Astro 3

UCLA

If Venus has an angular diameter of 30 arcseconds, how does this compare with the angular diameter of the full moon? Compared to the moon, Venus is about-

1/60 as large

What is the range of possible values for Right Ascension?

0 to 23 hours

The mean distance from the earth to the sun is 384,400 km. This can be written as-

3\.844 x 10^5km

If the moon rises at 6pm tonight, then tomorrow it will rise at-

7pm

The altitude of the Celestial Pole at your location is equal to your-

latitude

The moon subtends an angle of 30 arcminutes as seen from Earth. This angle is-

**all of these**

More than 60 arc seconds

hald a degree

less than one radian

The star alpha Centauri will return to exactly the same position in an observer’s sky in what time period?

23hr 56min

The direction of motion of the moon in the sky, against the background of stars, is-

always west to east

What is the zodiac?

The set of constellations through which the elliptical passes

When the moon is directly opposite the sun in the sky, its phase is-

full

When is Polaris at noon? Assume you are in LA.

33 degrees altitude 0 azimuth

Without some indication of uncertainty a scientific data point is useless.

True

A light year is defined as the-

Distance traveled by light in one year

About when is a full moon seen near the western horizon?

Sunrise

How long is the interval from full moon to full moon?

29 days

What is an ecliptic?

The sun’s yearly path on the celestial sphere

What is the interval from full moon to full moon called?

Synodic month

When a solar eclipse occurs, these are two different shadows, one being smaller and darker than the other. What is the name for the smaller shadow?

umbra

You are at a place where all the stars are circumpolar. What is your latitude?

90 degrees

Which of the following is the most difficult problem to solve when doing a statistical study of a sample population?

systematic error, or biases

According to Newton’s laws of motion and gravity. Mercury goes around the sun because-

a force acts on it, directed toward the sun.

Copernicus’ model for the solar system-

placed the sun at the center, but retained the idea of epicycles

For residents of Mars, which planets would always be found near the sun in the sky?

Mercury, Venus, Earth

From Kelper’s first law, we know that-

the distance of Earth from the sun is not constant

From Kepler’s second law, we know that-

the earth orbits the sun more quickly ar some times of year than others

Galileo discovered which of the following?

The phases of Venus

If the altitude of an artificial satellite that has been in synchronous orbit around the earth (geosynchronous) is boosted to twice the distance of its original orbit, its new period will be-

2\.8 days

If in a violent moment, you kick a wall, your foot will hurt. What physical principle is behind your aching foot?

Newton’s 3rd law

The 17th century astronomer who kept a continuous and accurate record of the positions of the sun, moon and planets was-

Tycho Brache

The fact that more massive objects require more force to get moving is described by-

Newton’s 2nd law

The model of Copernicus predicted planetary positions________ the Ptolemaic model

\-to about the same accuracy as-

The moon’s mass is 0.02 times the Earth’s mass. The gravitational force exerted by the moon on the earth is therefore- times the gravitational force exerted by the Earth on the moon.

1

The scientist who formulated three laws of planetary motion by analyzing precise data on the planets in the sky was-

Johannes Kepler

What is inertia, as defined by Newton?

The tendency of an object to remain at rest in uniform motion in a straight line unless acted upon by a force.

What was a major advantage of the Copernican model of the solar system over the Ptolemaic model?

It provided a natural expiation of retrograde motion of the planets.

When a planet, in its orbits, is closest to the sun, it-

moves more quickly than average

Which of the following is an example of acceleration?

A dime falling out of your pocket

Which of the following is **NOT** a fundamental force of nature?

inertia

Which of the following most closely expressed the principle of “Occam’s Razor”?

The theory requiring the fewest number of assumptions is the preferred explanation.

Which of the following was **NOT** a telescopic discovery made by Galileo?

phases of Uranus

While on the moon, the Apollo astronauts demonstrated Galileo’s Leaning Tower experiment by dropping a feather and a hammer. They reached the ground at the same time because-

the gravitational acceleration of each object is the same

Who proposed the first geocentric planetary model that was used for more than a thousand years?

Ptolemy

What are Newton’s 3 laws of motion?

1) Inertial law- a a body at rest or in uniform motion in a straight line remains in that state unless acted upon by a force

2) Force law- the change in a body’s velocity due to an applied force is in the same direction as the force and proportional to it, but it is inversely proportional to the body’s mass

3) Recreational law- for every applied force, a force is equal size but opposite direction results.

What are Kelper’s laws?

1) Planetary orbits are ellipses, with the sun at the focus

2) Planets move equal areas and equal times

3) period^2= C x semimajor axis^3

Newton’s 3 laws hold for the 4 fundamental forces which are?

1) Gravity (weakest force)

2) Electromagnism

3) Weak force

4) Strong force

A telescope’s ability to distinguish different sources of light is referred to as its-

resolving power

Electromagnetic radiation penetrates the earth’s atmosphere in what portions of the spectrum?

visible & radio , a little infrared

In which spectral region does the sun emit most of its energy?

visible

Light behaves like a-

both a wave and a particle

Light is a radiant form of energy that travels through pace in the form of fluctuating-

electric and magnetic fields

Photons in which portrait of the spectrum carry the least energy?

radio

The speed of light is-

300,000 k/ms

Viewed through a spectroscope, what kind of spectrum does a hot solid show?

continuous

What determines the color of the Great Nebula in Orion?

is the wavelength corresponding to the energy difference between the 3rd and 2nd energy levels of the hydrogen atom

What distinguishes the elements, i.e., hydrogen from helium, etc?

The number of protons in the atom

What is the dominant color of the Great Nebula in Orion?

red

What is the relation between wavelength & frequency? Frequency is-

Inversely proportional to wavelength

What property of light is responsible for the rainbow caused by the dispersion of light by the grooves on a DVD?

diffraction

Which has the higher surface temperature, a red star or a blue star?

