Our Planetary System Chapter 7
Key Concepts for Chapter 7 and 8 Inventory of the Solar System Origin of the Solar System
What does the Solar System consist of? The Sun: It has 99.85% of the mass of the solar system Eight planets. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune Several dwarf planets. Pluto is one of them There are around 169 satellites (moons). Except for three satellites orbiting the Earth and Mars (Moon, Phobos and Deimos) all the rest are in orbit around the Jovian planets. A bunch of other smaller object (comets, asteroids, Kuiper Belt Objects etc.)
What does the solar system look like?
The scale of solar system (distances between planets are not to scale) A way to remember the order of the planets: My Very Excellent Mother Just Sent Us Nine Pizzas
Where is everything? Note logarithmic scales! Me V E Ma J S U N P KB Terrestrial planets Jovian or giants planets 1 AU is the mean Sun-Earth distance = 150 million km For comparison: The nearest star (Proxima Centauri) is 4.2 LY=265,000 AU Me V E Ma Inner solar system Note 1.5 AU log scales! Outer solar system
The Sun An image in the visible light. The dark spots are sunspots
The Sun Provides most of the energy received by the Earth and other planets Radius: 696,000 km (108 radius of Earth) Mass: 333,000 mass of Earth It contains 99.8% of the mass of the solar system Composition (by mass): 70% H 2, 28% He, ~2% of heavier elements Surface temperaure:5,800 K Core temperature; 15 million K Source of energy: Conversion (Fusion) of H into He It is a nuclear fusion power plant Each second, it converts 600 million tons of H into 596 million tons of He What happens with the missing 4 million tons of matter? That matter is converted into energy according the Einstein equation E = mc 2 Its gravity determines the orbit of all the planets It is the closest Star
The four terrestrial (inner) planets Sizes to scale Small in size and mass Composed primarily of rock and metals High density Only 3 satellites. Earth (Moon), Mars (Phobos and Deimos) No rings
Mercury Average distance from Sun: 0.39 AU Radius: 2440 km, 0.38 Earth radius Mass: 0.055 Earth mass Average density: 5.43 g/cm^3. This suggest an iron core No atmosphere Composition: made of metal and rock; large iron core Average surface temperature: 700K (day), 100 K (night) The smallest of all planets Surface: heavily cratered; long, tall, steep cliffs Because of lack of atmosphere: very hot and very cold: 425 C (day), 150 C (night) Rotational period: 58.6 days, orbital period: 87.9 days. Resonance 2/3 No satellites Messenger spacecraft in orbit around the planet. First orbiting spacecraft.
Venus Average distance from Sun: 0.72 UA Radius: 6051 km, 0.95 earth radius Mass:0.82 earth mass Average density; 5.24 g/cm^3 Average surface temperature: 740 K Nearly identical in size to Earth; surface hidden by thick clouds of droplets of sulfuric acid. Dense atmosphere composed mainly of carbon dioxide Extreme greenhouse effect: Even hotter than Mercury: 470 C (880 F) both day and night Atmospheric pressure equiv. to pressure 1 km deep in oceans No oxygen, no water, No satellites Spacecraft in orbit to study the planet : Magellan (radar surface imaging), Venus Express
Earth and Moon to scale (distance not to scale) Earth Our home planet, the blue planet Average distance from sun; 1AU Radius: 6378 km. 1 Earth radius Mass; 1 Earth mass Average density:5.52 g/cm^3 Average surface temperature: 290 K The only object with surface liquid water in the solar system; about 3/4 of surface covered by water A surprisingly large moon. The most accepted theory for the formation of the Moon: The result of an impact with a large body (Mars-size)
Mars Average distance from Sun:1.52 AU Radius: 3397 km, 0.53 Earth radius Mass: 0.11 Earth mass Average density: 3.93 g/cm^3 Average surface temperature:220 K Satellites: two small ones,phobos and Deimos). Probably two asteroids captured Looks almost Earth-like, but don t go there without a spacesuit! The atmospheric pressure is low, 1/150 of the Earth. Temperature well below freezing No enough oxygen, in the atmosphere, just traces Giant volcanoes, a huge canyon, polar caps made of frozen carbon dioxide (dry ice) and water Water flowed in the distant past; maybe more recent as well Could there have been life?
