1. How Big is a Billion?

2. Size and scale
One galaxy, 200 billion stars!

3. The beach: a good place to contemplate the stars

4. Grains of sand as stars
1 sand grain = 1 star
Sand grain “star” = 1 mm

5. This is one cubic metre

6. One billion grains of sand
1 cubic metre
= 1000mm x 1000mm x 1000 mm
= 1,000,000,000 grains of sand

7. 200 cubic metres of sand = 200 billion grains of sand

8. Grains of sand as stars Star separation =4-5 light years
Sand grains separated by 30 km at this scale

11. Change Gears
HR8799: star with 3 planets

12. HR8799: star with 3 planets

13. HR8799: properties Young - 60 million years old 140 light years away
Mag = 5.96
1.5 solar mass
Bright A-type star
~5 solar luminosity
Planets ~ 10, 10, 7 Jupiter masses
Planets are 24, 37, 67 times Earth-Sun distance from their star
Star has massive dust disk
Probably more planets hiding in dust
Planets still warm from formation
Planets have atmospheres

19. The view through a telescope
Change Gears Again
The view through a telescope

20. Eyepiece expectations
Binoculars
Telescopes