July-September 2012 Newsletter 125

Newsletter

These charts have been drawn for mid-July at 21:00 GMT. Since the stars rise about 4 minutes earlier each day, one month on they rise 2 hours earlier. Consequently, the charts also show the stars as they will appear at 19:00 GMT mid- August and 17:00 GMT mid-September. The planets can move appreciably against the background constellations over this period. Remember to add on one hour for British Summer Time which began on March 25th.

MERCURY is best seen with the naked eye, in the eastern morning sky from 10th-31st August. Greatest western elongation occurs on August 16th, Mercury then being separated from the Sun by 19 degrees. On this date, the planet rises 1 hour and 45 minutes before the Sun. Remember, never look for Mercury unless the Sun is well below the horizon. VENUS is a glorious morning object, reaching western elongation on August 15th when it’ll be 46 degrees from the Sun. On August 10th, Venus lies 4.5 degrees (9 full Moon diameters) south of the open cluster M35 in Gemini. Roughly a month later, between 10th-16th of September, this most brilliant of planets passes to the south of the Beehive Cluster, M44 in Cancer. MARS isn’t well placed from July through to September, being on the edge of evening twilight as darkness falls. It remains quite close to Saturn and the star Spica in Virgo throughout this period, forming an equilateral triangle with these objects on the night of August 21st. JUPITER is a conspicuous morning object in Taurus visible low down in the east as dawn breaks during July. At the start of July, Jupiter and Venus are just 5 degrees apart. On the morning of July 15th, the Moon makes a close pass of Jupiter, appearing to move just below the planet from the northern part of the UK, partially hiding the planet from the southern-middle part of Britain and covering it completely from the extreme southeast. Through August and September, Jupiter becomes a prominent feature of the morning sky. Even small telescopes will show a wealth of detail here. SATURN is in Virgo and poorly positioned between July and September. URANUS reaches opposition on September 29th in Pisces and at magnitude +5.7 it’s theoretically visible to the naked eye. The planet passes extremely close to a simlar brightness star (44 Piscium) on the 23rd and 24th of September. PHASES OF THE MOON

ECLIPSES There are no lunar or solar eclipses visible from Britain during July-September 2012. METEORS August is the month for the Perseid meteor shower. The shower begins around 23rd July and is active until August 20th, reaching maximum activity this year, during daylight on August 12th. The Moon is a 29% lit waning crescent rising after midinght BST on August 12th, so it shouldn’t interfere too badly. For the best views, observe on the night of August 11th/12th and again on August 12th/13th. EVENTS As mentioned in the planets section, the Moon will pass very close to Jupiter on the morning of July 15th, and from some locations in the southeast of Britain, the planet will be completely hidden by the lunar disc; an event known as a lunar occultation. The best time to look for this is from 02:00 BST on the 15th. Both Jupiter and the Moon should be obvious, low in the east-northeast. The occultation is best seen with a telescope but binoculars or just your eyes should be able to see what’s going on quite clearly too.

THE STARS The summer sky is dominated by a giant pattern of three bright stars known as the Summer Triangle. The three stars which form this huge shape are Deneb, Vega and Altair, the brightest members of the constellations of Cygnus, Lyra and Aquila respectively. The constellation of Cygnus the Swan contains another large easily identifiable pattern known as the Northern Cross - a shape which represents the body of the swan. from a dark sky site the Milky Way can be seen ‘flowing’ down the vertical of the cross. As it does so, it appears to split due to intervening dark clouds of dust that block the distant light from the billions of stars that integrate to form the Milky Way. The centre of our galaxy skirts along the southern horizon at this time of year and here the Milky Way is at its brightest - or it would be if it were a bit higher up from the UK. This part of the sky is littered with interesting clusters and nebulae ideal for scanning with binoculars. Here you’re looking into the constellation of Sagittarius the Archer, a sprawling pat- tern of stars with one noticeable shape that resembles a teapot! Look out too for the fiery red star Antares, the brightest member of the constellation of Scorpius the Scorpion, low down to the west of Sagittarius. As we move into September the Great Square of Pegasus becomes domi- nant as the Summer Triangle slips further to the west. Extend the Square’s two right hand stars down to find Fomalhaut in the constellation of the Southern Fish. Ris- ing as Antares appears to set, Fomalhaut is the southernmost of the first magnitude stars visible from Britain. Heading off the upper left hand star in the square is a wedge shaped pattern of stars known as An- dromeda, the Chained Princess. Here is the home of the Milky Way’s nearest comparable size galaxy in space, known as M31, the Andromeda Galaxy. This object can be seen with just your eyes from a site with reasonably dark skies. Binoculars show it’s elongated elliptical core well.

SPACE MISSION NEWS At the time of writing the Mars Curiosity Rover is approaching an exciting part of its mission. Following a minor course correction on June 26th, the Rover is scheduled to land on the surface of Mars in early hours of August 6th. Approximately 3 times as long and 5 times as heavy as NASA’s previous rovers - Spirit and Op- portunity - Curosity will carry the most advanced payload of scientific instruments to the surface of Mars yet.

Compiled by Sir Patrick Moore and Pete Lawrence http://www.bbc.co.uk/skyatnight/