Question

The Crab Nebula is the home of the famous pulsar described in Destination 12. Below is a table of the radius of the nebula (really, half its major axis since the nebula is not circular

in appearance in the sky) and the date on which that radius was measured. This table starts in 1054 when the nebula was born during a bright supernova explosion observed that year. One of the first telescopic observations of the Crab was around 1755 by Charles Messier, with many subsequent measurements to the present day.

Date	Radius (pc)
1054	0.00
1755	1.09
1787	1.08
1810	1.14
1875	1.21
1928	1.32
1952	1.34
1995	1.42
2017	1.45

a) Using the data in the table, accurately plot the radius of the Crab Nebula (on the yaxis) versus the date (on the x axis). Be sure to note the units (keep in mind that ‘Date’ does have specific units . . .).

b) Estimate the slope of a line that fits the data well. This result is the expansion velocity of the nebula. Be sure to note the units of the slope!

c) Convert the result from part (b) to units of km/s .
d) The escape velocity from the Sun is about 11.2 km/s. How many times faster is the

Crab Nebula expanding compared to the Sun’s escape velocity?

Answer 1