Rare Sighting of a Supernova’s Companion Star in the Pinwheel Galaxy

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Institute for Astronomy researchers had a once-in-a-lifetime opportunity to study a newly discovered nearby supernova in 2011, but they had had just 10 minutes observing time to gather information on the supernova and little advance notice. Supernova SN2011fe had been observed for the first time only the night before by University of California, Berkeley scientists using a telescope in California. Discovered relatively close to earth –in the Pinwheel Galaxy–and early in its lifespan, it provided a rare opportunity to better understand the evolution of supernova.

With the Keck II telescope on Mauna Kea trained on the highly energetic and luminous stellar explosion 21 million light-years from Earth, astronomers Alan Stockton and Hsin-Yi Shih collected data during the precious few minutes after nightfall on August 25 that the supernova was within Keck’s range.

“It was clearly an opportunity that does not come along very often,” said Stockton, who usually focuses on radio galaxies and active galaxy nuclei..Bright and visible across vast cosmic distances, Type 1a supernova observations were key to the discovery that expansion of the universe is accelerating. The origins of the supernova themselves have remained unclear, however.

Astronomers believe the supernova are produced by the explosion of a white dwarf composed primarily of carbon and oxygen after it pulls matter from a binary companion, but they have been unable to classify the likely companion stars.

The California researchers used Keck’s high-resolution images to pinpoint the exact location of the supernova and examined red, green and blue wavelength observations to narrow the list of likely suspects. Excluding a red giant and most types of helium stars, they concluded the companion was most likely a normal star like the sun, a somewhat evolved star called a subgiant or perhaps a white dwarf.

The image below shows the Pinwheel Galaxy before the explosion of the supernova and in composite image (with supernova indicated by arrow); courtesy of B.J. Fulton, Palomar Transient Factory, Las Cumbres Observatory Global Telescope Network and the Space Telescope Science Institute.

Supernova

The Daily Galaxy via University of Hawaii

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