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A Lunar Corona with Jupiter and Saturn

Copyright: Alessandra Masi Why does a cloudy moon sometimes appear colorful? The effect, called a lunar corona, is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colors has different wavelengths, each color diffracts differently. Lunar Coronae are one of the […]

Jets from Unusual Galaxy Centaurus A

Copyright: The jets emanating from Centaurus A are over a million light years long. These jets of streaming plasma, expelled by a giant black hole in the center of this spiral galaxy, light up this composite image of Cen A. Exactly how the central black hole expels infalling matter remains unknown. After clearing the galaxy, […]

The Mountains of NGC 2174

Copyright: This fantastic skyscape lies near the edge of NGC 2174 a star forming region about 6,400 light-years away in the nebula-rich constellation of Orion. It follows mountainous clouds of gas and dust carved by winds and radiation from the region’s newborn stars, now found scattered in open star clusters embedded around the center of […]

A Plutonian Landscape

Copyright: This shadowy landscape of majestic mountains and icy plains stretches toward the horizon on a small, distant world. It was captured from a range of about 18,000 kilometers when New Horizons looked back toward Pluto, 15 minutes after the spacecraft’s closest approach on July 14, 2015. The dramatic, low-angle, near-twilight scene follows rugged mountains […]

Aurora Slathers Up the Sky

Copyright: Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this 2017 June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and […]

Arches Across an Arctic Sky

Copyright: Giulio Cobianchi What are these two giant arches across the sky? Perhaps the more familiar one, on the left, is the central band of our Milky Way Galaxy. This grand disk of stars and nebulas here appears to encircle much of the southern sky. Visible below the stellar arch is the rusty-orange planet Mars […]

A Historic Brazilian Constellation

Copyright: Rodrigo Guerra The night sky is filled with stories. Cultures throughout history have projected some of their most enduring legends onto the stars above. Generations of people see these stellar constellations, hear the associated stories, and pass them down. Featured here is the perhaps unfamiliar constellation of the Old Man, long recognized by the […]

Moon Phases in 2021

Copyright: What will the Moon phase be on your birthday this year? It is hard to predict because the Moon’s appearance changes nightly. As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible. The featured video animates images taken by NASA’s Moon-orbiting Lunar Reconnaissance Orbiter to […]

Star Cluster R136 Breaks Out

Copyright: In the center of nearby star-forming region lies a huge cluster containing some of the largest, hottest, and most massive stars known. These stars, known collectively as star cluster R136, part of the Tarantula Nebula, were captured in the featured image in visible light in 2009 through the Hubble Space Telescope. Gas and dust […]

Total Solar Eclipse 2020

Copyright: Miloslav Druckmuller Along a narrow path crossing southern South America through Chile and Argentina, the final New Moon of 2020 moved in front of the Sun on December 14 in the year’s only total solar eclipse. Within about 2 days of perigee, the closest point in its elliptical orbit, the New Moon’s surface is […]

Striped Sand Dunes on Mars

Copyright: Why are these sand dunes on Mars striped? No one is sure. The featured image shows striped dunes in Kunowsky Crater on Mars, photographed recently with the Mars Reconnaissance Orbiter’s HiRISE Camera. Many Martian dunes are known to be covered unevenly with carbon dioxide (dry ice) frost, creating patterns of light and dark areas. […]

The Small Cloud of Magellan

Copyright: José Mtanous What is the Small Magellanic Cloud? It has turned out to be a galaxy. People who have wondered about this little fuzzy patch in the southern sky included Portuguese navigator Ferdinand Magellan and his crew, who had plenty of time to study the unfamiliar night sky of the south during the first […]

Sprite Lightning at 100,000 Frames Per Second

Copyright: Thomas Ashcraft What causes sprite lightning? Mysterious bursts of light in the sky that momentarily resemble gigantic jellyfish have been recorded for over 30 years, but apart from a general association with positive cloud-to-ground lightning, their root cause remains unknown. Some thunderstorms have them — most don’t. Recently, however, high speed videos are better […]

21st Century Wet Collodion Moon

Copyright: Mike Smolinsky In the mid 19th century, one of the first photographic technologies used to record the lunar surface was the wet-plate collodion process, notably employed by British astronomer Warren De la Rue. To capture an image, a thick, transparent mixture was used to coat a glass plate, sensitized with silver nitrate, exposed at […]

Galaxies and the South Celestial Pole

Copyright: Petr Horalek The South Celestial Pole is easy to spot in star trail images of the southern sky. The extension of Earth’s axis of rotation to the south, it’s at the center of all the southern star trail arcs. In this starry panorama streching about 60 degrees across deep southern skies the South Celestial […]