Universe Recap / Objects in the Universe

Universe / Gravity Recap•Which planet has the lowest gravity?• Pluto (Dwarf Planet)

•Which planet has the highest gravity?• Jupiter

• On which planet were you the “lightest”?• Pluto

• On which object were you the “heaviest”?• Neutron Star

•Why do you think you were the heaviest on that object?• It has the most gravity

Universe / Gravity Recap

• Define mass• How much matter an object contains

• Define Weight• Force of attraction between you and the Earth

• What does the force of gravity depend on?• Your mass• Mass of the Planet you’re on• Distance from the center of the planet

• What equation can we use to determine the force due to gravity?• F = Mm

r2

Universe / Gravity Recap

•Between mass and weight which one changes depending on which planet you’re on?•Weight. Mass stays constant but weight depends

on gravity•Why did you have to jump 5 times?•To eliminate any experimental errors

Universe / Gravity Recap

•On which moon/planet could you jump the furthest?•Moon

•On which planet would you jump the shortest?• Jupiter

•Why would you jump the shortest on that planet?• It has more gravity so you would be “weighed”

down.

Objects in the Universe• Planets• Moons• Small Bodies in solar system with weak gravity and no

atmosphere• Dwarf Planets• Comets• Asteroids• Meteoroids

What is a planet?

• A planet is a celestial body that• (a) has sufficient mass for its self-gravity assumes a nearly round

shape, and• (b) is in orbit around a star, and is neither a star nor a satellite of a

planet

• But with this, Pluto should be a planet.

Theory changed• A planet is a celestial body that• (a) has sufficient mass for its self-gravity assumes a nearly

round shape, and• (b) is in orbit around a star, and is neither a star nor a

satellite of a planet, and• (c) has cleared the neighborhood around its orbit

• Is pluto a planet then?

Objects in the Universe• Planets• Moons• Small Bodies in solar system with weak gravity and no

atmosphere• Dwarf Planets• Comets• Asteroids• Meteoroids

Dwarf Planets• Orbits sun• Has own gravity

• Not enough mass to clear items out of orbit• 5 Dwarf planets

Comets• Small body of ice, rocks and dust• “Dirty Snowballs”• Gives off dust and gas in form of a tail when it gets

close to the sun• Tail always points away from the sun

Asteroids• Small, irregularly shaped, rocky object• Most are located between Mars and Jupiter• Asteroid Belt• Hundreds of thousands of asteroids• 570km to 4 m in diameter

Meteroid

• Rocky Body that varies in size. Smaller than asteroid• Enters Earths atmosphere and can become either a meteor or

meteorite• Meteor: Bright streak of light. Meteroid burns up as it enters atmosphere• Meteorite: Meteroid that reaches Earths surface and doesn’t burn up