Dundee Astronomical Society The Sky in April 2015 Sky at 10pm on 15th April 2015

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Dundee Astronomical Society

The Sky in April 2015

Sky at 10pm on 15th April 2015

[Chart courtesy of www.heavens-above.com]

By April, the constellation Leo dominates the southern evening sky. Next to Orion and the Plough in Ursa Major, Leo is probably the easiest constellation to identify and to relate to what it is meant to represent. Most people will easily see the outline of a crouching lion with the sickle of stars at the right hand end forming the head. The lion does have legs but, like Pegasus, its legs are marked by stars which are much less bright than the rest of the constellation. This is the lion which ancient Greek mythology tells us was killed by Heracles and is one of the 48 constellations defined by Ptolemy in the second century. The brightest star of Leo is Regulus, a blue-white star at a distance of 79 light years. Regulus is the twenty-first brightest star in the sky and lies close to the ecliptic, the apparent path which the Sun takes through the sky throughout the year. The Moon also follows fairly closely to the ecliptic and Regulus is quite frequently occulted, or hidden, by the Moon. The Moon will pass close to Regulus on the evening of 31st March this year but on the 18th December next year it will pass in front of the star. Remarkably, in 2017, the Moon will occult Regulus every month with the exception of August somewhere on Earth but UK observers will only see a single event that year on the 8th December. Leo is also well known for its relatively bright galaxies. Charles Messier, the 18th century astronomer and comet hunter, discovered a number of galaxies in Leo and these can be seen as hazy patches with moderate sized telescopes.

The brightest galaxies shown with Messier numbers above are quite easy to see with telescopes of 100mm plus. Choose a dark moonless night and use quite a low magnification and you will get the triplet M95, M96 and M105 in the same field of view. The same is true for M65 and M66 with the bonus of NGC 3628 making a triplet. There are quite a number of fainter galaxies in this area and it is worth just panning slowly over the area to see how many you can find.
Although Leo is best known for its galaxy collection there are a number of other interesting objects within the constellation. As noted in the table below, double and triple stars form the majority of the other objects and there is one good variable star, R Leonis which has a magnitude range of 4.4 – 11.3. R Leonis is a Mira type variable with a period of 312 days and is next expected to reach maximum on 2015 September 16.

A rather week display of meteors may be seen between the 18th and 25th of April with peak activity on the 22nd at 11pm. These are the Lyrids and the shower is quite favourable this year as the time of maximum is ideal for UK observers and the Moon is only four days old and its light will not interfere later in the evening. Don’t expect to see more than about 10 meteors per hour but there have been exceptional displays in the past, notably in 1803, 1922 and 1982. To have the best chance of seeing these meteors you should get away from bright street lights and allow time for your eyes to adapt to the dark.
As happens two weeks following (or preceding) an eclipse of the Sun there is an eclipse of the Moon when it is full. Following the solar eclipse of 20th March there is a total lunar eclipse on the 4th April. However, the UK will not be as fortunate as it was for the solar eclipse as none of the eclipse will be seen from here. It will be best seen from eastern Australia and Asia and western USA and Canada where it will be at its maximum at 12 noon GMT.

Area where the total lunar eclipse of 2015 April 04 will be seen
Mercury moves behind the Sun in early April but emerges and may be seen low in the north-west after sunset at the very end of the month.
Venus remains a brilliant object towards the west after sunset and itself sets at about 11pm in the north-west.
Mars, in Aries, moves towards the Sun and will be difficult to see, setting only an hour after the Sun.
Jupiter is still a brilliant object in Cancer, setting at about 3am.
Saturn rises at about 11pm and will be low in the south by 2.30am in Scorpius.
Uranus and Neptune are not well placed in April.
The Moon will be full on the 4th, at last quarter on the 12th, new on the 18th and at first quarter on the 25th.

Ken Kennedy

Director of Observations

Dundee Astronomical Society

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