Astronomers use many methods to determine this number, including gravitational lensing, the universe’s expansion rate, and more.

Get newsletters, updates and special offers via email from Astronomy.com!

Mars and Spica will appear in close proximity (2° separation) in the evening western sky shortly after sunset, setting before 9 PM local daylight time. Observations of Mars and Spica are best ...

Luna 2, launched by the Soviet Union in September 1959, achieved the first human-made object impact on a celestial body other than Earth (the Moon). The mission's journey to the Moon lasted ...

Equuleus, also known as the Foal, is a small and faint constellation located southwest of Pegasus. Unlike many constellations, Equuleus lacks bright stars, nearby stars, prominent meteor showers, or ...

Saturn, at magnitude 0.6 in Pisces, is observable in the southeast at approximately 30° altitude. Titan, Saturn's largest moon, undergoes an occultation behind Saturn, beginning around 11:10 P.M. EDT ...

The International Sun-Earth Explorer-3 (ISEE-3) mission, a joint NASA-ESA endeavor launched in 1978, initially studied the solar wind and Earth's magnetic field from the L1 Lagrange point. Following ...