Blue star

Which of the following would be a wavelength of an AM radio wave?

400 meters

If a light source is moving toward you at a speed close to the speed of light it will appear____ than it really is.

bluer

The Stefan-Boltzmann law says that the total energy radiated every second by a square meter of blackbody goes as the ____ power of the temperature of the blackbody

fourth

The earth’s atmosphere interferes with astronomical observations because

**all of the above**

it makes stars twinkle

some wavelengths are absorbed by the atmosphere

weather may make some observations impossible

The most important reason that astronomers build bigger telescopes is-

light-gathering power

The speed of light is 299,800,000 m/sec. This can be written as

2\.999 x 10^8 m/s

Viewed through a spectroscope, what kind of spectrum does a star show?

dark line

What is the correct ordering of optical colors, from longest to shortest wavelength (longest’ shortest)

red orange yellow green blue indigo violet

What property of light is responsible for how eyeglasses work?

refraction

Which is true of light?

**All of the above**

light behaves like a wave

light behaves like a particle

light is traveling electromagnetic force-field

The light property on which radio interferometers are based is-

diffraction

The most abundant element in the sun is

hydrogen

The type of spectrum you would observe from a hot solid or very dense gas is a-

gamma ray

Why is grass green in daylight?

the grass reflects green light but absorbs other colors

Imagine the sun to be about the size of a tennis ball in the center of the Inverted Fountain. Which of the following best describes the size and distance of planet Earth on the same scale?

Earth is about 1/2 the size of a ball point pen tip and would orbit at the edge of the Inverted Fountain

The technique called Adaptive Optics is used to correct for:

Blurred images caused by air turbulence above the telescope

If we imagine the entire history of the universe (13.8 billion yers) compressed into one year (12 months, 365 days), then the Earth was formed about-

About September 1st

Why does the earth exhibit seasonal changes?

The rotation axis of the Earth is tilted on its axis by 23.5 degrees from perpendicular, relative to the ecliptic plane

Use Kepler’s 3rd law to find (approximately) the orbital period og asteroid Ceres, which is 3 AU from the sun. \[Kepler’s 3rd law is p^2= a^3\]

**5 years**

A= 3 AU

P^2 = 3^3

P^2 = 27

5 x 5 = 25 is close to 27 , so the period must be 5 years

Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40) present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solicited. How old is the rock?

**3.75 billion years**

Half life is the time it takes for something to decay by 50% and that time never changes.

So in this case we start off with 80 micrograms of potassium-40, in a half life, it drops to 40. In 2 half lives, it drops to 20. And in 3, it drops to 10 micrograms. So the time required to reach 10 micrograms from 80 is 3 half-lives.

3 x 1.25 billion years= 3.75 billion years

From the **shortest** wavelength (highest energy) to the **longest** wavelength, what is the correct ordering of these regions of the electromagnetic spectrum?

Gamma rays, X-rays, Ultra violet, Visible light, Infrared, Radio

G R U V I R

Measuring the Doppler shift of an emission or absorption line in the spectrum of a star from its expected laboratory wavelength enables astronomers to determine the-

Velocity along the line of sight

Telescope efficiency depends on the area of the primary mirror. The faintest objects seen by a 30m diameter telescope are therefore _____ dimmer than the faintest objects seen by a 10m telescope.

**9 time**

Recall that area is proportional to the square of the diameter.

(30/10)^3 = 3^3 = 9

We can see things that are 9 times fainter in the 30m telescope than in the 10m telescope

In our Solar System, among the terrestrial planets, Earth and Venus have active geology, but Mars and Mercury do not. What is the correct explanation for this?

**The Earth and Venus are more massive and are able to retain their internal heat of formation and from radioactive decay, which drives geology.**

\
For terrestrial planets, greater mass means greater retention of the internal heat of formation and radioactive decay. Mars has volcanoes that are no longer active and has 1/10 the mass of Earth; Mars is essentially geologically dead.

Earth and Venus are both about the same mass and have retained the heat needed to drive geology in the from of volcanoes, etc.

According to our present theory of the solar system formation, which of the following best explains why the nebula ended up with a disk shape as it collapsed?

It flattened as a natural consequence of collisions between the particles in the nebula

According to Newton’s Law of Gravity, if you double the distance between two planets, the force of gravity between them is _____.

1/4th the original value

When we take a spectrum of an astronomical source, we often see dark lines at particular wavelengths in the spectrum. Which of the following is **NOT** true about these dark lines?

The dark lines can be used to measure the redshift of the source, which gives us the speed perpendicular to the line of sight.

Which of the following best describes how the Greenhouse effect works?

A planet’s surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.

The major constituent of the Martian atmosphere is

carbon dioxide

The most likely theory of the formation of Earth’s moon is that it

formed from a collision of Earth with a Mars-sized object

What are the two main constituents of Earth’s atmosphere?

O2 and N2

What caused the scarps on Mercury?

cooling of the planet & shrinking of the crust

What gas provides most of the greenhouse effect on Earth?

water vapor (H20)

What is one way that astronomers use to estimate the age of a planetary (or moon) surface?

Counting craters

What is the albedo of the Earth, approximately?

30%

What is the cause of plate tectonic motion on Earth?

Convection in the upper mantle

What is the most distant planet from the sun?

Neptune

Which is the LEAST likely type of planet to have an atmosphere?

small, high temperature

We are able to study the surface of Venus by bouncing _____ off the surface.

radio waves

What happens to the energy that the ground absorbs in the form of visible sunlight?

It is re-emitted upward in the form of infrared light

Which of the following provides evidence that water once flowed on Mars?

runoff & outflow channels