solstice

solstice [Lat.,=sun stands still], in astronomy, either of the two points on the ecliptic that lie midway between the equinoxes (separated from them by an angular distance of 90°). At the solstices the sun's apparent position on the celestial sphere reaches its greatest distance above or below the celestial equator (see equatorial coordinate system ), about 23 1/2 ° of arc. At the time of summer solstice, about June 22, the sun is directly overhead at noon at the Tropic of Cancer (see tropics ). In the Northern Hemisphere the longest day and shortest night of the year occur on this date, marking the beginning of summer. At winter solstice, about Dec. 22, the sun is overhead at noon at the Tropic of Capricorn; this marks the beginning of winter in the Northern Hemisphere. For several days before and after each solstice the sun appears to stand still in the sky, i.e., its noontime elevation does not seem to change from day to day.

solstice The time of most northerly or southerly declination of the sun from the equator. In the northern hemisphere, the summer solstice is around 22 June and the winter solstice around 22 December. These dates are reversed for the southern hemisphere.

solstice Either of the two points on the ecliptic at which the Sun reaches its greatest declination north or south of the celestial equator each year; or the dates on which this occurs—on June 21 (summer solstice in the northern hemisphere, winter solstice in the southern) and December21 or 22 (vice versa).