The added bonus of the clear skies here in Axarquia is that, along with the daily blue sky and sunshine, we have a clear
view of the night sky and planets.
With the aid of a simple pair of binoculars, there are wonderful close-ups of the
moon. Whilst, through a modest telescope, we are able to see the moons of Jupiter, the rings around Saturn, the phases of
Venus and transits of Venus and Mercury.
For newcomers to planet spotting, a good hint is that the planets always travel
within a few degrees of the path of the sun. The path that the sun appears to travel against the star background is
called the ecliptic. It marks the centre of the band of sky within which the moon and planets are found. This area is known
as the zodiac. The ecliptic passes through the 13 zodiacal constellations of Pisces, Aries, Taurus, Gemini, Cancer, Leo,
Virgo, Libra, Scorpio, Ophiuchus, Sagittarius, Capricorn and Aquarius. Ophiuchus does not appear in the astrologer's
zodiac although the planets spend more time in it than in Scorpio. Astrologers use a different zodiac from astronomers for
reasons of precession.
The earth moves on its axis with a wobbling motion like a spinning top, the axis tilted away
from the vertical by 23 1/2 degrees. Whereas the axis of a top takes only a few seconds to complete its reeling movement,
the period for the earth is 25,800 years.
This movement causes slow changes in which constellations make up the zodiac. Astronomers use the
real time zodiac, whereas astrologers use the zodiac of 2,000 years ago.
Did anyone spot the blue moon at the end of July? A blue moon is deemed to be a fairly rare event but is
simply a second full moon in a calendar month. On average it happens every two and a half years. So when you hear the
expression 'once in a blue moon' you'll know what is meant. Of course the moon doesn't really turn blue for certain dates
unless there is ash of a certain wavelength in the air from volcanoes or forest fires.
During August Neptune is at opposition on the 6th, Venus is at greatest western elongation on the
17th, Mercury is at inferior conjunction with the sun on the 23rd, Uranus is at opposition on the 27th, the full moon is
on the 30th and, best of all, there is a spectacular meteor shower:
11-12th August - The Perseids Meteor Shower.
Perseid meteors originate from comet Swift-Tuttle. Every 130 years, the comet swoops in from deep space (beyond Pluto)
and plunges through the plane of the solar system not far from Earth's orbit. The comet's orbit is littered with bits of
dust particles which bubble away from the comet's icy nucleus (propelled by evaporating ice) when Swift-Tuttle nears the
Sun. These particles form a cloud that the Earth plows through once a year. The shower began on July 17th and will last until
August 24th, the greatest intensity from the 11-12th August, with the radiant lying midway between the constellation of Perseus
and the W of Cassiopeia. Perseid dust particles are tiny, most no bigger than grains of sand. They travel very fast at
about 132,000 mph (59 km/s). Even a tiny dust speck can become a brilliant shooting star when it hits the atmosphere at
During the intense period the average hourly rate for the 2004 annual meteor shower is predicted to be greater than usual.
Conditions are favourable this year for two reasons. First, a new moon on the 16th means there is little moonlight to
interfere with the number of faint meteors that can be seen. Second, in addition to the usual shower, there is
predicted to be an additional filament of dust drifting across Earth's orbit causing further meteors on the 11th.
The filament is relatively young having boiled off the comet during 1862. The older cloud, up to thousands of years old,
is more dispersed. Observors are likely to see as many as 200 meteors per hour.
||During the first half of August Mercury is in bright twilight, too low and faint to
be visible. On the 23rd Mercury will be in inferior conjunction after which the planet is an early morning object becoming easily visible at -1.0 magnitude
The best times to observe Mercury 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.
||2004 is an exceptional year for observing Venus and during August the planet is a brilliant
-4.3 magnitude. On the 17th August Venus is at greatest western elongation (46 degrees) and rises almost 4 hours before the sun
at about 3.00h with the moon to the north on the 12th. Venus will remain as a brilliant morning object in the northeast sky
throughout the remainder of 2004.
On the 8th June, 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. The last two transits of Venus were in 1874 and 1882. June's transit
began at 7.20h and lasted 6 hours until 13.20h, the total event visible from Europe as a small black disc crossing
the lower part of the sun from left to right. The next transit will be in late June 2012. After that, transits of Venus
won't occur again until 2117 and 2125.
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. The dates of the next two inferior conjunctions are October 28th 2010 and October 26th 2018.
||After its brilliant August 2003 display a year ago Mars has faded to a faint 1.7 magnitude.
During August this year Mars sets only minutes after the sun and is therefore not observable. After conjunction in
September the planet will move away from the sun to be visible again against a dark morning sky in late October.
At opposition on the 28th August last year, 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 for another 15 years.
These favourable oppositions occur every 15 years but other oppositions occur at average intervals of 2 years 2 months. 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.
||Jupiter in Leo remains at -1.8 magnitude in western twilight setting only an hour after the
sun by the end of August. The moon is to the north on the 17th/18th.
Being 770 million kilometres from the sun, the difference in brightness between opposition and conjunction varies less than with Mars, from about -2.8 to -1.8 magnitude.
The 4 largest moons of Jupiter are easily visible through 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 is in Gemini throughout 2004. At 0.2 magnitude the planet will rise about 3.00h by the end
of August with the moon to the north on the 13th.
Saturn crossed the equator into the northern hemisphere in 1996 where it will remain until 2010 with the southern side of the ring system facing the 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 next single crossings will be in 2009 and 2025.
Saturn's largest moon, Titan, is visible in small telescopes orbiting outside of the ring system.
||Uranus is in Aquarius throughout 2004 and at opposition on the 27th August when it is due south
at midnight. The moon is closeby on the 2nd and 29th.
Brightness varies slightly reaching 5.6 magnitude at opposition. This is bright enough to see with the naked eye but identifying it against the stars is difficult.
||Neptune is in Capricorn throughout 2004. At 8.0 magnitude Neptune is at
opposition on the 6th August. The moon is closeby on the 6th.
Neptune has an average magnitude of 7.9 which varies little with changing distance.
||Never brighter than 13 magnitude, Pluto is only visible through powerful telescopes and we will therefore not be reporting on its position in the sky.|
||Last quarter: 7th at 24.00h
New moon: 16th at 3.00h
First quarter: 23rd at 12.00h
Full moon: 30th at 4.00h