It’s rare for a scientific non-observation to be of great significance, but there are exceptions. The non-observation of neutrinos of a particular type at the Sudbury Neutrino Observatory solved the solar neutrino problem. This latest non-observation may be of extreme importance.
We measure the distance to the far edge of the universe using Supernovae of Type 1a, that are created by the accretion of matter onto a white dwarf star. As the shock wave from explosion of the supernova slams into the matter around the white dwarf star it ought to generate X-rays. It doesn’t. That sort of throws into doubt the accuracy of everything we think we know about the distant universe.
The following quote is from http://apod.nasa.gov/apod/ap140816.html
Last January, telescopes in observatories around planet Earth were eagerly used to watch the rise of SN 2014J, a bright supernova in nearby galaxy M82. Still, the most important observations may have been from orbit where the Chandra X-ray Observatory saw nothing. Identified as a Type Ia supernova, the explosion of SN2014J was thought to be triggered by the buildup of mass on a white dwarf star steadily accreting material from a companion star. That model predicts X-rays would be generated when the supernova blastwave struck the material left surrounding the white dwarf. But no X-rays were seen from the supernova. The mostly blank close-ups centered on the supernova’s position are shown in the before and after inset panels of Chandra’s false color X-ray image of the M82 galaxy. The stunning lack of X-rays from SN 2014J will require astronomers to explore other models to explain what triggers these cosmic explosions.
The technical article that goes with this is http://arxiv.org/pdf/1405.1488v1.pdf
Whereas X-rays are strong from Gamma Ray Bursters in the distant universe, and are present in all Type II supernovae (collapsing giant stars), they have never been detected from any of the hundred or so Type 1a supernovae. The lack of X rays from this nearby supernova in 2014 and from another similar in 2011 put the tightest constraints on how Type 1a supernovas occur.
There are two dominant theories about what makes white dwarfs explode as supernovae and both, it now seems, are wrong. One theory is that the white dwarf is part of a close binary system with a normal star that is shedding material through its Roche lobe onto the white dwarf. When enough material is transferred the white dwarf goes bang. That theory is pretty well ruled out by the new results showing a lack of material around the white dwarf excited to X-rays as the shock wave passes.
The other theory is that Type 1a supernovae occur when white dwarfs collide/coalesce with another condensed object such as a white dwarf or neutron star. Previous studies have shown that there are nowhere near enough white dwarf pairs for this mechanism to dominate. And in addition, the newly observed lack of gas around the white dwarf means that any binary white dwarf will lose momentum (through gas drag) very very slowly so there should be even fewer Type 1a supernovae from a coalescence of this sort.
So, either the 2014 and 2011 supernovae are coincidentally very rare types of Type 1a supernova, or there is some completely unknown mechanism (such as little green men) creating these explosions.