August's remarkable astronomical events

For all astronomy professionals and amateurs, the month of August 2017 holds very interesting and unique astronomical events not to be missed. Here is what to expect...

August is generally speaking an excellent month for star gazing. While the heat of summer days still allow decent temperatures and typically very good weather conditions at night, the northern hemisphere milky way core is still largely visible under 55-50 degrees of latitude and the well-known constellation of Cygnus with its H-alpha emission nebulae (North American, Pelican, Sadr region...) pass right above our heads for a long part of the night. However after sunset and during the whole course of the night, the core of the milky way sets towards the wouth-west/west, so the best chances at peeking at it is in the early evening. Apart from the 'usual stuff', also including the conjunction of several celestial objects, August 2017 holds a great deal of other events that will satisfy more than one.


Courtesy of
Courtesy of

A lunar eclipse can only happen when the moon is full, ie. when it is around its most opposite point to the sun from the Earth. It does not occur at every full moon because the orbit of the moon relative to the Earth is tilted by a few degrees north or south. When the moon passes the Earth's shadow, bigger than former, we get an eclipse, though only visible in the night-time area of the world. If the moon passes at the edge of the shadow, area called 'penumbra', we get a penumbral eclipse, where only a small part of the moon is slightly dimmer. If the moon happens to pass through the central area of the Earth's shadow ('umbra'), we can witness a partial lunar eclipse where more or less of the moon's surface is completely shadowed. If the moon passes completely in the umbra, we can be in for total lunar eclipse turning the moon blood red because of the diffraction of the light on the edge of the Earth, much like a sunset. On August 7th, 2017, the moon will pass in the penumbra and partly in the umbra, giving a beautifully wedged moon. As shown on the map, people from Asia, Oceania, Africa and Europe will be able to get a glimpse at the show provided they have good weather. On the 7th, I went up the Jura mountain in France to have a clear view of the full moon rising over the Alps. As cumulus and cumulonimbus were approaching from the west, I only had a 10 minute window to peek at the beautiful and wedged orange disc rise over the snowy peaks of the Alps. The film has been taken with Sony alpha 7rII and Sigma 150-500mm for real-time, and Canon 6D + Samyang 135mm f/1.4 for the time-lapse. You can view it here:


The most iconic meteor shower of the year, the Perseid meteor shower is a very productive one in the month of August, and every one has probably seen its very bright and prolific fireballs emanating from its radiant in the constellation Perseus (associated with the comet Swift-Tuttle), as they lay still in the the grass at night, looking up. The meteor shower will be peaking on August 11-12 2017, meaning that more ephemeral meteors than usual will bright up the night sky (up to 120 meteors an hour!). Below: Composite picture from Petr Horálek, a tremendously skilled ESO astrophotographer who took the shot last year and got awarded by the APOD on Aug. 10th 2017:

APOD Aug. 10 2017: Credits Petr Horalek


Even though the Americas will have missed Aug. 7 partial lunar eclipse, the most talked about and anticipated celestial event of the year will grace the skies of the United States on Aug. 21st, as the moon covers the entire disk of the sun. The fully darkened sun will be visible for an average of two minutes to anyone inside a 70-mile-wide corridor that stretches from Oregon to South Carolina. This video probably explains it best:

On the other hand, the total solar eclipse provides a rare opportunity for scientists to study the Sun, particularly its atmosphere. As the Moon completely covers the Sun and perfectly blocks its light during an eclipse, the typically faint corona is easily seen against the dark sky. NASA is funding 11 science projects across America for scientists to take advantage of the unique astronomical event to learn more about the Sun and its effects on Earth’s upper atmosphere. And here is one of them:

Read NASA's full article:

Have a good time star gazing this month, and don't forget your safety glasses if you are lucky enough to be watching the eclipse on August 21!

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