The Sky Above You – April 2023

By Duncan Lunan

Map of the sky for April 2023 showing the position of the planets

The Moon will be Full on April 6th, and it will be New on April 20th, when there will be a solar eclipse visible across Indonesia, Western Australia and the Pacific.  This is a ‘hybrid’ eclipse because at the beginning and the end of the track it will be annular, when the rim of the Sun will be showing around the Moon until it’s at its nearest.  The Moon is between Venus and the Pleiades on the 22nd, which is also the night of the Lyrid meteors  (see below).

The Japanese company iSpace reached lunar orbit on March 20th with its Hakuto-R probe, which was launched on a low-energy trajectory last December.  First images from orbit have been received, and the spacecraft will soon attempt a landing, after which it’s intended to deploy the Emirates rover Rashid, with a Canadian artificial intelligence system for navigation.

Analysis of the samples returned to Earth by China’s Chang’e-5 has turned up a major surprise.  It’s been known for some time now that protons from the Solar Wind can combine with oxygen atoms in the lunar soil to produce a very thin water vapour over the sunlit face of the Moon.  But now it turns out that they can also penetrate the miniature beads of glass which are formed by impacts on the Moon, and as a result those beads have significant water content.  This may be a game-changer for the planned human presence on the Moon, because lunar bases could be established anywhere, rather than the present emphasis on the lunar south pole with its water ice on dark crater floors.

The planet Mercury is at its best for the year this month, at greatest elongation from the Sun on the 11th, setting at 11 p.m., before descending into the twilight the following week.

On the same night, 11th April, Venus passes the Pleiades, and is very bright now in the evening sky, setting after midnight.  The late John Braithwaite, Scotland’s last professional telescope maker, said, back in the 1960s, how much he would like to see Venus in a truly dark sky, and it’s too bad that he’s missing it now.  On the evening of the 22nd Venus will be below the crescent Moon, and in theory the Pleiades might still be visible below them.

Mars in Gemini, sets about 2.30 a.m. and is passed by the Moon on the 25th.  Mars will be approaching Castor and Pollux by the end of the month, and no longer brighter than either of them.

Jupiter is out of view behind the Sun in April, at superior conjunction on the 11th.  

As predicted in ‘Solar System Exploration’  (ON 5th March 2023), NASA’s Juno spacecraft is making successively closer approach to Jupiter’s volcanic moon Io.  On its 49th orbit of the planet, on September 29th 2022, Juno took a series of images of Io from distances between 52,515 and 64,944 km.  It’s the closest pass by any spacecraft since New Horizons in 2006, on its way to Pluto, and several changes due to volcanic activity can be seen even that that distance.  (Nancy Atkinson, ‘Just Dropped:  New Close-up Images of Io from Juno, With More to Come’, Universe Today, online, March 4th 2023.)

The next Io pass will be on the 51st orbit, on May 16th, at a distance of 35,000 km..  On February 3rd 2024, the closest pass will be at just 1,500 km, and the images should be spectacular.  Meanwhile, Europe’s Jupiter Icy Moons Explorer  (JUICE)  is poised for launch on April 14th, on one of the last Ariane V boosters  (famous most recently for the successful launch of the James Webb Space Telescope in December 2022).  It has another demanding task to perform, because the launch window for this mission has to be precise to the second.

Saturn in Aquarius is in the morning sky, rising about 5 a.m., and above the waning crescent Moon on the 16th.

Uranus in Aries sets at 10.00 p.m., disappearing in the second half of the month.

Neptune is out of the sight this month, on the far side of the Sun.

The Lyrid meteor shower from the 1861 Comet Thatcher  (not due back till 2283)  peak on the night of 22nd-23rd April, and as the Moon sets early in the night there’s a better chance of seeing them.

Duncan Lunan’s recent books are available through Amazon.  For more information see Duncan’s website,

Click on this link to download a copy of the Sky Map for April 2023

Map of the sky for April 2023 showing the position of the planets

Categories: Science

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