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This new cosmological map shines some light on dark energy


Dark energy is one of the greatest mysteries in science today. We know very little about it, other than it is invisible, it fills the whole universe, and it pushes galaxies away from each other. This is making our cosmos expand at an accelerated rate. But what is it? One of the simplest explanations is that it is a “cosmological constant” – a result of the energy of empty space itself – an idea introduced by Albert Einstein.

Many physicists aren’t satisfied with this explanation, though. They want a more fundamental description of its nature. Is it some new type of energy field or exotic fluid? Or is it a sign that Einstein’s equations of gravity are somehow incomplete? What’s more, we don’t really understand the universe’s current rate of expansion.

Now our project – the extended Baryon Oscillation Spectroscopic Survey (eBOSS) – has come up with some answers. Our work has been released as a series of 23 publications, some of which are still being peer reviewed, describing the largest three-dimensional cosmological map ever created.

Currently, the only way we can feel the presence of dark energy is with observations of the distant universe. The farther galaxies are, the younger they appear to us. That’s because the light they emit took millions or even billions of years to reach our telescopes. Thanks to this sort of time-machine, we can measure different distances in space at different cosmic times, helping us work out how quickly the universe is expanding.

[Read: Look, human, it’s the first photo of planets orbiting a sun 300 light years away]

Using the Sloan Digital Sky Survey telescope, we measured more than two million galaxies and quasars – extremely bright and distant objects that are powered by black holes – over the last two decades. This new map covers around 11 billion years of cosmic history that was essentially unexplored, teaching us about dark energy like never before.