Understanding dark energy is probably one of the largest mysteries in cosmology right now. Figure this out, and a Nobel Prize in physics is assured. But it won’t give up its secrets so easily. Since they can’t measure dark energy directly, astronomers can only measure its effects on the large-scale structures of the Universe, and then tease out some of its characteristics.
In a recent survey using the European Southern Observatory’s Very Large Telescope, and international team of 51 astronomers from 24 institutions gathered the light from more than 13,000 galaxies. This survey contains galaxies within a 25 million cubic-light years volume.
Using this survey, they were able to map out the large scale structures in the nearby Universe, including clusters of galaxies and filamentary superclusters. By measuring the velocity of the different clusters as they speed away from us, at different times in the past, the astronomers were able to measure the speed distortion contributed by dark energy.
Their conclusions lend evidence to the so-called cosmological constant theory originally introduced by Albert Einstein – there’s some constant repulsive force that exists throughout space. But the uncertainties in their calculations doesn’t rule out other possibilities.
One of the most popular of these is known as modified gravity. In this situation, gravity just acts differently at large scales than it does in the small scale.
But the researchers feel that a measurement that might cover 10 times the volume of this survey could be able to tell the difference between a dark energy force of exotic origin or an actual modification of theory of gravity.
Original Source: ESO News Release