• Q
1 We see the Crab Nebula is about 1.35 parsecs in radius and is expanding at a rate of 1400 km/s. Estimate when would the supernova have exploded?
•
•d.
920 years ago.
•
•Time =
distance/rate = 1400 km/s x 1.35 pc.
Must convert
parsecs to km using 1 pc = 3.1 x 1016 m
= 3.1 x1013 km, so we get 4x1013 km, which we can now divide by 1400 to get the answer in
seconds: 2.9x1010 s,
which must be converted to years (3.1x107 seconds per year), which gives us 920 years.