High Noon at the North Pole
The 1999 summer solstice occurs today at 19:49 UT
June 21st marks the beginning of summer in the Northern Hemisphere and the beginning of winter in the Southern Hemisphere. In the North it's the longest day of the year. At mid-latitudes there is sunlight for over 16 hours. Above the Arctic Circle the sun doesn't set at all!
Above: The Earth's axis (the black line) is tilted by 23.5 degrees relative to the plane in which our planet orbits around the Sun. That's why we have seasons. For three months of the year, centered on June 21, the north pole is tilted toward the Sun and the south pole is tilted away. Six months later the situation is reversed. The tilt of the Earth's spin axis is exaggerated in this figure.
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11 year sunspot cycle.
Left: Click on the image to see an animated gif simulating the Earth's rotation on a single day - June 21 - as seen from the Sun. The North Polar Cap is clearly visible throughout this 24 hour period - the sun doesn't set. And Antarctica cannot be seen - there, the sun doesn't rise. The images were generated by JPL's Solar System Simulator; the animated gif is 349KB.
During the "sunspot maximum" there are solar flares,
coronal mass ejections, and -- of course -- lots of sunspots.
The action isn't limited to the Sun. We feel the effects of the
solar maximum here on Earth, too. Power grids, radio communications,
and the intensity of aurorae are all affected.
Right: The Midsummer Sun. This white light image from the Big Bear Solar Observatory was recorded at 14:53:08 (UT) on June 20, 1999 with a 8-bit Kodak MegaPlus 1.4i CCD camera. [ ]
December 3: Mars Polar Lander nears touchdown
December 2: What next, Leonids?
November 30: Polar Lander Mission Overview
November 30: Learning how to make a clean sweep in space
The images below show today's solstice as viewed from web cams both ends of the Earth. Pictured right is a vista from Tromso, Norway above the Arctic circle. Pictured left is a view from the Automated Astrophysical Site-Testing Observatory near the US South Pole Station.
This week's sky at a glance -- from Sky &Telescope
The Sun - from the SEDS Nine Planets web site
Earth's Seasons -- A table of solstices and equinoxes from the US Naval Observatory
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