1.0 x 10 ^6 Mega

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6
Q

How far away are the nearest stars? How long would it take for light to travel from us to them?

A

~4 light years, ~4 years

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7
Q

Define light year.

A

The distance that light will travel in a year.

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8
Q

How many light years across is our galaxy?

A

~200 x 10^3 Ly across

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9
Q

Next nearest star?

A

Proxima Centauri 4.2 Ly (A Centauri A, A Centauri B)

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10
Q

Rough amount of stars in the galaxy?

A

(Vary in sizes but) ~ 200 x 10^9 stars

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11
Q

Voyager 1 send out date?

A

September 5th!! 1977 (became most distant probe)

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12
Q

Voyager 2 send out date?

A

August 20 1977 (was first! and slightly slower)

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13
Q

Disadvantages to sending out similar probes?

A

Data transfer times, at the mercy of space, would never return to Earth.

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14
Q

Individual galaxies are how many light years across?

A

100,000s of light years across.

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15
Q

Galaxy clusters are how many light years across?

A

Millions (1,000,000s) of light years across.

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16
Q

10^3 Ly with correct number of zeroes?

A

10,000 Ly

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17
Q

10^6 km with correct number of zeroes?

A

10,000,000 km

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18
Q

1,000 in sci notation?

A

10 x 10^2 OR 1 x 10^3

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19
Q

Web space telescope?

A

Infrared, sees heat, different colors.

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20
Q

Hubble space telescope?

A

Sees what you see, adds lens flares.

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21
Q

How many years for radiation (Cosmic Microwave Background) to reach us from universe edge?

A

13.7 x 10^9 years

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22
Q

How many light years across is the known universe?

A

~92.94 x 10^9 light years across.

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23
Q

“Speed limit” of the universe?

A

~300,000 kilometers per second (186,000 miles per second)

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24
Q

Only non-natural star color?

A

Green!

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25
Q

Zenith?

A

The point directly ABOVE an observer.

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26
Q

Nadir?

A

The point directly BELOW an observer.

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27
Q

What is the Celestial Sphere/What does it represent?

A

An imaginary sphere which the constellations are projected onto, made by extending the North and South poles and the equator infinitely. It represents what one could see in the night sky based off of their position on Earth.

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28
Q

What constellations could one not see in Erie?

A

The Southern Cross can only be seen in the Southern hemisphere, while Erie is in the North.

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29
Q

Define the equator.

A

Imaginary line around the center of the Earth.

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30
Q

Define the ecliptic.

A

The path of the sun in the sky over the course of a year. (Technically the plane of Earth’s orbit.)

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31
Q

Define equinox.

A

When the sun crosses over the Earth’s equator. (Vernal = start of spring/bottom, Autumnal = start of Autumn/top.)

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32
Q

Define solstice.

A

Points in the year when Earth’s axial tilt towards the sun is at its maximum.

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33
Q

Summer v.s. Winter solstices?

A

Winter = NORTH hemisphere is oriented AWAY from the sun.
Summer = SOUTH hemisphere is oriented TOWARDS the sun.

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34
Q

Why is it colder in the Northern hemisphere during winter?

A

During the winter solstice, Earth’s axial tilt is at its maximum, with the Northern hemisphere tilting away from the sun, resulting in the sun’s rays having longer to travel to reach Earth’s surface. (Energy is spread out over a larger area in winter.)

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35
Q

What are the 2 main astronomical coordinate systems?

A

Altitude and Azimuth (Alt-Az), Right Ascension and Declination (RA-Dec).

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36
Q

Explain Alt-Az.

A

Altitude is the angle of the object above the horizon. Azimuth is the angle from the North Pole.

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37
Q

Explain RA-Dec.

A

Right Ascension is the angle measured East from the Vernal equinox (ecliptic meets equator, measured in hrs, mins, secs but still an angle: 24 hrs = 360º, 1 hr = 15º). Declination is the angle North or South from the Vernal Equinox (0º at equator, 90º at N-Pole, -90º at S-Pole).

38
Q

How are Alt-Az and RA-Dec different from each other/any advantages to one over the other?

A

While Alt-Az can change quickly over time, RA-Dec is based off the Vernal equinox, which is stationary. RA is also used to time the position of objects. Alt-Az depends heavily on where one is, since it includes an angle based off of one’s horizon, however Alt-Az can be easier to calculate.

39
Q

Define a Circumpolar constellation and give examples.

