The Solar System - Its Origin and Early Development Sun and eddy
Solar System The Solar System consists of the Sun and the other celestial objects gravitationally bound to it: the eight planets, three dwarf planets and their 165 known moons. • 4 terrestrial planets or inner planets • The Asteroid Belt • 4 gas giants or outer planets • The Kuiper Belt • The Oort Cloud • Three dwarf planets scattered thru the solar system
General Characteristics of the Solar System • Planetary orbits and rotation • Planet and satellite orbits are in a common plane • Nearly all planet and satellite orbital and spin motions are in the same direction • Rotation axes of nearly all planets and satellites are roughly perpendicular to the plane of the ecliptic
General Characteristics of the Solar System • Chemical and physical properties of the planets • The terrestrial planets are small, have a high density, and are composed of rock and metallic elements • The Jovian planets are large, have a low density, and are composed of gases and frozen compounds
General Characteristics of the Solar System • The three dwarf planets are Pluto, the largest known Kuiper belt object; Ceres, the largest object in the asteroid belt; and Eris, which lies in the scattered disc.
Planetary Distances: In order of their distances from the Sun • Mercury 0.4 AU • Venus 0.7 AU • Earth 1.0 AU • Mars 1.5 AU • Jupiter 5.0 AU • Saturn 10.0 AU • Uranus 19.0 AU • Neptune 30.0 AU • Pluto (dwarf planet) 39.0 AU • Light travels through space at 300,000-km/s. • So it takes about 8 minutes for light from the sun to travel 1 AU and reach us. • How long would it take light from the sun to reach Pluto? • 39 x 8 = 312 minutes, or 5.2 hours!
Mass of the Solar System • Almost all the mass in our solar system is in the sun. • Mass of the Solar System • Sun 99.80% • Jupiter 0.10% • Comets 0.05% • Other 7 planets 0.04% • Total of Sun + Planets + Comets = 99.99%
Planets A planet is any body in orbit around the Sun that • has enough mass to form itself into a spherical shape and • has cleared its immediate neighborhood of all smaller objects. There are eight known planets that meets this qualification: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Dwarf Planets • On August 24, 2006 the International Astronomical Union defined the term "planet" for the first time, excluding Pluto and reclassifying it under the new category of dwarf planet along with Eris and Ceres. Images of the Asteroid Ceres As It Rotates One Quarter
Dwarf Planets • A dwarf planet is not required to clear its neighborhood of other celestial bodies. Other objects that may become classified as dwarf planets are Sedna, Orcus, and Quaoar.
Small Solar System Bodies • Natural satellites, or moons, are those objects in orbit around planets, dwarf planets and SSSBs, rather than the Sun itself.
The Solar System • The eight bodies officially categorized as planets are often further classified in several ways: • Chemical Composition • Size • Position Relative to the Sun • Position Relative to the Earth • By History
Chemical Composition • Terrestrial or rocky planets: Mercury, Venus, Earth, and Mars: • The terrestrial planets are composed primarily of rock and metal and have relatively high densities, slow rotation, solid surfaces, no rings and few satellites. • Jovian or gas planets: Jupiter, Saturn, Uranus, and Neptune: • The gas planets are composed primarily of hydrogen and helium and generally have low densities, rapid rotation, deep atmospheres, rings and lots of satellites.
Size • Small planets: Mercury, Venus, Earth, Mars. The small planets have diameters less than 13000 km. • Giant planets: Jupiter, Saturn, Uranus and Neptune. The giant planets have diameters greater than 48000 km. The giant planets are sometimes also referred to as gas giants.
Relative the the Sun • Inner planets: Mercury, Venus, Earth and Mars. • Outer planets: Jupiter, Saturn, Uranus, Neptune. • The asteroid belt between Mars and Jupiter forms the boundary between the inner solar system and the outer solar system.
Relative the the Earth • Inferior planets: Mercury and Venus. • closer to the Sun than Earth. • The inferior planets show phases like the Moon's when viewed from Earth. Earth. • superior planets: Mars thru Neptune. • farther from the Sun than Earth. • The superior planets always appear full or nearly so.
History • Classical planets: Mercury, Venus, Mars, Jupiter, and Saturn. Known since prehistorical times. Visible to the unaided eye • Modern planets: Uranus, Neptune. Discovered in modern times. Visible only with optical aid (telescopes) • The IAU has recently decided that "classical" should refer to all eight planets (Mercury thru Neptune, including Earth but not Pluto). This is contrary to historical usage but makes some sense from a 21st century perspective.
