# AST1002

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90 degrees

waning phase

### f the Moon's orbit around Earth were a little larger, solar eclipses would be

more likely to be annular

Gemini

### In the Figure below (Figure 0.20A - Parallax), a smaller Earth would result in

a smaller parallax angle.

### How, and by roughly how much, would the length of the solar day change if Earth's rotation were suddenly to reverse direction?

A solar day would be approximately 8 minutes shorter than the current one.

### If you watch Polaris all night, what does it do?

Not much! It just sits there.

### When is the Earth closest to the Sun?

In the winter in the northern hemisphere.

### What causes Earth's seasons?

23.5° tilt of Earth's rotational axis

### The angle of parallax increases as

the baseline gets larger.

### Why don't we have solar and lunar eclipses every month?

ecause the Moon's orbit around Earth is tilted by about 5° out of the ecliptic.

1.496 × 108 km.

3000

### Are the constellations seasonal?

Yes. On a summer night many of the constellations you can see are different from the constellations you can see on a winter night. But there are some constellations you can see all year long.

### At what time of the year in the northern hemisphere will your shadow in sunlight at midday be shortest?

first day of summer, about June 21

### How long does it take light to travel a distance of one light year?

One year or about π×107 seconds.

### What is the unit that we use to measure distances in the solar system?

The astronomical unit or AU is very convenient.

### The most southern location on Earth where the Sun can be seen directly overhead at noon is called

the Tropic of Capricorn

### Mars, Jupiter, and Saturn show retrograde motion because

Earth moves faster in its orbit.

### Copernicus' important contribution to astronomy was

proposing a simpler model for the motions of planets in the solar system.

moons of Jupiter

### Newton's law of gravity states that the force between two objects

increases with mass.

wanderer

### In the geocentric model of the solar system developed by Ptolemy, the planets move

in circular epicycles while the centers of the epicycles move in circular orbits around the Earth.

### he major contribution of Tycho Brahe to the development of modern astronomy was

measuring planetary positions very accurately.

### epler's second law states that a planet moves fastest when it

is closest to the Sun.

### to which point in a planetary orbit does the word perihelion refer?

point closest to the Sun

### hich of the following sentences correctly states the significance of Galileo's observation that Jupiter has satellites (moons)?

The observation showed that bodies can orbit an object other than the Earth.

### Suppose that a planet of the same mass as the Earth were orbiting the Sun at a distance of 10 AU. The gravitational force on this planet due to the Sun would be

1/100 of the gravitational force the Sun exerts on the Earth.

### stronomers analyze starlight to determine a star's

motion, temp, composition, all of the above

3.1 m

### Rigel appears as a bright bluish star, whereas Betelgeuse appears as a bright reddish star. Rigel is

hotter than Betelgeuse.

### the light from a distant star is approaching you, you will observe

its spectral lines are shorter in wavelength.

### he wavelengths of emission lines produced by an element

are identical to its absorption lines.

### For lecture on "Waves", a sound wave can travel through ________.

molten rock, solid rocks

4 times

### visible wavelengths of electromagnetic radiation have a range of wavelengths of

400 nm to 700 nm.

### forms of light have what property in common? (Light in this case refers to the whole spectrum, not just the visible range.

All forms of light are electromagnetic radiation.

### What is the one fundamental difference between X rays and radio waves?

the wavelengths of X rays and radio waves are very different.

blue

### What changes would you expect to see in the resulting spectrum of emitted light from a piece of metal when it is heated slowly in an intense flame from 500 K to 1500 K?

he intensity of radiation would increase greatly, and the color would change from red through white to blue.

### An ideal blackbody in physics and astronomy is an object that

absorbs and emits electromagnetic radiation at all wavelengths.

### According to the Doppler effect

the wavelength of light is shifted to a shorter wavelength if the source of light is moving nearer to the observer.

### The Doppler effect is the change in the wavelength of light caused by the source

moving with respect to the observer.

### he dark absorption lines in the solar spectrum are caused by

a cooler layer of gas overlying the hot solar surface, which contains many elements, including hydrogen, helium, magnesium, calcium, and iron.

### Atoms in a low-density, hot gas (e.g., in a fluorescent lamp or a neon tube) emit a spectrum that is

a series of specific colors unique to the type of atom in the tube but fixed in position when the gas temperature changes.

### The main reason that most professional research telescopes are reflectors is that

mirrors produce sharper images than lenses do since there is no chromatic aberration.

