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Enter comet Swan, speeding past Earth before it laps our sun and takes another long, elliptical trip through the outer solar system. Swan last waved at Earth 25 million years ago, when mammals grazed on sprawling grasslands in the Oligocene Epoch. Now, this sun-tinged cosmic snowball may illuminate our early morning sky this month. Swan was discovered by Michael Mattiazzo, an Australian amateur astronomer who analyzed images from the Solar and Heliospheric Observatory spacecraft that observes our sun. Swan is outgassing hydrogen from water-ice on its toasty approach to the sun. This hydrogen “burp” shows up in ultraviolet images from...

Comet SWAN Brightens Credit & Copyright: Michael Jäger & Gerald RhemannExplanation: A newly discovered comet has brightened enough to be visible this week with binoculars. The picturesque comet is already becoming a favored target for northern sky imagers. Pictured above just last week, Comet SWAN showed a bright blue-green coma and an impressive tail. Comet C/2006 M4 (SWAN) was discovered in June in public images from the Solar Wind Anisotropies (SWAN) instrument of NASA and ESA's Sun-orbiting SOHO spacecraft. Comet SWAN, near magnitude six, will be visible with binoculars in the northeastern sky not far from the Big Dipper...

The Ghostly Tail of Comet SWAN Credit & Copyright: Ray GralakExplanation: What causes the structure in Comet SWAN's tail? Comet SWAN, which unexpectedly flared up to naked-eye brightness last week, has been showing detail in its ion tail that might be described as ghostly. The ion tail is made of ionized gas, energized by ultraviolet light from the Sun and pushed outward by the solar wind. The solar wind itself is quite structured and sculpted by the Sun's complex and ever changing magnetic field. Following the wind, structure in Comet SWAN's tail can be seen to move outward from...

What had been a modest comet seen only with binoculars or telescopes flared up this week to become visible to the naked eye [images]. Comet Swan, as it is called, is in the western sky after sunset from the Northern Hemisphere. It remains faint, likely not easy to find under bright city lights but pretty simple to spot from the countryside. It is a "fairly easy naked-eye comet," said Pete Lawrence, who photographed the comet from the UK. "The tail is now showing some interesting features too." UPDATE: Late Thursday, however, Lawrence reported that the comet already may be getting...