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Part 3: A Trip through the Solar System 1. Measuring Distances Astronomical Units or AU:  One astronomical unit is equal to the mean (average) distance.

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Presentation on theme: "Part 3: A Trip through the Solar System 1. Measuring Distances Astronomical Units or AU:  One astronomical unit is equal to the mean (average) distance."— Presentation transcript:

1 Part 3: A Trip through the Solar System 1

2 Measuring Distances Astronomical Units or AU:  One astronomical unit is equal to the mean (average) distance of the Earth from the Sun.  1 AU = 149,597,000 km (rounded number)  Used to indicate distance to objects within our solar system 2

3 Major Features - Planets The definition of planet, set in 2006 by the International Astronomical Union (IAU) states that, in the Solar System, a planet is a celestial body which:  is in orbit around the Sun,  has sufficient mass to assume a nearly round shape, and  has "cleared the neighborhood" around its orbit. 8 Planets (In order from nearest the Sun): Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune 3

4 Major Features – Dwarf Planets A dwarf planet is a large body which meets the other criteria for a planet but has not cleared its neighborhood. The IAU currently recognizes five dwarf planets in the Solar System: Ceres Pluto Haumea Makemake Eris. 4 There are nearly 50 other known objects that may be dwarf planets and as many as 2,000 in all. Only two well observed. Ceres ErisPluto Pictures from Hubble Telescope

5 Major Features – Planets and Dwarf Planets 5

6 Major Features: Asteroids  Rocky, airless worlds that orbit our sun, but are too small to be called planets  Several hundred thousand discovered  Most are located in the doughnut-shaped asteroid belt between Mars and Jupiter  Also called "minor planets"  Near-Earth Objects (NEOs): Asteroids that pass close to Earth  May be composed of rocks, minerals, and/or metals 6 Image Credit: NASA/JPL/JHUAPL This picture of Eros is the first of an asteroid taken from an orbiting spacecraft.

7 Major Features: Comets  Cosmic, dirty snowballs of frozen water and gases, rock, and dust  When a comet's orbit brings it close to the sun, it heats up and spews dust and gases into a giant glowing head larger than most planets.  The dust and gases form a tail that stretches away from the sun for millions of kilometers. 7 This image of Comet C/2001 Q4 (NEAT) was taken at the WIYN 0.9-meter telescope at Kitt Peak National Observatory near Tucson, Ariz. on 7 May Credit: National Science Foundation

8 Major Features: Comets Parts of a Comet:  nucleus: relatively solid and stable, mostly ice and gas with a small amount of dust and other solids  coma: dense cloud of water, carbon dioxide and other neutral gases sublimed from the nucleus by the heat of the sun, may be hundreds of thousands of kilometers in diameter; high-speed solar particles (solar wind) blows the coma materials away from the sun, forming a long, and sometimes bright, tail. 8

9 Major Features: Comets Parts of a Comet:  dust tail: up to 10 million km long composed of smoke-sized dust particles driven off the nucleus by escaping gases; this is the most prominent part of a comet to the unaided eye  ion tail: as much as several hundred million km long composed of plasma and laced with rays and streamers caused by interactions with the solar wind 9

10 Major Features: Comets  Comets orbit the sun.  Short-period comets take up to 200 years to make one orbit; originate in the scattered disc beyond Neptune  Long-period comets: may take millions of years to make one trip around the sun; originate in the Oort Cloud 10 Credit: NASA

11 Major Features: Kuiper Belt  Discovered in 1992, but hypothesized as early as 1930, soon after the discovery of Pluto  AU from the sun  Similar to the asteroid belt in that it consists of small bodies that never reached planet size  Unlike asteroids, Kuiper belt objects (over 1,000 known so far) are composed largely of frozen substances such as methane, ammonia and water  Home of dwarf planets Pluto, Haumea, and Makemake 11 Kuiper rhymes with piper and viper.