A

Circumpolar constellations never rise or set, They can either be seen year-round or never depending on where one is on the Earth. Ursa Major + Minor, Draco, Cassiopeia, Cepheus, Cameleopardalis.

40
Q

All (non-circumpolar) objects…

A

Rise East, set West.

41
Q

Example of a constellation only seen in the winter months?

A

Orion (Can tell it’s not circumpolar due to all of the different names it has gotten from different cultures around the world.)

42
Q

How did ancient people use the sky to tell time?

A

Used to tell time on a larger scale of months or seasons. They used constellations, based on the times they could be seen prominently in the sky. (NOT circumpolar constellations!)

43
Q

Renaissance scientists used which group of people’s names while formalizing the names of the objects in the sky?

A

The Greeks. (Myths.)

44
Q

How many official constellations exist according to the International Astronomical Union.

A

88

45
Q

What is the “Big Dipper”?

A

An Asterism (NOT a constellation) and a part of Ursa Major. It is easy to point out but informal- the same goes for the “Little Dipper” with Ursa Minor.

46
Q

Explain the effect of Precession.

A

The effect of constellations visibly changing over time (1,000s of years). Due to the ‘wobbling’ movement of Earth’s axis, Earth’s North Pole precesses through a complete cycle about every 26,000 years. (Changes North star, currently Polaris.)

47
Q

Are constellations just stars grouped together physically?

A

NO! Constellations can be made up of galaxies, nebulae, novae, etc, and are only grouped together visually, in reality, stars could have far different depths in space from each other.

48
Q

What constellations fall on the ecliptic?

A

The Zodiac constellations.

49
Q

Red supergiant near Orion?

A

Betelgeuese

50
Q

Effect of precession on the position of stars in the sky?

A

As Earth rotates and precesses, the constellations that can be seen and where changes with it.

51
Q

What is the effect of proper motion?

A

Proper motion is the stars moving around the galaxy at 300km/sec. Due to this, stars can change their positions over time, affecting their appearance.

52
Q

What is relative motion’s effect on the stars?

A

Due to our vantage point on earth, though all stars move at the same speed, some appear to be moving faster than others. (Closer = faster [high velocity], farther = slower [lower velocity].)

53
Q

Ancient Sumerian astrological work?

A

Divided the sky in 360º, Gudea Cylinders in 2125 BC.

54
Q

Babylonian astrological work?

A

1st written evidence noting periodic changes in the sky (1959 BC), tablets with long-term observations (Venus!).

55
Q

Ancient Egyptian astrological work?

A

Noted their own figures in the sky, made star-clocks with 36 decans (groups of stars) (6 hours short per year), determined length of year based on rise/set of objects, accepted calendar at the time was solar not star based, 40 years solar was 10 days ahead of star.

56
Q

Ancient Greek astrological work?

A

Renamed constellations with their own mythology (similar acheivements to Babylonians and Egyptians).

57
Q

What word is “Planet” derived from?

A

Ancient Greek, “Planetai” meaning “Wanderer” because they didn’t follow the same paths as the stars.

58
Q

How can Mars be identified from a background star?

A

Planets, especially Mars, move differently than stars, Mara also has a retrograde motion where it seems to make a loop shape.

59
Q

List the 3 different models of the solar system that existed simultaneously.

A
  1. Earth-centered (Geo-centric)
  2. Sun-centered (Helio-centric)
  3. Tycho-Brahe’s Model (Geo/Helio-centric mix)
60
Q

Explain the Geo-centric model.

A

Incorrect, older model. Places Earth at the center of the solar system/universe with other objects revolving around it.

61
Q

Explain the Helio-centric model.

A

Correct. The sun is at the center of our solar system, everything else moves (us included).

62
Q

Explain Tycho Brahe’s model.

A

Also incorrect. States that Earth is unmoving at the center, with the sun revolving around it, and everything else moves around the sun.

63
Q

What evidence did Galileo present to suggest that the Helio-centric model is correct?

A

Galileo saw that Venus’ phases were similar to that of the Moon, disproving the Geo-centric model of the solar system which, if true, would result in Venus’ phases being only dark or light.

64
Q

Explain retrograde motion.

A

Planets usually move Eastward relative to stars (like sun). Planets appear to move irregularly due to their and the Earth’s progress. (Earth “looks back” at Mars.)

65
Q

Which scientist’s publication of a scientific work on the Helio-centric model caused controversy?

A

Copernicus published “De Revolutionibus Orbium Colelestium” simply stated the Helio-centric solar system model with proof but was suppressed due to the controversy it sparked.

