|Events during August
12th-13th - PERSEIDS METEOR SHOWER is visible from the 8th to 17th August,
at maximum on the 12th/13th August. An average hourly rate of 100 is expected.
Have a Perseids Party! See August snapshot below
13th/14th - MARS appears to make a rapid dash against the sky this month, commencing
August to the right of Saturn and Spica, traveling between them (13th/14th) and finishing
the month to the left near the border with Libra.
14th - SATURN, MARS and the star Spica will be in line and it will be interesting to compare
brightness and colours. Saturn - magnitude +0.8 - yellow, Mars - magnitude +1.1 - red.
Spica - magnitude +1.0 - blue-white.
15th - VENUS is at greatest western elongation (46 degrees).
16th - MERCURY is at greatest western elongation (19 degrees).
24th - NEPTUNE is at opposition in
MOON: Full - 2nd and 31st, New - 17th, Apogee - 404,125 kilometres - 10th, Perigee - 369,730 kilometres - 23rd.
11th/12th August - the Moon lies near Jupiter.
13th/14th August - the Moon lies near Venus in the mornings.
16th August - the very thin crescent Moon hangs to the lower right of Mercury.
21st/22nd August - the Moon forms a striking group with Mars, Saturn and Spica (the brightest star in
Virgo), low in the western evening sky.
24th August - the first quarter Moon is near Antares (a red supergiant in Scorpio).
31st July - the 2nd Full Moon in a calendar month is termed a Blue Moon.
THE PERSEIDS METEOR SHOWER
is visible from mid-July to late August, and at maximum and usually most intense on the 12th/13th August. This year,
an average hourly rate of 100 is expected. From our perspective, the maximum will occur during the day on Sunday 12th August, so the best time to observe them are
the nights before and after, ie overnight from from Saturday to Sunday and from Sunday to Monday, during the time before the Moon rises whilst the sky is still dark.
The meteors can be seen streaking out from the direction of the radiant point between the constellations of Perseus and Cassiopeia.
The best way to observe them is to
lie outdoors in a reclining chair or sun-lounger, facing north, in a comfortable position that allows you to see the largest field of sky possible. Provided you have
a clear horizon to the northeast, away from bright lights, any point of observation is good. You can carry on watching, as Perseus climbs higher in the sky, until dawn
when sunlight will prevent observation. The hours preceding dawn are best to watch for meteors, when the speed of the Earth's rotation combines with that of its orbital
motion, ploughing through the dust trail at maximum speed. Because meteor showers cover such a broad area of the sky, they are best viewed with the naked eye as binoculars
and telescopes restrict the field of vision.
The source of the Perseids shower is Comet Swift-Tuttle which has a period of 133 years and last passed near the Sun in 1992. Although nowhere near Earth, the comet's wide
tail intersects Earth's orbit and we pass through it every year in July and August. Also called shooting stars, meteors can vary in size from a grain of sand, through
pea-size producing a more spectacular display, to rare stunning fireballs the size of an apple. Upon collision with Earth's atmosphere, about 95 kilometres above Earth's
surface, they begin to glow white hot and we witness a streak of light as they burn up. The shower is observable to a lesser extent from the 8th to the 17th August when
Earth is in the dustiest part of the tail.
VEGA IN LYRA, one of the stars making up the Summer Triangle,
is almost overhead during August evenings. Most catalogues rate it as the 5th brightest star in the entire sky.
Mercury passed through inferior conjunction
at the end of July. It now
moves out to the west of the Sun, reaching greatest western elongation
of 19 degrees on 16th August. Not a favourable
elongation for observors anywhere, but the planet may be glimpsed in the dawn twilight, low in the east-north-east at the start of morning civil twilight about 30 minutes
Mercury will be at its brightest, and so easier to spot, after greatest western elongation as its magnitude increases from +2.1 on 7th August, to +0.1 at
elongation and -1.4 by the end of August.
The best times to observe Mercury in the northen hemisphere are when it is an evening star in the spring and a morning star in the autumn. In midsummer
the lighter skies make visibility difficult near the horizon.
Dazzling Venus reaches greatest western elongation of
46 degrees on 15th August. It is a brilliant object in the morning sky, although fading slightly from -4.4 to -4.2 magnitude during the month. By the end of August,
Venus will be rising four hours before the Sun from northern temperate latitudes but less from further south due to its northerly
Its rapid eastwards motion, carries the planet from Taurus into
Gemini during the month with its phase increasing from
42% to 58%. the waning crescent Moon will be close by on the morning of 14th August.
On the 8th June 2004 and 5th/6th June 2012, Venus was at inferior conjunction
and transited the sun. Transits of Venus are rare, taking place at greater
than 100 year intervals and usually in pairs. Prior to that, the last two transits of Venus were in 1874 and 1882. Transits of Venus won't occur again until 2117
Before and after inferior conjuction, when Venus is
the closest it comes to the Earth, are the times at which the planet is most brilliant and can be seen setting or rising
4 hours after or before the Sun.
