That heart-shaped purple glow amidst that cluster of galaxies isn't bursting with love — it's dark matter, as measured by NASA's Cosmic Lens, and it may be our best clue to the mysterious nature of dark energy.
According to NASA:
For the first time, astronomers using NASA's Hubble Space Telescope were able to take advantage of a giant magnifying lens in space - a massive cluster of galaxies - to narrow in on the nature of dark energy. Their calculations, when combined with data from other methods, significantly increase the accuracy of dark energy measurements. This may eventually lead to an explanation of what the elusive phenomenon really is. ...
Scientists aren't clear about what dark energy is, but they do know that it makes up a large chunk of our universe, about 72 percent. Another chunk, about 24 percent, is thought to be dark matter, also mysterious in nature but easier to study than dark energy because of its gravitational influence on matter that we can see. The rest of the universe, a mere 4 percent, is the stuff that makes up people, planets, stars, and everything made up of atoms.
In their new study, the science team used images from Hubble to examine a massive cluster of galaxies, named Abell 1689, which acts as a magnifying, or gravitational, lens. The gravity of the cluster causes galaxies behind it to be imaged multiple times into distorted shapes, sort of like a fun-house mirror reflection that warps your face.
Using these distorted images, the scientists were able to figure out how light from the more distant, background galaxies had been bent by the cluster - a characteristic that depends on the nature of dark energy. Their method also depends on precise ground-based measurements of the distance and speed at which the background galaxies are traveling away from us. The team used these data to quantify the strength of the dark energy that is causing our universe to accelerate.
Download a much bigger version of the image at the link. [NASA]