Five years ago, the Nobel Prize in Physics was awarded to three astronomers for their discovery, in the late 1990s, that the universe is expanding at an accelerating pace. Now, a team of scientists led by Professor Subir Sarkar of Oxford University’s Department of Physics has cast doubt on this standard cosmological concept.
A new mathematical model created by astrophysicists at the American Museum of Natural History details a way that dead stars called white dwarfs could detonate, producing a type of explosion that is instrumental to measuring the extreme distances in our universe. The mechanism could improve our understanding of how Type Ia supernovae form.
When Edwin Hubble discovered nearly 100 years ago that the universe was uniformly expanding in all directions, the finding was a big surprise. Then, in the mid-1990s, another shocker occurred: astronomers found that the expansion rate was accelerating, perhaps due to “dark energy.” Now, the latest measurements of our runaway universe suggest that it is expanding faster than astronomers thought.
Some supernovae have a reserve tank of radioactive cobalt-57 fuel that cuts in and powers their explosions for three times longer than astronomers had previously thought. The discovery by Australian and US researchers gives important new clues about the causes of Type Ia supernovae, which astronomers use to measure vast distances across the universe.
Astronomers have observed the debris field from the supernova of 1572, now known as Tycho’s supernova remnant, with NASA’s Chandra X-ray Observatory and the NSF’s Karl G. Jansky Very Large Array (VLA). By combining the X-ray data with some 30 years of observations in radio waves, astronomers have also produced a movie showing the expansion from the explosion is still continuing 444 years later.
Type Ia supernovae are violent stellar explosions that shine as some of the brightest objects in the universe, but there are still many mysteries surrounding their origin. Now a team of astronomers have witnessed a supernova smashing into a nearby star, shocking it, and creating an ultraviolet glow that reveals the size of the companion.