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PS1 Finds Record-breaking Stellar Explosion in a Distant Galaxy

PS1. Photo by Rob Ratkowski. 

An international research team used the Pan-STARRS 1 survey telescope at Haleakalā Observatories to probe a distant galaxy some 9.5 billion light-years away by observing the explosion of a dying star. This is the most distant stellar explosion of its kind ever studied.  The leader of this study, Edo Berger of Harvard University, said, “It’s like someone turned on a flashlight in a dark room and allowed us to see, for a short time, what this far-off galaxy looks like, what it is composed of.”

The study, published recently in the Astrophysical Journal, describes how the researchers used the light of the exploding star (called an ultraluminous core-collapse supernova) as a probe to study the gas conditions in the space between the host galaxy’s stars. Berger says the findings reveal that the distant galaxy‘s interstellar conditions appear “reassuringly normal” when compared to those seen in the galaxies of our local Universe. “This shows the enormous potential of using the most luminous supernovae to study the early Universe,” he says. “Ultimately it will help us understand how galaxies like our Milky Way came to be.”

“These are the types of exciting and unexpected applications that appear when a new capability comes online,” said IfA’s John Tonry, one of the study’s co-authors and a supernovae researcher. Tonry adds, “Pan-STARRS is pioneering a new era in deep, wide-field, time-critical astronomy—and this is just the beginning.”

The team made follow-up spectroscopic studies with the Multiple Mirror Telescope in Arizona and the 8-meter Gemini North telescope on Mauna Kea. These spectra revealed the signatures of a distant ultraluminous supernova, and equally important, the unique fingerprints of iron and magnesium within the distant galaxy that hosted the explosion. The galaxy itself contains a very young population of stars (about 15 to 45 million years old) with a total mass about 2 billion times that of our Sun.

The ultraluminous supernova explosion belongs to a relatively new and special breed of exploding stars. They are some 10–100 times more luminous than their less-energetic cousins, the Type I supernovae, and unusually blue in color. While the process leading to their demise is still being explored, evidence points to the central core-collapse of a star having as much 100 times the mass of our Sun. The collapse triggers an enormous explosion that blasts prodigious amounts of heavier elements through the star’s enormous outer layers before expanding into space.

 “The beauty of studying distant galaxies using ultraluminous supernovae as a tool is that it eliminates the need for satellites and offers more time for study,” says Alicia Soderberg of Harvard University. “A typical ultraluminous supernova can take several weeks to fade away.”

The study by Berger and his team provides the first direct demonstration that ultraluminous supernovae can serve as probes of distant galaxies. Their results suggest that with the future combination of large survey and spectroscopic telescopes, ultraluminous supernovae could be used to probe galaxies 90 percent of the way back to the Big Bang.

The Pan-STARRS Project, led by the IfA, exploits the unique combination of superb observing sites and technical and scientific expertise available in Hawai‘i. Funding for the development of the observing system has been provided by the United States Air Force Research Laboratory, with additional funding from the University of Hawai‘i, NASA, the National Science Foundation, and the members of the PS1 Science Consortium.