Astronomy flashcards 2
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 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°?
3,600
what is a circumpolar star?
A star that always remain above your horizon
which of the following is not a phase of the moon?
half moon
If the moon is setting at 6 A.M., 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 B.C.?
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 westwards, 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
8 astronomical units
what is meant by a hypothesis?
an explanation for a phenomenon that makes a prediction.
if your mass is 60kg 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 a 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 objects, then the gravitational force between them will
increase by a factor of 4
how are wavelengths, frequency, and energy-related to photons of light?
longer wavelength means lower frequency and lower energy.
From the lowest energy to the highest energy, which of the following correctly orders the different categories of electromagnetic radiation?
radio, infrared, visible light, ultraviolet, x-rays, gamma rays
the mass of Jupiter can be calculated by
measuring the orbital period and distance of once Jupiter’s moons.
if a material is highly opaque, then it
absorbs most light
At which lunar phases are tides most pronounced (the highest tides)?
both new and full moons
An atom is an excited state contains more of what type of energy than the same atom in the ground state?
electric potential energy
the wavelength of a wave is
the distance between two adjacent peaks of the wave
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 redshift. this means that their spectral lines
have wavelengths that are longer than normal
telescopes operating at this wavelength must be cooled to observe faint astronomical objects.
extreme infrared
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.
which of the following statements best describes the two principal advantages of a telescope over eyes?
telescope can collect far more light with far better angular resolution.
Suppose the angular separation of to stars is smaller than the angular resolution of your eyes. how will the star appear to your eyes?
the two stars will look like a single point of light
what two forces are balanced in what we call gravitational equilibrium?
outward pressure and gravity
which of the following is not an advantage of the Hubble space telescope over ground-based telescopes?
it is closer to the stars.
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
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 is granulation in the sun?
another name for the way sunspots look on the surface of the sun
approximately, what basic compositions are all stars born with?
3 quarter hydrogen, 1 quarter helium, and 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
the total amount of light that the star radiates over its entire lifetime.
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 4
suppose that you measure the parallax angle for a particular star to be 0.5 arcseconds. 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 stats that appear to change position in the sky, indicating that they are orbiting one another?
visual binary
on a Hertzsprung-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 any examples of first-generation stars?
The first-generation stars were all very massive and exploded as supernovas
what happens to the surface temperature and luminosity when gravity first assembles a protostar from a collapsing could?
its surface temperature and luminosity increases
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 contacts, but the outer layer expands 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 has 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 dwarfs
