The April 2017 night sky

Welcome to the April night sky. Now that the clocks have gone back, we are again in sync with solar time. This means that the Sun will be due south at local midday and, of course, at its highest at 12.00 hours for anybody close to the prime meridian of their time zone.

For us in Portugal and also in the UK, it is zero degrees longitude known as the Greenwich meridian. For those of us to the east of this line, the Sun will seem to be a little fast and for those of us to the west, it will be slightly slow.

The difference is not a lot, only amounting to four minutes of time for every degree of longitude and at our latitude one degree of longitude measures about 45 kilometres on the ground; this means that for every 10 kilometres east you travel, the Sun rises one minute earlier and for every 10 kilometres west you travel, the sunset is one minute later.

At any night during April, you could be lucky enough to see what has been called an April fireball. The origin of these very bright meteors is unknown but they are well worth looking out for as they could appear at any time of the night in any area of the sky.

We also have on the 22nd the normally reliable Lyrid meteors and these are dust left over from the tail of comet Thatcher that was last seen in 1861. On the night of the 28th we also have the Alpha Bootids meteor shower with an origin point close to the bright star Capella.

The month of April belongs to the giant gas planet Jupiter, as on the 7th it reaches its opposition point when it will be at its closest to the Earth. This also means that Jupiter will rise in the east at sunset and be at its highest in the south at local midnight.

Jupiter is at the moment a magnificent sight through a small telescope as the ever-changing cloud belts are easily visible along with the four large moons discovered over 400 years ago with a tiny home-made telescope.

Since July 4, 2016 the space probe Juno has been in a very elliptical orbit around Jupiter. One orbit takes 53 Earth days and at its closest point to the planet, Juno skims less than 3,000 miles above the cloud-tops of this gas giant.

Juno will stay with Jupiter until at least July 2018 when its mission is planned to end, but if Juno is not too badly damaged by the high radiation environment around Jupiter, it may be operational for longer.

When its mission is finally over, Juno will be allowed to enter into the atmosphere of Jupiter in order to burn up to avoid any possible contamination of any of the Moons of Jupiter, especially Europa where beneath its icy surface there is a relatively warm salt-water ocean where life may exist.

The moon is first quarter on the 3rd, full on the 11th, last quarter on the 19th and new on April 26.

By Clive Jackson
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Clive Jackson is the Director of the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach.
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To see the April Sky Map click on the pdf link below