For six months, each day has been shorter than the last, the Sun lower in the sky. Will it disappear altogether and leave the people bereft in the dark cold winter? The winter solstice is the shortest day of the year and is associated with more festivals than any other astronomical event.
The winter solstice on December 21 marks the beginning of astronomical winter in the northern hemisphere, but of astronomical summer in the southern hemisphere. The southern winter solstice is in June.
Last edited by Mona - Astronomy; 12/18/1711:00 AM.
For people living outside the tropics, June 21st is the longest or shortest day of the year, a solstice. It marks the first day of summer in the northern hemisphere and winter in the southern hemisphere. But why do we have seasons? And do other planets have them?
For readers in the southern hemisphere, of course you are coming up to the summer solstice. (Lucky you.) And it won't be St John's Day.
Each day for six months after the winter solstice, the Sun rises a bit higher in the sky. It reaches the maximum height at the summer solstice, the longest day. Evidence of rituals and festivals at the times of the solstices goes back thousands of years.
The December solstice this year will happen on December 21st at 16:28 UTC. UTC is the same as Greenwich Mean Time, five hours ahead of EST and eight hours ahead of PST in the USA. The astronomical solstice occurs when the Sun appears to be at its southernmost point on the celestial sphere.
The celestial sphere is "an imaginary sphere of which the observer is the centre and on which all celestial objects are considered to lie."
At today's solstice, the Sun is in the constellation Sagittarius near the center of our Milky Way galaxy. In fact, if it were possible to see today's Solstice Sun against the faint background stars and nebulae your view might look something like this composited panorama.
This amazing image was created by Stefan Seip. He photographed the The Milky Way under the dark skies of Namibia and stitched the images together to make the panorama. The Sun is a photo he took on the 2015 December solstice. Seip digitally overlayed it in what is the northern winter solstice position, close to the center of the Milky Way.
(Composite Image Credit & Copyright: Stefan Seip (TWAN) Description based on text by Robert Nemiroff (MTU) & Jerry Bonnell (UMCP))
Last edited by Mona - Astronomy; 12/21/1706:04 AM.
Newgrange in Ireland is known for an ancient mound aligned with the winter solstice. Within the mound is a chamber reached by a 19-meter passage. Above the entrance to the passage is an opening called a roof-box. On mornings on or near the winter solstice, a beam of light comes through the roof-box into the passage and chamber. As the sun rises higher, the beam widens so that the whole chamber is dramatically illuminated.