Variable Star #42 in Messier 4
The following images show the globular cluster Messier 4 (M4), a cluster that probably contains over 100,000 stars. On the left is
the full-field view; and on the right, a close-up of the region around
the variable star No. 42. The center part of M4 is so dense with stars that individual stars cannot be resolved.
While the individual images of the star are loading, take the time to
check the pattern of stars in the close-up region and see if you can locate that region in the outlying regions of the full-field view. Did you find it?
Images were taken of star No. 42 over a period of 12 hours one (winter?) night.
Following are 20 of those images, in random order to prevent any
measurement biases. (Images are shown as negatives so that the stars
are more apparent.)
After you have completed your
calibration of diameter vs apparent magnitude for the
standard stars, then go ahead and
click on any of the following images to get to the corresponding
interactive frame for star #42. Follow the directions given with the interactive page, first left-clicking on
the right-hand side of the variable star and then on the left-hand side. The script returns the
pixel number of each click for each frame. Record these two numbers. Subtract them and
write the diameter (Diameter 1 or Diameter 2) in the appropriate column for the appropriate time.
Remember,
you are doing two measurements of the diameter of the star for each frame.