66
Q

Did Galileo invent the first telescope?

A

No. “First man to point a telescope at the sky.” (Started by cheating his way through the stock market. Also found moon mountains and sunspots.)

67
Q

Why did the observation of the phases of Venus suggest the Geo-centric model was incorrect?

A

Venus is a bright inner planet- it orbiting the sun explains its phases similar to that of the moon, instead of just being light or dark like if it orbited Earth.

68
Q

Explain the effect of Parallax.

A

A celestial object can look different, or as if it is in a different place due to where the observer is on Earth. Points extremely far apart will seem to have different directions.

69
Q

Why is it difficult to measure the effect of stellar parallax?

A

It cannot be truly seen with the naked eye. Most stars are too far to get an accurate measurement and it is also difficult due to the effects of Earth’s atmosphere.

70
Q

Even after the Helio-centric model was accepted, the planetary positions still did not quite match the mathematical predictions. Why?

A

They assumed the planets’ orbits were circular but they are actually ellipses.

71
Q

Tell me some weird facts about Tycho Brahe.

A

He loved the Geo-centric model, teacher/colleague to Johannes Kepler (kinda hated each other), artificial gold nose (lost his real one in a duel over math), very paranoid, pet moose.

72
Q

Ptolemy?

A

Geo-centric, astrologer, incorrect but very advanced, “epicycles” explained retrograde motions, predicted patterns (ptolemaic).

73
Q

Copernicus re-popularized what?

A

The Helio-centric model originally proposed by Aristarchus (~300 BC) and provided proof.

74
Q

First published work of telescope observations?

A

Siderius Nuncius - Galileo

75
Q

Can we see both sides of the moon over time?

A

No. The near side is what we can see and the far side (dark side) is never visible. (Synchronized with Earth.)

76
Q

Explain the moon’s rotation.

A

The time it takes the moon to complete 1 orbit is almost the same as it takes to turn once on its axis. The moon does rotate on its axis!! It just keeps moving as it does.

77
Q

Moon’s size change?

A

The moon changes its apparent size in the sky based on its distance from the Earth by ~10%

78
Q

Explain the lunar orbit.

A

The moon orbits the Earth in 27.3 days (because Earth is also orbiting the sun), counterclockwise. But it returns to the same position in the sky every 29.5 days, which is why there is around a month for moon phases.

79
Q

Why does the moon glow?

A

It reflects light from the sun.

80
Q

What is the Terminator (not the robot)?

A

The delineation between light and dark on the moon from its phases.

81
Q

Waxing moons?

A

Visible in afternoon/evening, more full + rises later, GROWING.

82
Q

Waning moons?

A

Visible in late night/morning, reduces + sets later, SHRINKING.

83
Q

Briefly describe the phases of the moon.

A

New moon (can’t see it), waxing crescent, 1st quarter, Gibbous phases (“asymmetrically swollen”), full moon, waning phases.

84
Q

Are the phases of the moon the Earth creating shadows on it?

A

No! Its orbit is tilted (~5° inclined to ecliptic plane). The lunar phases are the parts of the moon reflecting light based on what part of the moon is facing the sun.

85
Q

Lunar motion relative to the stars?

A

The moon moves ~13° per night

86
Q

Explain a lunar eclipse.

A

SUN –> EARTH –> MOON
Always occurs on the full moon. About every year, now the Earth casts a shadow. Can be penumbral (imperfectly aligned), partial, or total.

87
Q

Explain a solar eclipse.

A

SUN –> MOON –> EARTH
Always occurs on the new moon.
Total: moon completely obscures the sun. Annular: moon and sun in line (moon is smaller than sun). Hybrid: Eclipse is total at some locations, annular at others. Partial: moon partially obscures sun.

88
Q

What is Bailey’s Bead?

A

The sunlight that shines through mountains on the edge of the moon.

89
Q

Is the moon moving away from Earth?

A

Yes, at ~3.8 cm per year. (Someday, in the distant future, all solar eclipses will be annular.)

90
Q

Why are lunar eclipses red?

A

The only sunlight reaching the moon must travel through Earth’s polluted atmosphere.

91
Q

How does one safely observe a solar eclipse?

A

ONLY AT TOTALITY. Glasses with ISO symbol, welder’s glass, a solar filtered telescope, or if it’s being projected.

92
Q

One of the conditions for an eclipse.

A

The moon must be near one of the 2 points in its orbit where it crosses the ecliptic plane (its nodes [plane of Earth’s orbit]).

Astronomy 💫 (2 decks)

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