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What's in the sky tonight?
December 6, 2013

-The waxing crescent Moon hangs high over Venus at dusk, with Alpha and Beta Capricorni now to its lower right.

-Have you noticed an extremely luminous star in the southwest after sunset? That's no star. It's Venus, and tonight it is at its brightest for all of 2013. Only the Moon itself outshines the 2nd planet from the sun.

Astronomers are mourning the loss of Comet ISON, which disintegrated when it flew past the sun on Thanksgiving Day (Nov. 28). Who needs it? There is another comet brightening in the morning sky--naked-eye Comet Lovejoy (C/2013 R1). Martin McKenna sends this report from Northern Ireland: "This morning, the comet was easily visible as a fuzzy star of 4th magnitude with a long straight tail between the constellations Bootes and Hercules." He took this picture using a Canon 450D digital camera.

"I could see 5 degrees of tail with my unaided eye," continues McKenna. "Using the camera the tail was at least 10o long!"

Telescopes and longer exposures reveal much more. A "disconnection event" disrupting the comet's tail on Dec. 5th was recorded. The disturbance could be caused by a gust of solar wind or perhaps an episode of vigorous outgassing in the comet's core.

Monitoring is encouraged. Comet Lovejoy is easy to find before dawn rising in the east before the sun.

Astro Picture of the Day:
December 6, 2013

Source:
For an Earth-orbiting gamma-ray telescope, Earth is actually the brightest source of gamma-rays, the most energetic form of light. Gamma-rays from Earth are produced when high energy particles, cosmic rays from space, crash into the atmosphere. While that interaction blocks harmful radiation from reaching the surface, those gamma-rays dominate in this remarkable Earth and sky view from the orbiting Fermi Gamma-ray Space Telescope's Large Area Telescope. The image was constructed using only observations made when the center of our Milky Way galaxy was near the zenith, directly above the Fermi satellite. The zenith is mapped to the center of the field. The Earth and points near the nadir, directly below the satellite, are mapped to the edges of the field resulting in an Earth and all-sky projection from Fermi's orbital perspective. The color scheme shows low intensities of gamma-rays as blue and high intensities as yellowish hues on a logarithmic scale. Our fair planet's brighter gamma-ray glow floods the edges of field, the high intensity yellow ring tracing Earth's limb. Gamma-ray sources in the sky along the relatively faint Milky Way stretch diagonally across the middle. Launched June 11, 2008 to explore the high-energy Universe, this week Fermi celebrated its 2,000th day in low Earth orbit.