Starguide: August

By Jenny Winder

What to look out for in the August night sky

We will be treated to not one but two full Moons this month. The first occurs on August 2nd and the second, or Blue Moon will be on August 31st. A Blue Moon used to mean any season that had four instead of the usual three full Moons, but is now generally accepted as being the second full Moon in any month. Although the term has come to be associated with a very rare event, on average we get a blue Moon every 2.66 years. You’ll have to wait until July 2015 for the next Blue Moon. We have no such special name for the second new Moon in a month although this happens as often, in fact if two new moons occur in a month, it usually follows that, four years later, two full moons will also occur in the same month.

Luckily the Moon will have faded to a pale waning crescent by August the 12th when the Perseid meteor shower peaks. This is one of the best showers of the year, producing fast, bright meteors that often leave persistent trails. The shower radiates from the constellation of Perseus to the Northeast and can have a Zenithal Hourly Rate (ZHR) of between 50 and 80 meteors. These represent the debris left behind by the comet Swift Tuttle.

The planets are all on display this month. Saturn dips to the western horizon in the early evening just after sunset, to be joined later in the month by Mars near Virgo’s bright star Spica . The three will form a line on August 14th and an equilateral triangle on the 21st. Around midnight, by the end of the month, Uranus will be in Pisces to the south while Neptune lies in Aquarius, reaching opposition on August 24th. In the morning, just before sunrise, Mercury lies in Cancer on the eastern horizon, with Venus above in Gemini and Jupiter higher again in Taurus.

The Summer Triangle still presides over the skies and it’s three main constellations contain many objects worth noting. Albireo in Cygnus lies toward the centre of the triangle. Even a small telescope will show that it is actually a superb double star, the brighter yellow star is itself a close binary system that contrasts beautifully with the fainter blue companion star. Cygnus also hosts The Veil Nebula Complex covering an area roughly 3 degrees in diameter andthe North America Nebula NGC 7000 which lies just to the left of Deneb. Two smaller constellations in the Summer Triangle areSagitta the arrow, which contains the star cluster Collinder 399 known as Al Sufi’s Cluster or Brocchi’s Cluster. The brighter members of which form the Coathanger asterism. Just above Sagitta lies Vulpecula, the little fox, whose alpha star Anser, represents a goose held in the fox’s jaws, binoculars show this is an optical binary system .

One event not to be missed this month is the landing on Mars of NASA’s Mars Science Laboratory rover Curiosity. This is the biggest planetary lander ever built and carries the most advanced payload of scientific gear to be used on Mars. Weighing 900kg and the size of an SUV it will employ the most complex landing procedure ever attempted, called the Seven Minutes of Terror. On August 6th At 05:31 am UTC Curiosity will enter Mars atmosphere at 21,000 km/h and within 4 minutes, will slow to 1,700 km/h. 10 km above the surface a 16 m parachute will deploy, slowing the lander to 360 km/h at 2 km above the surface. The entry capsuleā€™s back and heat shields will jettison, exposing the rover attached to a Sky Crane with 8 retro rockets. The lander brakes for less than a minute, stopping the Sky Crane 20m above Mars’ surface, when 3 cables will lower Curiosity till its 6 wheels touchdown and the cables are released. You can find information, videos and links to watch full coverage of the landing here

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