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Three planets, the Moon and more on December 2012

December 12, 2012  •  Leave a Comment

On December 2012 three planets: Saturn, Venus and Mercury were found aligned over the Eastern horizon before Sunrise. The conjunction took different configurations and was joined by the Waning Crescent Moon on December 10th and 11th. The thin Moon and the three planets displayed a beautiful show that was easy to see with the naked eye from all around the world. My views from the South Hemisphere will surely look upside-down or mirrored to observers in the North side of the globe.

With the night just ending and the horizon starting to glow by the sunrise two planets were already visible: Saturn and Venus. Since the sky was still dark enough several stars could be seen including Spica and Zubenelgenubi, those bright stars are very near the ecliptic so they can be occulted by the Moon and rarely by planets. Zubenelgenubi will be occulted by Mercury in 2052(!).


In this shot you can also see the bright stars Alpha and Beta Centauri and looking carefully the bright globular cluster is also visible, it's visible to the naked eye and even in a wide angle photo as this one with the sky not fully dark it appears as a diffuse blob, it's really magnificent.

Earthshine is visible in this photo. The bright side of the Moon is lit by the Sun and the dark part is lit by light reflected from Earth, hence the name "earthshine". In this photo you can also see clearly that Zubenelgenubi is a double star, the brightest star in Libra. Venus is just raising and looks very bright while Saturn is at the top of the frame. Zooming in a lot and eluding a couple of stars I was able to find Titan, Saturn's brightest satellite, in this photo. At magnitude 9 it's just visible below the planet, but you have to zoom a lot. 

This is from December 9th before the Moon joined the conjunction you can see Spica, Saturn, Venus, Zubenelgenubi and Mercury aligned over the ecliptic. Venus is displaying an oval aureole, a curious atmospheric phenomena that is not very common. Mercury was really difficult to see due to thin clouds, almost impossible with the naked eye but ok with binoculars.

Without clouds and with excellent transparency Mercury was easy to see with the naked eye, you will find it without problems in this photo. There's a thin window of time to catch mercury, it has to be a few degrees above the horizon to overcome atmospheric extiction but before the sky turns too bright to wash it. December is not the best month to observe Mercury from the south hemisphere because the nights are very short as we are in the Summer but the observation of Mercury actually favors the south hemisphere. In May, for example, you can see Mercury in the full darkness of the night.

The conjunction above Rio de La Plata with the city of Buenos aires on the right. This is almost exactly how the show looked to the casual observer, the Moon and Venus were very bright and Mercury was an easy naked eye catch but only if you looked for it. The blue color in the river and the glow of sunrise at the horizon made the event a very nice sight for those that were awake.

You can see more photos from this conjunction at this gallery.


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