Solstice Sun and Milky Way
20.12.2021

Welcome to December's solstice, first day of winter in the north and summer for the southern hemisphere. Astronomical markers of the seasons, solstice and equinox dates are based on the Sun's place in its annual journey along the ecliptic, through planet Earth's sky.

Messier Marathon
27.05.2011

In this action scene, red night vision lights, green laser pointers, tripods and telescopes in faint silhouette surround intrepid sky gazers embarked on the 10th annual Iran Messier Marathon. Completing the marathon requires viewing all 110 objects in 18th century French astronomer Charles Messier's catalog in one glorious dusk-to-dawn observing run.

Saturn: Shadows of a Seasonal Sundial
12.10.2011

Saturn's rings form one of the larger sundials known. This sundial, however, determines only the season of Saturn, not the time of day. In 2009, during Saturn's last equinox, Saturn's thin rings threw almost no shadows onto Saturn, since the ring plane pointed directly toward the Sun.

The Leo Trio
20.03.2024

This popular group leaps into the early evening sky around the March equinox and the northern hemisphere spring. Famous as the Leo Triplet, the three magnificent galaxies found in the prominent constellation Leo gather here in one astronomical field of view.

Spokes Reappear on Saturns Rings
2.06.2009

What causes the mysterious spokes in Saturn's rings? Visible in the above image as light ghostlike impressions, spokes were first discovered by the Voyager spacecraft that buzzed by Saturn in the early 1980s. Their existence was unexpected.

Manhattanhenge: A New York City Sunset
6.07.2014

This coming Saturday, if it is clear, well placed New Yorkers can go outside at sunset and watch their city act like a modern version of Stonehenge. Manhattan's streets will flood dramatically with sunlight just as the Sun sets precisely at each street's western end.

Cassini Spacecraft Crosses Saturn's Ring Plane
14.02.2010

If this is Saturn, where are the rings? When Saturn's "appendages" disappeared in 1612, Galileo did not understand why. Later that century, it became understood that Saturn's unusual protrusions were rings and that when the Earth crosses the ring plane, the edge-on rings will appear to disappear.

Evolution of the Moon
20.03.2012

What is the history of the Moon? The Moon was likely created from debris expelled when a Mars-sized object violently impacted the Earth about 4.5 billion years ago. Just after gravitationally condensing, as imagined above, the glowing-hot surface of the Moon cooled and cracked.

The Leo Trio
20.03.2025

This popular group leaps into the early evening sky around the March equinox and the northern hemisphere spring. Famous as the Leo Triplet, the three magnificent galaxies found in the prominent constellation Leo gather here in one astronomical field of view.

Manhattanhenge: A New York Sunset
13.07.2007

Today, if it is clear, well placed New Yorkers can go outside at sunset and watch their city act like a modern version of Stonehenge. Manhattan will flood dramatically with sunlight just as the Sun sets precisely on the centerline of every street.