View Full Version : Discussion: Astronomers Measure the Shape of ...

2003-Aug-06, 06:04 PM
SUMMARY: New data gathered by the European Southern Observatory's Very Large Telescope (VLT) seems to indicate that supernovae might not be symmetrical when they explode - their brightness changes depending on how you look at them. This discovery is important, because astronomers use supernovae as an astronomical yardstick to measure distances to objects. If they're brighter or dimmer depending on how you're looking at them, it could cause errors in your distance calculations. But the new research indicates that they become more symmetrical over time, so astronomers just need to wait a little while before doing their calculations.

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2003-Aug-11, 09:27 PM
This is a fascinating article. It reminds me of the axiom that the more we discover the more we realize how little we knew before. The central topic here I think is that we use Ia supernovas as one of the standard "yardsticks" to measure distances to distant galaxies due their unvarying peak brightness. If their peak brightness varies upon our angle of observation, than the distance measurement to that event will be less certain. I tend to think, however, when measuring many Ia events over a large area of sky that the differences of orientation would cancel each other out, and we could still make a general statement about distances to superclusters and still interpret expansion of the universe.
Another criticism I have of using this method to infer distance is that such interpretation may be neglecting another phenomenon. When looking back across space we are also looking back through time. Younger galaxies tend to have stars with fewer heavy metals to begin with. I would speculate that the peak brightness could vary as a function of the quantity and density of heavy metals involved in the explosion of the white dwarf. If the parent star had more heavy metals to begin with then would it not create an explosion with a higher peak brightness over time? If so, how much would that affect our calculation of the rate of expansion of empty space? Or are the only heavy metals involved in the explosion those that were produced in the interior of the star before it collasped into a dwarf?