In this lab, you will use the spectra of the Ia supernovae to calculate their distance then draw a
conclusion about redshift over distance. The maximum brightness is the top of the curve. You will
notice the lower magnitude is actually brighter and thus higher on the graph. Astronomers have
determined the maximum brightness (M) for this type of supernova is -19.12, but you can round to
-19.1 for this lab.
Since astronomers have no real way of "checking" their answers to see if they are right (for example
by using a meter stick to measure the 'actual' distance to a supernova), they must rely on many
different distance indicators and their estimation of error in those measurements to see how close
they think their estimates are. As is the case with real data, some of the points will not fall on a
straight line; this is because we are using a simple technique to estimate the distance to the
supernovae. When astronomers calculated this same table they got answers that fell much closer to a
straight line because they used a more complicated technique.
Directions: Supernova Lab
1. Examine the nine (9) light curve graphs (shown at the end of the lab) for each supernova to get
a feel for how they all look.
2. For each supernova find the maximum brightness (m) on the curve and record it in the table
below these instructions. Remember the lower the number, the brighter the supernova. (If
you are using the PDF version of this document, recreate this data table or add in text boxes).
3. Calculate and record the distance modulus for each supernova. The distance modulus is
defined: D=m-M, where m=the observed maximum brightness you recorded, and M is the
absolute brightness for supernova. Each Type la supernova can reach a maximum absolute
brightness M of about -19.1, so D = m – (-19.1)
4. Use the Distance modulus (D) to find and record the actual d (distance in parsecs):
d = 10(D+5)/5 then find the d in km (1 parsec = 3.09x1013 km).
5. Make a plot graph of the Distance modulus (D) (y-axis) versus the redshift (x-axis).
6. Draw a best fit line on the graph, trying to get an equal amount of data points on each side of
the line. The line should be straight and not go through every single point.
7. Write a discussion/conclusion paragraph: Try to find a relationship between the redshift and
the distance. How does one relate to the other, could you suggest a mathematical equation?
Remember this is real data, so there may be some error and the equation may not be exact.
