Astronomers Report the Brightest, Most Distant Supernovae Ever Discovered

Two of the brightest and most distant supernovae ever discovered are estimated to be 10 billion light years away from Earth and a hundred times more luminous than a typical supernova, according to new research that appears in the Astrophysical Journal.

When the extraordinarily distant objects were first discovered in 2006 and 2007, astronomers had no idea what they were as they did not fit into any of the typical astronomical models. This was largely due to their extreme luminosity. Typically supernovae are lit by the energy produced by the death of a giant star or normal neutron star, but these forces were unable to explain how objects so distant could appear so bright.

"At first, we had no idea what these things were, even whether they were supernovae or whether they were in our galaxy or a distant one," said D. Andrew Howell, lead study author and staff scientist at Las Cumbres Observatory Global Telescope Network (LCOGT). "I showed the observations at a conference, and everyone was baffled. Nobody guessed they were distant supernovae because it would have made the energies mind-bogglingly large. We thought it was impossible."

Howell and his colleagues report that one of the newfound supernovae, named SNLS-06D4eu, belongs to an emerging class of space objects called superluminous supernovae, of which it is the most distant and most luminous of all known examples.

The two superluminous supernovae detailed in the Astrophysical Journal report have been placed in a special subclass because they have no hydrogen.

Howell and his team contend that these superluminous supernovae are likely powered by the creation of a magnetar, which is a supremely dense, extraordinarily magnetized neutron star that spins at a speed of several hundred times per second. Magnetars are no bigger than a large city, yet they have the mass of the Sun and a magnetic field a hundred trillion times greater than Earth's.

Only a handful of superluminous supernovae have been discovered, and astronomers believe them to be quite rare, occurring perhaps once per 10,000 normal supernovae.

The two superluminous supernovae detailed in the study are ancient, having exploded when the universe was only 4 billion years old, the researchers said.

"This happened before the sun even existed," Howell explained. "There was another star here that died and whose gas cloud formed the sun and Earth. Life evolved, the dinosaurs evolved and humans evolved and invented telescopes, which we were lucky to be pointing in the right place when the photons hit Earth after their 10-billion-year journey."

Howell continued: "These are the dinosaurs of supernovae. They are all but extinct today, but they were more common in the early universe. Luckily we can use our telescopes to look back in time and study their fossil light. We hope to find many more of these kinds of supernovae with ongoing and future surveys."