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Events during September
· The autumn equinox when the Sun crosses the equator into the southern hemisphere is on the 22nd.
· The Moon: Full - 15th, New – 29th.
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Mercury
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Fading from 0.0 to +1.1 magnitude, Mercury can be observed in the evenings from latitudes south of 30ºN until the last week of
September. Mercury, Venus and Mars are just a few degrees apart around 11th September.
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.
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Venus
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Venus remains at -3.9 magnitude still moving away from the Sun and is visible low in the western horizon after
sunset.
On the 8th June 2004, 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.
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Mars
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Mars remains an evening object at +1.7 magnitude, visible only in the tropics and southern latitudes. From the 9th to the 11th
Mars appears in line with Venus and Mercury, much closer to the former on the right than the latter on the left.
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 oppositions during autumn and winter months
when it is higher in the sky.
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Jupiter
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Jupiter, at -2.4 magnitude, remains the most conspicuous planet in our skies. Jupiter reaches its second stationary
point on the 8th and then resumes an easterly direct motion.
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. 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 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.
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Saturn
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Saturn, at magnitude +0.9, is in conjunction with the Sun on the 13th
and therefore not visible until the last few days of September when it can be seen low above the eastern horizon before morning twilight.
Saturn moves more slowly than Jupiter and can remain in the same constellation for several years. The brightness of the planet depends on the
aspect of its rings, as well as its distance from Earth and the Sun.
The planet 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.
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Uranus
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Uranus is at opposition on 13th September in the constellation of Aquarius, when it will be
2,856 million kilometres (1,775 million miles) from Earth.
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.
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Neptune
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Neptune has an average magnitude of 7.9 which varies little with changing distance.
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Pluto
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No longer an offical planet and never brighter than 13 magnitude, Pluto is only visible through powerful
telescopes.
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Moon
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September
First quarter: 7th
Full moon: 15th
Last quarter: 22nd
New moon: 29th
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Other Events |
EQUINOXES
2008
Spring equinox (when the Sun crosses the equator into the northern hemisphere): March 20th
Autumn equinox (when the Sun crosses the equator into the southern hemisphere): September 22nd
2007
Spring equinox: March 21st
Autumn equinox: September 23rd
2006
Spring equinox: March 20th
Autumn equinox: September 23rd
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SOLSTICES
2008
Summer solstice (when the Sun reaches its most northerly point over the Tropic of Cancer): June 20th
Winter solstice (when the Sun reaches its most southerly point over the Tropic of Capricorn): December 21st
2007
Summer solstice: June 21st
Winter solstice: December 22nd
2006
Summer solstice: June 21st
Winter solstice: December 21st
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PERIHELION & APHELION
2008
The Earth is at perihelion (147 million kilometres - its closest to the Sun) on the 2nd January.
The Earth is at aphelion (152 million kilometres – its furthest from the Sun) on the 4th July.
2007
Perihelion: 3rd January
Aphelion: 7th July
2006
Perihelion: 4th January
Aphelion: 3rd July
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SUMMER / WINTER TIME
Spanish and British summer time begins on March 30th 2008.
Spanish and British winter time begins on October 26th 2008.
Note: Spanish summer time is 2 hours ahead of Greenwich Mean Time and British summer time is 1 hour ahead of GMT.
Spanish winter time is 1 hour ahead of GMT and British winter time equals GMT.
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PRECESSION
Earth moves on its axis with a wobbling motion like a spinning top, the axis tilted away from
the vertical by 23 1/2º. Whereas the axis of a top takes only a few seconds to complete its reeling movement, the period for
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. After 2,000 years, the first point of Aries is
actually in Pisces. So, for example, when an astrologer says the Sun or a planet is in Aquarius it will physically be
against the background of the preceeding constellation Capricorn. |
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From left to right (sun to outer solar system), the objects represented are: Sun, Mercury, Venus, Earth, Moon, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.
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. I am constantly amazed when friends, of all nationalities, who visit at night declare that they have never had the opportunity to look at the sky in detail before.
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 explained in the notes on precession.
Above we note the planets and some of the other objects that can be seen by the naked eye during the current
month and year. Unless otherwise stated, time references are local Spanish time. |
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