1. Who's who in orbit

1 A.U. = 1.5 x 10⁸ km

c = 3 x 10⁵ km/s

light travel time = A.U. / c

500 seconds per A.U. (8.33 minutes)

2. What's (who's) next?

The Oort cloud:

50,000 A.U. from the sun (guess)

light days!

What comes from this cloud of Oort's?

comets!

And then what?

The interstellar medium .... stay tuned (week 8)

What defines the edge of the solar system?

the heliopause

...where the pressure from sun's wind (solar wind) equals the pressure from the interstellar medium.

The sun's radiation blows a bubble (a cocoon?) in the disk of our galaxy.

Where is the heliopause?

We don't know

Why not ? (since we know so much about the Sun's radiation)

We don't know enough about the local interstellar medium.

Voyager 1 and 2 may find out in your lifetime!

3. Comparative Planetology

How and why did planets form to be so different?

distance from sun

mass

size (radius)

density = mass / volume

(volume = radius³

composition

spin (tilt and speed)

Example:

composition

distance from sun

internal heat

mass and composition

distance from sun

escape velocity

mass and temperature

distance from sun

4. Key Planetary Properties

(a) distance from the Sun

(b) the tilt of rotation axis

(c) the rotation period

(d) the age

(e) the number of moons