DARK ENERGY MAPPERS 1

A new generation of instruments promises to hunt down dark energy, exposing its secrets

“Galaxy clusters are like Russian dolls, with smaller ones having a similar shape to the larger ones” Andrea Morandi

1 Dark Energy Survey

This was a visible and near-infrared survey of the universe using the four-metre (13-foot) Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile. The telescope was fitted with the state-of-the-art robotic Dark Energy Camera (DECam), which surveyed 300 million extremely faint galaxies and thousands of supernovae over an eighth of the total sky. The DECam instrument made repeated observations of certain areas of the sky in various wavelengths, as well as more longperiod observations to pick out the faintest galaxies. The project’s results hope to discover if dark energy’s density changes over time.

2 Square Kilometre Array

The Square Kilometre Array (SKA) will span two continents when it begins operation in

2027. As the largest radio telescope network in history, all of the SKA’s individual elements will be able to act like a single super-continental radio dish, giving it the ability to study the universe in resolutions never before seen in radio wavelengths. In particular, emissions from hydrogen gas – the most abundant element in space – will be mapped in three dimensions from the distant past to the present day. The SKA’s high resolving power could reveal dark energy’s effects from ripples in the gas and more information on galactic evolution.

3 Euclid space telescope

How has dark energy contributed to the universe’s acceleration over cosmic time? This is what the Euclid spacecraft will try to ascertain when it’s launched in 2023. It will do this by measuring the redshifts of galaxies back to when the universe was just 28 per cent of its current age. It will also look at gravitational weak lensing as well as ripples in normal matter – usually in hydrogen gas between galaxies. To get decent results, Euclid will survey at least half the entire sky with its visible and nearinfrared cameras.