Posted on July 27, 2018
Tonight, Friday July 27th, when the moon comes out we will see a reddish color, is what is known as "Blood Moon", because our satellite crosses the shadow cast by the Earth, resulting in a total eclipse of the Moon.
It will also be the longest of the 21st century, with a duration of 103 minutes in its entirety. The show can be enjoyed at a glance, although numerous museums, observatories and associations of astronomers have organized parallel activities.
The total eclipse of the moon will undoubtedly be one of the astronomical events of summer, especially in Europe, where for more than two years there has not been a total eclipse of the Moon.
This Friday, July 27, we will be able to observe it when the sun sets and look towards the east: a reddish moon eclipsed by the Earth will appear on the horizon.
HOW IS A LUNAR ECLIPSE PRODUCED?
This phenomenon happens when the Earth interposes between the Sun and the Moon, projecting a shadow that obscures our satellite. For this, it is necessary that the three objects are aligned, something that does not happen every month because the orbit of the Moon around our planet is inclined with respect to that of the Earth-Sun.
In this case, the lunar eclipse is total because the entire Moon passes through the umbra, the darkest and most central part of the shadow. Other times it is partial if only a part enters the threshold; or penumbral, when it crosses the terrestrial gloom.
Unlike solar eclipses, moon eclipses can be observed from anywhere in the world, with the condition that our satellite - always in a phase of the full moon - is on the horizon at the time of the eclipse and there are no clouds that prevent your vision.
WHERE WILL THIS ECLIPSE BE SEEN?
The total lunar eclipse of July 27 will be observed in all its phases in the Indian Ocean and the surrounding continental areas, such as East Africa, the Near East and India. In other parts of Asia and Africa, as well as in Australia, Oceania, South America and Europe, only some of its phases will be visible, even if they include the most spectacular: the whole.
In Western Europe (Spain, Portugal, United Kingdom, France or Italy) we will see the second part of the eclipse when the moon rises in the east.
WHAT TIME CAN IT BE OBSERVED?
It will be visible in the UK from 8.50pm on Friday evening if viewers look to the South East - but rain clouds and thunderstorms could scupper skygazers' attempts to watch the celestial spectacle.
WHY IS THE TOTAL LONGEST ECLIPSE OF THE CENTURY MOON?
The time it takes for the Moon to pass through the conical shadow projected by the Earth determines the duration of the eclipse, and this time it passes closer to the center and lasts longer than other times.
In its different stages, it will run for 6 hours and 13 minutes, although to assess the duration of the eclipses astronomers usually fix at the time of the partial eclipse (3 hours 55 minutes in this case); and above all, in the phase of totality, which will last for 1 hour and 43 minutes (103 minutes, exactly 01h 42m 57s according to NASA), which makes it the longest of the 21st century.
WHAT CAN BE SEEN?
You can see how the moon is darkening before the start of the total phase. During the whole, the moon acquires a reddish or coppery hue when entering the umbra.
The Earth's atmosphere acts as a lens that diverts sunlight, while filtering its blue components and passing only the red light that is reflected by the satellite. That's why it's called 'moon of blood'.