Astronomy Essentials
Saturn at opposition August 1-2, near Jupiter
Don't miss Saturn at opposition on and around the night of August 1-2, 2021. That's when our planet Earth passes between the sun and Saturn.
Tonight
Moon sweeps by Taurus August 2, 3 and 4 mornings
The waning moon sweeps through Taurus the Bull on the mornings of August 2, 3 and 4, 2021. Let it guide you to the Bull's prominent stars.
Human World

August 2021 has a Friday 13th

Any calendar month starting on a Sunday always has a Friday 13th. In 2021, August 1 is on a Sunday. August 13 must fall on a Friday!
Astronomy Essentials

EarthSky’s August 2021 guide to visible planets

In August 2021, at nightfall, watch for the visible planets. Venus descends in the west as Jupiter and Saturn ascend in the east. Mercury and Mars hide in evening twilight.
Space

Neutron-star mountains are tiny (but you can’t climb ’em)

Researchers in the UK have found that neutron-star mountains are less than a millimeter tall. These dense, dead stars are nearly perfectly smooth spheres.
Brightest Stars

Exquisite Albireo, a much-loved double star

Albireo, in the constellation Cygnus the Swan, is a favorite among stargazers. Through a small telescope, it appears as a stunning gold star with a dimmer blue companion.
Moon Phases

Moon phases for meteor watching in 2021

Use our calendar to find out what phase the moon is in. Dates closest to new moon provide the darkest skies and the best opportunities to spot meteors.
Human World
Space

A Dyson sphere harvests the energy of stars

Dyson spheres are named after inventor Freeman J. Dyson. A Dyson sphere is a megastructures that civilizations could use to harness the power of stars.
Space

Jupiter X-ray aurora mystery solved, after 40 years

A Jupiter X-ray aurora mystery has perplexed astronomers for decades. Now they think ions responsible for the X-rays "surf" electromagnetic waves into Jupiter's atmosphere.
Astronomy Essentials

Transits of Jupiter’s moons ahead: A triple!

Observers using a good pair of binoculars or a small telescope can see events called transits on Jupiter, when a moon or its shadow passes in front of the giant planet.