Cloud shape changes dramatically from the equator to the pole while the lower latitude cloud shape is fragmented due to vigorous convective movement. This movement is powered by the sun’s radiation heating the atmosphere. The bright white visible above the darker cloud deck is made of freshly formed droplets of sulphuric acid. Toward mid latitude, the convective clouds become streaky shapes. In higher latitudes, clouds appear dense and featureless, a type of haze. The dark, circular feature visible at the right edge of the image is a dark streak usually present in the polar region, indicating atmospheric spiralling towards the pole.
May 30, 2008
March 13, 2008
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The Venus Express space probe has been eyeing the southern polar region of Venus and has found an atmospheric phenomenon that looks very much like a hurricane with a center resembling an eye like those found in hurricanes on Earth. This hurricane is causing scientists to scratch their heads as the Venus version seems to morph and change shape rapidly over the course of several days.
The vortex of the hurricane is 2,000 km (1,240 mi) wide and was actually discovered in 1974 by the Mariner 10 spacecraft. A similar entity exists near the north pole of the planet, observed by the Pioneer spacecraft in 1979.
Scientists have been recently analyzing the southern polar hurricane in the thermal infrared wavelength hoping to understand the temperature in the upper reaches of the clouds. In this analysis, the vortex appears very bright, indicating the downward movement of atmospheric gases through the vortex creating a depression in the upper reaches and generating heat there. Various shapes of the vortex appear in the pictures at left.
In June 2006, the vortex was hourglass shaped matching the earlier observing in the north by the Pioneer mission. The images show the hurricane changes its shape in a matter of days. A video of the phenomenon can be viewed at the European Space Agency web site here: http://www.esa.int/esaCP/SEMIZFM5NDF_index_0.html
The changing dynamic of the vortex can be seen quite well in the video. The structure is very complex with different wind dynamics at different altitudes.
Scientists are uncertain how to account for the activities of the vortex. One theory is that gases in the atmosphere get heated by the Sun near the equator. These gases rise upward, then migrate to the polar regions. The gases cool, then sink down to the surface. As the gas moves toward the northern and southern poles, they are deflected due to the rotation of the planet. This is similar to the way winds at the center of Earth-born hurricanes operate. The planetary rotation adds to the unpredictability of the hurricane-like winds, just as the rotation of the Earth does for our hurricanes.
Venus Express was launched in November 2005 and its mission is scheduled to run through May 2009. Scientists plan to continue to monitor the hurricane and the wind activity in the polar regions of Venus.
A video illustrating the cloud structure of Venus can be found here: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=64
January 26, 2008
In the pre-dawn sky here at the end of January and for a week or so into February, Venus and Jupiter will appear closest together in the sky, peaking around February 1. Our moon will join this alignment, 2 – 3 days later, making all three celestial objects in conjunction. The moon will be in its waning crescent phase.
Venus and Jupiter rise out of the east to southeast a couple of hours before sunrise. They will be so close to one another and so bright as to appear to be a double planet. On February 4, about forty-five minutes before sunrise, the moon will join the two planets to form an isosceles triangle, or pyramid shape, with the planets three degrees apart and the moon at the vertex five degrees apart from the other two.
The moon will be 247,000 miles (397,000 km) out, Venus 126 million miles (203 million km), and Jupiter 560 million miles (901 million km). Another conjunction of Venus and Jupiter will occur in the evening sky on December 1. Two and one-half years later in 2011, Venus and Jupiter will be in conjunction in the morning sky once again.
For more information, view these links:
January 5, 2008
This link leads to a wonderful site run by the BBC that contains episodes of the British television show “The Sky at Night” going back to 2001. I often buy the magazine which contains a video CD of the show with a lot of extras as well and recently discovered the web site. I couldn’t let a gem like this site go by without mentioning it.
The show has been on British television for fifty years hosted by the same man, Sir Patrick Moore, who is eighty-four and an amateur astronomer. Some recent episodes talk about the moon landings, the Perseid meteor showers, the Milky Way doomed to collide with the Andromeda galaxy, black holes, the Saturn missions, Venus, Mars, and on and on and on. The shows last about a half hour, are absolutely packed with information and are commercial free. The January episode is about cosmic debris like asteroids and meteor showers.
If you’re an astronomy geek like me, you’ll love it.