The four Jovian (outer) planets They are large in comparison with the Earth and all the terrestrial planets Composed primarily of gases (mostly hydrogen and helium), liquids, and ices All of them have low density 169 known satellites All the four Jovian planets have rings
Jupiter Average distance from the Sun: 5.2 AU Radius: 71,492 km (11.2 Earth radius) Mass: 318 Earth mass Average density: 1.33 g/cm^3 Composition: Mainly H and He Cloud top temperature: 125 K Satellites: at least 67 Four large satellites discovered by Galileo (Galilean satellites): Io, Europa, Ganymede and Callisto The volume of Jupiter is more than 1000 of Earth volume Long-lived storm: The Great Red Spot No solid surface It has rings, too faint to see them from ground-based telescopes. Discovered by Voyager spacecraft Spacecrafts: Pioneer 10 and 11 (1970 s), Voyager 1 and 2,(1980 s) Galileo (orbit), Cassini
The Galilean satellites Io (shown here) has several active volcanoes. The most volcanic active body in the solar system Europa has an icy crust with a subsurface ocean. Is a candidate for the search of life in the subsurface ocean Ganymede is the largest moon in solar system larger than Mercury Callisto: a large, cratered ice ball with unexplained surface features
Saturn Average distance from the sun: 9.54 AU Radius: 60,268 km, 9.4 radius of Earth Mass: 95.2 mass of Earth Average density: 0.70 g/cm^3 Composition: Mostly H and He Cloud-top temperature: 95K Satellites: At least 62 It is a giant and gaseous planet like Jupiter It has the most spectacular ring system. Easily visible even in small telescopes Large number of satellites The largest is the cloud-covered Titan. This is another body targeted for search life in the solar system. It has high content of hydrocarbons. Titan has lakes and small oceans of liquid methane and ethane Currently under study by the Cassini spacecraft in orbit around the planet
Saturn s rings The rings are NOT solid; they are made of countless small chunks of ice and rock, each orbiting like a tiny satellite.
Uranus Average distance from Sun: 19.2 AU Radius: 25,559 km, 4.0 radius of Earth Mass: 14.5 Mass of Earth Average density: 1.32 g/cm^3 Composition: H, He, water, ammonia, methane Cloud-top temperature: 60K Satellites: at least 27 Orbital period: 84 years Sidereal rotation period: -72 earth days Much smaller than Jupiter and Saturn, but much larger than Earth Made of H, He gas, hydrogen compounds (gas and ices of H 2 O, NH 3, CH 4 ) The bluish green color is due to the presence of methane in the atmosphere. Methane absorb the red part of spectrum and reflect the blue. Extreme axis tilt, 97 degrees nearly tipped on its side makes extreme seasons during its 84-year orbit. The satellites and ring system also tipped in their orbits around 97 degrees The extreme tilt probably caused by a collision with a large body
Neptune Average distance from Sun: 30.1 AU Radius: 24,764 km, 3.9 earth radius Mass: 17.1 Earth mass Average density: 1.64 g/cm^3 Composition: H, He, water, ammonia, methane Cloud-top temperature: 60K Satellites: at least 13 Orbital period: 165 years Rotational period: 16 hours Absorption of red due to methane content in the atmosphere make it appear blue The largest satellite Triton (shown here) orbits the planets in backward direction. Triton is probably a captured body. It is larger than Pluto. Triton has geysers of nitrogen gas
Pluto Pluto is one of the largest dwarf planets (Eris is slightly larger). They are located farther than Neptune Average distance from Sun: 39.5 AU Radius: 1160 km, 0.18 Earth radius Orbital period: 248 years Mass: 0.0022 Mass of Earth Average density: 2.0 g/cm^3 Average temperature: 40K Satellites: 5
Pluto and four of its satellites: Charon, Nix, Hydra and P4 (Image by Hubble Space Telescope)
Pluto and its 5 satellites P5 discovered in 2012 (Hubble telescope image)