### he PRIMARY reason professional observatories are built on the highest mountain tops is to

reduce atmospheric blurring

### the Spitzer Space Telescope is stationed far from Earth because

This infrared telescope actually does not orbit the Earth, but follows our planet around the Sun, reducing the heat interference from Earth

infrared light

4 times more

Twice as much.

### Seeing in astronomy is a measurement of

the image quality due to air stability.

### Resolution is improved by using

larger telescopes and shorter wavelengths.

### an advantage of CCDs over photographic film is

they don't require chemical development,digital data is easily store and transmitted, CCDs are more light sensitive than film, CCD images can be developed faster.
All of the above are true.

### Radio dishes are large in order to

improve angular resolution.

reducing atmospheric blurring using computer control.

### Radio telescopes are useful because

observations can be made day and night, radio waves are not blocked by interstellar dust, we can see objects that don't emit visible light, they can be linked to form interferometers.
Correct: All of the above are true.

### The Hubble Space Telescope (HST) offers sharper images than ground telescopes primarily because

HST orbits above the atmosphere.

### the light-gathering power of a telescope depends directly on the

area of its primary mirror or lens.

### What is the main reason for placing astronomical telescopes and detectors on satellites?

to get above the absorption in the Earth's atmosphere

### The major difference(s) between the terrestrial and jovian planets involve(s)

mass and density.

### The asteroid belt is evidence of

ancient material from the formation of the solar system.

### Pluto seems to be more similar to

the moons of jovian planets.

### What causes a meteor shower?

Earth runs into the debris of an old comet littering its orbit.

### Any theory of the origin of the solar system must explain all of these EXCEPT

the direction that planets orbit the Sun is opposite to the Sun's spin.

### The condensation sequence theory explains why

terrestrial planets are different from jovian planets.

### xtrasolar planets the size of Earth have NOT been seen yet with current techniques because

large planets orbiting near to their stars are more easily detected.

True

true

false

400k

### Strong evidence for the existence of planetary systems in the process of formation around other stars comes from

photographs and infrared observations of disks of dust.

### The Moon's internal structure is similar to Earth's, but the Moon lacks

a hydrosphere.
a magnetosphere.
an atmosphere.
Correct: It lacks all of the above

### The principal greenhouse gases in our present atmosphere are

water vapor and carbon dioxide.

### At what lunar phase would the variation between high and low tides be greatest?

both new and full moon

They are equal.

### he magnetic field of the Earth probably arises from what process or condition?

A dynamo effect due to the motion of the electrically conducting molten iron core.

### Without the greenhouse effect operating in our atmosphere,

Earth would have an average temperature of -23 degrees Celsius.

### The Moon's near side always faces Earth due to

Earth's tidal force.

### What are the two most abundant gases in the Earth's atmosphere

Nitrogen and Oxygen

### Why did Earth's earliest atmosphere, composed primarily of hydrogen and helium, not last long?

Hydrogen and helium are light gases, and they soon escaped into space.

### What is the distribution of maria on the Moon's surface?

Maria are largely confined to the hemisphere facing Earth; there is only one small mare on the distant side.

### How do the atmospheres of the Moon and Mercury compare?

Neither body has a permanent atmosphere.

### Mercury has extreme high and low temperatures between night and day because

it has no atmosphere to moderate temperatures over the globe.

venus

carbon dioxide

### enus' surface shows all of the following EXCEPT

many impact craters of all sizes.

### Venus and Mars probably evolved differently from Earth because

they orbit at different distances from the Sun.

### How does Mercury's rotation rate relate to its orbit around the Sun?

Its rotation rate is 2× as long as its year, due to tidal resonances.

### Venus' rotation once about its axis

takes longer than its orbit around the Sun.

carbon dioxide.

### Why are Mars's seasons more extreme than those of the Earth?

weather is driven by evaporation from the polar ice in its summer.
orbit is more eccentric than our almost circular one.
seas dried up long ago.
axial tilt is slightly more than our 23.5 degrees.
Correct: All of the above contribute to the huge barometric changes that Mars experiences.

### Why doesn't Venus have a magnetic field?

Its extremely slow rotation doesn't produce a significant dynamo effect.

### The craters on the Moon and on Mercury surfaces are due to

impacts from meteorites and asteroids.

### The surface temperature on Venus is

much higher than that on the surface of the Earth.

### Mercury can be seen easily from the Earth only

when Mercury is near the Sun, just after sunset or just before sunrise.

### the best images of the overall topology of Venus have been produced by

reflection of microwave and short radio wave radiation from the surface by an orbiting spacecraft.

### The most likely explanation for the retrograde rotation (rotation in a direction opposite that of most other planets) of Venus is the

impact of a massive object on it early in its history

Example: