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).

In July 1969, Man first walked on the Moon. Over the course of three more years, we did it five more times. Despite the return of hundreds of kilos of rocks, thousands of pictures, and independent ...

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 ...

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.