How do astronomers measure distance

How do astronomers measure distance

Have you ever measured anything?

Rulers

Tape measures

Yardsticks

Open Ended

What are some units we measure things in. Example (cm)

Measuring Distances

• Most distances on the Earth can be measured in meters or kilometers.

• How would you measure the distance from the Earth to the stars?

Measuring Distances

• You might use kilometers as a unit of measurement. However, astronomers have found that the distance to even the nearest start is too great to measure in kilometers.

• The distances are so great that the numbers are too large to work with easily.

Proxima Centauri

This is the closest star to Earth, other than the sun. It is 40,000,000,000,000 km (forty trillion) from the Earth.

As you can see this is a very large number so astronomers had to create their own units to measure distances in space.

Open Ended

Why is it hard for scientists to measure the distance from the Earth to the stars?

Multiple Choice

In order to solve the problem from the previous question, astronomers had to create their own

• ruler

• unit of measurement

• measuring device

• nothing

Light Year (To Infinity and Beyond)

• Astronomers measure the distance to an object in space in light year.

• A light year is equal to the distance light travels in one year.

• Light travels through space at a speed of 300,000 km/sec.

Light years

• One light year is equal to almost 10 trillion km. the light from the sun reaches the earth in a little more than 8 minutes

• Light from the North star, Polaris, takes about 300 years to reach the Earth.

Open Ended

What unit is light measured in? (Think of Buzz!)

Multiple Choice

Light travels at the speed of

• 3 km/sec

• 300 km/sec

• 3000 km/sec

• 300,000

Multiple Choice

The light from the sun reaches Earth in about how many minutes

• 7 minutes

• 100 minutes

• 2 minutes

• 8 minutes

Astronomical Units

One of the units astronomers is equal to the distance from the Earth to the Sun.

Poll

Do you know how far away the sun is? Take a guess below!

• 1 million km from earth

• 15 million km from earth

• 150 million km from earth

• one plan ride away

Astronomical Units

• The sun is actually 150 million km from Earth.

• Astronomers call this distance and astronomical unit.

• 1 astronomical unit or 1 AU is equal to 150 million km.

Distance of Planets from the Sun in AU