How Big is a Billion?

Size and scale One galaxy, 200 billion stars!

The beach: a good place to contemplate the stars

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

This is one cubic metre

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

200 cubic metres of sand = 200 billion grains of sand

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

Change Gears HR8799: star with 3 planets

HR8799: star with 3 planets

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

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

Eyepiece expectations Binoculars Telescopes