With its shrunken polar cap and its large apparent angular size, Mars is viewed here during Martian summer and while Earth nears opposition: where the Sun, Earth, and Mars all form a straight line.

Intuitively, we all know that when we see an image of an object, it could either be large and far away or small and close by. Only with a three-dimensional measurement can we actually know what's ...

It's a big day for astronomy (and all humans, really). The first image of a black hole has been released. It was created using the Event Horizon Telescope—a collaboration of radio telescopes around ...

Using the unique capabilities of telescopes specialized on cosmic gamma rays, scientists have measured the smallest apparent size of a star on the night sky to date. The measurements reveal the ...

THE existence of a source in the Crab Nebula with an angular diameter of less than 1 sec of arc has been revealed by observations of interplanetary scintillation at a frequency of 38 Mc/s (ref. 1).