What's up in
A roundup of some of the most important discoveries gleaned so far from the Gaia space observatory’s new map of the galaxy.
Two ways of measuring the universe’s expansion rate yield two conflicting answers. Many point to the possibility of new physics at work, but a new analysis argues that unseen errors could be to blame.
A surprise discovery announced a month ago suggested that the early universe looked very different than previously believed. Initial theories that the discrepancy was due to dark matter have come under fire.
The amount of energy infusing empty space seems too small to explain without a multiverse. But physicists have at least one alternative left to explore.
Two methods of measuring the neutron’s longevity give different answers, creating uncertainty in cosmological models. But no one has a clue what the problem is.
It weighs as much as 780 million suns and helped to cast off the cosmic Dark Ages. But now that astronomers have found the earliest known black hole, they wonder: How could this giant have grown so big, so fast?