Lec 2 Flashcards
(29 cards)
planets fall into 2 major categories
1) small, rocky terrestrial planets
-small in mass and size
-close to the Sun
-made of metal and rock
-few moons and no rings
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2) large, hydrogen rich jovian planets
-large mass and size
-FAR from sun
-made of He, H and H compounds
-rings and many moons
asteroids and comets that populate the solar system
Asteroids are made of metal and rock, and most orbit in the ASTEROID BELT b/w Mars and Jupiter
Comets are ice-rich, and many are found in KUIPER BELT beyond Neptune’s orbit
Even more comets orbit the Sun in the distant, spherical region called the Oort cloud, and only few plunge into inner solar system
Why does Mercury have an unusual rotation pattern?
Tidal forces from the sun have forced it into an unusual pattern with an 58.6 day rotation period
-meaning it rotates exactly 3 times for every 2 of its 87.9 day orbits of the sun
-this combo of rotation and orbit gives Mercury days and nights that last about 3 Earth MONTHS each
Mercury surface
-heavily cratered, like moon’s surface
-shows evidence of past geological activity (e.g. plains created by ancient lava flows)
-high density (indicates large iron core)
Venus
2nd planet from the Sun
-nearly identical to Earth
-rotates slowly on axis and in OPP direction of Earth (days and nights very long)
-extensive evidence of past volcanic activity
Extreme greenhouse effect bakes its surface to 470deg, trapping heat so it remains hot day AND night
-caused by CO2
Earth
-only planet in solar system with oxygen to breathe, ozone to shield surface from deadly solar UV and surface water
-first planet with a moon
Mars
-last of the 4 inner planets
-half of Earth’s size in diameter
-has 2 tiny moons: Phobos and Deimos
-freezing with ancient volcanoes
Jupiter
-must pass asteroid belt to get to it
-contains long-lived storm called Great Red Spot
-made primarily of H and He, has NO solid surface
-4 moons called Galilean moons
Saturn
-2nd largest planet
-mostly made of H and He, with NO solid surface
-famous for its rings
Uranus
-larger than Earth and made up of H, He and hydrogen compounds (H20, NH3)
-lacks solid surface
-entire system tipped on its side
-extreme axis tilt gives extreme seasonal variations
Neptune
-higher density makes it more massive
-has rings and many moons
-one moon called Triton, is the only large moon that orbits BWD (opp direction to neptune’s rotation)
pluto
-dwarf planet
–too small to qualify as official planets but large enough to be round in shape
Patterns of motion among large bodies
■ All planetary orbits are nearly circular and lie nearly in the same plane
■ All planets orbit the Sun in the same direction: counterclockwise as viewed from high above Earth’s North Pole
■ Most planets rotate in the same direction in which they orbit, with fairly small axis tilts. The Sun also rotates in this direction
■ Most of the solar system’s large moons share similar properties in their orbits around their planets, such as orbiting in their planet’s equatorial plane in the same direction as the planet rotates
terrestrial planets
Terrestrial means Earth-like
-4 planets of the inner solar system:
–Mercury, venus, earth and mars
-Small and dense
-Rocky surfaces with abundance of metals
-Few moons and no rings
jovian planets
Jovian means “jupiter-like”
-4 large planets of OUTER solar system: Jupiter, saturn, uranus, neptune
-larger in size and lower in average density
-have rings and many moons
-lack solid surfaces and made mostly of H, He and hydrogen compounds
sometimes called gas giants bc they are gases under earthly conditions
Kuiper belt
donut-shaped region beyond orbit of Neptune that contains icy objects
Oort cloud
2nd cometary region, farther frm sun and contains a trillion comets
-these comets have orbits randomly inclined to the ecliptic plane, giving the Oort cloud a roughly spherical shape
Correctly describe the shape of objects in the solar system
Shape and structure
The solar system is highly organized, not random.
All major planets orbit the Sun in nearly circular paths and lie in the same flat plane, called the ecliptic.
The system is shaped like a thin, rotating disk with the Sun at the center.
Correctly describe the major motions (orbits, rotation) of objects in the solar system
Major motions: orbits and rotation
Planetary orbits
All planets orbit the Sun counterclockwise (as viewed from above Earth’s North Pole)
Their orbits are nearly circular and lie in the same direction and plane.
The orbits follow a pattern that reflects how the solar system formed from a rotating disk of gas and dust.
Planetary rotation
Most planets rotate in the same direction as their orbit (counterclockwise).
Most planets have a small axis tilt, but:
Uranus rotates almost on its side.
Venus rotates backward (clockwise).
Moons
Most large moons orbit in the same direction as their planet’s rotation and lie close to the planet’s equatorial plane.
Types of objects and their motions
Terrestrial planets (mercury, venus, earth, mars)
Small, rocky, closer to the Sun.
Few or no moons, no rings.
Short orbital periods (days to years)
Jovian planets (Jupiter, saturn, uranus, neptune)
Large, gaseous, far from the Sun.
Many moons and ring systems.
Longer orbital periods (years to centuries).
Rotate quickly (e.g., Jupiter’s day is ~10 hours).
Asteroids and comets
Asteroids: Rocky, orbit mainly between Mars and Jupiter in the asteroid belt.
Comets: Icy, mostly in the Kuiper Belt and distant Oort Cloud.
Their orbits can be highly elliptical and inclined to the ecliptic plane.
Key properties of Jupiter
Largest planet, mostly H and He, strong magnetic field, many moons and faint rings
Its moon I0 is the most volcanically active body in the solar system
Jovian
key properties of saturn
Known for its spectacular rings, many moons, low density (less than water)
Moon titan has a thick atmosphere and liquid
methane lakes
Jovian
key properties of uranus
Composed of H compounds, pale blue, faint dark rings, many moons
Rotates on its side (98 deg tilt), leading to extreme seasons
Jovian
key properties of neptune
Similar to Uranus in size and composition, deep blue, large moon Triton
Triton orbits backward
Jovian
