Because the Sun is on the celestial equator at the equinoxes, its declination is of course 0 o. 12 hours) hence the term equinoxes (equal nights). At the equinoxes, at all places on Earth, the nights and days are of equal duration (i.e. The Sun crosses the celestial equator on two occasions during the course of a year and these occasions are known as the equinoxes. Declination can be summarized as the celestial equivalent of Latitude since it is the angular distance of a celestial body North or South of the Celestial Equator. 5 o South and back again during the course of a year. The declination of the Sun changes from 23.5 o North to 23. The Declination of a celestial body is its angular distance North or South of the Celestial Equator. Permission is granted for one-time, nonexclusive use in print and broadcast media, as long as appropriate credits (as noted in each caption) are included. Sky & Telescope is making the following illustrations available to the news media. Despite calendar reforms, these celebrations and the observance of Christmas by early Christians remained locked to the 25th. the winter solstice fell around December 25th. Earlier in Rome it was the time of Saturnalia, the Roman solstice holiday. Prior to the Christian era, Romans called this day Dies Natalis Invicti Solis, the Birthday of the Unconquered Sun. There are more known rituals associated with this solstice than for any other time of the year. Winter-solstice celebrations could well be the world’s oldest holidays. It meant the end of declining hours of sunlight and provided a sense of renewal as the Sun began its daily climb higher in the sky. In ancient cultures, the winter solstice was an auspicious moment. It is also the time when the days begin to grow longer and the nights shorter. The word solstice comes from the Latin solstitium - sol meaning 'sun' and –stitium 'stoppage.' The winter solstice marks the shortest day and longest night of the year.

A solstice comes when the Sun is at the upper or lower end of its journey an equinox comes when the Sun is halfway through each journey. The effect is opposite for inhabitants of the Southern Hemisphere for them the December solstice signals the beginning of summer, while winter starts at the June solstice.įor a skywatcher on Earth (at north temperate latitudes), the effect is to make the Sun appear to move higher in the midday sky each day from December to June, and back down again from June to December. North of the equator, the June and December solstices mark the beginning of summer and winter, respectively. The solar rays come in at a lower slant to this part of the world and heat the ground less, making winter. When we’re on the opposite side of our orbit, the Northern Hemisphere is tipped away from the Sun. So when we’re on one side of our orbit, the Northern Hemisphere is tipped Sunward and gets heated by more direct solar rays, making summer. Earth’s axis is tilted with respect to our orbit around the Sun. The Sun appears to move north and south in our sky during the year because of what some might consider an awkward misalignment of our planet.

The start of winter (for the Northern Hemisphere) is defined as the moment when the Sun hovers over Earth’s Tropic of Capricorn (the line of latitude 23½° south of the equator) before heading north - a moment called, by Northerners, the winter solstice. The seasons’ starting times are governed by the Earth’s motion around the Sun - or equivalently, from our point of view, the Sun’s annual motion in Earth’s sky. This moment marks the December solstice, the official beginning of winter in the Northern Hemisphere and a time of great celebration in many northern cultures. Eastern Standard Time, the Sun will reach its southernmost point in the sky for the year and begin its six-month return journey northward. Note to Editors/Producers: This release is accompanied by a high-quality animation and illustration see details below.

Solstice and equinox animation