• Astronomy An unusual panorama of the center of the Milky Way

Summer is here, the longest of the four seasons.

The solstice takes place at dawn on Monday, June 21.

We tell you everything you need to know about the longest day of the year and about the celestial phenomena that will take place during the summer period.

Ten keys

1)

Home

.

Summer in the Northern Hemisphere (and winter in the South) will begin on June 21 at 5:32 a.m. peninsular time (4:32 a.m. in the Canary Islands).

2)

The longest day

. The shortest boreal night takes place on the day of the summer solstice. On that day, in Madrid the night will last 8 hours and 57 minutes, while there will be 15 hours and 3 minutes of sunlight. Oddly enough, the longest day of the year is not the day the Sun rises earlier nor is it the day the Sun sets later. This is because the Earth's orbit is an ellipse and the axis of this ellipse is not related to the inclination of the Earth's axis that defines the seasons. The earliest sunrise in 2021 occurred on June 14, while the latest sunset will occur on June 27.

3)

Tropic of Cancer

.

At the summer solstice, the Earth's North Pole is closer to the Sun than the South Pole.

Seen from Earth, the Sun is at noon at the "Tropic of Cancer", its northernmost possible position.

4)

Aphelion

.

The paradoxical circumstance occurs that the summer of the Northern Hemisphere arrives when the Earth, in its elliptical movement around the Sun, is as far away as possible from the king star.

The farthest point, called aphelion, will be reached on July 5, 2019, when the Earth is about 152 million kilometers from the Sun, that is, 5 million kilometers further than at the perihelion position we are passing through. last January 2.

5)

Still sun

.

The days before and after the 21st the maximum height of the Sun at noon does not change much in the sky.

This is where the word solstice comes from, which means 'Static Sun' or 'Still Sun'.

6)

Polo without night

.

At the North Pole, the nightless period that began on March 20 now reaches its midpoint, with another three months of sunlight left until fall arrives and a six-month period of night begins.

7)

A supermoon and a blue moon.

This summer will have four full moons, including a supermoon and a blue moon. The first full moon of the season, called 'strawberry moon' will happen on June 24 with our satellite in its closest possible position to Earth (perigee), it is what is sometimes called 'supermoon'. The other full moons will be on July 23, August 22 and September 20. When a season has four full moons, the Anglo-Saxons call the third of them 'blue moon', blue moon (the second full moon of a month that has two is also called 'blue moon'). So the full moon on August 22 will be a 'blue moon', but naturally this has nothing to do with the color of the Moon.

8)

Planets in sight.

During early summer sunrises, Jupiter and Saturn will be visible. Both giant planets will be present for almost all the nights of August and will remain in the sunsets at the end of the season. Venus will act as the evening star and Mars will also be visible in the evening towards the end of August.

9)

Tears of Saint Lawrence

. This is a good year to observe the Perseids, the most important meteor shower of the summer. This is due to the fact that the maximum activity of the rain, on August 12, will take place with the waxing moon that will go to bed around midnight, leaving most of the night very dark. The observation conditions will be similar for the Aquarid Delta that have their maximum on July 30, during the first quarter, although on this date it will be the first part of the night that will not have a moon.

10)

93 days and 15 hours

.

Summer will last 93 days and 15 hours.

It will end on September 22, 2021 with the arrival of autumn.

In fact, summer is always the longest season of the four.

This is due to Kepler's Second Law: the line that joins the Earth to the Sun sweeps equal areas in equal times.

Because the Earth is now in its farthest positions from the Sun, it is moving with less speed, which translates into the longest duration of summer compared to the other three seasons.

____________________________________________________________________

Rafael Bachiller is director of

the National Astronomical Observatory

(National Geographic Institute) and academic of the

Royal Academy of Doctors of Spain

.

According to the criteria of The Trust Project

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