Gas Giants (maybe liquid giants) Composition is mainly hydrogen and helium. Uranus & Nepture: Ice giants H/He atmospheres, No metallic hydrogen layer Mantle is an “ocean” of compressed water, ammonia, & methane - superheated, but under high pressure ‣ What are jovian planets like? ‣ Thick hydrogen, helium atmospheres ‣ Layered interiors with very high pressure and cores made of rock, metals, and hydrogen compounds ‣ Very high pressure in Jupiter and Saturn can produce metallic hydrogen ‣ All have strong storms and winds ‣ What kinds of moons orbit jovian planets? ‣ Moons of many sizes ‣ Many major moons show signs of geological activity ‣ Tidal heating drives activity ‣ Titan is the only moon with a thick atmosphere ‣ What are Saturn’s rings like? ‣ Made up of countless individual ice particles ‣ Extremely thin with many gaps ‣ How do other jovian ring systems compare to Saturn’s? ‣ Much fainter ring systems with smaller, darker, less numerous particles ‣ Why do the jovian planets have rings? ‣ Ring particles are probably debris from moons Lecture 19 – Asteroids & Comets ‣ What are asteroids like? ‣ Rocky leftovers from the era of planet formation ‣ Generally irregular in shape ‣ Some are “rubble piles” ‣ The majority are found in the asteroid belt, between the orbits of Mars and Jupiter ‣ What are comets like? ‣ Comets are like dirty snowballs ‣ Most are far from Sun and do not have tails ‣ Tails grow when comet nears Sun and the nucleus heats up ‣ Comets come from Kuiper Belt and Oort cloud ‣ What are meteoroids, meteors, & meteorites? ‣ Meteoroid - small debris in space ‣ Meteor - bright streak in the air cause by falling debris ‣ Meteorite - space rock on the ground ‣ Most meteors are comet debris, but meteorites come from asteroid debris ‣ Did a meteorite impact kill the dinosaurs? ‣ An iridium-rich sediment layer and an impact crater on the Mexican coast show that a large impact occurred at the time the dinosaurs died out, 65 million years ago Lecture 20 & 21 – The Sun The Sun is a huge, glowing ball of mostly hydrogen and helium gas at the center of our solar system. The sun's diameter is about 1.4 million km (864,000 miles), approximately 109 times Earth's diameter. Its mass is roughly 2 X 10^27 tons. Only 2% of the Sun’s mass is made of elements other than hydrogen and helium ‣ Sun’s energy output = 3.8 x 10^26 Watts Temperature: 5800 K, Luminosity: 1 LSun, Radius: 1 RSun, Color: Yellow. Photosphere (Sun’s “surface”) has a temperature of about 5,800 K. It has a mottled appearance. This is because it is made up of dark-edged regions called granules. Granules result from convection. In convection, energy is moved by hot material rising and cool material falling. Chromosphere - lower atmosphere, Roughly 1,000x fainter than the photosphere, Temps: 4,500 - 500,000 K Corona - outer atmosphere, Temps up to 2,000,000 K!, But very faint Thermal Radiation : (Spectral curves) ‣ Represent the composition of the light from an object with a spectral curve ‣ Wavelength (or color) of the light on the horizontal axis ‣ Intensity (or energy output per second) on the vertical axis 1.Hotter objects emit more light per unit surface area at all wavelengths
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