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Introduction to the Solar System. Edward M. Murphy Space Science for Teachers 2005. The Solar System. The Terrestrial Planets. The Jovian Planets. The Jovian Planets, Earth and Sun. Properties of the Planets. The Sun. Orion Molecular Cloud. Orion Molecular Cloud.
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Introduction to the Solar System Edward M. Murphy Space Science for Teachers 2005 Lecture 21: The Solar System
The Solar System Lecture 21: The Solar System
The Terrestrial Planets Lecture 21: The Solar System
The Jovian Planets Lecture 21: The Solar System
The Jovian Planets, Earth and Sun Lecture 21: The Solar System
Properties of the Planets Lecture 21: The Solar System
The Sun Lecture 21: The Solar System
Orion Molecular Cloud Lecture 21: The Solar System
Orion Molecular Cloud • The closest and best studied giant molecular cloud is the Orion molecular cloud. • Distance 1500 LY. • Diameter 100 LY. • Mass 430,000 MSun. • It includes the Orion Nebula and the Horsehead Nebula. Lecture 21: The Solar System
Orion Molecular Cloud Lecture 21: The Solar System
Visible Light Lecture 21: The Solar System
Visible Light Lecture 21: The Solar System
Infrared Light (0.1 mm) Lecture 21: The Solar System
Radio (CO at 2.6 mm) Lecture 21: The Solar System
Orion Nebula • The Orion Nebula is a young cluster of hot stars (ages 3x105 – 1x106 years). • Most of the young stars are hidden from view by the dust in the molecular cloud. • Infrared radiation, with its longer wavelength, can penetrate this dust to show us the interior of the cloud. Lecture 21: The Solar System
Orion Nebula • Visible light images of the central cluster in the Orion Nebula reveal the four bright stars (called the Trapezium). • Infrared images reveal more than 500 stars in this cluster. • Star formation is not very efficient. Only a few percent of the gas in the cloud is converted into stars. Lecture 21: The Solar System
Orion Nebula • Distance to the Trapezium Cluster is about 1530 LY. • It consists of about 1800 stars • The average age of the stars is less than 1 million years old, some are as young as a few hundred thousand years. • The largest star is an O6 has a mass of 50 Msun. Lecture 21: The Solar System
Ground Based Image Lecture 21: The Solar System
HST Image Lecture 21: The Solar System
IR Ground Image Lecture 21: The Solar System
Formation of Planets • Observations show that at least 50% of protostars are surrounded by disks of material. • These disks a a typical mix of interstellar material • Hydrogen and helium in gaseous form • Ice and dust grains – solid particles – contain most of the heavy elements. • These disks typically contain 1-10% of the mass of our Sun. Lecture 21: The Solar System
Protostars in Orion Lecture 21: The Solar System
Formation of Planets • Early on, the dust grains in the disk collide and begin to stick together. • These small clumps stick to other clumps. • Eventually, this accretion of material creates planetesimals, objects the size of small moons. • Planetesimals are large enough that their gravity begins to attract more material, including other planetesimals. Lecture 21: The Solar System
Formation of Planets • Planetesimals have been constructed from the solid particles in the disk and are made mostly of elements other than hydrogen and helium. • Billions of these objects will continue to collide and grow until all that is left is a handful of large planets and some leftover planetesimals – asteroids and comets. • This processof growth by accumulation, which builds planets, is called accretion. Lecture 21: The Solar System
Formation of Planets • Although most of the material was swept up by 100 million years, the intense bombardment of the planets continued for a billion years. • Many smaller objects are destroyed by collisions, with the resulting debris swept up by the large planets (fragmentation). Lecture 21: The Solar System
Formation of Planets • Even today, the Earth sweeps up many tons of material every day (mostly tiny dust grains). • When you see a meteor streak across the sky you are watching accretion happen! Lecture 21: The Solar System
Formation of Planets • The temperature of the dust disk surrounding the star indicates its distance from the star. • The inner disk is hot (1000 K at 0.1 AU). • The middle disk is cool (100 K at 1 AU). • The outer disk is cold (30 K at 10 AU). Lecture 21: The Solar System
The local temperature determines what materials existed as solids • 500-2000 degrees – Metals and rocks • 100-500 degrees – Water ice (and metal and rocks) • 20-100 degrees – Methane ice (and water ice and metal and rocks) Lecture 21: The Solar System
Composition of the Planets Lecture 21: The Solar System
The temperature in the solar nebula determines the typical composition of the planets and their satellites • Close to the Sun, objects are made of metal and rock • Far from the Sun objects are made mostly of ice with some rock and metal Lecture 21: The Solar System
HST Image of Jupiter Lecture 21: The Solar System
Formation of the Giant Planets • The Jovian planets started as icy/rocky seeds from the accumulation of solid planetesimals • They grew in an area rich in ice • Cores grew quickly and became sufficiently massive to attract and retain gas from the nebula. • The Jovian planets have “slushy” cores left over from this early stage. Lecture 21: The Solar System
Age of the Solar System • Using the radioactive decay of certain elements, we can determine the ages of bodies in the solar system. • The decay of radioactive elements is a statistical process. • The half-life is the time it takes for ½ of the atoms of the original parent element to decay into the daughter element. • Over time, the ratio of parent to daughter element decreases (that is, there is less of the parent element and more of the daughter element as rocks get older). Lecture 21: The Solar System
Radioactive Decay Lecture 21: The Solar System
Radioactive Decay Reactions Used to Date Rocks Lecture 21: The Solar System
