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  • Appointment with the sky: the face of the Moon, between Jupiter and Saturn

The Moon will form a beautiful conjunction with Mars on the night from Saturday to Sunday.

From the Canary Islands and South America, you can see how our satellite completely hides the red planet.

Increasing brightness

The reddish glow of Mars stands out splendidly on these September nights.

Earth's little brother rises in the east shortly after sunset to remain visible all night.

It reaches its maximum elevation around 5:00 a.m. (Peninsular time) and its brightness

only fades with the first light of dawn

.

Mars and Earth move on their orbits as if they were two vehicles on two parallel lanes of a highway.

Now our planet is behind the red planet, but as the days go by, and as the Earth advances on its orbit, we are getting closer to the small planet, which makes its apparent brightness increase night by night.

Earth will 'catch up' with Mars, catching up with it, on October 6.

At that time, both planets will be at the shortest possible distance from each other, separated by only 62 million kilometers, a distance about twelve times less than that which will then separate Jupiter from Earth.

That is why, despite its much smaller size, in those days Mars will look even brighter than Jupiter.

On October 13,

the red planet will be in opposition, that is, that day from Earth we will see its disk completely illuminated by sunlight

, thus reaching its maximum brightness which will be approximately twice what we see now.

Concealment

But, while the opposition from Mars arrives, let's enjoy this weekend the magnificent conjunction of the red planet with the Moon.

Our satellite, which went through the full moon phase on September 2, now presents that peculiar gibbous shape and is decreasing in brightness every night.

On the night of Saturday 5 to Sunday 6,

Selene will get very close to Mars, seeing both stars practically in contact from the Peninsula

.

The scene takes place in Pisces, an area of ​​the sky devoid of bright stars that could detract from the stars that gather here.

The approximation between Mars and the Moon will be greater and greater as the night progresses and, already after dawn, when the sky is completely blue, the planet will be hidden by the Moon.

The occultation will therefore not be visible from the Peninsula, but the perspective means that the further south we are, the closer the two stars are seen during that night before dawn.

Thanks to this, from the Canary Islands and from South America it will be possible to witness the concealment of the small red planet by the lunar upper limb.

Interest of concealments

In general terms, an occultation is the phenomenon that occurs when an object is hidden by another star that passes between that object and the observer.

Thus, lunar occultations can refer to planets or stars.

A solar eclipse can even be considered to be a particular type of lunar occultation in which the Moon hides the Sun.

Observing the precise moment when the Moon hides a planet or a star can have great scientific utility.

For example, this way it is possible to observe very fine details on the edge of the Moon, or characteristics of the astro that is hidden can be studied.

By observing their lunar occultations, the diameters of some stars have been measured and a good number of

very close

binary stars have been discovered

.

In the early days of radio astronomy, when radio telescopes did not have sufficient astrometric precision, occultations of radio sources were observed to measure their positions well.

Thanks to this method, the location of the bright radio source 3C273 could be located, which turned out to be exactly coincident with that of a quasar previously observed at the optical.

It was in this way that it was discovered that quasars were actually extremely luminous galaxies located at the far reaches of the universe.

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

Royal Academy of Doctors of Spain

.

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