Astronomy 104 Final
Terms in this set (128)
What causes Jupiter and Saturn to have larger radii at their equator than at their poles?
they spin fast
How does the light-gathering power of a 4 m telescope compare to that of 2 m telescope?
it is 4 times as much
Which of the following choices is produced when white light is shined through a cool gas:
an absorption spectrum
when sunlight is passed through a spectroscope an absorption spectrum is observed because the Sun
has a hot interior that shines through cooler low density gas
Recent Radar observations of Mercury have suggested that
Mercury may have ice on a part of its surface
Why is it relatively difficult to observe Mercury from Earth?
because it is a small object and always appears close to the Sun in the sky
In a physical system in which there is rotation what happens to the rotation rate when the mass of the systems condenses toward the center of rotation?
Which type of electromagnetic radiation must be observed using a space-based telescope?
Neptune's predominantly blue appearance is caused by
absorption of the red end of the spectrum of sunlight by methane in its atmosphere
Mean temperatures in Europe during the Maunder minimum, when virtually no sunspots were seen between 1645 and 1715, were
lower than average
Much of the mass of our Galaxy appears to be in the form of "dark matter", which can be detected at present because
its gravitational pull affects orbital motion in the Galaxy
By measuring the motion of the small moon around Saturn we can find the approximate mass of
Two objects of different mass are dropped from the same height from a window. Ignoring air resistance, they have the same
When we determine the angular resolution of an interferometric array of radio telescopes using the formula Θ=𝛌/D, the variable D stands for
separation between the telescopes
The advantage of Hubble telescope compared to the ground based ones arises from
absence of atmospheric interference
A blackbody emits visible light. As it gets hotter, it becomes _______ and ________.
more luminous, bluer
A black car left in the sunlight becomes hotter than a white car left in the sunlight under the same conditions because
the white car reflects more sunlight than the black car
Doppler shifts are typically measured when
a gas with emission or absorption lines is moving away from the observer
Who developed the first reflecting astronomical telescope?
Why was adaptive optics developed?
to compensate for image distortion by the Earth atmosphere
The main reason for building large optical telescopes (e.g. 10 m) on the Earth surface is
to collect more light from faint objects
Kepler's third law can be described in which of the following ways?
The larger the orbit, the longer it takes for the planet to complete one revolution
In which country did Galileo make his astronomical discoveries?
How many forces need to be applied to a body in empty space to keep it moving with a constant velocity?
If the mass of the Sun were doubled, the gravitational force on Jupiter due to the Sun would
be twice its present value
If the radius of the Sun were doubled, the gravitational force on Mars due to the Sun would
be the same
How does angular resolution for a given diameter of telescope depend upon wavelength?
Angular resolution worsens as the wavelength increases.
Which of the following situations will most closely exhibit the characteristics of a perfect blackbody, as defined by a physicist?
a small hole in a hollow steel sphere
a geocentric model of the solar system.
Galileo's observations of the sky with his telescope included
the fact that Venus showed phases, similar to those of the Moon
Eclipses do not happen all the time because
the orbit of the Moon around the Earth is inclined slightly to the plane in which the Earth's orbit around the Sun lies
Jupiter is about 5 times farther from the Sun than the Earth is. About how long is Jupiter's year? (very approximately)
11 Earth years
As a new star evolves from cool dust and gas into a hot star, the peak wavelength of its spectrum of electromagnetic radiation will
The light from an object gets redshifted due to
its motion away from us
Which of the following is produced when warm gas is seen by itself:
an emission spectrum
A high mountaintop such as Mauna Kea in Hawaii is a good site for an infrared observatory because it is
above most of the moisture in the Earth's atmosphere
What is the main reason for placing astronomical telescopes and detectors on satellites?
to get above the absorption in the Earth atmosphere
Most of the mountains on the Earth have been produced by
tectonic plates colliding as they move
The early phases of planetary formation into protoplanets are characterized by
accretion of small particles by gravitational attraction and collisions
Two satellites are in circular orbits 1000 km above Earth's surface. One satellite is 500 kg and the other is 1000 kg. Which satellite has the larger orbital velocity?
