earth sci chps 17-19.doc

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Western University
Earth Sciences
Earth Sciences 1086F/G

UNIT 6 – Plutoids, TNOs, and Comets ­ Introduction: o Beyond Neptune are million of icy bodies called Trans-Neptunian Objects (TNOs).  Pluto is one of them, and Eris, Makemake, and Haumea (all dwarf planets) ­ When Pluto changed over from a planet to a dwarf there was much commotion for their termed it a Plutoid: o A celestial object that satisfies three conditions:  It orbits around the sun at an average distance greater than Neptune  It is massive enough that its own gravity beings it to equilibrium, making it near-spherical  It has NOT cleared the neighborhood around its path from other orbiting debris. ­ Comets: aggregates of ice, frozen gasses and rock dust/fragments travelling through the solar system. o Usually on paths that are anchored with the Oort Cloud (long-period comets). o Tiny fragnets falls off and that is bright light we see o Most live for hundreds of passes. Chapter 17: pLuToIdS and TNOs ­ Introduction: Definitions and Locations o Pluto had to be dwarf because so many like it very being discovered that we couldn’t have 50 planets. o Plutoids: Pluto, Makemake, Haumea, and Eris. o TNOs: any size object in te solar system that orbit Sun at a greater distance than Neptune. Includes the Kuiper Belt and Oort Cloud. ­ Pluto: o Tombaugh used a blink comparer o 1930 he discovered it – but it was not as large as they thought ­ Planetary Facts: o Highly elliptical orbit – goes from 49 to 29 Au distance from the Sun o 2.03 density o Tilt: 119 degrees o Satellites: 3 (Charon is the biggest) o Rings: None o Usually the farthest from the Sun, b/c Pluto’s orbit is not circular, it is elliptical. It swings inside the orbit of Neptune sometimes. o The planets will never collide though. o Very cold. 50K (-223) o Best guess at the interior  Frozen nitrogen, water icce, mic of silicate rock and water ice.  It must have a component of rock (2/3 the size of the moon but twice as dense as water)  Nitrogen makes up most of the atmosphere. ­ Charon o 1979 discovery o Orbits Pluto in a nearly circular orbit o Tidally locked to each other o Must contain 35% ice and 65% rock (both Pluto and Charon) o Surfaces contrast o Both go through dramatic seasons o Most of the surface is covered with ices from seasonal freezings. New Horizons will figure this out for us. o Charon doesn’t fit the label of satellite  Why? Because the centre of gravity of a planet-satellite system is within the parent planet. But the centre of gravity is in the space between Pluto and Charon ­ Trans-Neptunian Objects o Where dwarf planets are classified. o Eris: orbits the Sun in a space farther out that Pluto, but closer than the main part of the Kuiper Belt.  Scattered Disc: the inner section f the Kuiper Belt – indicates the population of objects it in th  Eris originally called the 10 planet as it is bigger than Pluto.  Dysnomia orbits Eris as it’s satellite. ­ The first object of the Kuiper belt was not found until 1992. o Now TNOs are being found at a high rate. o The Kuiper Belt will be a much bigger version of the Asteroid Belt. Chapter 18 – CoMeTs ­ Introduction: o What are comets? Small icy objects that streak throught he Solar system, along sun-orbital elliptical tracks  The frozen gases begin to vaporize as they go along and leave visible tracks across space. o Why study comets?  They brought evidence that comets brought water to Earth, providing life.  They brought the amino acids to Earth – 40, 000 tons of particles from comets fall to Earth every year.  Comet nucleus is cold  Life cannot start ON them ­ Anatomy o Diagram of a comet: (replace plasma tail with Ion Tail) ­ The Nucleus: o Nucleus + coma are called the heat of the comet. o Centrally located, contains dust and frozen gases. Not solid objects. o Irregular bodies with voids. o Can fragment into more than one piece ­ The Coma: o An atmosphere surrounding the nucleus o Dominated by water then CO2 ­ The Tail o Sprout 2 tails when close to Sun o One: Dust tail  It reflects sunlight – made of dust o Two: Ion Tail  Made of glowing gas because it is releasing light energy  Pushed away from the sun by solar wind  Points ina different direction ­ Orbits o Long-period comets – majority take thousands of years to go around the sun o Short-period comets – 200 years or less orbital period, they dotn go much past Pluto o Don’t follow a strict orbit ­ Life and Death o Active comets (short-life) – mass loss at rates that cannot be sustained forever. o The active comets are under the gravitational control of the planets
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