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Caltech star survey plots two cosmic explosions

Two new papers based on star survey data highlight the tremendous capabilities of modern astronomical survey technologies.

Stars trails streak across the sky at Acadia National Park, Maine. Our understanding of the behavior of the universe's stars is becoming ever better, thanks to higher powered astronomical survey technologies.

Robert F. Bukaty/AP

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On 11 November 1572, the Danish nobleman Tycho Brahe plotted on his map of the star-salted skies a flash of light, brighter than a planet, in the W-shaped constellation Cassiopeia. He called it “Stella Nova.” It would later be called a supernova, or SN 1572.

The celestial world above, it would later unfold in Brahe’s subsequent star catalogues, was inconstant. Stars were born, and stars died. And it was possible, Brahe found, to chart the evolution of the universe, mapping the cataclysmic events of deep space as denotations of what spot of light was there one night and what spot of light was gone the next.

Since Brahe’s star maps, sky surveys have underpinned astronomical research. Over the last 440 years or so, they have stippled in maps of local galaxies, supplied the data for revisions in how we think the universe operates, and turned up new stars, galaxies, and other celestial regions and objects. And now, these surveys are better than ever before.

Two new papers published based on data from Caltech's intermediate Palomar Transient Factory (iPTF), the robotic observing system mounted this winter on the 48-inch Samuel Oschin Telescope, near San Diego, highlight the tremendous capabilities of modern astronomical survey technologies. Both papers – one pinpointing the unusual star responsible for a particular kind of supernovae, and the other tracing the origins of a long gamma ray burst – make new discoveries and precise calculations using the iPTF alone.

The first paper, published in Astrophysical Journal Letters, describes a Type Ib supernova, also known as a “stripped envelope” supernova. In these explosive star deaths, the star is missing its outer layer of hydrogen, or its hydrogen “envelope,” and whose outermost layer is helium. These supernovae are distinguished from other types of star explosions based on the lack of a hydrogen line in their spectra.


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