1 Solar System Debris: Comets and Asteroids Primarily found in two zones in the solar system. The Asteroid Belt (rocky, between Jupiter and Mars) The Edgeworth/Kuiper Belt (beyond Neptune) and Oort Cloud (way out there) sources of comets (icy)
Solar System Debris: Comets and Asteroids Why do these things exist?... Solar system formation is a messy process. 2
Solar System Debris: Comets Beyond the orbit of Neptune material was sparse and planetary accumulation times were very slow. Some icy planetesimals remain. Some were ejected to great distances by encounters with the giant planets. Occasionally one has an orbit modified so that it falls into the inner Solar System. Warmed by the Sun, ices sublimate away and dust is released making a comet. 3
4 Comets Comets originate in the Oort Cloud and the Edgeworth/Kuiper belt. Collisions and gravitational tugs can send them falling into the inner solar system.
5 Cometary Orbits Since comets can fall into the inner solar system from great distances, many have highly eccentric elliptical orbits outside the plane of the planetary orbits.
What Happens When You Heat Up an Icy Asteroid Note that the ices involved include CO2 and ammonia in addition to water vapor. 6
What Happens When You Heat Up an Icy Asteroid Gasses and debris stream away from the evaporating nucleus. Comet Hartley 2 observed by the (recycled) Deep Impact spacecraft. 7
8 Cometary Nuclei Cometary nuclei are basically dirty snowballs a few kilometers in size. Although small, this lump of ices (water, carbon dioxide, ammonia,...) is the source of all of the interesting phenomena.
9 Cometary Nuclei Comets are basically dirty snowballs a few kilometers in size. When close to the Sun, volatile ices such as CO2 and water sublimate and create jets of gas and dust.
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Comets Comets are basically dirty snowballs a few kilometers in size. During the brief time they are close to the Sun, water, CO2 and other ices are vaporized and create a cloud of gas and dust around the tiny nucleus. Pushed away from the Sun by the solar wind and sunlight, this tenuous debris can stretch a distance equal to the diameter of the Earth's orbit. 13
Cometary Nuclei 14 Comets are basically dirty snowballs a few kilometers in size. When close to the Sun, volatile ices such as CO2 and water sublimate and create jets of gas and dust. Jets and rotation combined The Nucleus of Comet Halley with jets Sunlight and solar wind push back a tail
15 Cometary Tails Gases and dust vented by the nucleus get pushed back by the pressure of sunlight and solar wind. Comet tails point away from the Sun Jets and rotation combined The Nucleus of Comet Halley with jets Sunlight and solar wind push back a tail
16 Cometary Tails Comets have two tails A gas tail pushed directly away from the Sun by solar wind and sunlight A dust tail also pushed away from the Sun, but with some memory of the comet's path.
17 Cometary Tails Comets are basically dirty snowballs a few kilometers in size. Comets have two tails A gas tail pushed directly away from the Sun by solar wind and sunlight A dust tail also pushed away from the Sun, but with some memory of the comet's path.
18 Cometary Tails Comets have two tails A gas tail pushed directly away from the Sun by solar wind and sunlight A dust tail also pushed away from the Sun, but with some memory of the comet's path.
19 Cometary Tails Comets are basically dirty snowballs a few kilometers in size. Comets have two tails A gas tail pushed directly away from the Sun by solar wind and sunlight A dust tail also pushed away from the Sun, but with some memory of the comet's path. STEREO mission
Notable Cometary Exploration Missions Giotto and Vega missions to Halley's comet Stardust (afterlife in progress) Fly through a cometary coma, collect material and return it to Earth! Deep Impact (afterlife in progress) European and Soviet missions providing the first closeup look at a cometary nucleus (1986). Formation fly two spacecraft. Fly one, about the size and mass of a washing machine into the comet while the other one collects data. Rosetta (in progress) Formation fly with a comet and monitor its activity. 20
Stardust 21
Stardust 22
Stardust 23
Stardust 24
Deep Impact Launch a pair of spacecraft. Have one observe while the other (about the size of a washing machine) impacts the comet. 25
Deep Impact Launch a pair of spacecraft. Have one observe while the other (about the size of a washing machine) impacts the comet. 26
Deep Impact Launch a pair of spacecraft. Have one observe while the other (about the size of a washing machine) impacts the comet. 27
Deep Impact Launch a pair of spacecraft. Have one observe while the other (about the size of a washing machine) impacts the comet. 28
Deep Impact/Stardust-NExT Re-visit the comet using the Stardust spacecraft and look for changes after six years. 29
Deep Impact/Stardust-NExT Re-visit the comet using the Stardust spacecraft and look for changes after six years. 30
Deep Impact/Stardust-NExT Re-visit the comet using the Stardust spacecraft and look for changes after six years. 31
Meteor Showers Comets are messy objects and spread debris around their orbits If the Earth intersects this debris trail we experience a meteor shower. Since the intersection point is a fixed location in the Earth's orbit, the shower associated with a given comet will occur annually on the same date. 32
33 Meteor Showers Prominent Reliable Showers Perseids Aug 11-13 Geminids - December 12-14 These showers produce 50-100 meteors per hour.
Watching a Meteor Shower Two required items a lawn chair and patience Expect to see a meteor a minute at best. Know your radiant (if the constellation is not up you can't see the shower). Moonlight is a killer. Some years are off years for the best showers. 34
Meteor Showers When a meteor shower occurs the meteors all appear to originate (radiate) from the same point in the sky (known as the radiant ) The shower is named after the constellation that contains the radiant. A shower can only be observed when it's radiant is above the horizon. Perseids after 1 a.m.; Geminids after 10 p.m. 35
36 Meteor Showers The illusion of a radiant is the effect of perspective. All meteors are moving through the atmosphere on parallel paths.
37 Meteor Showers The illusion of a radiant is the effect of perspective. All meteors are moving through the atmosphere on parallel paths.
Meteor Storms Occasionally the Earth moves through a dense clump of cometary debris. http://www.astro.virginia.edu/class/skrutskie/images/leo_1499_double.mpg 38