Origin of the Solar System • The Solar System is believed to have formed according to the nebular hypothesis, first proposed in 1755 by Immanuel Kant and independently formulated by Pierre-Simon Laplace.
Origin of the Solar System • This theory holds that 4.6 billion years ago the Solar System formed from the gravitational collapse of a giant molecular cloud. This initial cloud was likely several light-years across and probably birthed several stars.
Origin of the Solar System • About 4.5 billion years ago it is believed that the Solar System consisted of a large cloud of gas and dust, called a nebula. • This cloud started rotating, and the dust particles combined to form planetesimals. As the cloud rotated faster, it flattened, and the planetesimals formed. • The Sun is at the center, and secondly, the planets in orbit around the Sun. This model explains qualitatively many features of the Solar System, including the fact that the planets essentially all revolve around the Sun in the same plane.
The Terrestrial Planets • Terrestrial planets seem to have experienced a similar early history, with extensive volcanism, cratering, and internal differentiation • Each has a metallic core and a silicate mantle crust, and shows evidence of continuing lava flows and meteorite impact • Outgassing produced an atmosphere as light gases from the interior rose to the surface during volcanism
MERCURY Mercury, the planet nearest the Sun, is the second smallest planet in our solar system. It is only slightly larger than the Earth's moon. The surface is covered with craters. This tiny planet does not have any rings or moons. Evidence of craters
MERCURY • Diameter: one third the size of Earth • Distance: 0.4 AU • Atmosphere: no atmosphere • Features: Craters with smooth plains and most extreme temperature range • No life because of atmosphere • No moons or satellites
Mercury • Closest to the sun. • Temperature ranges from 427°C in daylight to -173°C at night. • Revolves slowly, in two Mercury years three Mercury days will have passed. • One third the size of the Earth. • Period of Rotation = 88 days • Period of Revolution = 59 days
Mercury Missions • Environment, Geochemistry, and Ranging (MESSENGER) is the first mission sent to orbit the planet closest to the sun. • On Oct. 6, 2008, the probe flew by Mercury for the second time this year, using the planet’s gravity for a critical assist needed to keep the spacecraft on track for its orbit insertion around the planet three years from now.
VENUS lava flows impact craters Venus is one of the brightest objects in our sky, so it is clearly visible to the naked eye. It can be tricky to spot because it is always near the Sun. It rises and sets with the Sun each day. Ancient civilizations believed Venus was actually two different objects, so they called the one that rose the Morning Star, and the one that set the Evening Star.
VENUS • Period of Rotation = 108.2 days • Period of Revolution = 243 days • Almost same size as the Earth. • Hottest surface in our solar system. The average daytime surface temperature is 464°C, compared to the Earth’s 15°C. • This is hot enough to melt lead. • Named for the Roman goddess of love and beauty. Originally the Greek goddess Aphrodite.
VENUS Missions Venus Express is ESA’s first mission to Venus. Launched in November 2005, the spacecraft arrived at the planet on 11 April 2006 and began science observations within a month. Since then, it has continuously been making new discoveries and revising our knowledge of Venus. • Venus is covered by a thick layer of clouds that extends between 45 and 70 km above the surface. These rapidly-moving clouds are mainly composed of micron-sized droplets of sulphuric acid and other aerosols (fine solid or liquid droplets suspended in a gas), the origin of which is unknown.
EARTH and MOON What similarities and differences do you notice between the Earth and the Moon? Why do they have such different surface features?
MARS Mars is very bright, which makes it easy to spot in the night sky. It was named after the Roman god of war because its reddish color reminded the people of blood. Olympus Mons is the largest volcano in our solar system! Although people have never landed on Mars, we have sent robotic explorers there. Martian crater
Mars • Mars is the Latin name for Ares, the Greek god of war. • Mars has an atmosphere that is mainly carbon dioxide. • It is very thin, only 0.01 atmosphere’s at the surface. • Mars even has clouds, but they are thin also. • The winds can create dust storms that cover much of the planet and last for months.
A surprising find made by Mariner 9 was the existence of several canyons that are much larger than Earth’s Grand Canyon. The largest, Valles Marineris, is thought to have formed by slippage of material along huge faults in the crustal layer. In this respect, it would be comparable to the rift valleys of Africa.
Mars • Mars has two very small moons, Phobos and Diemos. • They are named after the horses that pulled Mars’s chariot. • The larger Deimos is only 23-km in diameter. • Mars is about half the size of the Earth. • A 100 pound sixth grader would weigh 39 pounds on Mars. • It is very cold on Mars, with the average temperature ranging from -140° C to 20° C.
