Astronomy final exam study guide

What is the most accurate method for determining the distance to the Moon?

Laser Ranging

What can we infer about the Moon's composition based on its lower average density compared to Earth?

The Moon must contain less iron and heavy elements.

What are the dark, flat, roughly circular regions on the Moon called?

Maria

True or False: Laser-ranging can determine the distance to the Moon to an accuracy of a few centimeters.

True

True or False: The Moon rotates on its axis about once per week.

False

True or False: The Moon has a significant atmosphere.

False

True or False: The Moon has nighttime low temperatures of 900 K, well below the freezing point of water.

True

True or False: Large craters are formed frequently today on the surface of the Moon.

False

True or False: The Moon has an extensive iron core.

False

What are craters on the Moon primarily due to?

Meteoric impacts

Where might sheets of water ice exist on the Moon?

Polar regions

What was the lunar maria's dark, dense rock originally part of?

The lunar crust

What is the most likely scenario for the formation of the Moon?

A collision between Earth and a planet-sized object.

What conclusion can be drawn from the comparison of the Moon's and Earth's average densities?

The Earth has more iron and nickel.

Which fact supports the hypothesis that the surface features of the Moon did not change substantially over the past 3 billion years?

The Moon does not have an atmosphere.

What is the origin of regolith?

Rock crushed by impacts.

What is the probable origin of some mountain chains observed near the lunar maria?

They were formed by material pushed up by the impact that created the maria.

What do astronomers attribute the lack of atmosphere on the Moon to?

The low gravitational force of the Moon, which is too weak to keep gases from escaping.

What would an astronaut on the far side of the Moon be able to see?

Would not be able to see Earth.

What explains the fact that maria is uncommon on the far side of the Moon?

The crust on the far side is thicker than the near side; therefore molten rock could not break through.

Why do astronomers claim that the features on the Moon's surface are older than those observed on Earth?

The surface of the Earth is subject to water and wind erosion, which do not occur on the Moon.

Which statement about the lunar maria is not true?

The maria does not show signs of cratering.

Because of the Moon's synchronous rotation, how much of the Moon's surface can an observer on Earth see?

About 50%

How can the Moon's tidal interactions with the Earth affect the Earth's axial tilt?

They can stabilize it.

What phase of the Moon occurs simultaneously with the new 'Earth' phase as seen from the near side of the Moon?

Full

Where can regolith be found on the Moon?

Both highlands and maria.

What is true about the sunspot cycle?

The number of spots rises and falls approximately every 11 years.

What is the temperature at the Sun's core?

About 15,000,000 K.

What are the two main components of the Sun's atmosphere?

Photosphere and corona.

What part of the Sun has a temperature of 5,780 K?

Photosphere.

What part of the Sun has a temperature of 4,500 K?

Bottom of chromosphere.

What part of the Sun has a temperature of 1,000,000 K?

Corona.

Where on the Sun are spicules located?

Chromosphere.

Why is the Earth's density about 4 times larger than the Sun's density?

The Sun consists mainly of hydrogen and helium.

Where on the Sun are holes located?

Corona.

What is the average distance of the Earth to the Sun?

About 1.5 x 10^8 kilometers.

What is the approximate temperature of the Sun's surface?

About 6,000 K.

In the outer part of the Sun, just below the photosphere, how is energy transported?

Convection.

When does the solar corona become visible?

During a total solar eclipse.

What are sunspots?

Cooler regions on the photosphere.

What is the energy source of the Sun?

The energy source of the Sun is the fusion of hydrogen to helium.

What is true about the Sun's photosphere?

The Sun's photosphere has a temperature of 5780 K, has a granular appearance due to hot rising material, shows dark regions known as sunspots, and is the layer where material changes from opaque to transparent.

Which statement about solar neutrinos is not true?

Solar neutrinos carry electric charge (this statement is not true; they are electrically neutral).

Why does the proton-proton chain require high temperatures?

The proton-proton chain requires high temperatures because at high temperatures, protons have enough speed to overcome the electrical repulsion.

What explains the origin of solar flares?

Solar flares are brief eruptions of hot gas in the chromosphere resulting from the readjustment of highly twisted magnetic loops.

What happens in the convection zone of the Sun?

In the convection zone, hot gas rises and cool gas sinks.

What are the main regions of the solar atmosphere when traveling outward from the solar surface?

The main regions are the Chromosphere, Transition zone, and Corona.

What lies below the solar surface in order of increasing depth?

Below the solar surface, the order is Convection Zone, Radiative Zone, and Core.

What percentage of the Sun's composition is made up of the two most abundant elements?

The two most abundant elements in the Sun make up approximately 90% of its composition.

What is the average size of sunspots?

