MessageToEagle.com -The largest ever search for supernovae starts in August this year and researchers
from 25 institutions and consortia, including six universities in the UK, will cooperate in the project.
They will use a massive new 570 Megapixel camera (DECam) installed on the four-meter diameter Blanco telescope,
high in the mountains of Chile.
For the next five years, the Dark Energy Survey (DES) will look for these cosmic explosions, which can be used
to measure precisely the growth of the universe over time.
Aerial view of Cerro-Tololo Inter-American Observatory, with the most prominent dome
belonging to the 4m diameter Blanco telescope, where the Dark Energy Camera is installed and from where DES
operates. Credit: NOAO/AURA/NSF
"Thanks to the extreme sensitivity of the camera and to the large area of sky that can be imaged through the
telescope at once (about 15 times the size of the full moon), we expect DES to find more supernovae than any
previous experiment, said D'Andrea, a researcher at the University of Portsmouth's Institute of Cosmology
"During the verification phase, we have already identified at least 200 good candidates."
More than just numerous, these supernovae are very old, with the light from the most distant having travelled
towards Earth for over 8 billion years. Of particular interest are Type Ia supernovae, which all have nearly
the same luminosity when they reach their brightest phase.
By comparing the brightness of Type Ia supernovae, scientists in DES will be able to determine accurately the
distance to the supernovae and measure how the universe has expanded over time.
This method was used in the Nobel Prize-winning research that led to the discovery of the accelerated expansion
of the universe 15 years ago.
While those researchers used a few dozen supernovae in their study, DES will find
over 3500 of these objects. This glut of data poses a challenge for the team to analyse.
"Traditionally, astronomers have identified supernovae by analysing the spectrum of light from candidates.
Because DES will give us so many candidates -- we already have hundreds just from the commissioning phase --
we don't have the resources to do this for each individual candidate supernova. We need to use other techniques
to confirm which of the objects we observe really are exploding stars," said D'Andrea.
An alternative method for identifying supernovae is to monitor changes in the brightness and colour of their
light over time. However, the scientists also need to know how much the universe has expanded since the star exploded.
This information can be gathered by analysing the spectra of light from galaxies in which supernovae have occurred
-- unlike a supernova, a galaxy does not quickly fade away.