Challenger Mission: Rendezvous with a Comet
Rendezvous • To meet up in a location
A probe entering a comet Courtesy: Pat Rawlings - Deep Impact -NASA & JPL
Simulation • Acting out an activity (space mission)
Earth is a part of The Solar System
Our Solar System is part of the Milky Way Galaxy Which is part of the Universe.
Our Sun Hot ball Of gases
asteroids Rocky metallic objects that orbit the sun
1801 Year Giuseppe Piazzi discovered the first asteroid, Ceres
4.6 Earth years it takes the asteroid Ceres to travel around the sun (Ceres – Biggest Asteroid with a 960 km circumference)
2880 Year asteroid 1950 DA will pass close to Earth – The greatest known impact hazard
Asteroids • Asteroids are small, rocky worlds. • Most asteroids revolve around the sun between the orbits of Mars and Jupiter. (asteroid belt)
100 km • 212 Million years old • Canada
A S T E R O I D B E L T
Meteor shower A chunk of metal or rock that reaches Earth from space meteorite
Meteoroid • A meteoroid is a chunk of rock, metal, or dustin space.
A Meteor: “A shooting star” Shooting stars are not actually stars. These flashes of light across the sky are small bits of rock burning up in the Earth’s Atmosphere.
Meteorite Meteoroids that survive as they pass through the atmosphere and hit Earth’s surface are called meteorites.
http://www.meteorlab.com/METEORLAB2001dev/Open1.htm There are three major types of meteorites: stone, iron and stony-iron.
Barringer Meteor Crater, Arizona A meteorite can make a hole, or crater, in the ground when it hits it. The larger the meteorite, the bigger the hole.
METEOROID:A piece of stone or metal that travels in outer space. METEOR:An object from space that becomes glowing hot when it passes into Earth's atmosphere. METEORITE:A piece of stone or metal from space that falls to Earth's surface.
comets • Lumps of ice and dust that periodically come to the center of the solar system from the outer reaches.
Dirty Snowballs • Comets are dusty chunks of ice • During each orbit around the sun they partially vaporize • Have elliptical orbits • They are about the size of an earth mountain. (dirt and ice) • Comets’ orbits are usually very long, narrow ellipses. • They produce tails of gas and dust when they approach the sun. Courtesy: Calvin J. Hamilton
History • Unlike the other small bodies in the solar system, comets have been known since antiquity. There are Chinese records of Comet Halley going back to at least 240 BC. The famous Bayeux Tapestry, which commemorates the Norman Conquest of England in 1066, depicts an apparition of Comet Halley. • As of 1995, 878 comets have been cataloged and their orbits at least roughly calculated. Of these 184 are periodic comets (orbital periods less than 200 years); some of the remainder are no doubt periodic as well, but their orbits have not been determined with sufficient accuracy to tell for sure.
The history of comet watching dates back to 1000 BC from the Chinese records and Chaldea, a place in present Iraq. • Comets have been regarded as omens, even as recently as 1986. • Battle of Hastings - 1066 • Today astronomers study comets from scientific perspectives, and our understanding of these fascinating objects have grown tremendously.
Structure of a Comet • Solar heat vaporizes the nucleus to produce • Coma - Hydrogen gas Envelope • Dust tail • Ion tail Courtesy: Deep Impact - NASA & JPL
Parts of a Comet • When they are near the Sun and active, comets have several distinct parts: • 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; • hydrogen cloud: huge (millions of km in diameter) but very sparse envelope of neutral hydrogen; • 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.
Comet Nucleus (plural: Nuclei) • A drawing of what the surface of a comet might look like. • The nucleus of a comet is the central portion of the head of a comet. It is a solid part of the comet, made of a special sort of dust which is called "fluffy" because it could be as light weight and full of holes as a sponge. The holes of this "sponge" are filled with ices like water, carbon dioxide (dry ice), and carbon monoxide (what comes out of your car).
Coma • This cloud, called the coma, is the atmosphere of the comet and can extend for millions of miles. The cloud is very thin, however, 10,000 times thinner than a cloud in the Earth's atmosphere! • The neutral particles that are in the coma can actually become excited by the solar wind causing the particles to become ions. A continual stream of neutral particles is produced as long as the nucleus is evaporating, and these neutral particles are continually converted to ions. These ions are what help form the comet tail.
Tails • A comet generally has two tails, not one. One tail is due to the comet's dust particles, the other is due to ionized gas from the comet coma. Dust particles form the first tail. This comet tail generally points back along the comet path (so if the comet is traveling right, the dust tail extends to the left). • Ions (electrically charged particles), which first come from the nucleus as (neutral) gaseous particles, are swept into the second comet tail. Because of the special interaction with the Sun's magnetic field, this tail always points directly away from the Sun.
Schematic of a Comet • This image is a schematic of a comet. The center part of the comet, or nucleus, is represented by the flame. The solar wind particles are shown as green dots with arrows. And the ionized particles are shown as green/red dots with arrows. Neutral particles are shown by the other dots (without arrows).
Orbits of Comets Aphelion distance • Elliptical in Shape • Randomly oriented Comet Sun Earth Perihelion distance
Comet Hunters • Comet are named by International Astronomical Union (IAU) after the person who first discovers them. • Many comets are discovered by amateur astronomers. • Charles Messier, E. E. Bernard, Shoemaker and Levy, Hale and Bopp, Ikeya, Seki and Hayakutake are popular comet hunters.
Origins of Comets • Comets are thought to be the left over debris from during the time of formation of the solar system. • The elliptical orbits of comets suggest that they underwent gravitational pull from the giant planets. • This all lead us to infer two possible locations where comets could start their journey towards the sun.
Possible Homes for Comets • Kuiper Belt • Oort Cloud Courtesy - Deep Impact - NASA - JPL
Kuiper Belt • Discovered by Gerard Kuiper in 1951 • The belt is 30 to 500 AU from the Sun • The plane of the belt is close to the ecliptic • Probably contains more than 100,000 objects • Some of these objects are 100 km or larger in diameter
Oort Cloud • Hypothesized by a Dutch Astronomer Jan Oort in 1950. • Shape is spherical distribution around the Sun. • 50,000 AU from the Sun. • May contain 5 trillion objects. • Probably created 4.6 billion years ago.
Comets and their Spectra • Spectroscopy is a technique in which light is broken into its component colors. Each chemical element show their fingerprint in the spectrum of the object. • We can thus find the composition of comets by identifying the fingerprints. • Most of the information on comets comes from infrared radiation, because comets are cold objects they radiate strongly at infrared radiation.