A Quadruple Lunar Halo Over Spain
3.12.2012

Sometimes falling ice crystals make the atmosphere into a giant lens causing arcs and halos to appear around the Sun or Moon. This past Saturday night was just such a time near Madrid, Spain, where a winter sky displayed not only a bright Moon but as many as four rare lunar halos.

Exceptional Rocket Waves Destroy Sun Dog
23.02.2010

What created those rocket waves, and why did they destroy that sun dog? Close inspection of the above image shows not only a rocket rising near the center, but unusual air ripples around it and a colorful sundog to the far right.

Official Star Names for Orion
4.12.2016

Familiar stars in Orion and constellations across the sky now have official names. Over the past year, the International Astronomical Union, the only body officially tasked with naming stars, approved names already in common use for 227 of the brightest stars, including the most famous stars on the sky Sirius, Polaris, and Betelgeuse.

Anemic Spiral NGC 4921 from Hubble
15.05.2019

How far away is spiral galaxy NGC 4921? It's surpringly important to know. Although presently estimated to be about 300 million light years distant, a more precise determination could be coupled with its known recession speed to help humanity better calibrate the expansion rate of the entire visible universe.

The Perseid Meteor Shower
9.08.1996

From a radiant point in the constellation of Perseus, Comet Swift-Tuttle presents -- The Perseid Meteor Shower -- coming to your night sky this weekend! A bookish E. C. Herrick of New Haven, Connecticut correctly suspected in 1837 that this meteor shower was an annual event.

Sonified: The Matter of the Bullet Cluster
16.12.2020

What's the matter with the Bullet Cluster? This massive cluster of galaxies (1E 0657-558) creates gravitational lens distortions of background galaxies in a way that has been interpreted as strong evidence for the leading theory: that dark matter exists within.

Fast Gas Bullet from Cosmic Blast N49
30.06.2010

What is that strange blue blob on the far right? No one is sure, but it might be a speeding remnant of a powerful supernova that was unexpectedly lopsided. Scattered debris from supernova explosion N49 lights up the sky in this gorgeous composited image based on data from the Chandra and Hubble Space Telescopes.

APOD: 2020 July 22 Б The Structured Tails of Comet NEOWISE
22.07.2020

What is creating the structure in Comet NEOWISE's tails? Of the two tails evident, the blue ion tail on the left points directly away from the Sun and is pushed out by the flowing and charged solar wind.

M51: Tidal Streams and H-alpha Ciffs
13.12.2024

An intriguing pair of interacting galaxies, M51 is the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with whirlpool-like spiral structure seen nearly face-on is also cataloged as NGC 5194. Its spiral arms and dust lanes sweep in front of its smaller companion galaxy, NGC 5195.

Hale-Bopp, Jupiter, and the Milky Way
23.07.1996

Shining brightly, the mighty Jupiter rules this gorgeous Kodacolor photo of the Milky Way near Sagittarius. Astronomer Bill Keel took the picture earlier this month (July 7) while standing near the summit of Hawaii's Mauna Kea contemplating the sky in the direction of the center of the Galaxy (right of picture center).