Astronomy Picture Of the Day (APOD)Halloween and the Ghost Head Nebula
Halloween's origin is ancient and astronomical. Since the fifth century BC, Halloween has been celebrated as a cross-quarter day, a day halfway between an equinox (equal day / equal night) and a solstice (minimum day / maximum night in the northern hemisphere). With our modern calendar, however, the real cross-quarter day will occur next week.
Comet Holmes Coma Expands
Go outside tonight and see Comet Holmes. No binoculars or telescopes are needed -- just curiosity and a sky map. Last week, Comet 17P/Holmes underwent an unusual outburst that vaulted it unexpectedly from obscurity into one of the brightest comets in recent years.
A Telescopic View of Erupting Comet Holmes
What's happened to Comet Holmes? A normally docile comet discovered over 100 years ago, Comet 17P/Holmes suddenly became nearly one million times brighter last week, possibly over just a few hours. In astronomical...
Noctilucent Clouds Over Sweden
Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun, sunset rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on clouds above.
The Great Carina Nebula
A jewel of the southern sky, the Great Carina Nebula, aka NGC 3372, spans over 300 light-years, one of our galaxy's largest star forming regions. Like the smaller, more northerly Orion Nebula...
Comet Holmes in Outburst
Comet 17P/Holmes stunned comet watchers across planet Earth earlier this week. On October 24, it increased in brightness over half a million times in a matter of hours. The outburst transformed it from...
Apogee Moon, Perigee Moon
Tonight, those blessed with clear skies can enjoy a glorious Full Moon, (exact full phase at 0452 UT, October 26). In fact, the Moon will reach its full phase within a few hours of perigee, the closest point in its elliptical orbit, making it the largest Full Moon of 2007.
Scroll right and cruise above the thin, icy rings of Saturn. This high resolution scan is a mosaic of images presented in natural color and recorded in May, over about 2.5 hours as the Cassini spacecraft passed above the unlit side of the rings.
Saturn never shows a crescent phase -- from Earth. But when viewed from beyond, the majestic giant planet can show an unfamiliar diminutive sliver. This image of crescent Saturn in natural color was taken by the robotic Cassini spacecraft in May.
Victoria Crater on Mars
Scroll right to see the largest crater yet visited by a rover on Mars. Reaching the expansive Victoria Crater has been a goal for the robotic Opportunity rover rolling across Mars for the past two years. Victoria crater has about five times the diameter of Endurance Crater, which Opportunity spent six months exploring.