Transcript Wednesday, Oct. 1 - Department of Physics and Astronomy

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Phys 1810 Lecture 12:
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Planets: Use material in lecture as a guide for topics to
read about in text book on each planet.
Upcoming topics:
– Solar System Chapt 6
– Greenhouse effect P. 166-167, P. 231
– formation of the moon 8.8
– exoplanets Chapt 15
Topics include
– scale, objects
– terrestrial vs jovian
– planetary system formation including (differentiation)
– Mars
– Earth – climate change
– planetary system formation including differentiation
Please join us this week,
and the first Thursday of
every month, rain or shine.
Friends and family are
welcome too!
October 2 at 7:30 pm
Meet at Lockhart Planetarium
(University College Room 394)
Also this month:
Oct 1-30: An exhibit of astronomy images in
Degrees Café.
October 8: total lunar eclipse!
October 14: Astronomy in the restaurant – The
Tallest Poppy at 7:30 PM. A panel
presentation & opportunity for the public to ask
questions. Special guest Professor Ken
Freeman (Australian National University).
Topic: dark matter – The stuff that makes up
90% of the matter in the universe.
October 23: partial solar eclipse!
Solar System Overview: What does the class already know about the classical planets?
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• For each planet:
– revolve & rotate in the same
direction as other planets?
– primarily composed of rock or of
gas? # Earth Masses, # Earth radii
– small or large? (i.e. closer to Earth
size or Jupiter size?)
– in outer region or inner region of
solar system?
– hot or cold? surface T in Kelvin
– Lots of moons?
– Any other details are welcome 
(eg. Does it have rings? B field?)
Solar System Overview
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• The density in kg/m3
– 1000 for water; if less than this, floats in water.
– 2000-3000 for rocks; 8000 for iron
• Note 2nd last column & density of Earth.
• Ask yourself which planets have densities like rocks/iron? Float on water?
Tour of the Solar System
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Mercury
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Messenger: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Mercury
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Messenger: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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NASA’s Messenger Mission
• fly-bys until orbit in 2011
Mercury
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Messenger: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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• Colour-enhanced:
• Yellow -> volcanic activity
in the last billion years
Mercury
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Messenger: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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• Thin
atmosphere called
“exosphere”
• Tail created by wind from
sun  seasonal changes.
• Several possible
processes:
• vaporization of rocks
by impacts
• evaporation by
sunlight
summary
Mercury
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Due to tidal pull of sun on Mercury we
expect a synchronous orbit.
P_rotation: P_orbit
3:2 resonance
Mercury rotates 3 times for every 2 revolutions about sun.
Why? Kepler’s Law about sweeping
out equal areas.
Venus:
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Venus Express/European Space Agency
Ultraviolet Image
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Slow, retrograde rotation.
Venus Express/ESA
Tour of the Solar System: Venus
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Venus Express/ESA
• Similar to Earth: R~0.95 * Earth_R, M~ 0.85
* Earth_M.
• Atmosphere 90 *Earth’s; mostly CO2 bit of
N, water vapour, sulfuric acid.
• CO2 -- outgassing of volcanoes.
• T~750K  hottest planet in Solar System.
 Greenhouse effect.
summary
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A Day in
the Life
of Venus
Express
• Venus might have had plate tectonics,
& even an ocean of water
• ‘super-rotating’ atmosphere -- whips
around Venus in just 4 Earth-days,
much faster than 243 rotation about
its axis.
summary
Tour of the Solar System: Venus
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Venus Express/ESA
Vortex at South Pole of Venus
• A polar vortex is created by an area
of low air pressure which sits at the
rotation pole of a planet. This causes
air to spiral down from higher in the
atmosphere.
• vortex at both poles.
Earth
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Mars
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Mars Express/European Space Agency
Hebes Chasma
Rheasilvia
Olympus Mons
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Height of Olympus Mons on Mars: 25 km
Height of Rheasilvia on Vesta (asteroid): 22 km
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Jupiter
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Jupiter’s Giant Red Spot
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Jupiter
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New Horizons/NASA
IR image.
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Tour of the Solar System: Jupiter
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Jupiter emits more energy
than it receives from Sun
NOT because of nuclear
processes taking place
within its core.
