OUR PLANETARY SYSTEM.pdf

Our Planetary System Our Planetary System Earth, as viewed by the Voyager spacecraft This updated version of the iconic "Pale Blue Dot" image taken by the Voyager 1 spacecraft uses modern image-processing software and techniques to revisit the well-known Voyager view while attempting to respect...

Our Planetary System Our Planetary System Earth, as viewed by the Voyager spacecraft This updated version of the iconic "Pale Blue Dot" image taken by the Voyager 1 spacecraft uses modern image-processing software and techniques to revisit the well-known Voyager view while attempting to respect the original data and intent of those who planned the images. Carl Sagan later reflected on the profound significance of this image in his 1994 book titled Pale Blue Dot: A Vision of the Human Future in Space. Here, he eloquently describes how the image emphasizes the fragility and insignificance of Earth in the vast cosmic arena, yet also underscores the need for humans to cherish and protect our only home. The "Pale Blue Dot" has since become a powerful symbol of Earth's place in the universe and a call to stewardship of the planet. Family Portrait/Portrait of the Planets NASA/JPL - Solar System Image/Mosaic featuring individual frames of six planets and a partial background indicating their relative positions. Studying the Solar System Our goals for learning: – What does the solar system look like? – What can we learn by comparing the planets to one another? What does the solar system look like? What does the solar system look like? What does the solar system look like? There are eight major planets with nearly circular orbits. Dwarf planets are smaller than the major planets and some have quite elliptical orbits.  What does the solar system look like? Scale in terms of size Mercury Earth Venus Mars Jupiter Saturn Uranus Neptune https://informal.jpl.nasa.gov/museum/sites/default/files/ResourceLibrary/Planets%20to%20Scale.pdf What does the solar system look like? Planets all orbit in same direction and nearly in same plane. Thought Question How does the Earth–Sun distance compare with the Sun's radius? a) It's about 10 times larger. b) It's about 50 times larger. c) It's about 200 times larger. d) It's about 1000 times larger. Thought Question How does the Earth–Sun distance compare with the Sun's radius? a) It's about 10 times larger. b) It's about 50 times larger. c) It's about 200 times larger. d) It's about 1000 times larger. What can we learn by comparing the planets to one another?  Comparative Planetology The study of the solar system by examining and understanding the similarities and differences among worlds. We can learn more about a world like our Earth by studying it in context with other worlds in the solar system. Stay focused on processes common to multiple worlds instead of individual facts specific to a particular world. Comparative Planetology Comparing the planets reveals patterns among them. Those patterns provide insights that help us understand our own planet. What are the major features of the Sun and planets? Sun and planets to scale Planets are very tiny compared to distances between them. Sun Over 99.9% of solar system's mass Made mostly of H/He gas (plasma) Converts 4 million tons of mass into energy each second Mercury Made of metal and rock; large iron core Desolate, cratered; long, tall, steep cliffs Very hot, very cold: 425C (day), –170C (night) Mercury Venus Nearly identical in size to Earth; surface hidden by clouds Hellish conditions due to an extreme greenhouse effect Even hotter than Mercury: 470C, day and night Venus NASA/JPL Earth An oasis of life The only surface liquid water in the solar system A surprisingly large moon Mars Looks almost Earth-like, but don't go without a spacesuit! Giant volcanoes, a huge canyon, polar caps, more Water flowed in distant past; could there have been life? Mars Curiosity rover landed in August 2012 Mars Jupiter Much farther from Sun than inner planets Mostly H/He; no solid surface 300 times more massive than Earth Many moons, rings Jupiter Jupiter's moons can be as interesting as planets themselves, especially Jupiter's four Galilean moons. Io (shown here): active volcanoes all over Europa: possible subsurface ocean Ganymede: largest moon in solar system Callisto: a large, cratered "ice ball" Saturn Giant and gaseous like Jupiter Spectacular rings Many moons, including cloudy Titan Saturn Rings are NOT solid; they are made of countless small chunks of ice and rock, each orbiting like a tiny moon. Saturn Cassini probe arrived July 2004 (launched in 1997). Saturn Uranus Smaller than Jupiter/Saturn; much larger than Earth Made of H/He gas and hydrogen compounds Extreme axis tilt Moons and rings Neptune Similar to Uranus (except for axis tilt) Many moons (including Triton) Neptune Dwarf Planets Much smaller than major planets Icy, comet-like composition Pluto: Recent New Horizons Fly-by Majestic ice mountains and frozen planes Pluto: Recent New Horizons Fly-by Tartarus Dorsa mountains on Pluto, showing a curious snake-skin like appearance. Pluto: Recent New Horizons Fly-by Pluto’s moon, Charon, is large compared to Pluto It has a huge “Grand Canyon”, spanning almost the entire surface Pluto: Recent New Horizons Fly-by Pluto has a heart…. https://nssdc.gsfc.nasa.gov/planetary/factsheet/planet_table_british.html Thought Question What process created the elements from which the terrestrial planets were made? a) the Big Bang b) nuclear fusion in stars c) chemical processes in interstellar clouds d) their origin is unknown. Thought Question What process created the elements from which the terrestrial planets were made? a) the Big Bang b) nuclear fusion in stars c) chemical processes in interstellar clouds d) their origin is unknown. What have we learned? What does the solar system look like? – Planets orbit Sun in the same direction and in nearly the same plane. What can we learn by comparing the planets to one another? – Comparative planetology looks for patterns among the planets. – Those patterns give us insight into the general processes that govern planets. – Studying other worlds in this way tells us about our own planet.  Patterns in the Solar System Our goals for learning: – What features of our solar system provide clues to how it formed? What features of our solar system provide clues to how it formed? 1. Motion of Large Bodies All large bodies in the solar system orbit in the same direction and in nearly the same plane. Most also rotate in that direction. 2. Two Major Planet Types 3. Swarms of Smaller Bodies Many rocky asteroids and icy comets populate the solar system. 4. Notable Exceptions Several exceptions to the normal patterns need to be explained. What have we learned? What features of the solar system provide clues to how it formed? – Motions of large bodies: all in same direction and plane – Two main planet types: terrestrial and jovian. – Swarms of small bodies: asteroids and comets – Notable exceptions: rotation of Uranus, Earth's large moon Spacecraft Exploration of the Solar System Our goals for learning: – How do robotic spacecraft work? Why do we need robotic spacecrafts? How do robotic spacecraft work? Flybys A flyby mission flies by a planet just once. Cheaper than other mission but less time to gather data Orbiters Go into orbit around another world More time to gather data but cannot obtain detailed information about world's surface Probes or Landers Land on surface of another world Explore surface in detail Sample Return Missions Land on surface of another world Gather samples Spacecraft designed to blast off other world and return to Earth Apollo missions to Moon are one example, Hyabusa to an asteroid is another. Combination Spacecraft Cassini/Huygens mission contains both an orbiter (Cassini), around Saturn, and a lander (Huygens), landed on Titan. https://www.jpl.nasa.gov/missions What have we learned? How do robotic spacecraft work? – Flyby: flies by another world only once – Orbiter: goes into orbit around another world – Probe/Lander: lands on surface – Sample return mission: returns a sample of another world's surface to Earth SOLAR SYSTEM BOUNDARIES Heliosphere - bubble created from the solar wind, emanating from the Sun that extends far past the orbits of the planets. It is shaped like a long wind sock as it moves with the Sun through interstellar space. Heliosheath - outer region of the heliosphere, just beyond the termination shock, the point where the solar wind slows abruptly, becoming denser and hotter. The solar wind piles up as it presses outward against the approaching wind in interstellar space. Heliopause - boundary between solar wind and interstellar wind where the pressure of the two winds are in balance. This balance in pressure causes the solar wind to turn back and flow down the tail of the heliosphere. Bow Shock - forms in front of the Heliosphere as the sun moves through the interstellar medium. Termination Shock - region just interior to the heliopause is the where the solar wind is slowed down. WHAT IS A PLANET? IAU Resolution 2006 *A planet is a celestial body that: (1) is in orbit around the Sun, (2) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape and (3) has cleared the neighborhood around its orbit. We adopt the following definitions, which are consistent with current IAU nomenclature: Star: self-sustaining fusion is sufficient for thermal pressure to balance gravity (±0.075 Solar mass ≈ 80 Jupiter mass) for solar composition; the minimum mass for an object to be a star is often referred to as the hydrogen burning limit  Stellar remnant: dead star – no more fusion (or so little that the object is no longer supported primarily by thermal pressure) Brown dwarf: substellar object with substantial deuterium fusion – more than half of the object’s original inventory of deuterium is ultimately destroyed by fusion  Planet: negligible fusion (≤ 0.012 Solar mass ≈ 13 Jupiter mass, with the precise value again depending on initial composition), plus it orbits one or more stars and/or stellar remnants. Planetary Properties (1) Orbit (2) Mass, distribution of mass (3) Size (4) Rotation rate and direction (5) Shape (6) Temperature (7) Magnetic field (8) Surface composition (9) Surface structure (10) Atmospheric structure and composition RECAP  Comparative Planetology  Features that provide clues to SS Formation  Types of Robotic Spacecraft  Solar System Boundaries  Planet Definition  Other definitions