Mercury, crescent moon, Comet Lovejoy make the dawn sparkle

Comet Lovejoy's two tails rise at dawn this morning as seen from Western Australia. Details: 73mm lens at f/4, ISO 3200 and 12-second exposure. Click image to see an awesome video of the comet rising. Credit: Colin Legg

Just in time for Christmas, Comet Lovejoy is putting on a wonderful show for observers in the southern hemisphere this week. The two photos show the comet’s beautiful, feather-like tail standing high at dawn. Legg took three cameras with him this morning – one to make the time-lapse video and two for still shots. In his words:

“At around 3:10 (Australian time) the first hint of tail appeared above the trees, and by 3:15 I could see it visually. It stayed in clear view – non-averted vision – from then until around 4:10 (deep twilight). An awesome sight.”

Comet Lovejoy captured at dawn today from Brazil. Click image to see more photos and blog. Credit: Reginaldo Nazar

Others were out to see the marvel including Reginaldo Nazar of Curitiba, Brazil, who also took photos at dawn this morning. Many observers have pointed out and you can see for yourself that the head of the comet has become very faint, while the tail continues to hold its own. As Lovejoy moves ever higher into darker sky and the moon departs the scene, the tail should continue to dazzle for some time.

Compare the dramatic change in the comet's head and nucleus (bright spot) on Dec. 19 (left) and Dec. 21. Credit: Jakub Cerny, Jan Ebr, Martin Jelinek, Petr Kubanek, Michael Prouza and Michal Ringes

As the comet’s distance from the sun increases, that too will eventually fade. The rapid dimming of the head may indicate that the major portion of the comet – its nucleus – is nearly spent or perhaps broken apart. Two recent examples  of comets that “lost their heads” are Comet Elenin earlier this year and C/1999 S4 (LINEAR) in 2000. This normally happens when a comet is closest to the sun and the nucleus breaks apart in the solar heat. Perhaps the same has occurred post-perihelion with Comet Lovejoy. Or it might be that the comet has simply exhausted its material.

Chris Wyatt got some great shots of the Lovejoy' tail and faint head from Bendemeer, New South Wales, Australia on Dec. 22 Australian time today. He estimated the tail length at about 14 degrees. Credit: Chris Wyatt

Updated light curves, which are predictions on the brightness behavior of a comet, indicate that Lovejoy will be 6th magnitude or brighter through the end of the month. By the time it’s visible in the southern U.S. around January 20, it might still be magnitude 10 and visible in medium-sized telescopes.

The moon and planet Mercury are together at dawn Thursday morning Dec. 22. Created with Stellarium

I’m happy that southern observers have so much to look forward to at dawn. Even if northern hemisphereans can’t see the comet, we can still share in a fortunate pairing of a most delicate crescent moon and the planet Mercury tomorrow morning December 22. If you look very low in the southeastern sky about 45 minutes before sunrise, the moon will hover some 1o degrees (one fist at arm’s length) above the horizon. Mercury is a degree lower and 5 degrees to the moon’s left. Starved of starlight, I’m hoping to re-charge tomorrow morning with an elixir of moonlight, Mercury and spring stars.