|Events during March
· The spring equinox, when the Sun crosses the equator into the northern hemisphere - 20th
· Uranus is in conjunction with the Sun - 21st.
· Mercury is at greatest eastern elongation (19º) - 23rd.
· Clocks go forward by one hour - 27th.
· Moon: New - 4th, Full - 19th, Apogee - 406,580 kilometres - 6th, Perigee - 356,575 kilometres - 19th.
Mercury moves rapidly east of the Sun and reaches greatest
(19º) on March 23rd. It is visible in the evening western sky for two weeks in the middle of March for observors in tropical and northern
latitudes. In the northern hemisphere this is the most favouable evening apparition of 2011.
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.
Venus, at magnitude -4.0, moves from Sagittarius
early in March but its southerly declination
makes it difficult to observe from northern temperate latitudes. On March 1st the waning crescent Moon and Venus are close together in the early morning sky making a
fabulous spectacle. Observors in the tropics and southern hemisphere have the best view from where the planet is a beautiful sight in the dawn twilight, rising more
than two hours before the Sun. On March 31st the waning crescent Moon and Venus again come together in the eastern sky.
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.
Mars was at superior conjunction
on the far side of the Sun, on February 4th and remains too close to the Sun to be visible during March. There will be no opposition of Mars in 2011.
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, at magnitude -2.0, is in conjunction
with the Sun in early April and will be lost in the evening twilight by the third week of March. In the middle of March, Jupiter will be visible low in the western sky not
far from Mercury as twilight falls.
As Jupiter moves further from Earth and closer to the Sun the planet is becoming dimmer. February was the last month for good viewing. After spending
the past six years in the southern skies, Jupiter moved north of the celestial equator on February 5th to spend the next six year 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 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 rises in the eastern sky during early evening, moving
retrograde in Virgo. The planet is at
opposition at the beginning of April and brightens from +0.5 to +0.4 magnitude during March.
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 remained 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 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.
Uranus is in conjunction with the Sun on the
Brightness varies slightly, reaching a maximum of +5.6 magnitude at opposition. This is bright
enough to see with the naked eye but identifying it against the stars is difficult. At closest approach, Uranus is 2,856 million kilometres (1,775 million miles)
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.
New moon: 4th
First quarter: 12th
Full moon: 19th
Last quarter: 26th