When you look up at the night sky, how do you know whether the specks of light that you see are bright and far away, or relatively faint and close by? One way to find out is to compare how much light the object actually emits with how bright it appears. The difference between its true luminosity and its apparent brightness reveals an object's distance from the observer.

Einstein's theory of general relativity—the idea that gravity is matter warping spacetime—has withstood over 100 years of scrutiny and testing, including the newest test from the Event Horizon Telescope collaboration, published today in the latest issue of Physical Review Letters.

When a star unleashes as much energy in a matter of days as our Sun does in several billion years, you know it's not going to remain visible for long.

Gravitational wave scientists looking for evidence of "lensing," in which the faintest gravitational wave signals become amplified, are unlikely to make these detections in the near future according to new analysis by scientists at the University of Birmingham.

Scientists at CU Boulder have laid out a roadmap for a decade of scientific research at the moon.