Dec. 18 – Satellites and Distances

Unfortunately it was too cloudy last night for you to make use of your star finders.  Hold onto them and try them out over the holidays.  One day we might get a hight without snow!

Learning Goals: 

• Understand the basic functions of satellites.
• Understand how astronomical distances are described.

Success Criteria:

• You can describe how satellites orbit and describe some major uses of artificial satellites.
• You can convert between kilometers, astronomical units and light years.

The Earth has one natural satellite... the Moon.

But there are many artificial satellites that are made by humans.

These satellites provide us with many useful functions:

Uses of artificial satellites.

• Spying
• Communication (phones, radio, tv)
• GPS (Global Positioning System)
• Weather
• Maps
• Scientific Research
• International Space Station (ISS)

Chris Hadfield is a Canadian astronaut who was the commander of the ISS earlier this year. 

While Commander Hadfield was up on the International Space Station he took many photos and made many videos which he posted online.  Here's one of them:

How does the ISS and other satellites stay in orbit?

- They move at a specific speed to stay in orbit.

- They are constantly falling, but never reach the Earth.

Types of orbit.

 - The higher the altitude the longer the orbit.  The ISS is 350 km up and orbits in 90 mins.

    -  Low Earth Orbit (under 2000 km)

        eg. Polar Orbit

    -  Medium Orbit (under 35 000 km)

        eg. GPS satellite in geostationary orbit (24 hr period)

     - High Elliptical Orbit (over 40 000 km)

CHAPTER 9: Beyond our Solar System

The Moon is about 384 400 km away from the Earth.

Earth is about 150 million km away from the Sun.

  1.5 e 8 km = 1 AU (astronomical unit)

• Mars is 1.5 AU from the Sun.
• Jupiter is 5.2 AU from the Sun.
• Pluto is about 30 AU from the Sun.

The nearest star to the sun is Proxima Centauri.  It is 4.0e13 km away from the sun, about 270 000 AU.  Clearly we need a unit that is even larger than AU.

Light Years

Light travels at a speed of 

300 000 km/s.  How far does light travel in one year?

300 000 km/s x (60 s/min) x (60 min/hr) x (24 hr/day) x (365 days/year) x (1 year)

    =  9.46 e 12 km

This is one light year.

How many light years away is Proxima Centauri?

Here's how you do the calculations:

For some comparison, Polaris is 400 ly away.

The closest galaxy to the Milky Way, Andromeda, is 2 600 000 ly away!

Here are some other distances,

How do we measure these distances?

Parallax - apparent change of position due to location.

We can use the apparent change in position to triangulate the distance.

Homework:

• P. 343 # 1-5, 7-10