Friday 27th is the longest lunar eclipse of the century!



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Lunar eclipses follow each other but are not alike. Partial, total, visible or not, one can legitimately lose one's Latin. But the eclipse of Friday, July 27 is worth the detour, and depending on your place of residence, you may have the opportunity to admire a beautiful show.

A lunar eclipse, how does it work? [19659003UnlikethesolareclipsewherethemoonwillhidethestarofthedaythelunareclipseinvolvestheshadowoftheEarthThisisalsoagoodwaytoseetheroundnessofourgoodoldplanetandsee that it is not flat in case you still doubt it.

The eclipse lunar occurs on a full moon, when the Moon and the Sun are each on one side of the Earth. For someone on the surface of the Moon, the Earth would pbad in front of the Sun.

Why then is there no eclipse every month, every full moon? Simply because the lunar orbit is inclined, and sometimes the Moon pbades over the shadow of the Earth, sometimes below. Eclipses occur only when the Moon pbades in the shadow.

The eclipse can be total or partial, depending on where the Moon pbades. It can cross only part of the shadow (partial eclipse) or pbad entirely (total eclipse).

The Moon also crosses the penumbra, a part of the space where the rays of the Sun are only partially obscured by the Earth. During a total eclipse, like that of Friday, the Moon will first darken a little, marking its pbadage in the dark, before becoming dark and glowing when it is in the shade.

The mechanism of a lunar eclipse (Nasa)

Why will it last longer?

It is a combination of two factors. First of all, the Moon will pbad exactly in the center of the shadow of the Earth, so will travel as far as possible inside it.

Then, the eclipse occurs just the day the moon is at its peak, the point of its orbit where it is farthest from the Earth. It will therefore look smaller, and spend more time in the shadow.

The different stages of the eclipse. The hours are in universal time, so we must add two hours to get the legal time in metropolis (Tomruen / Wikimedia Commons)

Why the moon is it red during an eclipse?

As the moon pbades in the shadow of the Sun, one would expect not to see it at all. It is not so simple because of the earth's atmosphere. This one will intercept solar rays, and divert them towards the Moon. In addition, the particles of the earth's atmosphere will block certain wavelengths of light, and in the end, only the most red will pbad. It is a similar phenomenon that occurs at sunset, and explains the red-orange tints that are observed there.

During the eclipse, the exact color will depend on the state of the atmosphere that day, clouds and dust that the sun's rays will have to cross. The more particles there are, the darker the moon will appear.

Mars and shooting stars as a bonus

The sky of July 27: the eclipse of Moon, Mars and the shooting stars (Stellarium.org) [19659006] On the 27th, Mars will be in opposition, which means that it will be exactly the opposite of the Sun in relation to the Earth. In addition, on the 31st, she will reach the point of her orbit where she will be closest to us. The last time Mars has come so close, it was in 2003, and the next event of this type will only occur in 2035.

These two events together will bring us a particularly bright red planet, especially between July 27th and 30th. It will be even brighter than Jupiter, and we will see it, not far from the moon, during the eclipse of 27! However, it will rise a little later than the Moon.

With a little luck, you could also see shooting stars. The meteor shower Alpha Capricornides delivers indeed some bright cars, even if they are rather scattered.

Where to observe it?

According to your place of holidays, you will be lucky … or not. For example, if you are in the Balearic Islands, you will see more than in the Canaries. In France, the best place to see the eclipse is Reunion. There, you will be entitled to the entire show, weather permitting. On the other hand, if you are in the West Indies, you will miss most of it.

The Moon will begin to enter the penumbra at 19:15 (Paris time). She will touch the shade at 8:24 pm, and will be there at 9:30 pm. It will begin to emerge from the shadows at 23:13, and the eclipse will be completely finished at 1:28.

In metropolis, we will not be able to observe the very beginning of the eclipse, but the phase of totality, that during which the Moon is entirely in the shadow of the Earth (which will last 1h43), will be visible on all the territory:

  • The Moon will rise at 9:07 pm Strasbourg while the Moon continues its path of the penumbra Towards the Shadow
  • A Paris The inhabitants and visitors to the capital will see a rising moon at the very beginning of the total eclipse phase, around 9:30 pm
  • A Brest we will see even less since the Moon will get up only a few minutes before 22h, but it will still be entirely in the shadow of the Earth.

Visibility zones of the July 27th eclipse. P1 is the moment when the lunar disk touches the penumbra. U1 is the first contact with the shadow of the Earth. U2 indicates the moment when the moon is entirely in the shadow. U3 is when the Moon begins to emerge from the shadows, and U4 when it is completely out. Finally, P4 indicates the exit of the penumbra, the end of the eclipse. (Piruliton / Wikimedia Commons )

Those who can not attend the show will have another chance to observe a total lunar eclipse 21 January 2019 in the morning, at sunset of the Moon. But it will be shorter …

 Jean-Paul Fritz

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