Lesson 3: Galaxies, Black Holes and Satellites

• Expected Learning– To learn about galaxies and black holes– To understand what Satellites are and how

they ‘stay up there’!

Galaxies

Three Types of Galaxies

1) Elliptical – oval shaped, no arms, little gas or dust clouds

2) Spiral – bulging nucleus (the center) with a least two arms that contain great clouds of gas & dust coming out on opposite sides

3) Irregular – stars spread unevenly, no distinct shape, least common

• Q. What do you call a crazy moon?• A. A Luna-Tick!

Elliptical

Spiral

Barred Spiral

Irregular

Black HolesThe intense gravitational field left when a giant star collapses

Black holes• The gravity of neutron stars, white dwarfs

and black dwarfs is so strong that it crushes atoms, so the matter in stars is millions of times denser than anything on earth.

• A black hole is formed if enough of this dense matter is left behind after a supernova explosion then the gravitational field is so strong that nothing can escape not even light.

• Scientists know they exist using x-rays

Black Holes

• There is general consensus that supermassive black holes exist in the centers of most galaxies.

• In particular, there is strong evidence of a black hole of more than 4 million solar masses at the center of our galaxy, the Milky Way.

Project – Galaxy maker

• Using Plasticine, chose a type of Galaxy and produce a mock up of it.

• Take a picture of the completed Galaxy and either– print it and include it in your workbook for

marking at the end of the unit– Download it and include it in your e-workbook

for marking at the end of the unit

Lets get back down to Earth!

• Satellites• The world's first artificial satellite, the

Sputnik 1, was launched by the Soviet Union in 1957.

• Since then, thousands of satellites have been launched into orbit around the Earth; also some satellites, notably space stations, have been launched in parts and assembled in orbit.

Satellites

• Artificial satellites originate from more than 50 countries and have used the satellite launching capabilities of ten nations.

• A few hundred satellites are currently operational.

• Thousands of unused satellites and satellite fragments orbit the Earth as space debris.

Non Earth Satellites

• A few space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, and the Sun.

• Q. What type of saddle do you put on a space horse?

• A. A saddle-lite!

Sputnik I

• ISS – Considerably bigger than Sputnik I

ISS – International space station

Satellites

Path followed by satellite

Path followed if gravity switched offPull of

gravity

Earth

How do satellites stay in orbit?

• http://spaceplace.nasa.gov/how-orbits-work/

• All satellites (even the moon) are falling towards the Earth. Because they are moving so fast horizontally they don’t hit it.

• To stay in orbit an object must be;– Moving very fast horizontally– Be above the Earths atmosphere so it doesn’t

get slowed down

Orbit prac

• In groups of 3-4, complete the experiment.

• Answer the questions onto the sheet and hand in one sheet for each group (put names on it!)

Useful orbitsThere are TWO main orbits that are useful called POLAR and EQUATORIAL.

POLAR -The orbit is close to the Earth, only just above the atmosphere. With a good camera you can see the headlines on a newspaper!

Because the Earth spins the satellite will ‘see’ every part of the Earth once every 24 hours.

This orbit is used for spy and weather satellites.

Polar orbits

Equatorial orbits

At the right distance the satellite will take 24 hours to orbit the Earth. Because the Earth is also spinning once each 24 hours the satellite stays above the same place on the Earth all the time. We call this a GEOSTATIONARY orbit.This orbit is used for communication satellites, like Sky TV.

Environmentally friendly!

• Video – ‘How many satellites’ (1min)• http://

www.youtube.com/watch?v=cfSaztUiw5s• Video – ‘Space debris’ (4min)• http://

www.youtube.com/watch?v=L915JJMcu4s&feature=endscreen&NR=1

Homework

• Star gazing – due 21/5/12– Below the level: planisphere made and

handed in– At the level: planisphere made and labelled

star diagram handed in– Above the level: planisphere made, labelled

star diagram and star information poster handed in

Homework Reflection

• Find out whether a satellite has ever been hit by a meteor/asteroid or comet