Our Solar Neighbourhood

“protoplanet hypothesis” = model to explain the birth of solar systems

1. cloud of dust and gas begins to swirl2. most material accumulates in the

center and forms the sun3. remaining material accumulates in

smaller clumps circling the center to form the planets

“Protoplanet Hypothesis”

The Sun

• Telescopes with special filters have allowed us to look at the sun

• The sun is almost 110 times wider than Earth• Surface of the Sun is about 5500 C, core is

about 15 000 000 C• Solar wind is release charged particles that

flow from the sun at about 400 km/s (we are protected by it on Earth due to our magnetic field)

The Planets

• Those objects that:– Orbit the Sun– Have sufficient mass to assume a round shape– Have their own gravitational pull

SUN > Mercury > Venus > Earth > Mars > Jupiter > Saturn >

Uranus > Neptune

The Planets• Can be divided into two distinct groups: – The inner planets (terrestrial – “Earth-like” planets);

tend to be smaller and rockier in composition– The outer planets (Jovian planets or gas giants); are

large and gaseous and are located great distances from the Sun

• All the planets, (except Pluto) have been visited by space probes (unmanned satellites, or remote-controlled “landers” used to explore areas or objects in space that are too dangerous to send humans to)

Other Solar Bodies• Asteroids = between Mars and Jupiter lies a

narrow belt of small, rocky or metallic bodies travelling in space

Comets

• Also called “dirty snowballs” are objects made of dust and ice that travel through space

• They appear to have bright long tails that glow only when they get close to the Sun; this is because the Sun heats the materials and gases are released and pushed away by solar wind

• When comets get close enough to the inner solar system they can begin to orbit the sun

• Halley’s Comet last visited in 1986 and will return again in about 2062

Meteoroids, Meteors, Meterorites

• Meteoroid = small pieces of rocks flying through space with no particular path

• Meteor = when an meteoroid gets pulled into Earth’s atmosphere by gravity the heat causes it to give off light (“shooting star”)

• Meterorite = when a meteor actually hits the Earth’s surface

Eclipses

• Because we know the path of planets is elliptical, we can accurately predict events such as Eclipses

• Solar Eclipses occur when the moon passes between Earth and the Sun and thus casts a shadow on Earth

• Lunar Eclipses occur when Earth passes between the Sun and the Moon, casting its shadow over the Moon

Solar Eclipses

•Occurs 2-5 times a year•Only lasts a few minutes

Solar Eclipse

http://www.teachersdomain.org/resource/ess05.sci.ess.eiu.eclipse/

Lunar Eclipse

SEM

•Occurs every 6 months •Can last a few hours

Lunar Eclipse