Astronomy 2 Flashcards
Where are the asteroids located?
Most asteroids have orbits between the orbits of Mars and Jupiter, but there are gaps caused by resonances with Jupiter.
Only the few largest asteroids are found to be spherical. Why is this?
Self-gravity for the most massive asteroids was sufficient to pull them to this shape during their early history.
A meteoroid is the name for a solid particle that
is drifting around in space.
Interplanetary material
falls on Earth at the rate of almost a hundred tons per day, mostly as cosmic dust.
Most comet nuclei are believed to be
chunks of dirty ice left over from the formation of the solar system.
A comet’s tail points
away from the Sun regardless of the comet’s motion.
The orbits of comets are
randomly oriented in the solar system and can extend far beyond the orbit of Pluto.
What is the Kuiper belt?
a relatively flat distribution of objects in the plane of the ecliptic, extending from around the orbit of Pluto out to about 50 AU from the Sun
The Oort cloud is
an approximately spherical distribution of comets centered on the Sun, extending out to about 50,000 AU.
A meteor shower occurs when
Earth passes through a swarm of dust particles in space.
How was Uranus discovered?
by accident, by an astronomer conducting a sky survey
Neptune was discovered by
the careful application of Newton’s laws to the motion of other planets.
The major planet whose spin axis lies almost in its orbital plane is
Uranus
What gives Uranus its blue-green coloration?
absorption of the red and yellow sunlight by methane gas
The Great Dark Spot on Neptune
disappeared sometime between the Voyager 2 flyby and when the Hubble Space Telescope photographed Neptune in 1994.
How do the densities of Jupiter, Saturn, Uranus, and Neptune compare?
Uranus and Neptune are more dense than Jupiter or Saturn.
In what way do Uranus and Neptune differ from Jupiter and Saturn?
Hydrogen and helium make up a smaller fraction of the total mass of Uranus and Neptune.
How were the rings of Neptune first discovered?
occultation of a star as the rings moved in front of it
Triton, the giant moon of Neptune, differs from all other major moons of planets in that
it orbits in a retrograde way, opposite to the planet’s rotation.
What future awaits Triton, the largest satellite of Neptune?
tidal breakup as it slowly spirals closer to Neptune
The four giant moons of Jupiter were discovered by
Galileo.
Which satellite of Jupiter is volcanically active?
Io
Io would probably be less active geologically if
its orbit were circular.
The most active volcanic object in the solar system is
Io, the inner Galilean moon of Jupiter.
Jupiter’s magnetic field is caused by
the planet’s rapid rotation coupled with liquid metallic hydrogen in its interior.
All of the following exist on Titan except
liquid water on the surface.
(Rain, Nitrogen vapor and clouds=there)
The largest satellite (moon) in our planetary system is
Ganymede, a moon of Jupiter.
Titan is Saturn’s largest satellite. It is unusual among all the planetary moons because of its
dense atmosphere.
Extensive volcanic activity observed on Jupiter’s satellite Io is caused by
tidal stresses from Jupiter and the other Galilean moons.
Which of the planets fits the following description: “a solid, cool surface, with occasional dust clouds and a thin CO2 atmosphere”?
Mars
Venus appears to be very bright in our skies at certain times because
it is relatively close to the Sun, Earth is close to it, and it is covered by very reflective clouds.
Craters on Mercury appear to have been produced by
impacts from objects early in the planet’s history.
Phobos and Deimos are moons of which planet?
Mars
The clouds in the atmosphere of Venus consist primarily of
droplets of H2SO4 or sulfuric acid.
The most common surface features on Venus are
volcanoes and lava flows.
Hot-spot volcanism is a process that
produces gigantic volcanoes on Venus and Mars but produces chains of smaller volcanoes on Earth (e.g., the Hawaiian Islands).
The internal structure of Mercury is a
dense iron core taking up almost half of the volume of the planet and a rocky mantle surrounding the core.
A major feature of the atmosphere of Mars is
occasional strong winds and dust storms.
The polar caps on Mars are most likely made up of
water and CO2 ices.
The rotation period of the Moon on its axis with respect to space (its absolute rotation) is
27.3 days, the sidereal revolution period.
The Moon has
no measurable atmosphere or liquid water.
Maria are
ancient lava floodplains.
The mountain ranges on the Moon are
the walls of craters caused by impacts of large objects early in the geological history of the Moon.
How many times have human beings landed on the Moon?
6
The age of Moon rocks has been determined primarily by what method?
measurements of radioactive decay products
How quickly is the Moon spiraling away from Earth?
a few centimeters per year
One distinct difference between Earth and its neighboring planets, Venus and Mars, is
the presence of
liquid water on its surface and water molecules chemically locked into rocks.
Earth’s mantle is composed largely of what chemical materials?
silicon-rich rocks and minerals
Approximately how many tectonic plates make up Earth’s surface?
~10
What are the Van Allen belts?
Regions of high-energy charged particles in Earth’s magnetosphere.
The major layers of Earth’s atmosphere from the surface upward in correct order are
troposphere, stratosphere, mesosphere, thermosphere.
At the present time, the energy of the Sun is generated
in its central core only, by fusion of hydrogen nuclei.
The total time that the Sun will spend converting hydrogen to helium in its core is
about 10 billion years (1010 years).
The phrase “’hydrostatic equilibrium”’ in the Sun refers to the
balance of gravity inward and gas pressure outward.
Just outside the radiation zone lies the
convection zone.
From the center outward, the order of the layers or parts of the Sun is
radiative zone, convection zone, photosphere, chromosphere, corona.
What is the photosphere of the Sun?
the visible “surface” of the Sun
Granulation on the surface of the Sun is caused by
convective currents carrying heat from beneath the surface.
What is the corona on the Sun?
the Sun’s outer atmosphere
What is the solar wind?
the Sun’s outer atmosphere streaming out into space
At the present time, how many extrasolar planets have had confirmed discoveries?
thousands
What is the astrometric method used in searches for planets orbiting stars other than the Sun?
a search for tiny wobbles in the position of the star due to the gravitational pull of a planet orbiting around it
