The Sky at Night
I mentioned the constellation Leo last Month and it is now sitting high towards the south on April evenings. It is easy to imagine a lion formed from the shape of the stars and this has been recognised since ancient times, certainly as long ago as 4,000 BC. Regulus is the brightest star in the constellation and is directly below the sickle forming the lion’s head and neck. Directly eastwards, at the other end of Leo is the star Denebola, a name which means ‘the lion’s tail’. Beneath a line drawn between these two stars are a number of reasonably bright galaxies which can just be seen with binoculars or a small telescope. The comet hunter Charles Messier catalogued the brightest of these galaxies although it is believed that Pierre Méchain actually discovered them around 1780. There are a number of galaxies in the Leo Group but there are also around 70 major galaxies in what is known as the Leo Cluster. The Leo Group are at a distance of around 37 million light years while the galaxies of the Leo Cluster are much more distant at 330 million light years. Don’t expect to see all of these galaxies if you have a look with binoculars but if the night is Moon free and you observe from a dark place you may just see a few as fuzzy spots rather than sharp stars. Perhaps not very spectacular, but amazing to think that you have just observed light which is 37 million years old!
Hanging high in the sky at this time of year is Ursa Major with the well know pattern of the Plough almost overhead. Ursa Major is another constellation well blessed with fairly bright galaxies but these are more widely scattered than the galaxies of the Leo group and so a bit more difficult to locate. Follow the handle of the Plough and it points towards one of the brightest stars in the sky, Arcturus, the brightest star in the constellation Boötes. We will leave these constellations for another month as they deserve rather more detailed descriptions.
The Lyrid meteor shower will be on display in April with a peak of activity on the evening of the 21st and improving into the small hours of the 22nd. The prediction for the number of meteors per hour at maximum this year is 18 although in the past there have been outbursts with more than 100 per hour. The Lyrid shower is one of the oldest recorded having been observed as long ago as 687 BC. The particles which strike Earth’s atmosphere to produce bright meteors are from the associated Comet Thatcher which orbits of the Sun every 415 years. The comet itself will not return until the year 2276 but Earth will fly through its debris every year in April. The first quarter Moon will interfere with observations until after midnight but, as always, try to find a dark spot to observe from.
- Mercury will not be visible during April.
- Venus will remain low but bright in the west after sunset and will set around two hours after the Sun during the month.
- Mars rises at about 1.30am but will be low in the sky until it fades in twilight at 5am.
- Jupiter remains in Libra and rises at about 10pm. It will be well placed in the south at 2am but is still quite low in the sky.
- Saturn is just a bit further west than Mars and slightly higher but it will also be lost in the brightening morning sky by 5am.
- The Moon is at last quarter on the 8th, new on the 16th, at first quarter on the 22nd and full on the 30th April.
Sky at Night Chart
- Sky at Night Chart April 2018 (153KB )