Mars • Period of Rotation = 108.2 days • Period of Revolution = 243 days • Mars surface has a wide variety of landscapes. • Olympus Mons is the largest volcano in our solar system. Its base would cover the state of Colorado. • It is three times taller than Mt. Everest. • There are many other volcanoes on Mars, but none seem to be active at this time.
Mars Missions • There have been many missions to Mars, starting with the Viking craft in 1976. • There are currently two orbiters and two rovers collecting data on Mars. • Manned missions are also currently being planned, around 2025 or so.
Mars Missions • Next NASA Mars Mission Rescheduled For 2011NASA's Mars Science Laboratory will launch two years later than previously planned, in the fall of 2011. The mission will send a next-generation rover with unprecedented research tools to study the early environmental history of Mars. The composition and markings of some Martian rocks indicate that liquid water was once present on Mars’s surface. The marking shown in the center of the rock, however, was created by a NASA rover during chemical analysis.
ASTEROID BELT Most asteroids can be found in the Asteroid Belt, which is located between Mars and Jupiter. Asteroids are rocky and metallic objects that orbit the Sun, but are too small to be considered planets. They are known as minor planets. Asteroids range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles.
The main asteroid belt occupies the orbit between Mars and Jupiter, between 2.3 and 3.3 AU from the Sun.
Asteroid Belt: Ceres • Ceres (2.77 AU) is the largest body in the asteroid belt and its only dwarf planet. It has a diameter of slightly under 1000 km, large enough for its own gravity to pull it into a spherical shape. Ceres was considered a planet when it was discovered in the 19th century, but was reclassified as an asteroid in the 1850s as further observation revealed additional asteroids. It was again reclassified in 2006 as a dwarf planet.
Gas Giants • Separated from the 1st zone by the asteroid belt, the 2nd Zone contains the gas giants. • Made of the lightweight elements Hydrogen, Helium, Carbon, Oxygen, and Nitrogen. • All are much larger than the Earth, with 15-300 times the mass, and 4-11 times the diameter. • Not believed to have solid surfaces. • Have rings and many satellites.
JUPITER Jupiter, the fifth planet from the Sun, is the largest planet in our solar system. Jupiter is so big that over 1,000 planets the size of Earth could fit into it. It has over 60 moons and 2 rings. Can life exist on Jupiter's moon, Europa? The “Great Red Spot” Is actually a huge Storm system! Here are a few of Jupiter’s moons
Jupiter • Named for Jove, the King of the Roman Gods. • Roman name for the Greek god Zeus. • Often the term Jovian is used to describe things pertaining to Jupiter. Example: the Jovian moons.
Jupiter • Believed to be a failed star, lacking the mass to become a small star. • Most massive planet in solar system. • Has over 60 satellites. • Density is 1.33g/cm3. • Rotates every 10 hours. • Takes 12 years to orbit the sun. • Gravity almost 2.5 times that of the Earth.
Jupiter • The red spot is a huge storm that has been continuously going on Jupiter for over 400 years. Winds inside this storm reach speeds of about 270 mph. With a diameter of 15,400 miles, this storm is almost twice the size of the entire Earth. Period of Rotation = 778.3 days Period of Revolution = 11.86 years
Moons of Jupiter • The New Horizons Long Range Reconnaissance Imager (LORRI) captured these two images of Jupiter's outermost large moon, Callisto, as the spacecraft flew past Jupiter in late February. New Horizons' closest approach distance to Jupiter was 2.3 million kilometers (1.4 million miles), not far outside Callisto's orbit, which has a radius of 1.9 million kilometers (1.2 million miles). • However, Callisto happened to be on the opposite side of Jupiter during the spacecraft's pass through the Jupiter system, so these images, taken from 4.7 million kilometers (3.0 million miles) and 4.2 million kilometers (2.6 million miles) away, are the closest of Callisto that New Horizons obtained.
SATURN Saturn, the sixth planet from the Sun, is the second largest planet in our solar system. It is often called the ringed planet because many rings of dust and rocks surround it. Saturn also has over 31 moons. Saturn with some of its moons Some of Saturn’s rings Titan is a moon of Saturn that may have some Conditions necessary for life! The picture on the right shows an artist’s drawing of how Titan might have looked when the Cassini-Huygen’s probe dropped into its atmosphere in Dec., 2004.