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August 2010
As the month begins, the Sun is passing through the stars of Cancer, until around 23h on the 10th, when it crosses the boundary into Leo, where it remains for the rest of the month. From the beginning of the month, truly dark nights begin again in northern UK.
The Moon
The Moon is at perigee, its nearest to the earth, at 17h57 on the 10th, and at apogee (furthest from the earth) at 05h52 on the 25th
Last Quarter Moon is on the 3rd at 05h in the constellation of Aries, 6° south of Hamal, the chief star.
New Moon is on the 10th at 03h09 on the Cancer /Leo border, the moon passing 4° south of the sun.
First Quarter Moon at 18h15 on the 16th is low in the constellation of Libra.
Full Moon occurs at 17h96 on the 24th in central Aquarius.
It may be possible to glimpse earthshine on the night hemisphere of the waning crescent moon from the 5th to the 9th.
The Planets
Mercury is at greatest eastern elongation (27°) on the 7th, but the shallow angle of the ecliptic at that time means that the planet sets within 40 minutes of the sun and is unlikely to be seen.
Venus reaches greatest elongation east of the sun (46°) on the 20th. Although more readily visible than Mercury because of its brightness, it is very low in the western sky, setting around one hour after the sun. This is again due to the small angle made by the ecliptic with the horizon.
Mars continues to move rapidly eastwards through Virgo increasing its angular distance from Saturn, but is overtaken by the much brighter planet Venus at 20h on the 20th. Look into the WSW sky in evening twilight and see if you can spot the pair at around 19h45. Venus lies 2° below Mars and binoculars may be necessary to glimpse the red planet in the twilight because it is 15 times dimmer. The two planets are within 10° of the horizon at this time. Throughout August Mars sets around an hour after the sun.
Jupiter dominates the eastern night sky during the hours of darkness in August, rising just before 22h at the start of the month, but around 19h30 at the end. The planet is very bright and shines steadily, not twinkling as the stars do because the planet is not a point of light but a small disc which can be seen readily in binoculars. The bright gibbous waning moon may be seen approaching Jupiter overnight on the 26th and 27th, and by the onset of morning twilight the moon may be seen passing 6° above Jupiter, in the southern sky.
Saturn may be glimpsed low in the western sky duding the first half of the month but by the end of August is lost in evening twilight.
Uranus and Jupiter still accompany each other in the western part of the constellation of Pisces, Uranus lying some 3° to the west of Jupiter. The planet rises during the early evening on the threshold of unaided eye visibility.
Neptune is at opposition and its nearest to the earth on the 20th, at which time it lies due south at astronomical midnight. Even so, this remote planet is three times fainter than can be detected by the unaided eye. It lies exactly on the Capricornus-Aquarius border 1° to the upper left of the faint star mu Capricornii. Neptune is about 30 times further from the sun than is the earth.
One of the best shooting star showers of the year peaks overnight between the 12th and 13th. These meteors are called the Perseids, or the ‘Tears of St Lawrence’. Expect to see 75 or more shooting stars each hour, and especially in the early morning sky. Conditions are favourable this year as the moon is absent from the sky during the hours of darkness.
The Perseid meteors are associated with the Swift-Tuttle comet discovered in the nineteenth century which passes close to the earth every 100 years or so.
Constellations visible in the south around midnight, mid-month, are as follows: Capricornus, Aquarius, Equuleus (the Little Horse), Delphinus (The Dolphin) and Cygnus, almost overhead. The Milky Way is at the zenith, and spans the sky from the NE to the SW.
All times are GMT 1° is one finger width at arm’s length.
