Eric Hsiao, Howie Marion, and Mark Phillips
from the April 2013 issue
The Earliest Near-infrared
Spectroscopy of a
Type Ia Supernova
Gemini Near-infrared Spectrograph (GNIRS) observations have led to surprising
results on the nature of Type Ia supernovae (SNe Ia). Time-series, near-infrared
spectra of SN 2011fe in M101 reveal that more SNe Ia harbor unprocessed
carbon than previously believed, and what we thought was the main driver of
the luminosity-decline rate relation may not be correct.
Figure 1.
Color image of SN
2011fe in M101.
(Credit: B. J. Fulton/
LCOGT/PTF)
Type Ia supernovae (SNe Ia) provide the most direct measure of the expansion history of the universe and have led
to the discovery of the accelerated expansion, which was
awarded the 2011 Nobel Prize in Physics. The unknown
cause of the accelerated expansion is commonly referred
to as “dark energy.”
SNe Ia are not perfectly homogenous, showing significant
variation in the shapes and peak brightnesses of their
light curves. Rather, their utility as cosmological distance
indicators at optical wavelengths rests on the discovery
of an empirical correlation between the SNe Ia’s peak absolute magnitude and the rate at which the brightness
declines (luminosity-decline rate relation; Phillips, 1993).
Most astronomers agree that these explosions result from
the total thermonuclear disruption of a carbon-oxygen
white dwarf in a close binary system; however, the details
of the explosion mechanism and the mass-donating companion star are still unclear.
January2014 2013 Year in Review
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