Class Notes (1,100,000)
CA (630,000)
UTSG (50,000)
AST (700)
AST101H1 (500)

September 15

Astronomy & Astrophysics
Course Code
Michael Reid

of 1
assignment #1 is posted on
office hours. teaching prof will stick around after
R. 12-1 on Thursdays: AB129
S. Kelly - online office hours, on Portal
T. assignments due monday at 11:59 pm
our solar system is special. the ones we’ve found are really different. special feature: the
way our planets are spaced out. all the small planets crammed against the sun, that’s
unique. means it’s warm for us = life. other planets are spaced out a whole lot.
1AU = average distance from Earth to Sun
intuitive unit. Mars is 1.5 AU from sun, so, 1.5x the distance the earth is from the sun
t takes a light a few years to travel between stars
the distance between the sun and the center of the galaxy is 26,000 light years = it
takes light 26,000 years to reach us from the center of the galaxy
galactic bulge, at the center of it, supermassive black hole, billion times bigger than our
milky way’s a pretty big galaxy
*light travels at a finite speed* = anywhere you look, you’re looking back in time, always