The
Milky Way rises over the Cerro Tololo Inter-American Observatory in
northern Chile. The Dark Energy Survey operates from the largest
telescope at the observatory, the 4-metre Victor M. Blanco Telescope
(left). Credit: Andreas Papadopoulos. https://www.ras.org.uk/images/stories/NAM/2014/des1.jpg
Before (left) and after (center) images of the region where DES13S2cmm was discovered. On the right is a subtraction of these two images, showing a bright new object at the center -- a supernova. Credit: Dark Energy Survey. https://www.ras.org.uk/images/stories/NAM/2014/des2.jpg
The first images taken by the Dark Energy Survey
(DES) after the survey began in August 2013 have revealed a rare,
‘superluminous’ supernova that erupted in a galaxy 7.8 billion light
years away. The stellar explosion, called DES13S2cmm, easily outshines
most galaxies in the Universe and could still be seen in the data six
months later, at the end of the first of what will be five years of
observing by DES. The event was discovered by Andreas Papadopoulos, a
postgraduate student from the University of Portsmouth, who will present
the discovery at the National Astronomy Meeting 2014 in Portsmouth on Wednesday, 25 June.
upernovae are very bright, shining anywhere from one hundred million
to a few billion times brighter than the Sun for weeks on end. Thousands
of these brilliant stellar deaths have been discovered over the last
two decades, and the word ‘supernova’ itself was coined 80 years ago.
But superluminous supernovae are a recent discovery, only being
recognized as a distinct class of objects in the past 5 years. These
cosmic explosions are 10-50 times brighter at their peak than the
brightest normal type of supernovae and, unlike other supernovae, their
explosive origins remain a mystery.
"Fewer than forty such supernovae have ever been found and I never
expected to find one in the first DES images!" said Papadopoulos. "As
they are rare, each new discovery brings the potential for greater
understanding – or more surprises."
It turns out that even within this select group, DES13S2cmm is
unusual. The rate that it is fading away over time is much slower than
for most other superluminous supernovae that have been observed to date.
This change in brightness over time, or 'light curve', gives
information on the mechanisms that caused the explosion and the
composition of the material ejected.
Dr Mark Sullivan of Southampton University led the program to obtain
spectroscopy of DES13S2cmm using the Very Large Telescope at Cerro
Paranal, Chile. "Its unusual, slow decline was not apparent at first,"
said Sullivan, "but as more data came in and the supernova stopped
getting fainter, we would look at the light curve and ask ourselves,
'what is this?'"
Understanding the origins of DES13S2cmm is proving difficult.
Radioactive decay is known to power normal supernovae, but not from such
extreme amounts of material.
"We have tried to explain the supernova as a result of the decay of
the radioactive isotope Nickel-56," explained Dr Chris D'Andrea of the
University of Portsmouth, co-author on the research, "but to match the
peak brightness, the explosion would need to produce more than three
times the mass of our Sun of the element. And even then the behaviour of
the light curve doesn’t match up."
The team are now investigating alternative explanations, including
that DES13S2cmm is a normal supernova that has created at its core a
magnetar -- an exotic neutron star spinning hundreds of times per
second, producing a magnetic field a trillion times stronger than that
on Earth. Energy from the magnetar is then injected into the supernova,
making the explosion exceptionally bright. "Neither model is a
particularly compelling match to the data," noted D’Andrea.
With DES starting its second season in August, the hunt is on for more superluminous supernovae.
"With so few known, it’s hard to really understand their properties
in detail," said Prof. Bob Nichol of the University of Portsmouth. "DES
should find enough of these objects to allow us to understand
superluminous supernovae as a population. But if some of these
discoveries prove as difficult to interpret as DES13S2cmm, we’re
prepared for the unusual!"
