Imagine how bright something must be in order for us to see it from 10 billion light-years away, or approximately 9.5 x1025 meters. Often it is bright enough to keep us awake during an all-night finals study session.
In science, some of the greatest discoveries are made by accident. This is exactly what happened during a five-year project of the Supernova Legacy Survey (SNLS) aimed at measuring dark energy. Instead, the survey came across two of the brightest and most luminous supernovae ever discovered. These 10 billion light-year away supernovae are said to be a hundred times brighter than a normal supernova.
The Canada-France-Hawaii Telescope, a 3.6-meter telescope located on the Mauna Kea Mountain on the Big Island in Hawaii, captured the supernovae during their visibility period that lasted a few months.
The supernovae exploded when the Earth was only four billion years old, yet they became visible only a few years ago as the photons of light emitted reached Earth after a 10 billion-year-long journey. This delayed visualization is the result of an effect called “time dilation.”
Co-author on the study Chris Lidman of the Australian Astronomical Observatory said that redshift, the displacement of spectral lines toward longer wavelengths, distorts how we perceive the distance of radiation emanating from celestial objects.
“When we see an object that is so far away, it stretches time,” Lidman said. “Something that would take one month to see if it was nearby would take several times longer if it was at high redshift.”
After their discovery in 2006 and 2007, astronomers did not understand what they were. The mechanisms that explain supernovae did not fit the characteristics of these supernovae. Typically, a supernova is the result of one of two mechanisms: either a core-collapse supernova or a reignition of a white dwarf star. Neither of these, however, could explain the amount of light observed by the two supernovae. It was not until a spectrum was taken of the light, that the phenomena were confirmed to be supernovae.
Lead author D. Andrew Howell, a researcher at Las Cumbres Observatory Global Telescope Network and UCSB staff scientist in the physics department, said that initially researchers were uncertain whether they were observing supernovae because the photons were redshifted into the visible part of the spectrum.
“We had never seen these types of supernovae that far into the ultraviolet before,” Howell said. “Ultimately we found nearby supernovae that showed some of the same features, and that is how we could tell they were supernovae. Observations indicated that there was an explosion with gas flying apart at 12,000 km/s. Only a supernova can achieve something like this.”
According to Howell, researchers are now trying to understand what mechanism created these extremely bright supernovae, which are believed to have no hydrogen and are likely powered by a magnetar.
“A magnetar is a highly magnetized, rapidly spinning neutron star, which transfers some of its energy to the expanding supernova as it slows down. It has the mass of the sun and a magnetic field a hundred trillion times that of the Earth,” Howell said. “It is now a goal of many astronomers to theorize what led to these supernovae.”
A version of this story appeared on page 8 of Wednesday, January 15, 2014’s print edition of the Daily Nexus.
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