Sunspots are roughly 100,000 km on average.

How long do sunspots last on average?

Sunspots last on average about 11 years.

Where are sunspots usually found?

Sunspots are usually found above 30 degrees North and South of the Equator.

What is the temperature of the Sun at the equator and poles?

The Sun's temperature is about 6,000 K at the equator and 5,500 K at the poles.

Is there any other star within 1 parsec of the Sun?

False, there are no other stars within 1 parsec of the Sun.

Can parallax be used to measure stellar distances out to about 1000 parsecs?

True.

Do most stars have radii between 0.5 and 2 times the radius of the Sun?

True.

Are differences among stellar spectra mainly due to differences in composition?

True.

Do stars with very weak hydrogen lines in their spectra contain very little hydrogen?

True.

Are red giants very bright because they are extremely hot?

False, red giants are bright due to their large size, not necessarily their temperature.

Are the brightest stars visible in the night sky generally found in the upper part of the H-R diagram?

True.

What is the distance of a star that is 10 parsecs from the Sun in light years?

The distance of the star is 32.6 light years.

What is the surface temperature of a star that radiates most strongly in the infrared (about 1,000 nm)?

The surface temperature of the star is approximately 3,000 K.

How does the apparent brightness of a star vary with the star's distance from the Sun?

The apparent brightness is related to the distance by the inverse square law.

What can be concluded about two identical stars, X and Y, with apparent magnitudes 2 and 4?

Star X is much closer to the Sun than Star Y.

Which star appears brighter to an observer on Earth: Procyon with apparent magnitude 0.4 or Rigel with 0.1?

Rigel appears brighter to an observer on Earth.

What can be calculated knowing the luminosity and apparent brightness of a star?

Knowing the luminosity and apparent brightness allows calculation of the distance of the star.

Which of the following stars is hotter: A B star, F star, L star, or G star?

A B star is hotter than the others.

Which star is hotter than a K star but cooler than an F star?

A G star is hotter than a K star but cooler than an F star.

Which of the following is a main-sequence star hotter than the Sun?

An F type star is a main-sequence star hotter than the Sun.

What does the H-R diagram plot?

The H-R diagram plots stars according to their luminosity and temperature.

What does the absolute magnitude of a star indicate?

The absolute magnitude tells us how bright the star would appear if placed at a distance of 10 parsecs from the Sun.

Is a star with an apparent magnitude of 10 visible by the naked eye?

False, a star with an apparent magnitude of 10 is not visible by the naked eye.

Does the sequence OBAFGKM order stars in decreasing temperature and decreasing mass?

True.

What happens to spectral lines of a star approaching the Earth?

Spectral lines are shifted to shorter wavelengths.

What is a white dwarf star?

A stellar remnant that is composed mainly of carbon and oxygen and produces energy by fusion of hydrogen.

What is a brown dwarf star?

A star smaller than 0.1 solar mass that cannot compress its core enough to initiate hydrogen fusion.

Why do high mass stars have a short life on the main sequence?

Because high mass stars burn their hydrogen very fast.

How do most of the heavier elements up to iron form in the Universe?

By nucleosynthesis in the cores of massive stars.

Where do most of the elements heavier than iron form?

In supernova explosions.

What is hydrostatic equilibrium?

The balance between the internal pressure forcing out and gravity forcing in within a star.

Which main sequence star will not produce a planetary nebula?

An O type star.

What is the Chandrasekhar limit?

The largest mass a white dwarf can have.

What is the least amount of atoms required to form a star?

10^57 atoms.

What is the Schwarzschild radius of a black hole of 10 solar masses?

About 30 km.

How would replacing the Sun with a black hole of equal mass affect the planets?

The orbits of the planets would not be affected.

How do astronomers detect black holes?

From the fact that some binary stars have an invisible member.

Which statement about pulsars is incorrect?

They have a thin iron crust.

What is the ratio of a supermassive black hole compared to the galactic mass?

1/700th.

Which of the following objects spins faster?

A neutron star.

How many times per second do millisecond pulsars rotate?

About 1000 times per second.

Is it true that a black hole has an escape speed about half the speed of light?

False.

What is the force particle of electromagnetism?

Photon.

Which star remnant has the stronger magnetic field?

Magnetar.

Do neutron stars have mass smaller than the Chandrasekhar limit?

False.

Do quarks fall apart in the presence of a gluon field?

True.

What warps space according to general relativity?

Mass.

What classes are found inside fermionic matter?

Baryons, quarks, leptons, bosons, and gluons.

What is the diameter of a typical neutron star?

1-2 km.

How are neutron stars characterized?

By fast rotation rates and strong magnetic fields.

In which part of the electromagnetic spectrum were pulsars discovered?

Gamma Ray.