(1) Distinguish between:
(a) a star and a planet - A star is big enough that the pressure in the interior is enough for nuclear reactions inside - which make the star glow intensely - they make their own like. Planets are too small for nuclear reactions - you see them because they reflected sunlight.
(b) a planet and a satellite - Satellites orbit planets. Planets orbit the Sun.
(c) a moon and the Moon - The Moon is the moon of the Earth.

(2) Which planets were not detected until after the telescope was invented? When was each planet discovered? - Uranus (1781), Neptune (1846) and Pluto (1930).

(3) Below is a table of days of the week in different languages. Note how they relate to the Sun, Moon and the 5 planets that can be seen with the naked eye. Do you know of any other languages where this relationship holds? Is this a coincidence? Many other languages have the days of the week named after the Sun, Moon and planets. I suspect it is not a coincidence - do you?

(4) Look at the masses of planets. For comparison, mass of the Sun is 1.99 x 10³⁰ kg.

(a) which is the most massive planet? Jupiter
(b) How many of this heaviest planet's masses are equivalent to the Sun's mass? Dividing the mass of the Sun by that of Jupiter we get 1.99 x 10³⁰ kg / 1.9 x 1027 kg = 1 x 10³. So, it takes 1000 Jupiters to make up the mass of the Sun.

(5) Find the planet with the biggest value in each column:

(a) The farthest planet is how many times farther from the Sun than the Earth? Pluto is the farthest planet from the Sun - on average it is at 39.54 AU.
(b) The most massive planet is how many Earth' masses? Jupiter is 318 Earth masses.
(c) The largest planet is how many Earth diameters across? Jupiter is 11 Earths across.
(d) The planet with the highest density is . . .? Earth.

(6) Look at this table of physical parameters from The Nine Planets website.

(a) Which moons are bigger than Mercury? Ganymede and Titan are larger than Mercury.
(b) Which moons are bigger than Pluto? Moon, Io, Europa, Ganymede, Callisto, Titan and Triton are all larger than Pluto.
(c) How many moons are bigger than the biggest asteroid? The largest asteroid is Ceres which is 466 km - there are 16 moons larger than Ceres.

(7) (a) Which planet (not moon/satellite) has the largest inclination? Pluto
(b) How many degrees? 17.15 degrees
(c) Look at the diagram below of orbital inclinations (the angles are correct but the horizontal distances are not to scale). From our viewpoint standing on Earth, where in the sky are the planets located? Looking out from the Earth, we see the planets all close to the ecliptic - that's the line along which the Sun appears to move.

(8) Between which 2 planets' orbits are the asteroids? Mars and Jupiter.

(9) Which two planets appear to have intersecting orbits? Neptune and Pluto. But the are in an orbital resonance - for every 3 times Neptune goes around the Sun, Pluto goes around 2 times. The net result is that whenever either planet is at the place where the orbits intersect, the other planet is on the other side of the orbit. So, they never collide.

(10) Which planet has the greatest eccentricity? What is its value of e? Pluto has the greatest eccentricity - e=0.248.

(11) (a) Do all or most planets spin the same way as Earth? Most do
(b) Which planet(s) spin retrograde? Venus, Uranus and Pluto.

(12) Look at the list of comparisons between Terrestrial and Jovian planets in the table. Which of the characteristics are related to the planet's size and which are related to the planet's distance from the Sun? Well, at first glance, you could say that the small mass, high density, solid surface and lack of moons might be all related to the small size of the inner planets - while the temperature is related to the planet's distance from the Sun. It turns out that the distance from the Sun explains ALL - as you will see.....

(13) Why do you think there are only two types of planets - not 3 or four types or a continuous range of types? (The answer is not obvious - more about this issue at the end of the course). ...we'll talk about this later....

(14) Have you seen a meteor shower? Or a meteorite? Describe what you saw. Meteors look like bright objects streaming through the sky.

(15)Read the text, look at the sites below and think about some examples of 4. Notable exceptions to 1 are the retrograde spins (Venus, Uranus, Pluto), the high eccentricity of Pluto's orbit. Exception to 2 is Pluto.

(16) Pick a planet - any planet - find at least one past or future mission to that planet. Use the SEDS site or any of the links below to find a picture of the spacecraft. What instruments did it have on board? Did it take any pictures? Can you find some of the pictures on the net? So, what did you find?