Sky Notes for August 2012, with James Abbott #stargazing
There are 2 Full Moons this month – in the early hours of the 2nd August, and in the afternoon of the 31st, so the best starry late evening skies are from around the 10th until the last week of the month. The Full Moon at the end of the month reaches an altitude of 35 degrees and so will be noticeably higher in the sky than the Full Moons of preceding months. It is interesting to note when looking at the Full Moon when due South that it is approximately where the Sun will be in 6 months time, albeit the declination can be a bit higher or lower than where the Sun will be. This is because the Moon’s orbit around the Earth is inclined by about 5 degrees to the orbit of the Earth around the Sun.
Early in August it may still be possible to see the triangle of Mars, Saturn and Spica low in the West as it gets dark but for useful telescopic observation from Essex, these 2 planets are now lost in the murk.
Towards the end of the month, Jupiter is making an appearance just after midnight, low down in the East in Taurus. The gas giant planet will be fairly close to Aldeberan, the brightest star in Taurus, and also the Pleiades star cluster. For those with binoculars, this is a good opportunity to see a range of astronomical sights in one small area of the sky; the disc of Jupiter and its brightest Moons, the sparkling Pleiades stars and the orange colour of the giant star Aldebaran, which itself is next to the V shape of stars that makes up part of the Hyades star cluster. With access to a telescope in the 10″ or 12″ class at medium to high power, it is possible to see the binary companion to Aldebaran, a 14th magnitude red dwarf about 30 arc seconds from the primary star.
One of the main highlights of the night sky calendar is the August Perseid meteor shower. The Perseids are one of the most active of the regular showers but are also at a time of year when being out at night for lengthy periods under a clear sky is usually fairly comfortable. Those who have tried long Geminid watches in December will appreciate the difference !
This year circumstances for the Perseids are good. The nights of August 11th/12th and 12th/13th are expected to have the maximum meteor rates, which happens to be over a weekend. The waning Moon rises just after midnight BST on the 11th/12th, giving a couple of hours of dark skies late evening. On the night of 12th/13th the moonless observing window extends until after 1am BST. The Perseids dash across the sky in all directions from a radiant situated just below the “W” of the constellation Cassiopeia, which is in the North East, half way up the sky at 11pm BST.
Like most meteor showers, the Perseids are grains of dust left behind by a comet as it orbits the Sun. With an entry velocity of 61 kilometers per second into our upper atmosphere, Perseids are some of the fastest – quite literally if you blink you will miss them. But their speed also produces many events with “persistent trains”. These are bright streaks typically lasting for a few seconds, caused by tubes of glowing gas heated by the meteor grain as it burns up.
James Abbott is an astronomer, NEAS member and CfDS Regional Information Officer.
Posted on 1 August, 2012, in Astronomy News, Popular Science, Society News, Stargazing and tagged jupiter, meteor shower, meteors, moon, perseids, shower. Bookmark the permalink. Comments Off on Sky Notes for August 2012, with James Abbott #stargazing.