MondaySeptember 20,

2010(Asteroids, Comets, Dwarf Planets, Video – Journey to

Edge of Universe)

The Launch PadMonday, 9/20/10

Identify

Announcements

We will have a test this

Friday.

Assignment Currently Open Pages Date of Notes

on Website Date Issued Date Due

Current Events in Earth/SpaceJupiter is approaching Earth for the closest encounter between the two

planets in more than a decade.The night of closest approach is Sept. 20-21st. This is also called "the night of

opposition" because Jupiter will be opposite the sun, rising at sunset and soaring overhead at midnight. Among all denizens of the midnight sky, only

the Moon itself will be brighter.Earth-Jupiter encounters happen every 13 months when the Earth laps Jupiter

in their race around the sun. But because Earth and Jupiter do not orbit the sun in perfect circles, they are not always the same distance apart when Earth passes by. On Sept. 20th, Jupiter will be as much as 75 million km closer than

previous encounters and will not be this close again until 2022.

Minor Members of the Solar System

Asteroids• Most asteroids lie between the

orbits of Mars and Jupiter.• They are small bodies – the

largest is Ceres, which is about 620 miles in diameter.

• Some asteroids have very eccentric orbits

• Many of the recent impacts on the Moon and Earth were collisions with asteroids

• They usually have irregular shapes and their origin is uncertain .

• We have landed a spacecraft on the asteroid Eros.

The Eccentric Orbits of Some Asteroids

Figure 22.25

Asteroids

Eros

Courtesy: NASA/JPL-Caltech

Eros

Dr. Frank SummersSpace Telescope Science Institute

March 28, 2008

Asteroid Impact Sites on Earth

Manicouagan, Quebec, Canada - a 200-million-year old eroded

impact structure

This impact crater in Winslow, Arizona, is one of about 200 on Earth. At 50,000 years old, it’s also one of the newest. The crater is 1.1 km

(.7 mi) in diameter and 150 m (495 ft) deep. The meteorite that made it weighed 100,000 tons. Most meteorites that hit the ground are too

small to leave a crater, but anything larger than a house explodes just before or during impact and leaves a crater that is much larger

than itself. Photo © Charles and Josette Lenars/CORBIS

Minor Members of the Solar System

Comets• Comets are often described

as large, dirty snowballs.• Composition of comets

▪ Frozen gases▪ Rocky and metallic

materials• The frozen gases vaporize

when near the Sun ▪ This produces a glowing

head called the coma.▪ Some comets may develop

a tail that points away from Sun due to radiation pressure and the solar wind

Minor Members of the Solar System

Comets

Orientation of a Comet’s Tail

as it Orbits the Sun

Figure 22.27

Minor Members of the Solar System

Comets• The origin of comets

is not well known because they form at great distances from the Sun.

• The most famous short-period comet is Halley’s comet, with a 76-year orbital period and potato-shaped nucleus (16 km by 8 km.)

Halley’s Comet

Minor Members of the Solar System

Meteoroids• Called meteors when

they enter Earth’s atmosphere

• A meteor shower occurs when Earth encounters a swarm of meteoroids associated with a comet’s path

• Meteoroids are referred to as meteorites when they are found on Earth

Minor Members of the Solar System

Meteoroids• Meteoroids are

referred to as meteorites when they are found on Earth ▪ Types of meteorites

classified by their composition • IronsMostly iron5%–20% nickel

•StonySilicate minerals with Inclusions of other minerals

Minor Members of the Solar System

Meteoroids• Meteoroids are referred to as

meteorites when they are found on Earth ▪ Types of meteorites classified by

their composition • Stony - irons – mixtures• Carbonaceous chondrites

Rare Composition – simple

amino acids and other organic material

May give an idea as to the composition of Earth’s core

Give an idea as to the age of the solar system

Dwarf Planets Dwarf planets are a new class of

planet.• They orbit the Sun.• They are not the only objects to occupy

their area of space.• The former planet Pluto is the prototype

of this new category.• Many dwarf planets are located in the

Kuiper belt, a band of icy objects found beyond the orbit of Neptune.

Dwarf Planets Pluto

• Pluto is not visible to the unaided eye.

• Discovered in 1930• Now classified as a

dwarf planet• Pluto’s moon Charon

was discovered in 1978.

• Pluto’s average temperature is -210ºC

Video (Part 2)