Winter

The beginning of winter

The winter of 2024-2025 in the northern hemisphere will begin on December 21, 2024 at 10:21 hours official Spanish mainland time according to calculations by the National Astronomical Observatory (National Geographic Institute - Ministry of Transport, Mobility and Urban Agenda). This season will last approximately 88 days and 23 hours, and will end on March 20, 2025 with the beginning of spring.

The onset of winter in the northern hemisphere is defined by the moment when the Earth passes through the point in its orbit from which the Sun has its maximum southern declination. On the day when this happens, the Sun reaches its lowest elevation above the horizon at noon and describes the shortest arc in the sky. As a result, this is the day with the fewest hours of sunlight of the year. In addition, for several days the maximum height of the Sun at noon does not seem to change, and because of this, the beginning of winter is also called the winter solstice (from the Latin solstitium, still Sun).

The beginning of winter in the northern hemisphere coincides with the beginning of summer in the southern hemisphere.

 

 

The sky during winter 2024-2025

Winter nights are long and often dry, making them excellent for observing the sky. During winter 2024-2025 we will be able to see different planets and constellations throughout each night.

During the winter, we will be able to see the two large gaseous planets at dusk, Saturn and Jupiter, along with Venus , but as the months go by, Saturn will move closer to the Sun, disappearing from the evening sky in late-February. Mercury will make a brief appearance from mid-February to mid-March. Mars will begin to be visible at dusk from mid-January.

The dawn sky in winter, on the other hand, will begin with Mars and Mercury visible. Both will dissapear from the morning sky by the end of January, therefore no planet will be visible at that time until the end of winter.

In addition to the different planets, the winter evening sky will show us some of the constellations that are favourites among amateurs, as they contain the brightest stars. These include Orion, with the bright (and variable) Betelgeuse, Taurus, with the reddish Aldebaran, Can Major with Sirius, the brightest star of the night sky, and Gemini, with the pair Castor and Pollux. Joining some of these stars with other adjacent stars forms an asterism known as the winter hexagon as it is characteristic of the evening sky of the season.

Other phenomena of astronomical interest during the winter of 2024-2025 include the ursids meteor shower, expected to peak around December 22 and the quadrantids, expected to peak around January 3. Winter full moons will occur on January 13, February 12 and March 14.

On January 4, 2025 the moment of maximum annual approach between the Earth and the Sun, called perihelion, will occur. At that time, our distance from the Sun will be just over 147 million km, which is about 5 million km less than at the time of maximum separation (aphelion), which will occur on July 3, 2025.

During the winter of 2024-2025 there will be a total lunar eclipses. The eclipse will take place on 14 March, it will be visible from America, the west of Africa and Europe, and the east of Asia and Oceania. It will be visible from Spain, although the Moon will set before the end of the totality.

 

Some interesting facts about winter

At just under 89 days, winter in the northern hemisphere is the shortest season of the year. This is 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 Earth moves faster in its orbit (according to what is known as Kepler's second law), and therefore needs less time to reach the point where the next season begins, which is spring.

The onset of winter can occur on at most four different dates in the calendar (20-23 December). Throughout the 21st century, winter will begin on 20-22 December (official Spanish date), with the earliest onset in 2096 and the latest in 2003. The variations from year to year are due to the way the sequence of calendar years (some leap years, some not) fits in with the length of each orbit of the Earth around the Sun.

Although the day of the winter solstice corresponds to the day with the least number of hours of sunlight, the difference in hours between day and night depends on the latitude of the location. For the latitude of Madrid, the winter solstice day will have 9 hours and 17 minutes of sunlight, compared to 15 hours and 3 minutes of sunlight on the longest day (summer solstice). The difference between the shortest and the longest day is therefore almost six hours. As we get closer to the equator, this difference decreases, while at the Earth's poles the difference is at its maximum.

the difference is at its maximum. For more information on the astronomical phenomena of the year, please consult the Almanak of the Astronomical Observatory, published by the National Geographic Institute.

Information provided by the National Astronomical Observatory (IGN, Ministry of Transport and Sustainable Mobility). Reproduction in whole or in part is authorised provided the source is acknowledged.