Cassini-Huygens/NASA/ESA
• “mini”-sun: T higher than just due to
sunlight at 5 AU
• gravitational contraction when forming
heated interior -- heat is now leaking
outward
summary
Tour of the Solar System: Jupiter
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Cassini-Huygens/NASA/ESA
• Jupiter's moon Europa casting
shadow (left).
summary
Tour of the Solar System: Jupiter
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Cassini-Huygens/NASA/ESA
• Red Spot is a storm that is at least 300
years old. Its diameter is about 2 Earth
diameters.
summary
Tour of the Solar System: Jupiter
Voyager/NASA
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• limb (distorted by motion of
spacecraft)
• rings are orange lines.
Jupiter’s rings in IR
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Tour of the Solar System: Jupiter’s North Pole
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Cassini-Huygens/NASA/ESA
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UV filter:
Haze traces
molecules
called
hydrocarbons
(e.g. CH4
methane)
•
•
•
•
black area at the pole -- no presentable data
white circle marks 60 degrees latitude
region with a persistent aurora marked in blue.
Note a dark vortex forms.
Tour of the Solar System: Jupiter
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• Dark spot due to small comet or asteroid
plunging into Jupiter.
• Impact object size of several football fields.
• “Bruise” - diameter of Canada.
• Some of Jupiter’s moons --captured
comets.
Tour of the Solar System: Jupiter’s Io
summary
Galileo/NASA
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• Volcanic activity due to tidal forces
causing internal heat.
Tour of the Solar System: Jupiter’s Europa
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Galileo/NASA
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• Enhanced colour image.
• Ocean under ice crust.
• Cracks in ice crust may be sites for
microbes.
summary
Saturn
Cassini/NASA
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Saturn
Cassini/NASA
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Tour of the Solar System: Saturn
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Cassini-Huygens/NASA/ESA
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• About 10 AU
• M ~ 95 * Earth mass
• This is not an illustration but an image.
Tour of the Solar System: Saturn
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Cassini-Huygens/NASA/ESA
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Very thin optical ring system:
• Outer radius of last optical ring ` 8 Saturn
radii or 280,000 km.
• Thickness typically a few 100 m (up to 1km)
Tour of the Solar System: Saturn
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Cassini-Huygens/NASA/ESA
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• How did the rings form? Two possibilities.
1. Similar to a planetary disk formation but on a
smaller scale. (We’ll do planetary disk formation shortly.)
2. Tidal forces causing orbiting low density moons
to fragment.
Saturn’s Moon Enceladus
summary
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Other moon’s with
atmospheres:
- Enceladus
- Triton
- Io
- Titan
- Dione
3) Spewing ice plumes through (“blue”)
tiger stripes
 E ring
• has an atmosphere
Tour of the Solar System: Saturn
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Spitzer/NASA
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• Large Infra-red ring! (Moon Phoebe orbiting
within this ring.)
• diameter equivalent to 300 Saturns.
• ~ 20 Saturns for its vertical height.
• Too large for field of view of HST and too faint
in visual range for optical telescopes.
Tour of Solar System: Saturn
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• South pole vortex.
summary
Saturn’s North Pole Hexagonal Vortex
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• This can be created in the laboratory
Tour of Solar System: Saturn
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• South pole aurora.
summary
Tour of Solar System: Saturn’s Moon Titan.
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Cassini-Huygens/NASA/ESA
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UV in false color
• Atmosphere: Note upper layer of haze.
• Thick enough to have polar vortex.
• Seasonal changes due to tilt of spin axes.
Titan’s Atmosphere
summary
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Sound of
Huygens
Mission
descending
• Huygens Mission Landing Site:
the view from Huygens
Tour of Solar System: Saturn’s Moon Titan.
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Cassini-Huygens/NASA/ESA
Visible
+ IR
Ontario Lacus at
South Pole
• Ethane lake. Ethane created by
sunlight breaking apart methane.
• Only other solar system object
known to have liquid on the surface.
summary
Uranus
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Voyager2/NASA
“True” Colour
False Colour
Tour of the Solar System: Uranus
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Keck Observatory IR
Weather
• Rings
Neptune
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Voyager2/NASA
Tour of the Solar System: Neptune
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Visible +IR
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Voyager2/NASA
• Rings.
• Seasons due to inclination of
rotation axis to orbital plane.
Moon of Neptune: Triton
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• Triton has an atmosphere.
• possibly a Pluto-like object that Neptune
pulled into orbit.
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