New data from the Hubble telescope since the Space Telescope Imaging Spectrograph was repaired last year are showing some interesting behavior in the debris bubble surrounging the site of supernova 1987A, in the Large Magellanic Cloud, one of the two largest dwarf galaxies surrounding the Milky Way.
Supernova 1987A is surrounded by a ring of debris that was thrown out by the star 20,000 years before it exploded into a supernova. The team's most recent observations of hydrogen radiation in the visible and ultraviolet spectra show that emissions from the supernova are brighter than those observed in 2004. The researchers suggest that the shock waves of gas sent out by the supernova are brightening the ring of debris round it.
They also think that some of the shock waves are bouncing back off the debris. The team has used Hubble's imaging spectrograph to map the velocity and chemical composition of this moving gas.
"Although we always knew it was there, this is the first time we've actually been able to see this reverse shock [in supernova 1987A]", says Richard McCray, an astrophysicist at the University of Colorado and a co-author on the study.
Having a supernova occur practically in our back yard, while we were watching, has been a treasure trove of data for astronomers studying supernovae.
In unrelated news, sophisticated new measurements of G, Isaac Newton's Universal Gravitational Constant, have reported a value of 6.67349 × 10−11 m3 kg−1 s−2, with an uncertainty of 26 parts per million. That doesn't sound much different from the previously accepted value of 6.67234 × 10−11 m3 kg−1 s−2 with uncertainty of 21 parts per million; but in this context, it represents a discrepancy of ten standard deviations, and that is huge.
The meaning of this discrepancy is not currently known. But it does raise an interesting speculation: What if the Universal Gravitational Constant is not, in fact, constant? What would be the effect upon the behavior and evolution of the universe if there were a miniscule gravitational tide in the universe, and the value of G depended upon when you measured it — or perhaps if it depended upon where you were when you measured it?