Next Saturday is winter solstice! ..but what is it?
1 of 4: winter solstice in fairbanks, alaska
2 of 4: when do they happen and what causes it?
3 of 4: Decoding the ancient astronomy of Stonehenge
4 of 4: tilt is not only the reason for solstice but even for climate !
The time lapse on the left shows the eerie scene in Fairbanks — the sun basically skims the horizon for a brief while and then vanishes.
What is the definition of a solstice, and when do they happen? Is the winter solstice always the first day of winter?
Find out what causes these bi-annual astronomical events, as well as how they bring about the shortest and longest days of the year.
4 of 4: Are there
solstices on other
Yes! All the planets in our solar system rotate on a tilted axis and therefore have seasons, solstices, and equinoxes. Some of these tilts are minor (like Mercury, which is tilted at 2.11 degrees). But others are more like the Earth (23.5 degrees) or are even more extreme (Uranus is tilted 98 degrees!).
To the left, see a beautiful composite image of Saturn on its equinox captured by the Cassini spacecraft (RIP) in 2009. Saturn the gas giant is tilted 27 degrees relative to the sun, and equinoxes on the planet are less frequent than on Earth.
Saturn only sees an equinox about once every 15 years (because it takes Saturn 29 years to complete one orbit around the sun).