ExoplanetsBig Science: Big Telescopes

Jodrell Bank Discovery Centre

ContentsPart 1: Big Telescopes– Why do we need so many

telescopes?– Why build big telescopes?

Part 2: Big Science– Hunting for exoplanets– Are We Alone in the Universe?

Part 1: Big Telescopes Why do we need so many telescopes?

Light is an electromagnetic wave that travels through space...

...but light is not the only EM wave travelling through space

An object can give off any of these EM waves...

Radio waveskm to metres

Microwavescentimetres

Infraredmicrometres

Visible lighttenths of amicrometre

Ultravioletnanometres

X-raystenths of

nanometres

Gamma rayshundredths ofnanometres

Astronomers observe the universe in all of these waves

Part 1: Big Telescopes Why do we need so many telescopes?

Part 1: Big Telescopes Why do we need so many telescopes?

The Lovell Telescope

Telescopes collect EM waves and bring them to a focus

Part 1: Big Telescopes Why build big telescopes?

Part 1: Big Telescopes Why build big telescopes?

• Larger telescopes collect more waves• Fainter objects can be seen• Like a pupil dilating in dim light!

Larger telescopes can also create sharper images

Why build big telescopes?

Part 1: Big Telescopes Why build big telescopes?

The Square Kilometre Array

• Planned for 2020, it will be the most powerful radio telescope ever• It will be so sensitive it could detect an airport radar 50 light years away• It will collect enough data every day to fill 15 million 64 GB iPods

Quick Quiz!

1. How do you think it would it affect your vision, if your eyes were half the size?

2. If your eyes could see radio waves, what do you think a mobile phone mast would look like?

Quick Quiz!

1. How do you think it would it affect your vision, if your eyes were half the size?

Your eyes couldn’t collect as much light, so things would be darker. Also, things would be more blurry.

2. If your eyes could see radio waves, what do you think a mobile phone mast would look like?

It would look bright, like a streetlamp!

Part 2: Big Science The hunt for exoplanets

The hunt for exoplanets

Part 2: Big Science The hunt for exoplanets

Before we continue…

1. Multiply your time by 100 days(e.g. 2 seconds becomes 200 days)This is to make your results more realistic!

2. How many Earth years does it take for your planet to orbit its star?

Part 2: Big Science The hunt for exoplanets

32 A.U.in Sun from DistanceyearsEarth in Orbit

Kepler’s third lawFor planets orbiting the Sun…

32 DT

1 A.U. (or ‘Astronomical Unit’) is just the distance between the Earth and the Sun

How far away would your planet be from

its star?

Analysing your results: How far out is your planet?

32 DT

Part 2: Big Science The hunt for exoplanets

DT 3 2

Mercury = 0.4 AUVenus = 0.7 AU

Earth = 1 AUMars = 1.5 AU

Jupiter = 5 AUSaturn = 9.5 AUUranus = 19 AU

Neptune = 30 AU

Compare your planet to our Solar System.Distance from Sun to…

Analysing your results: How far out is your planet?

Part 2: Big Science The hunt for exoplanets

Area of a circle?

You have already calculated the percentage starlight blocked by your planet (B)

22 RBr Radius of Sun = 700,000 km

What’s the radius of your planet?

Analysing your results: How big is your planet?

star of AreaB planet of Area

Part 2: Big Science The hunt for exoplanets

Radius of Earth = 6,400 kmRadius of Jupiter = 70,000 km

2BRr

Analysing your results: How big is your planet?

Compare your planet to our Solar System.

22 RBr

Part 2: Big Science Are we alone?

Are we alone in the universe?August 2013: Scientists have detected a total of 929 exoplanets

Star Kepler-22

Part 2: Big Science Are we alone?

620 light years away

Part 2: Big Science Are we alone?

In 2011, astronomers found planet ‘Kepler-22B’ around this star…

Kepler-22B is…• Approximately Earth sized.• About the same distance away from its star as the Earth is from the Sun.AND, its star is very similar to the Sun!

(this is only a drawing of

what it might look like!)

Are we alone?What do you think?

Part 2: Big Science Extension activity

What type of exoplanets do you think are the easiest to find?Why?

1. Larger exoplanets2. Exoplanets that are closer to their stars

Both of these cause a larger dip in the star’s light, making them easier to detect.

So far, most of the exoplanets found have been “hot Jupiters”.These are large gas planets, but very close to their star.

Part 2: Big Science Extension activity

What assumptions did we make when calculating the distance and size of your exoplanet?

• That your star is like the SunIn actual fact, the star may be a different mass. This will change how quickly a planet orbits around it, which will affect the distance calculation.Also, the star may be a different size. This will affect the planet size calculation.In real life, astronomers take measurements of a star’s light to see if it is like the Sun or not.

• That your planet passes next to your starIn actual fact the planet will likely be hundreds of millions of km closer to us than the star, which will make it look slightly bigger. This will also affect the planet size calculation.In real life, astronomers estimate the distances to stars and planets, so they can take this into account.

Part 2: Big Science Extension activity

Consider the following questions...

1. Can you think of any situations where the method we have used to detect exoplanets would not work? (hint: look at the animation below for one way)

2. We assumed that your stars were identical to the Sun. What effect would it have on the size of your planet if the star were actually…

a) Larger than the Sun

b) Smaller than the Sun

3. What effect would it have on your planet’s distance from the star if your star was…

a) More massive than the Sun (more gravity)

b) Less massive than the Sun (less gravity)

4. If your star is like the Sun, do you think there is any chance of there being life on your planet? Why?

5. Would there be more or less chance of life if your star was…

a) Hotter than the Sun

b) Colder than the Sun

Part 2: Big Science Extension activity

Answers…

1. This method only works if, from our point of view, the planet passes in front of the star. If the planet orbits the star on a different plane, we will not see a dip in the light.

2. We calculated the size of your planet by comparing it to the size of your star, which we said was the same as the Sun. If your star was…

a) Larger than the Sun; the planet would be larger than calculated.

b) Smaller than the Sun; the planet would be smaller than calculated

3. We calculated the distance of your planet from its star by looking at how fast your planet was orbiting its star. We assumed the relationship was the same as the planets of the Solar System going around the Sun. If your star was…

a) More massive than the Sun (more gravity), then the planet would orbit quicker than expected. Therefore, the planet may be further out than calculated.

b) Less massive than the Sun (less gravity), then the planet would orbit slower than expected. Therefore, the planet may be closer to its star than calculated.

Questions 4 and 5 depend on your results.