Astronomy Picture of the Day
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NASA
Astronomy Picture of the Day
Six Moons of Saturn Explanation: How many moons does Saturn have? While the total will likely continue to grow, as of June 2026 the ringed gas giant had 293 confirmed moons. That’s easily more than any other planet of the Solar System, including ruling gas giant Jupiter with a mere 115 confirmed moons. Most of Saturn’s known moons are small, irregular satellites. Many are…
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NASA
Astronomy Picture of the Day
Contemplating the Sun Explanation: Have you contemplated your home star recently? Featured here, a Sun partially eclipsed on the top left by the Moon is also seen eclipsed by earthlings contemplating the eclipse below. This spectacular menagerie of silhouettes was taken in 2012 from the Glen Canyon National Recreation Area near Page, Arizona, USA, where park rangers and astronomers expounded on the unusual event to interested gatherers. Also, faintly visible on the Sun’s disk, just to…
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NASA
APOD: 2026 August 10 – Three Galaxy Pairs
Three Galaxy Pairs Explanation: Each of these pairs of galaxies is different. The two galaxies at the top are likely not interacting, at least presently. However, the top galaxy with the blue stripe, NGC 4650A, is a polar ring galaxy and may be the result of a past galaxy collision. The two galaxies in the middle of the featured image appear like they could be interacting gravitationally — but their relative speeds make this…
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NASA
Astronomy Picture of the Day
A Messier Moment for Tempel 2 Explanation: Which of these is not a comet? You guessed it – the one on the right is a globular star cluster. The diffuse greenish coma of periodic comet 10P/Tempel 2 is at left in the frame. In fact the globular star cluster is Messier 30, also known as M30, or the 30th entry in astronomer Charles Messier’s catalog of…
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NASA
Astronomy Picture of the Day
Rubin’s COSMOS Field Explanation: There are more than half a million galaxies in the central panel of this image from the NSF-DOE Vera C. Rubin Observatory in Chile. This is the COSMOS field, a patch of sky several times larger than the full moon, first observed by Hubble. It has also been observed by Webb and other telescopes because it contains comparatively few bright stars from our own galaxy, offering a relatively unimpeded view of…
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NASA
Astronomy Picture of the Day
New Sharpest Image of the Sun Uncovers Instability Explanation: What does the new sharpest image of our Sun show? Instability. To be clear, a certain kind of interactive process called the Kelvin-Helmholtz instability (KHI). This instability can create waves and swirls when two streams flow past each other — in this case variable streams of solar magnetic plasma. Long hypothesized to occur on the Sun’s surface, KHI…
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NASA
Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. Spokes on Saturn’s B Ring Explanation: Don’t get spooked by Saturn’s ghostly spokes! Today we feature a nearly two-hour timelapse of Saturn and its rings looping forwards and backwards. If you look closely, a ghoulish shadow…
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NASA
Astronomy Picture of the Day
Curious Cometary Knots in the Helix Nebula What causes unusual knots of gas and dust in planetary nebulas? Seen also in the Ring Nebula, the Dumbbell Nebula and NGC 2392, the knots’ existence was not initially predicted, and their origins are still not well understood. Pictured here is a fascinating image of part of the Helix Nebula by the James Webb Space Telescope showing tremendous detail in infrared light. The cometary knots have masses similar…
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NASA
Astronomy Picture of the Day
Vaporizing Meteor Photobombs the Lacerta Nebula Explanation: What’s happening to this meteor? This bright meteor streak appeared and disappeared quickly during a long exposure of the Great Lacerta Nebula, seen faintly in red toward the center of the image. The meteoroid, likely a small pebble, creates its glow partly by heating and exciting surrounding air in Earth’s atmosphere, but itself vaporizes and leaves wind-blown gas and dust with colors that…
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NASA
Astronomy Picture of the Day
A Fire Rainbow over West Virginia Explanation: What’s happening to this cloud? Ice crystals in a distant cirrus cloud are acting like little floating prisms. Known informally as a fire rainbow for its flame-like appearance, a circumhorizon arc appears parallel to the horizon. For a circumhorizontal arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds present below — in this…
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