Media contacts
NAM 2014 press office landlines: +44 (0) 02392 845176, +44 (0)2392 845177, +44 (0)2392 845178
An ISDN line is available for radio interviews. To request its use, please contact Sophie Hall via sophie.hall@port.ac.uk
Science contact
Andreas Papadopoulos
Institute of Cosmology and Gravitation
University of Portsmouth
andreas.papadopoulos@port.ac.uk
Institute of Cosmology and Gravitation
University of Portsmouth
andreas.papadopoulos@port.ac.uk
Dr Chris D’Andrea
Institute of Cosmology and Gravitation
University of Portsmouth
chris.dandrea@port.ac.uk
Institute of Cosmology and Gravitation
University of Portsmouth
chris.dandrea@port.ac.uk
Further information
The Dark Energy Survey
is a 5 year, 525 night optical imaging survey using DECam, a
purpose-built wide-field imaging camera installed and commissioned on
the 4-meter Blanco Telescope at Cerro Tololo Inter-American Observatory,
Chile. Over the course of the survey DES will find and measure over
5000 supernovae and map 300 million galaxies. Six universities in the
United Kingdom (Cambridge, Edinburgh, Nottingham, Portsmouth, Sussex,
UCL) are members of the International DES Collaboration. The DES optical
corrector was constructed at UCL with funding provided by STFC and the
UK DES collaboration.
Funding for the DES Projects has been provided by the U.S. Department
of Energy, the U.S. National Science Foundation, the Ministry of
Science and Education of Spain, the Science and Technology Facilities
Council of the United Kingdom, the Higher Education Funding Council for
England, the National Center for Supercomputing Applications at the
University of Illinois at Urbana-Champaign, the Kavli Institute of
Cosmological Physics at the University of Chicago, Financiadora de
Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do
Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento
Científico e Tecnológico and the Ministério da Ciência e Tecnologia, the
Deutsche Forschungsgemeinschaft and the Collaborating Institutions in
the Dark Energy Survey.
The Collaborating Institutions are Argonne National Laboratories, the
University of California at Santa Cruz, the University of Cambridge,
Centro de Investigaciones Energeticas, Medioambientales y
Tecnologicas-Madrid, the University of Chicago, University College
London, the DES-Brazil Consortium, the Eidgenoessische Technische
Hochschule (ETH) Zurich, Fermi National Accelerator Laboratory, the
University of Edinburgh, the University of Illinois at Urbana-Champaign,
the Institut de Ciencies de l'Espai (IEEC/CSIC), the Institut de Fisica
d'Altes Energies, the Lawrence Berkeley National Laboratory, the
Ludwig-Maximilians Universität and the associated Excellence Cluster
Universe, the University of Michigan, the National Optical Astronomy
Observatory, the University of Nottingham, the Ohio State University,
the University of Pennsylvania, the University of Portsmouth, SLAC
National Accelerator Laboratory, Stanford University, the University of
Sussex, and Texas A&M University.
Notes for editors
The RAS National Astronomy Meeting
(NAM 2014) will bring together more than 600 astronomers, space
scientists and solar physicists for a conference running from 23 to 26
June in Portsmouth. NAM 2014, the largest regular professional astronomy
event in the UK, will be held in conjunction with the UK Solar Physics
(UKSP), Magnetosphere Ionosphere Solar-Terrestrial physics (MIST) and UK
Cosmology (UKCosmo) meetings. The conference is principally sponsored
by the Royal Astronomical Society (RAS), the Science and Technology
Facilities Council (STFC) and the University of Portsmouth. Meeting
arrangements and a full and up to date schedule of the scientific
programme can be found on the official website and via Twitter.
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League Table 2014 and is ranked in the top 400 universities in the
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Rankings 2013. Research at the University of Portsmouth is varied and
wide ranging, from pure science – such as the evolution of galaxies and
the study of stem cells – to the most technologically applied subjects –
such as computer games design. Our researchers collaborate with
colleagues worldwide, and with the public, to develop new insights and
make a difference to people's lives. Follow the University of Portsmouth on Twitter.
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