They have the same orbital velocity
The birthplace of the Sun and planets is thought to have been
in cool gas and dust clouds
How was Neptune discovered?
by a careful application of Newton's laws to the motion of other planets
What are the most abundant gases in the atmosphere of Uranus?
methane and water
Particles in Saturn's main ring are made of (or covered with)
An AU is the distance between
Sun and Earth
A rocket that is accelerated by the force from the ejection of hot gases represents an example of which physical law, originally stated by Newton?
His third law of motion, concerning action and reaction forces
The cores of Jupiter and Saturn are
hot rock and iron of Earth size
If the temperature of an object were halved, the wavelength where it emits the most amount of radiation will be
2 times longer
Which of the following are you least likely to find in an asteroid
There are very few craters on the surface of Venus compared to the surface of Mercury because
lava flows have destroyed most of the craters
The rotational periods of Jupiter, Saturn, Uranus and Neptune are
about 10 to 20 hours
Detailed observations of Jupiter's rotation suggest that
it is not a rigid object, because equatorial regions rotate faster than polar regions
Jupiter's satellite Europa is believed to be made up of
a large rocky core covered by icy ocean
The structure of Callisto is thought to be
a thick ice crust and a slushy mantle of ice and water over a core of rock
How does the orbital period of particles moving round in the rings of
squared period is proportional to the distance cubed
What does Uranus look like from space?
blue-green and featureless
What are most abundant gases in the atmosphere of Uranus?
methane and water
What does Neptune look like from space?
blue-green with white, high-altitude clouds and dark storms
The asteroid belt is believed by most astronomers to be composed of
rocky debris left over from the formation of solar system
The ionized gas tail of a comet is always aligned with
the comet-sun line
A tail of a comet
is longest when the comet is closest to the Sun
The Tunguska explosion in Siberia in 1908, which had an explosive power of several hundred kilotons of explosives, was probably caused by
a small stony asteroid of 80m across, disintegrating explosively in the atmosphere before hitting the ground
Where in the solar system would you look for liquid hydrogen?
in the deep interiors of Jupiter and Saturn
The brown ovals seen in Jupiter atmosphere are
vortices of a similar nature to the Great Red Spot
The reason for the slightly flattened or oblate shape of Jupiter is
its rapid rotation
A solar eclipse can occur only when
the Moon comes between the Earth and the Sun
The epicycle, in the Greek planetary model, is
the small circle through which the planet moves, as the center of this circle orbits the Earth
Retrograde motion of a planet when viewed from Earth is caused by
the relative motions of Earth and planet
Which of the following objects cannot transit (pass in front of) the Sun when viewed from Earth?
Nicolaus Copernicus was the first person to
develop a rigorous model for a Sun-centered solar system
Acceleration of a body is its rate of change
An accelerating body must
have a changing velocity
The careful description of the velocity of a moving object at a particular time requires that one defines
the speed and the direction of the object
Suppose two asteroids are located at the same distance from the Sun. One asteroid had twice the mass of the other. According to Newton's law of gravitation
the more massive asteroid feels twice the force that the other does
Kepler's second law states that a planet moves fastest when it
is closest to the Sun
It is thought that terrestrial planets have dense iron cores because
in earlier molten sates, the heavy elements sank and lighter materials floated to the surface
Continental drift on the Earth is a result of
large scale circulation of partly molten or plastic rock in the Earth's interior
Which of the following situations is not acceptable orbital path for a body gravitationally bound to the Sun?
a parabolic path, beginning at the center of the Galaxy
What changes do you expect to see in the resulting spectrum of emitted light from a piece of metal when it is heated slowly in a flame from 500K to 1500K?
intensity of radiation would increase greatly, and its color would change from red through white to blue
What will happen with the gravitational force between the Sun and the Earth, if the Sun collapses into 1 solar mass black hole
the force will stay the same
Suppose the Sun suddenly collapsed in on itself, dropping to one quarter of its current radius. How big would the escape velocity from the surface be, compared to its current value?
2 times bigger
Astronauts inside International Space Station appear weightless because
both the space station and the astronauts are orbiting the Earth, therefore, the astronauts appear weightless because both objects are falling together towards the Earth
Pluto has a density that is roughly equal to two times that of
Where are asteroids found?
between Mars and Jupiter
Most asteroids are
very small (<1 km).
The most straightforward way to determine the mass of an asteroid is if it has
The nucleus of the typical comet is approximately _________ in size.
