ASTRO 0005

Which of the following has your "address" in the correct order?

you, earth, solar system, milky way, local group, local supercluster

Roughly how many stars are in the Milky Way Galaxy

100 billion

Which scientist played a major role in overturning the ancient idea of an Earth-centered universe and about when?

Copernicus, Kepler, and Galileo; about 400 years ago

What is an astronomical unit?

The average distance from Earth to the Sun

Which of the following statements about the celestial sphere is NOT true?

The "celestial sphere" is just another name for our universe

Which of the following statements about the celestial equator is true at all latitudes?

It represents an extension of Earth's equator onto the celestial sphere

What is the ecliptic?

The Sun's apparent path along the celestial sphere

Which of the following correctly describes the meridian in your sky?

A half-circle extending from your horizon due north, through your zenith, to your horizon due south

How many arcseconds are in 1 degree?

3600

What is a circumpolar star?

A star that always remains above your horizon

Which of the following is not a phase of the Moon?

half moon

If the Moon is setting at 6 am the phase of the moon must be

full

Which of the following never goes in retrograde motion

The Sun

How did Eratosthenes estimate the size of Earth in 240 BC?

By comparing the maximum altitude of the Sun in two cities at different latitudes

Why did Ptolemy have the planets orbiting Earth on "circles upon circles" in his model of the universe?

to explain the fact that planets sometimes appear to move westward, rather than eastward, relative to the stars in our sky

Where was the Sun in Ptolemy's model of the universe?

Between the orbits of Venus and Mars

the controversial book of this famous person, published in 1543 (the year of his death), suggested that Earth and other planets orbit the Sun.

Copernicus

He discovered that the orbits of planets are ellipses

Kepler

He discovered that Jupiter has moons

Galileo

From Kepler's third law, an asteroid with an orbital period of 8 years lies at an average distance from the sun equal to

4 astronomical units

What is meant by a hypothesis?

an explanation for a phenomenon that makes a prediction

If your mass is 60 kg on Earth, what would your mass be on the Moon?

60 kg

What would happen if the Space Shuttle were launched with a speed greater than Earth's escape velocity?

It would travel away from Earth into the solar system

The movement of a pool ball, rolling on a table at constant velocity, is an example of

Newton's first law of motion

The force of gravity is an inverse square law. This means that, if you double the distance between two large masses, the gravitational force between them

weakens by a factor of 4

According to the universal law of gravitation, if you double the masses of both attracting object, then the gravitational force between them will

increase by a factor of 4

The mass of jupiter can be calculated by

measuring the orbital period and distance of one of jupiter's moons

At which lunar phase are tides most pronounced

both new and full moons

An atom in an excited state contains more of what type of energy that the same atom in the ground state

electric potential energy

if a material is highly opaque, then it

absorbs most light

the wavelength of a wave is

the distance between two adjacent peaks of the wave

how are wavelength, frequency, and energy related for photons of light?

longer wavelength means lower frequency and lower energy

From lowest energy to highest energy, which of the following correctly order the different categories of electromagnetic radiation?

radio, infrared, visible light, ultraviolet, x rays, gamma rays

When an atom loses an electron, it becomes

ionized

when an electron in an atom goes from a higher energy state to a lower energy state, the atom

emits a photon of a specific frequency

If two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits

81 times more energy

The spectra of most galaxies show redshifts. This means that their spectral lines

have wavelengths that are longer than normal

From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers. The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?

The star is moving away from us

Telescopes operating at this wavelength must be cooled to observe faint astronomical objects

extreme infrared

Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes?

The two stars will look like a single point of light

Which of the following statements best describes the two principal advantages of telescopes over eyes?

Telescopes can collect far more light with far better angular resolution

Which of the following is NOT an advantage of the Hubble space Telescope over ground-based telescopes?

It is closer to the stars

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?

radio

The core of the Sun is

hotter and denser than the surface

What two forces are balanced in what we call gravitational equilibrium?

Outward pressure and gravity

What is the average temperature of the surface of the Sun?

