Researchers working with the Supernova Legacy Survey have discovered two most ancient and brightest supernovae ever recorded.
The supernovae are 10 billion light-years away and are 100 times brighter than a normal supernova, according to a press release.
A supernova is powered by the collapse of a giant star to a black hole or normal neutron star. If this fact is taken into account, it fails to explain the abnormal radiance of the newly discovered supernovae. Though these celestial bodies were discovered way back in 2006 and 2007, their unusual brightness left researchers perplexed.
"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 lead author D. Andrew Howell, a 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."
SNLS-06D4eu, the name given to one of the supernovae, is the most distance and brightest in a class of explosions known as superluminous supernovae. Both the new discoveries belong to a special subclass of superluminous supernovae that have no hydrogen.
These are rare supernovae occurring perhaps once for every 10,000 normal supernovae.
"These are the dinosaurs of supernovae," Howell said. "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."
A newly created magnetar may be sourcing theses supernovae, scientists assumed. Magnetars are magnetized neutron stars that spin hundreds of times per second. Their mass is that of the Sun packed into a star the size of a city. Magnetars have a magnetic field hundred trillion times bigger than that of the Earth. Superluminous supernovae were first discovered in 2009 and are believed to be powered by these magnetars. Ever since their discovery, Howell and his team have been constantly working on matching detailed observations to human-created models to determine what these explosions may look like in reality.
According to a model created by Daniel Kasen from UC Berkeley, one of these supernovae was actually the explosion of a star, which was the size of the sun and rich in oxygen and carbon. Kasen speculated that the star may have been much bigger but shed its out layer way before the actual explosion, leaving behind a "small, naked core."
"What may have made this star special was an extremely rapid rotation," Kasen said. "When it ultimately died, the collapsing core could have spun up a magnetar like a giant top. That enormous spin energy would then be unleashed in a magnetic fury."
To properly identify the two supernovae and determine their exact location, researchers analyzed subsequent observations of the faint host galaxy with the VLT in Chile. The distance of the supernovae from Earth was so vast that the ultraviolet (UV) light emitted in the explosion was stretched out by the expansion of the universe until it was redshifted, according to a Nature report. This was why it took time for researchers to accurately identify the explosions.
Howell said that the origin of both these supernovae dates back to when the Universe was only 4 billion years old.
"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."
