Two weeks ago a group of astronomy students from the University of
London Observatory were
getting an introductory demonstration on how to use a telescope-mounted
camera. With clouds shrouding much of the sky, professor Steve Fossey
decided to point the University’s 14-inch
telescope at nearby galaxy Messier 82 (M82) and saw a very bright object
that wasn't supposed to be there. After a bit of detective work,
the group put out an Astronomical Telegram to the world’s scientific
community.
It was soon determined that M82 was hosting a rare,
Type 1a supernova explosion – one of the brightest events in the sky and
a once-in-a-century event. It was named SN2014J.
The phones rang
at Keck Observatory, home of the two largest and most scientifically
productive telescopes on the Earth. Although time on the Keck telescopes
is scheduled 6 months in advance and is highly coveted, the two
different teams
observing on Keck I and Keck II that night both agreed to interrupt
their research and point the mighty 10-meter telescopes at M82 and
gather valuable data and rare
insight into the life cycle of type 1a supernova.
"It was
very exciting: this was the second nearest supernova in recent history,"
said Michael Liu, the University of Hawaii astronomer who made
the decision to observe the exploding star using the Keck II telescope.
"Usually, we know what we are going to be observing for months before we
get here."
While it’s known that Type 1a supernovae form from
collapsing white dwarfs – the densest forms of matter after black holes
and neutron stars – their formation theories come in two flavors: the
single degenerate scenario in which a normal star is consumed by a white
dwarf; and the double degenerate scenario in which two white dwarfs
merge.
To determine which one this is,
scientists need to compare the before and after images to determine
which stars became the supernova, said Shriharsh Tendulkar, a
post-doctoral researcher at the California Institute of Technology.
“Keck‘s
Adaptive Optics system allows you to get very sharp images of the sky,
as you would from space, and allows a very precise position of the
supernova," he said. “We can compare it to old images to possibly
determine the progenitor system."
With the NIRC2 instrument and
Keck II's Adaptive Optics system (AO), Liu’s team was able to capture very clear images
of the supernova and the surrounding stars in Messier 82.
"While
there are many supernovae explosions in the Universe, this one is
important because it is close enough that with Keck’s AO, we have an
excellent chance of identifying the progenitor," said Bob Goodrich, head
of night-time operations for W. M. Keck Observatory
Critically,
the supernova was discovered two weeks
before its predicted peak luminosity, allowing an unprecedented
opportunity to study the process of this stellar explosion.
"The
physics of supernovae is very interesting," Shriharsh said. "For example, it’s really hard to model these
explosions in [computer] simulations. These observations will help us make our
simulations better."
Yale
University astronomer Meg Urry also took time from her program on Keck I to
gather data on M82 using the Observatory's newest instrument, MOSFIRE, the
Multi-Object Spectrograph for Infrared Exploration. She wrote about her perspective in an interesting article for CNN.
"In
addition to giving insight on how these supernovae are formed,
gathering data on SN2014J will give us more accurate distances to other
type 1a supernovae," Goodrich said. "Because the distance of M82 is
precisely known, we can clearly determine the absolute brightness of
SN2014J. Since all type 1a supernovae are equally bright, this valuable
measurement can be used to calibrate data on all former (and future)
such studies, including the one that lead to the Nobel Prize."
Type
1a supernovae have already played a profound role at the Keck
Observatory when a team of astronomers were awarded the 2011 Nobel
Prize in Physics. The scientists trained the mighty Keck telescopes at
known
supernovae and used their findings to determine that the expansion of
the
Universe was not slowing down, as was expected, but in fact was speeding
up – driven
by a mysterious repelling force now called Dark Energy.
By Steve Jefferson
Source: W. M. Keck Observatory
