The winter astronomical will arrive on Wednesday, December 21, at 10:48 p.m. (peninsular time) in the northern hemisphere, while summer will begin in the southern hemisphere.
winter season it will last 88 days and 23 hours and will end on March 20, 2023when spring will begin, according to calculations by the National Astronomical Observatory, belonging to the Ministry of Transport, Mobility and Urban Agenda.
The beginning of winter in the northern hemisphere is defined by the instant in which the Earth passes through the point in its orbit from which the Sun presents its maximum southern declination. The day this happens, the so-called 'king sun' reaches its lowest elevation above the horizon at noon and describes the shortest arc in the sky. Consequently, that is the day with the fewest hours of sunshine of the year.
Furthermore, the maximum height of the Sun at noon appears to not change for several days. Due to this, at beginning of winter it is also called the winter solstice (from the Latin 'solstitium', that is, 'quiet sun'). At that moment summer begins in the southern hemisphere.
The National Astronomical Observatory points out in a report on winter, collected by Servimedia, that winter in the northern hemisphere is the shortest season of the year, because the Earth's orbit around the Sun is not circular, but elliptical, and winter coincides with the time of year when the Earth is closest to the Sun. When this happens, the planet moves faster in its orbit -according to what is known as Kepler's second law- and, therefore, it takes less time to reach the Sun. point where the next season begins, which is spring.
The onset of winter can occur, at most, in four different calendar dates (from December 20 to 23). Throughout the 21st century, it will begin on December 20 to 22 (the official Spanish date), with its earliest start in 2096 and the latest in 2003. Variations from one year to the next are due to the way in which fits the sequence of years according to the calendar -some leap, others not- with the duration of each orbit of the Earth around the Sun.
DAY WITH LESS SUNLIGHT
Although the day of solstice winter is the one with the least hours of sun, the difference in hours between day and night depends on the latitude of the place. Thus, Madrid will have 9 hours and 17 minutes of sunlight next Wednesday, compared to 15 hours and 3 minutes on the longest day (summer solstice).
Therefore, there is almost a six-hour difference between the shortest and longest days, which depends a lot on the latitude of the place, since this gap decreases the closer to the equator and is maximum (24 hours) at the terrestrial poles. .
It is precisely in the Antarctica where some days a year around December 21 the phenomenon of the Midnight Sun occurs, in which the star is visible above the horizon during 24 hours a day.
Las winter nights are long and often dry, so they are excellent for observing the sky. During this winter there will be no eclipse of the Sun or Moon, but different planets and constellations can be seen throughout each night.
In early winter, five planets will be visible at dusk (Mercury, Mars, Venus, Saturn, and Jupiter), but some planets will move closer to the Sun and gradually disappear from the sky as the months go by. Thus, Mercury will do so at the beginning of January and Saturn at the beginning of February, so the season will end with three planets visible at dusk.
For its part, the sky at dawn will begin winter no planets visible. In mid-January Mercury will make a brief appearance and in mid-March Saturn will begin to become visible.
In addition to the different planets, the sky at dusk in winter will show some of the fan-favorite constellations, as they contain the brightest stars. Among them, Orion stands out with the bright (and variable) Betelgeuse, Taurus with the reddish Aldebarán, Can Mayor with Sirius (the brightest star of the night) and Gemini with the couple Castor and Pollux. The union of some of these stars with other adjacent ones forms an asterism known as the winter hexagon, as it is characteristic of the evenings of the season.
Other phenomena of astronomical interest during this winter include the ursid meteor showerwhose maximum is expected around December 22, and the quadrantids, with the maximum around January 4. The winter full moons will take place on January 7, February 5 and March 7.
On January 4, 2023, the moment of maximum annual approach between the Earth and the Sun, called perihelion. At that time, the distance between planet and star will be just over 147 million kilometers, that is, about five million less than at the moment of greatest distance (aphelion), which will happen on July 6, 2023.