When a comet comes close to the Sun, its volatile ice sublimates and transforms directly from the solid to _________ phase.
Why does the dust tail separate from the ion tail?
Dust particles are more massive than ions, so their accelerations are less
Which type of meteorite is most commonly found on Earth?
A large meteor shower will often occur once a year because
Earth passes through the debris left behind by a specific comet.
Antarctica is the best hunting ground for meteorites for all of the following reasons except
more meteorites fall there than on other locations on Earth.
Meteorites contain clues to all of the following except
changes in the rate of cratering in the early Solar System.
Which of the following likely helps replenish the zodiacal dust in the vicinity of Earth the most?
In 1994, dozens of fragments of Comet Shoemaker-Levy 9 collided with
Assume that we discover a new moon of Jupiter. It orbits Jupiter at a large distance
and in the opposite direction that Jupiter rotates. It is much smaller than most of Jupiter's other moons and has a density close to that of Earth rocks. Therefore, this moon is most likely
an irregular moon that is most likely a captured asteroid.
How does the geological activity on Io compare to the activity on other moons?
It is very active on a regular basis.
Io has the most volcanic activity in the Solar System because
its interior is tidally heated as it orbits around Jupiter.
Which of the following moons is thought to have a vast ocean of water beneath its frozen surface?
How do particles from the moon Enceladus wind up in Saturn's E ring?
Water geysers erupt from the surface and expel them into space.
How do astronomers take such detailed, close-up pictures of ring systems?
They send satellites to the outer planets to take pictures for us.
Which giant planets have rings?
All of them
Which of the following planets has the most complex and conspicuous ring system?
Which of the following is not a way to renew particles in a ring system?
a planet's gravity drawing particles from the nearby interstellar medium
Why do the giant planets have the largest share of moons in the solar system?
Being the most massive planets in the solar system, they were able to gather more material to form moons than the terrestrial planets
improved the geocentric models by including epicycles
Devised a heliocentric (Sun-centered) model in which everything, including the Earth, revolves around the Sun
1) Found sunspots
2) Found craters on the moon
3) Discovered four moons of Jupiter
4) Observed the rings of Saturn
5) Observed that Venus passed through all phases, just like the moon
Using Tycho Brahe's data, discovered that planets do not move in circles around the Sun, rather, they follow ellipses with the Sun located at one of the two foci
Kepler's THIRD Law
The amount of time a planet takes to orbit the Sun (its period) P is related to its orbit's size, a, by
P^2 = a^3
P = Time to complete orbit
a = Semimajor axis
Kepler's FIRST Law
Planets move in elliptical orbits with the Sun at one focus of the ellipse
Kepler's SECOND Law
Planets move faster when near the Sun, and slower when farther from the Sun
Newton's First Law
A ball rolling along a flat, frictionless surface will keep going in the same direction at the same speed, unless something pushes or pulls on it
Newton's Second Law
The force (F) acting on an object equals the product of its acceleration (a) and its mass (m)
F = m x a
Newton's Third Law
When two bodies interact, they create equal and opposite forces on each other
If one skateboarder has more mass than the other, the same push will send the smaller person off at a higher speed, and the larger one off in the opposite direction at a smaller speed
Orbital velocity equation:
Escape velocity equation:
Light moves at ___________ in a vacuum
Light is a wave of combined electricity and magnetism, called an
When viewed through a cloud of gas, a continuous spectrum will have
The hotter an object is, the more _________ and ________ it is.
luminous and bluer
Dispersion of light is a problem in refracting telescopes, as the focal planet will be at a slightly different location for each wavelength of light
What wavelengths are / aren't absorbed by Earth's atmosphere?
Visible, radio and some infrared wavelengths are not absorbed readily by the atmosphere.
Gamma Rays, X-rays, and UV photons are absorbed
measure the amount of atmospheric turbulence with lasers, and then adjust the mirrors in their telescopes with tiny motors to eliminate the effect
What causes the "twinkling" effect of stars?
Cool patches of air in the atmosphere, causing incoming light to refract
Larger apertures (openings light can pass through) have _________________, and therefore _______________ than smaller apertures
less diffraction, higher resolution
larger particles (> 100 m in size)
asteroids and comets are today's remaining planetesimals