12 Major Features: Scattered Disc  A region of space beyond the Kuiper Belt  The innermost portion overlaps with the Kuiper Belt, but its outer limits extend much farther away from the Sun  Now thought to be the origin of short-period comets  Sparsely populated with icy minor planets.  Home of dwarf planet Eris  Scattered Disc Objects, or SDOs, are among the most distant, and thus the most cold, objects in the solar system. 12 Eris and its moon Dysnomia Eris, 27% more massive than Pluto, was discovered in Hubble Photograph

13 Major Features: The Oort Cloud  A vast, spherical, icy cloud 50,000AU or more from the sun (almost a light year); remnant of the original protoplanetary disc  Believed to be the origin of long-period comets  Only hypothesized, no direct evidence exists – why? 13

14 The Planets: Mercury  Closest to sun  Rocky  Slightly larger than the moon  Almost no atmosphere to stop impacts so covered with craters  Very long day (59 Earth days) leads to very hot days (427°C) and very cold nights (-170°C) 14 One of the first images to be returned from MESSENGER's second flyby of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

15 Planets: Venus  Second from the sun; closest to Earth  About the same size, mass, and density as Earth  Highly volcanic  Rotates east to west, or retrograde (reversed from Earth)  A Venusian day (243 Earth days) is longer than a Venusian year (225 days)  Thick, toxic atmosphere (mostly CO 2 ) traps heat in a runaway "greenhouse effect," with temperatures hot enough to melt lead. (Hotter than Mercury) 15 Image of Venus in real color. The surface is obscured by a thick blanket of clouds of sulfuric acid. Credit: NASA/Ricardo Nunes

16 Planets: Mars  4 th from the sun  A cold, desert world with a thin atmosphere  ½ the diameter of Earth  Often called the Red Planet due to the reddish color of the high levels of iron oxide (rust) on its surface  Has seasons, polar ice caps, dormant volcanoes, canyons and weather  2 small moons, Phobos and Deimos  Largest known volcano in the solar system, Olympus Mons 16 Water-ice clouds, polar ice, polar regions, and geological features can be seen in this full-disk image of Mars. Credit: NASA/JPL

17 Planets: Jupiter  5 th planet from the Sun  Most massive planet in our solar system  A gas giant resembling a star in composition (mostly H and He) but did not get large enough to ignite nuclear fusion  Covered in clouds  Great Red Spot is a massive storm that has lasted for hundreds of years 17 A true-color image of Jupiter taken by the Cassini spacecraft. The Galilean moon Europa casts a shadow on the planet's cloud tops. Credit: NASA/JPL/University of Arizona

18 Jupiter’s Moons  Jupiter has dozens of moons  Four were discovered by Galileo Galilei and are called the Galilean satellites or moons Io – innermost; most geologically active object in solar system Europa - close to size of our moon; one of the smoothest objects in the solar system, covered in ice Ganymede – largest natural satellite in the solar system (larger than Mercury) Callisto – 3 rd largest moon in solar system; heavily cratered 18 Montage of Jupiter's four Galilean moons, in a composite image comparing their sizes and the size of Jupiter. From top to bottom: Io, Europa, Ganymede, Callisto Credit: NASA/JPL/DLR

19 Planets: Saturn  6 th planet from the sun  Rings of mostly ice particles (water); discovered by Galileo  A gas giant composed of mainly H and He  Spins so fast it is flattened at the poles  Has a density less than that of water (0.7g/cm 3 )  Has 62 known (53 named) satellites  Titan, 2 nd largest moon in the solar system, has a nitrogen- rich atmosphere 19 Saturn in natural color, photographed by Cassini Credit: NASA/JPL/Space Science Institute

20 Planets: Uranus  7 th planet from the sun  Discovered in 1781  A gas giant or sometimes called an ice giant  Like Venus, rotation is retrograde (east to west)  Axis tilted almost 90° so appears to be rotating on its side.  Methane in its atmosphere gives it a blue tint  13 known rings; 27 known moons, named after characters from works of Shakespeare and Alexander Pope 20 Uranus' moon Ariel (white dot) and its shadow (black dot) were caught crossing the face of Uranus in this Hubble Space Telescope image. Credit: NASA/Space Telescope Science Institute

21 Planets: Neptune  8 th planet from the sun  Discovered in 1846  Orbit takes 165 years  4 th largest by diameter after Uranus  Also a gas or ice giant  Blue due to methane plus some unknown substance in the atmosphere  6 known rings; 13 known moons (Triton, the largest, has a retrograde orbit) 21 Voyager 2 captured this image of Neptune in The picture shows the Great Dark Spot and its companion bright smudge. Credit: NASA

22 Meteoroids, Meteors, and Meteorites  Meteroids: chunks of metal or stone that orbit the sun  Meteor: a streak of light produced by a meteoroid burning due to friction as it plunges through the atmosphere; a shooting star  Meteorite: a meteoroid that strikes the Earth’s surface Most contain iron, nickel, and stone 22 The Hoba meteorite in Located in Namibia, it is the largest known meteorite on Earth, about 54,000kg.


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