Know about Pluto Know about the Asteroids Know about Comets Comprehend the Oort Cloud and Kuiper Belt Asteroids and Kuiper Belt Objects
The Discovery of Pluto Percival Lowell predicted the existence of an additional planet in 1905 Clyde Tombaugh used a device called a blink comparator, spotting the “jump” of a tiny dot on a photograph on 18 Feb 1930
Pluto’s Orbit and Atmosphere Pluto’s orbit is eccentric Averages 40 Aus from the Sun, but it ranges from 30 units to 50 units An Astronomical Unit, or AU, is the mean distance between the Earth and the Sun, about 93 million miles A Parsec is also a measure of distance, roughly (3.26 LY or 19 Trillion Miles)
Pluto’s Orbit and Atmosphere Pluto has an atmosphere, but not year-round At perigee it “warms up” At apogee it receives so little solar energy that its surface is below the temperature at which methane freezes
So Why is Pluto Not a Planet? August 24, 2006, the International Astronomical Union (IAU), an organization of professional astronomers, passed two resolutions that collectively revoked Pluto's planetary status By definition, a planet: Orbits around the Sun Has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape Has cleared the neighborhood around its orbit
Asteroids The asteroid belt – the region between Mars and Jupiter where most asteroids orbit Jupiter’s gravitational pull has created gaps in the asteroid belt at 2.50 AU and 3.28 AU
The Origins of Asteroids Astronomers once thought that asteroids were the remains of a planet that had exploded Explanation that seems more plausible today: asteroids are simply primordial material that never formed into a planet Jupiter’s gravity keeps pulling on objects in the asteroid belt and stirring them up
Project Dawn
Comets’ Predictable Orbits Around the Sun In 1705 Halley boldly predicted the comet’s return in 1758 On Christmas night of 1758, Comet Halley appeared in the sky Scientists have traced Halley sightings back to 239 BC Halley's Comet's last appearance was in 1986, and its average period of revolution around the Sun is 76 years. But it turns out that the gravitational pull of the giant planets creates variations in that period of up to a few years (so the time between successive appearances isn't always exactly 76 years). Its next appearance should be in 2061.
A Comet’s Three Main Parts A comet consists of a head and a tail 1. Head is made up of a nucleus—the solid core of a comet—and a coma 2. A coma is the part of a comet’s head made up of diffuse gas and dust 3. The tail of a comet is the gas and/or dust swept away from the comet’s head
The Shell of Comets Surrounding the Solar System In 1950 Oort revived an idea that in a space far beyond Neptune’s orbit, a great number of comets orbit the Earth Oort cloud - a theoretical sphere, between 10,000 AU and 100,000 AU from the Sun, containing billions of comet nuclei
The Small Band of Comets That Make Up the Kuiper Belt In 1951 Kuiper proposed a second, smaller band of comets within the Oort cloud The Kuiper belt is a disk- shaped region beyond Neptune’s orbit, 30 AU to 1,000 AU from the Sun and the presumed source of short-period comets
Meteors vs. Meteorites Meteor – a streak of light in the sky caused when a rock particle falling to Earth is so heated by friction with the atmosphere that it emits light Fireball – an extremely bright meteor Object that causes the meteor is a meteoroid Meteorite is an interplanetary chunk of matter that has struck a planet or a moon
Know about Pluto Know about the Asteroids Know about Comets Comprehend the Oort Cloud and Kuiper Belt Asteroids and Kuiper Belt Objects