An international team of researchers has discovered an ultra-luminous supernova in a distant galaxy some 9.5 billion light-years away and used it as a tool to study the interstellar medium of the host galaxy.
This supernova, dubbed PS1-11bam, is the most distant stellar explosion of its kind ever studied.
Ultra-luminous supernovae belong to a relatively recently-identified and special breed of exploding stars. They are some 10-100 times more luminous than their ordinary less-energetic cousins 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 as 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.
“It’s like someone turned on a flashlight in a dark room and suddenly allowed us to see, for a short time, what this far-off galaxy looks like, what it is composed of,” said Dr Edo Berger of Harvard University, lead author of a study published in the Astrophysical Journal (arXiv.org version).
The study describes how the researchers used the exploding star’s light as a probe to study the gas conditions in the space between the host galaxy’s stars.
“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,” Dr Berger explained.
“This shows the enormous potential of using the most luminous supernovae to study the early Universe,” he said. “Ultimately it will help us understand how galaxies like our Milky Way came to be.”
To discover PS1-11bam, the astronomers have used images from the Pan-STARRS1 survey telescope on Haleakala in Maui, Hawai‘I.
“These are the types of exciting and unexpected applications that appear when a new capability comes on line,” said study co-author Dr John Tonry, supernovae researcher at the University of Hawai‘i at Manoa’s Institute for Astronomy. “Pan-STARRS is pioneering a new era in deep, wide-field, time-critical astronomy – and this is just the beginning.”
After the Pan-STARRS discovery, spectroscopic follow-up studies using the Multiple Mirror Telescope in Arizona and the 8-meter Gemini North telescope on Mauna Kea, Hawai‘i provided the data used by the team to probe the gas of the distant galaxy’s interstellar environment.
The spectroscopic data revealed the signatures of a distant ultra-luminous 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 mass totaling some 2 billon Suns.
“The beauty of studying distant galaxies using ultra-luminous supernovae as a tool is that it eliminates the need for satellites and offers more time for study,” said co-author Dr Alicia Soderberg of Harvard University. “A typical ultra-luminous supernova can take several weeks to fade away.”
The new study provides the ﬁrst direct demonstration that ultra-luminous supernovae can serve as probes of distant galaxies. The results suggest that with the future combination of large survey and spectroscopic telescopes ultra-luminous supernovae could be used to probe galaxies 90 percent of the way back to the Big Bang.
Bibliographic information: E. Berger et al. 2012. Ultraluminous Supernovae as a New Probe of the Interstellar Medium in Distant Galaxies. ApJ 755, L29; doi: 10.1088/2041-8205/755/2/L29