Rain of stars: the supermoon will tarnish the Perseids this year

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The Perseids

, one of the most popular celestial shows of the year, will be marred this year by the full moon.

It will be preferable to observe them several days before or after the maximum that is expected for the early hours of

.

full moon at perigee

The full moon of August will have its

.

In addition, at that time, our satellite will be at a point very close to its closest approach to Earth (perigee), which is what some call a "

".

At this position, the Moon appears up to 14 percent larger and 30 percent brighter than when it is at its furthest point (apogee).

It is something difficult to perceive with the naked eye, but there is no doubt that on August 11 the Moon will be splendid.

This magnificent full moon will, however, be disastrous for the observation of the

, which present their maximum on the following night, on the 12th, when the Moon will still be practically full and, due to its intense brightness, it will

.

Most of the meteors will be camouflaged behind this curtain of light.

Only the brightest Perseids, as they burn up in our atmosphere, will be visible.

The number of observable Perseids per hour is highly variable.

The years in which the Moon is not in the way, at the time of maximum activity (early mornings of August 12 and 13), in a very dark place, and with the radiant high above the horizon, the number of Perseids per hour can exceed the hundred.

It is in these conditions that the astrophotographers

, from the Astroguada association, took the spectacular image that heads this article, in August 2021, with the meteors before the

and over the evocative silhouette of the

.

However, due to the full moon, the number of visible meteors will be greatly reduced this year, and obtaining images of this caliber will be even more difficult than usual.

Perseids until the end of the month

Although their peak activity occurs on the nights of August 11-13, the Perseids usually begin to be seen around July 23 and end around August 22.

Due to the full moon, this year it will be more convenient to observe the meteors outside their peak.

It is true that, as the days progress, from the 13th the activity of the Perseids will decrease.

But the Moon will also lose prominence, because each day it will rise later and smaller, until the new moon is reached on the 27th. For this reason, the observation of meteors can also bear very good fruit

, according to The nights get progressively darker.

For example, if we look at the sky on the weekend of August 19 to 20, the Moon, in the last quarter, will not rise until 1 or 2 in the morning (depending on the day) and, at the beginning of the night , it will not be an impediment to see the shooting stars.

That is to say, we will be able to have

until the Moon begins to illuminate the horizon in the east.

Even later we can explore the western area, which will still be reasonably dark.

Radiant

Meteor showers seem to have a single center of origin, a point from which all shooting stars seem to emerge:

.

The location of that point in a constellation is used to name the meteor shower.

Thus, the Perseids have their radiant in the

.

But, although its radiant is in the constellation of Perseus, it is not necessary to know the constellations, nor is it essential to look towards Perseus, to see the Perseids.

Shooting

can appear anywhere in the celestial vault.

However, the local conditions and the location of the observer are decisive: it is always preferable to monitor the

.

The radiant of the Perseids.

What are the Perseids?

Shooting stars are not stars, they

.

Indeed, as comets describe their orbits around the Sun, they throw a trail of

(rocky materials) into space that remains in an orbit very similar to that of the parent comet.

Each periodic comet, throughout its repeated turns around the Sun, thus forms a ring in which innumerable fragments are found.

When the Earth, in its orbital movement, encounters one of these rings, some of the rocky fragments (meteoroids) are trapped by its gravitational field and fall at high speed through the atmosphere forming a

.

The friction with the atmospheric gases calcines and vaporizes the meteors that appear bright for a fraction of a second, forming what we popularly call shooting stars.

The height at which a meteor becomes bright depends on the rate at which it penetrates the atmosphere, but is usually around 100 km.

However, the high brightness and high transverse speed of some meteors have a spectacular effect, creating the illusion for the observer that they are very close.

Meteoroids with a mass less than a kilogram burn up completely in the atmosphere, but larger and denser ones (rocky or metallic in consistency) form meteorites: burnt debris that falls to the ground.

The Perseids occur when the Earth reaches the trail left by the Swift-Tuttle.

a huge comet

Like every year around this time, the Earth, on its path around the Sun, passes through an area populated by rocky fragments that are thrown out by the periodic comet

every time it visits this region every

.

Swift-Tuttle is the largest object that visits us regularly: its huge core reaches 26 kilometers in size.

The Perseids were particularly active in

, the year this comet passed close to the Sun. The comet's next approach to the Sun (its next perihelion) will be in the year

.

The Perseids are visible from the entire Northern Hemisphere in midsummer.

The speeds of these meteors can exceed

(180,000 kilometers per hour).

Its high activity, coupled with the favorable atmospheric conditions for observing during the boreal summer, make the Perseids the most popular, and the most easily observed, meteor shower that occurs throughout the year.

In order of importance of their activity, on average, the Perseids constitute the third meteor shower of those that occur in the year.

Both the

(visible in January) and the

(in December) tend to generate more meteors per hour.

Finally, although they show a more irregular behavior, the

(in mid-November) can be as spectacular as the Perseids.

Due to the proximity of the maximum of the meteor shower to August 10, the feast day of the Spanish martyr who was burned on a grill in Rome in the year 258, the Perseids are also called the

.

What if we don't see Perseids?

If we are not very lucky with the Perseids, we can always take the opportunity to see

that, these days, shine spectacularly throughout the night, as both are close to their opposition (frontal lit by the Sun): Saturn's opposition will have place on

and that of Jupiter on

.

The two gas giants are visible in the southeast after dark, rising and moving south and west as the night progresses.

They are followed by

, which rises around 1 a.m. and, finally,

, which dominates the dawn in the east after 6 a.m.

In any case, take advantage of these warm nights, perhaps on vacation, to look up at the sky, escape the miseries of everyday life and think about our place in the cosmos.

To observe both the Perseids and the planets well, we only need to choose the darkest sky time (no moon, at the beginning of the night after day 12), a place protected from artificial light, clear of clouds and an arrangement of serene and contemplative spirit.

Sit comfortably, without haste, looking at the sky and let yourself be intoxicated by the show.

Rafael Bachiller is the director of the National Astronomical Observatory (National Geographic Institute) and an academic of the

.

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