Hubble's Variable Nebula

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The image with the earlier date has been subtracted from the image with later date, so darker than average areas on the combined image mean that position lost light over the elapsed time.

The images have be processed so that the background and average star brightness agree to within 1%.

The stars do not subtract to a null value because their shape is slightly different in each image. This is due to variations in seeing, focus and guiding.

The stars show non-concentric registration errors if their centres differ by as little as 1/10th of a pixel. In contrast the features of the nebula span many pixels and require much larger registration errors to display misalignment artifacts.

R Mon is imbedded in the bright ellipsoidal lobe of material at the base (south end) of the nebula.

Some of the subtracted images show a torus-like feature immediately north of (above) R Mon. This is either an imaging artifact of some kind or evidence that the nebula changes brightness in a highly organized way. See Dust Artifact and Reflection Analysis for a discussion of this feature.
 

Last modified April 18, 1999