mercury Smallest terrestrial planet, 1/3 size of Earth Thin atmosphere which makes it alternate between very cold (side away from the sun) and very hot (side facing the sun); the atmosphere does not keep heat in. Very dense planet.

Venus About the same size and density as Earth, so it is often called “Earth’s twin” Thick (THICK) atmosphere that traps heat, so it is the hottest planet in the solar system Takes huge meteors to be able to make it through the atmosphere Spins the opposite way (clockwise) to most planets It rains sulfuric acid. In case you were thinking of moving there. Surface is brownish red

Earth Largest of the 4 terrestrial planets. Only one with water Atmosphere contains water vapor, which helps moderate daily temperatures

mars Mars has the largest mountain the solar system (78,000 feet above the surface) Polar ice caps made of CO2 Less dense than Earth Called the “red planet” because of its red soil. Probably caused by iron-rich materials.

Gas giants Jupiter, Saturn, Uranus, Neptune (sometimes Uranus and Neptune are labeled “ice giants”) Large planets not primarily composed of rock or other solid matter. Primarily gas and liquid forms. Thick atmospheres of hydrogen and helium ALL have rings, but Saturn’s are the most noticeable. Rotate more rapidly than Earth Landing on a gas giant may or may not be possible. No one knows.

Why are some terrestrial, then gas, then ice? Has to do with how they formed and in what proximity to the Sun they formed. Forming close to the sun causes ices to melt and other things to vaporize, leaving hard rocks

What are the rings made of? Dust, ice, particulate, debris

Jupiter Largest planet in the solar system (still only 1/1000th of the sun) 2 ½ times the mass of ALL the other planets combined Giant red spot – probably a storm of some kind 67 satellites (like moons); 51 are less than 10 km in diameter (tiny) 4 biggest moons are Io (eye-oh); Europa, Ganymede (gan-eh-meed), Callisto

Saturn Has a pale yellow hue due to ammonia crystals in its atmosphere 1/8th density of Earth, but 95 times more massive Very prominent ring system 62 moons, 53 named. Titan is the largest (larger than the planet Mercurcy) and has its own atmosphere.

Whoa wait, that moon has its own atmosphere? I thought moons were like, subplanet things with no planet stuff, like OUR moon that’s just a big empty rock. No no no  Moons are just satellites of other planets. They can also be planet-like.

Uranus (I wish they’d rename it) Although considered a “gas giant”, it and Neptune are slightly different in that they have more “ices” than “gases” Ammonia, methane, and hydrocarbons are all found in ice form Has a complex cloud structure Only planet whose name comes from Greek rather than Roman mythology Uranus has an axial tilt (ours is 23.5) of 97.7 degrees. Meaning it turns on its side, like a ball rolling. Has rings (all gas giants do), has moons

neptune 4th largest planet by diameter and 3rd largest by mass. 17 times the mass of Earth but not as dense. Largest moon is Triton (13 others) Similar in composition to Uranus Has rings Great dark spot – like Jupiter’s Red Spot (storm of some kind)

Okay great, stars, galaxies, planets, super duper what else do I need to know about? There’s an asteroid belt between Mars and Jupiter. A big one.

There’s also a Kuiper belt Like an asteroid belt, but beyond Neptune. It goes for 50 AU (astronomical units – remember, that is the distance between the earth and the sun).

What are asteroids? They’re like tiny planets. They orbit the sun but are not quite planets and not quite comets. There are millions. Usually short, circular orbits. Group together in belts.

What’s a comet? Comets are made of ice, dust, and rocky material. Like asteroids, but with ice. Only about 3500 known comets. The differences between asteroids and comets is what they are made of, comets have tails, and comets have longer and more extended orbits. What’s a comet’s tail? Comets are made up of ice, and when they heat up, they leave a vapor trail.

What’s a meteor? An asteroid or other object that breaks through the atmosphere and hits a planet (like Earth)

Oh yeah, whatever happened to poor pluto? Pluto takes over 200 years to orbit the sun. In the time we have known about it, it hasn’t even made one revolution. We got bored. ALSO, in the Kuiper belt, we found more objects that are similar to Pluto, so we decided to downgrade Pluto to a dwarf planet.

Other dwarf planets Probably hundreds of thousands in our solar system alone.