WARM UP 1 TrueFalse The Earth is closer

WARM UP 1. True/False: The Earth is closer to the sun during the summer. 2. True/False: The Earth is slimmer at the equator. 3. What is a solstice? Equinox? 4. What causes seasons? 5. When you’re done, get a Chromebook for the quiz. Quiz code is on the whiteboard.

PLANETS There are 8 recognized planets. They can be divided into 2 groups.

INNER PLANETS • 4 closest to the sun. • Mercury, Venus, Earth and Mars • Also called terrestrial planets • Traits: • small, but dense • Rocky surface

OUTER PLANETS • 4 farthest from the sun. • Jupiter, Saturn, Uranus, and Neptune • Also called the Jovian planets • Traits: • Large, but not very dense • Gaseous surface • Atmosphere of hydrogen and helium

TO BE A PLANET 1. Has to be rounded by gravity 2. Has to orbit a star 3. Has to have everything pushed out of its orbit Which one does Pluto not meet? https: //www. youtube. com/watch? v=Fq. X 2 Ydnwt. Rc

BARYCENTER • The point between two unequal objects where they balance each other • The center of mass where two or more celestial bodies orbit each other. • When a moon orbits a planet, or a planet orbits a star, both bodies are actually orbiting around a point that lies outside the center of the larger body. (1, 710 km)

• The Sun is not stationary in our solar system. • It actually moves as the planets tug on it, causing it to orbit the solar system’s barycenter. • The sun never strays too far from the solar system barycenter. • http: //www. youtube. com/watch? v=1 i. SR 3 Yw 6 FXo

• Change in the direction of the axis of the Earth, but without any change in tilt • This changes the stars near (or not near) the Pole, but does not affect the seasons • The Earth’s axis currently points at Polaris as the “Northern Star”, but it won’t always be. PRECESSION Each gyration around the cone takes 26, 000 years

NUTATION • Wobbling around the precessional axis • Change in the angle: ½ degree one way or the other • Occurs over an 18 year period and is due to the Moon • Very slightly increases or decreases seasonal effects

Barycenter Lab Follow the instructions on your lab sheet.