Mars is visible in the early evening, low in the west-south-western sky setting less than two hours
after the Sun. Its rapid eastwards motion carries Mars past Saturn in mid-August, both planets in Virgo. From northern
temperate latitudes, Mars is rather low in the twilight sky by the end of the month, although much better placed for observors further south.
On 14th August Mars, Saturn and the star Spica will be in line and it will be interesting to compare brightness and colours. Saturn at magnitude +0.8 (yellow),
Mars at magnitude +1.1 (red) and Spica at magnitude +1.0 (blue-white).
Mars appears to make a rapid dash against the sky this month, commencing August to the right of Saturn and Spica, traveling between them and finishing the month
to the left near the border with Libra.
At opposition on the 28th August 2003, Mars was only 56 million kilometres from the Earth. It showed a
disc of 25.1 seconds of arc across which is almost as large as it can ever appear. Mars started 2003 at 310 million kilometres from
the earth at 4.5 seconds of arc and 1.6 magnitude. By opposition it brightened 50 times to reach -2.9 magnitude but faded to 0
magnitude by December. Even to the naked eye Mars was a striking object in the summer and autumn sky, easily identifiable by its
reddish hue in an area of sky poor in bright stars. Mars will not be as close again until 2018.
These favourable oppositions occur every 15 or 17 years but other oppositions occur at average intervals of 2 years 2 months during
which time the planet makes a complete circle of the Earth. In general Mars is observable every other year, being too close to the sun for favourable conditions
during other times. Brightness at opposition varies from -1.0 to -2.9 magnitude, and when furthest from the earth it fades to 1.7 magnitude. The planet can be
identified by its orange-red colour.
As in 2003, Mars comes nearest to the Earth at oppositions at the end of August. At these times it can be brighter than Jupiter,
although low in the sky in Aquarius for northern observors. In the northern hemisphere, the planet may be better seen at oppostions during autumn and winter months
when it is higher in the sky.
Jupiter begins to pull its weight this month, shining at -2.1 magnitude, increasing to -2.3, in
Taurus. The giant planet rises before 02.00h in early August and late evening by the end of the month.
The waning crescent Moon will be close by on the morning of 12th August.
After spending the past six years in the southern skies, Jupiter moved north of the celestial equator on February 5th 2011 to spend the next six years
in northern skies.
Varying from 603 (at its closest) to 770 million kilometres from the sun, the difference in brightness between opposition and conjunction varies less than
with Mars, from about -2.9 to -1.8 magnitude. Always a bright planet, Jupiter comes to opposition a month later each year, moving approximately from one zodiacal
constellation to the next.
The 4 largest of Jupiterīs 60+ moons are easily visible through binoculars or a small telescope, ranging from 4.6 to 5.6 in magnitude. The innermost,
Io, takes 1.8 days to orbit the planet making its motion easily detectable within a few minutes.
Saturn, at magnitude +0.8, is visible low in the west-south-western sky as darkness falls but sets
less than two hours after the Sun by the end of August. The ringworld is moving direct in
Virgo and will be close to a slightly fainter Mars during the middle of the month. It is rather low in the twilight sky at
dusk by the end of August, although easier to observe further south.
The planet crossed the equator into the northern hemisphere in 1996 where it remained until 2010 with the southern side of the ring system
facing Earth. Because of its distance, its brightness varies little between opposition and conjunction but is affected by the huge ring system. Seen edge on the
rings contribute little or no light.
Every 15 years the plane of Saturn's rings passes through the Sun, illuminating first the north and then the south side. For a few days the
rings are edge on to the Sun. About the same time the Earth passes through the ring plane and, depending on the Earth's position, this may happen just once or 3 times.
During 1995/96 there was a triple crossing and the next will be 2038/39. The last single crossing was in 2009 and the next will be in 2025.
Saturn's largest moon, Titan, is visible in small telescopes orbiting outside of the ring system.
Brightness varies only slightly, reaching a maximum of +5.6 magnitude at opposition. Although this is
bright enough to see with the naked eye, identifying it against the stars can be difficult. At closest approach, Uranus is 2,856 million kilometres (1,775 million miles)
Neptune is at opposition on 24th August in the constellation of
Neptune has an average magnitude of 7.9 which varies little with changing distance. At its closest,
Neptune is 4,341 million kilometres (2,697 million miles) from Earth.
No longer an offical planet and never brighter than +13 magnitude, Pluto is only visible through powerful telescopes.
Full moon: 2nd and 31st (the 2nd full Moon in a calendar month is termed a Blue Moon)
Last quarter: 9th
New moon: 17th
First quarter: 24th