6,000 K

Which layer of the Sun do we normally see?

photosphere

At the center of the Sun, fusion converts hydrogen into

helium, energy, and neutrinos

What is granulation in the Sun?

the bubbling pattern on the photosphere produced by the underlying convection

Approximately, what basic composition are all stars born with?

three quarters hydrogen, one quarter helium, no more than 2 percent heavier elements

Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?

mass they are formed with

a star's luminosity is the

total amount of light that the star radiates each second

If the distance between us and a star is doubled, with everything else remaining the same, the luminosity

remains the same, but the apparent brightness is decreased by a factor of four

Suppose that you measure the parallax angle for a particular star to be 0.5 arcsecond. The distance to this star is

2 parsecs

The spectral sequence sorts stars according to

surface temperature

Which of the following terms is given to a pair of stars that appear to change position in the sky, indicating that they are orbiting one another?

visual binary

On a Herzsprung-Russel diagram, where would we find stars that are cool and dim?

lower right

On a Hertzsprung-Russel diagram, where on the main sequence would we find stars that have the greatest mass?

upper left

The spectral sequence in order of decreasing temperature is

OBAFGKM

Which of the following best describes the axes of a Hertzsprung-Russel diagram?

surface temperature on the horizontal axis and luminosity on the vertical axis

The typical size of an interstellar dust grain is

1 micrometer

If you wanted to observe a molecular cloud, in what wavelength of light would you most likely observe?

infrared

What is the likely reason that we cannot find an examples of the first generation stars?

The first generation stars were all very massive and exploded as a supernova

What happens to the surface temperature and luminosity when gravity first assembles a protostar from a collapsing cloud?

Its surface temperature and luminosity increase

What is the smallest mass a newborn star can have?

80 times the mass of Jupiter

What happens when a star exhausts its core hydrogen supply?

Its core contracts, but its outer layers expand and the star becomes bigger and brighter

Compared to the star it evolved from, a red giant is

cooler and brighter

How many helium nuclei fuse together when making carbon?

3

What is a planetary nebula?

the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star

Which of the following sequences correctly describes the stages of life for a low-mass star

protostar, main-sequence, red giant, white dwarf

What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?

The core contracts and becomes a black hole

After a supernova event, what is left behind?

either a neutron star or a black hole

why is supernova 1987A particularly important to astronomers?

it was the nearest supernova detected in nearly 400 years

White dwarfs are so called because

they are both very hot and very small

What kind of pressure supports a white dwarf?

electron degeneracy pressure

How does a 1.2-solar-mass white dwarf compare to a 1.0-solar-mass white dwarf?

It has a smaller radius

Which of the following is closest in size (radius) to a white dwarf?

Earth

Which of the following is closest in size (radius) to a neutron star?

a city

From a theoretical standpoint, what is a pulsar?

a rapidly rotating neutron star

What is the basic definition of a black hole?

any object from which the escape velocity exceeds the speed of light

Which of the following statement about black holes is NOT true?

If the sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into the black hole

If you were to come back to our solar system in 6 billion years, what might you expect to find?

a white dwarf

What is the diameter of the disk of the Milky way?

100,000 light-years

Which of the following comprise the oldest members of the milky way?

globular cluster

What produces the 21-cm line that we use to map out the milky way galaxy?

atomic hydrogen

approximately how long does it take the Sun to orbit the Milky Way Galaxy?

230 million years

Which constellation lies in the direction toward the galactic center?

Sagittarius

Compared to spiral galaxies, elliptical galaxies are

redder and rounder

The disk component of a spiral galaxy includes which of the following parts?

spiral arms

Why are Cepheid variables important?

Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as “standard candles” for distance measurements

What is Hubble’s law

The recession velocity of a galaxy is directly proportional to its distance from us

What is the most accurate way to determine the distance to a very distant irregular galaxy?

using a white-dwarf supernova as a standard candle

Based on current estimates of the value of Hubble’s constant, how old is the universe?

between 12 and 16 billion years old

I observe a galaxy that is 100 million light-years away: what do I see?

the light from the galaxy as it was 100 million years ago and it is redshifted

Why should galaxy collisions have been more common in the past than they are today?

Galaxies were closer together in the past because the universe was smaller

What is a quasar?

the extremely bright center of a distant galaxy, thought to be powered by a massive black hole

What is meant by “dark energy”?

the agent causing the universal expansion to accelerate

The distribution of the dark matter in a spiral galaxy is

approximately spherical and about the same size as the galaxy halo

If all the “dark matter” in the Universe were to be, somehow, instantaneously removed, which of the following would NOT happen?

The Solar system wold fly apart

What is the evidence for an accelerating universe?

White-dwarf supernovae are slightly dimmer than expected for a coasting universe