|Events during April
The Moon: Full – 2nd, Last quarter – 10th, New moon – 17th, First quarter – 24th.
This snapshot shows the position of deep-sky objects in and around the constellation of Ursa Major.
M51 (Whirlpool galaxy) – a spiral galaxy in Canes Venatici at 8.4 magnitude.
M63 (Sunflower galaxy) – a spiral galaxy in Canes Venatici at 8.6 magnitude.
M81 (Bode´s galaxy) – a spiral galaxy in Ursa Major at 6.9 magnitude.
M82 (Cigar galaxy) – an irregular galaxy in Ursa Major at 8.4 magnitude.
M94 – a spiral galaxy in Canes Venatici at 8.2 magnitude.
M97 (Owl nebula) – a planetary nebula in Ursa major at 9.9 magnitude.
M101 (Pinwheel galaxy) – a spiral galaxy in Ursa Major at 7.9 magnitude.
M102 (Spindle galaxy) – a lenticular galaxy in Draco at 9.9 magnitude.
M106 – a spiral galaxy in Canes Venatici at 8.4 magnitude.
M108 – a spiral galaxy in Ursa Major at 10.0 magnitude.
M109 – a spiral galaxy in Ursa Major at 9.8 magnitude.
||Mercury rises just minutes prior to the Sun and is therefore not visible during April.
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.
||Venus moves from Aries into Taurus at a brilliant –4.1 magnitude. It sets about 1.30h by the end of
April with the Moon nearby on the 19th and Pleiades above on the 12th.
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 is at 1.0 magnitude in Aquarius and remains in morning twilight until June. It rises about 5.00h
by the end of the month with the Moon nearby on the 14th.
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 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 Ophiuchus at –2.5 magnitude, rises before 1.00h by the end of April. The planet is
stationary on the 6th and close to the Moon on the 8th.
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 Leo at 0.4 magnitude, setting about 4.30h by the end of the month. Saturn is stationary on
the 20th and is close to the Moon on the 24th.
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 in Aquarius, rises about 5.0h by the end of the month and has the Moon closeby on the 15th.
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 in Capricorn, rises about 4.00h by the 30th with the Moon closeby on the 14th.
Neptune has an average magnitude of 7.9 which varies little with changing distance.
||No longer an offical planet and never brighter than 13 magnitude, Pluto is only visible through powerful
telescopes and we therefore do not report on its position in the sky.
Full moon: 2nd
Last quarter: 10th
New moon: 17th
First quarter: 24th
The Moon in 2007:
The Moon was seen unusually high and low in the sky during 2006 (see Moon). Although the extremities occurred last year, the Moon will still be seen very
high and very low each month this year, most noticeable around full Moon. It will be near full and high around the 2nd and 29th January, the 25th February
and the 24th March; and near full and low around the 1st and 28th June.
During each month of 2007, the Moon will pass through the Pleiades. This will mostly be in daylight but observable 01.00-04.00h 7th August,
0.00-03.00h 28th October and 22.00-01.00h on the 21st to 22nd December. Binoculars will give a clearer view.