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Dark Energy Survey on BBC

November 1, 2011 By Leave a Comment
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The Cerro Tololo site in Chile, where the Dark Energy Survey will be carried out

The BBC website  ran a story a few days ago on the UK’s invovlement in the Dark Energy Survey, for which hardware is currently being assembled and tested in the lab where I spent my 3 1/2 PhD years, at University College London. The survey will be carried out with the 4-m Victor Blanco telescope at Cerro Tololo in Chile, using a dedicated new instrument, the Dark Energy Camera.

DECam will be placed at the telescope’s prime focus, above the telescope’s primary mirror. From this location, the camera will image huge swathes of sky with its wide 2 square degree field. To have access to such a large field, and to ensure great image quality over the full area, the camera needs an impressive set of 5 large lenses, up to almost 1 meter in size. In case you’re wondering, meter-sized science-grade lenses are very costly, and very challenging to produce.

In the full Dark Energy Survey, to be completed over 5 years from next September, the large international science team aims to image some 300 million galaxies in several filters, which will allow them to tackle the dark energy question on a number of fronts: by studying Type Ia supernovae, weak gravitational lensing, galaxy clustering, and the large scale distribution of galaxies on the sky to study baryonic acoustic oscillations.

The Optical Science Lab at UCL was just getting involved in this exciting project around the time I was finishing my PhD there, and the group is now working on the assembly and alignment of these lenses in the lab. It’s really great to see some coverage of this project and of UCL’s instrumentation work in the media. New science results are exciting, but all the technical work that makes them possible is just as fascinating.

 

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Great Day for Cosmology

October 4, 2011 By Leave a Comment

Exciting times for cosmology. It’s Nobel Prize week again, and in the first bit of good news for the day, the Physics Nobel was awarded to Saul Perlmutter, Adam Riess and Brian Schmidt. These three scientists were leaders in the studies of type Ia supernovae that led to the discovery of dark energy in 1998 [here's a primer on the science by Schmidt] – the mysterious phenomenon that causes the Universe to expand at a faster rate than we had previously thought.

Truly groundbreaking new results don’t happen very often in science – in fact, trying to think of those that are is quite a fun exercise. Of the last few decades, the discovery of dark energy from observations of distant supernovae is by far the most prominent groundbreaker I can ever think of. So it’s really no surprise that they are now receiving one of the highest honours, and it’s much deserved. (Of course so many physicists are deserving of big prizes, and these things are notoriously hard to predict.)

The second bit of good news for cosmologists is that ESA have officially selected the Euclid mission as one of its next medium-sized mission. Scheduled for launch in 2019, Euclid’s main objective is to study the nature of dark energy by measuring shapes and redshifts of a huge number of objects in the Universe over the entire sky. It’s a fascinating mission, both scientifically and technically, that we’re also involved in at MPIA. Great news for everyone involved.

We know so little about dark energy, a huge targeted survey like Euclid is bound to throw up some really intriguing new questions – perhaps even some answers? If you combine that with the fascinating stuff that’s going on in particle physics, faster than light neutrinos and such, it’s safe to say that cosmology is heading towards some really fun times!

[Very little blogging in recent weeks..... I'm having an exceptionally busy time at work at the moment, with proposal deadlines, and instrument deadlines, and the handover of MIRI to NASA on the immediate horizon. My Rule #1 for blogging is that blogging cannot cause me any extra stress - so for now it's on the backburner. More activity soon!]

 

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‘Arrested development’ at work in the Universe

December 17, 2008 By

Left: Composite image of galaxy cluster Abell 85, using X-ray data (purple) from Chandra and optical image from the Sloan Digistal Sky Survey. Right: Snapshots of the Universe's evolution from a simulation by Volker Springel of MPA, at 0.9, 3.2 and 13.7 billion years.

A cross-continental team of astronomers led by Andrei Vikhlinin have used data from the American X-ray space telescope Chandra to help pin down the nature of the most enigmatic stuff in the Universe, dark energy. By observing clusters of galaxies over a range of different ages, the team were able to track how their masses have evolved over the history of the Universe. Using the statistics of this evolution and comparing them with results from several other complimentary studies, they have significantly narrowed the constraints on the precise nature of dark energy.

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A Cosmic Challenge

October 30, 2008 By
Galaxies Magnified by Galaxy Cluster Abell 1689's "Gravitational Lens"

Galaxies Magnified by Galaxy Cluster Abell 1689

Cosmology, the study of the Universe on the very largest of scales, is a frustrating business. The vast majority of the matter in the Universe is unaccounted for, and of a large fraction, which we call Dark Energy, we have no idea what it even might look like, let alone how to find it. One important source of information comes from the study of gravitational lenses. When light from the most distant sources travels across the Universe, it is distorted by intervening matter, as predicted by Einstein’s general theory of relativity. By studying the distortions seen in these distant objects, cosmologists gather information about the properties of the large-scale matter distribution along the line of sight.

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