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YOU CAN WEIGH JUPITER
AST 1022L
RELATIVE SIZES OF THE PLANETS
DISTANCE SCALES OF THE SOLAR SYSTEM
If the Earth were ~1 cm across:• The Sun would be ~1.5 m across and ~150 m away• The Moon would orbit Earth ~30 cm away• Jupiter would be ~15 cm across and orbit the Sun at a
distance of ~5 city blocks (750-800 m away)
PORTRAIT OF JUPITER
• More massive than other 7 planets combined
• Comprised mostly of H & He
• >60 moons
• Great Red Spot alone is nearly 3x Earth’s diameter & has existed at least as long as Jupiter has beenobserved
GALILEAN MOONS
• 4 major moons of Jupiter are:
• Io (Jupiter-I),
• Europa (Jupiter-II),
• Ganymede (Jupiter-III), &
• Callisto (Jupiter-IV)
• First 3 orbit in a 1-2-4 resonance (for every 4 orbits Io completes, Europa completes 2 and Ganymede completes 1)
THE GALILEAN MOONSFirst objects ever observed that clearly did not orbit Earth one of the first arguments against the geocentric (Earth-centered) model of the universe
SO HOW DO YOU WEIGH A PLANET?
KEPLER'S LAWS OF PLANETARY MOTION
• 1st Law: A planet orbits in an ellipse with the Sun at one focus.
• 2nd Law: A line from the planet to the Sun will “sweep out” equal areas in equal times
KEPLER'S 3RD LAW (ALSO APPLIES TO PLANET-MOON SYSTEMS!)
*
* With T in years, a in AU and M in Solar Masses (M⨀)
Remember: T = Period, which is sometimes given as P (like on your data sheet)
Original form:Original Form
Newton’s Correction:
Simplification for M>>m:
SINE FUNCTION REVIEW
SINE FUNCTION REVIEW CONT.When viewing the orbital plane edge on, plotting the positions of one body orbiting another as a function of time produces a sine wave (as you will see in your own plots)
LAB PROCEDURES
1. You & a partner will observe 1 of Jupiter's Moons in a simulation.
2. Set your observation intervals to times appropriate for your Moon: 3 hours for Io, 5 hours for Europa, 10 hours for Ganymede, or 22 hours for Callisto. These times were chosen so the given Moon completes at least 1 orbit within about 20 data points.
• Your starting date can be arbitrary, but the hour must be set to 0
3. Record date, time, & position in Jupiter Diameters. The computer will give you position in terms of East & West, which you should record as Negative (-) and Positive (+) respectively. E.g.:
• X = 3.12W should be recorded as +3.12
• X = 1.41E should be recorded as -1.41
Note: You will see the same number without the E/W distinction output elsewhere as R. Ignore that one.
LAB PROCEDURES CONT.:
• Plot distance (in Jovian diameters or JD) vs. decimal days on provided graph paper
• Scale your axes appropriately – don’t squeeze everything to one side or you’ll have a hard time measuring amplitude & period!
• Note that X=0 in the middle, not at the bottom
• Answer questions on pages 8.9 through 8.11
• Distance & time conversion factors are given on your worksheets
FOR NEXT WEEK:
• Read “Measuring the Hubble Constant” (#10 in the manual)
• Dual Moon/Deep Sky Night-Lab Makeup on Tuesday Nov. 8th – starting at 7:30 PM sharp!