The Sky Above You – June 2023

By Duncan Lunan

map of the night sky for JUne 2023

The Moon will be New on June 4th, and it will be Full on June 18th, near Venus and Mars on the summer solstice, June 21st.  More than four years after the re-erection of the Sighthill stone circle at its new site in Glasgow, on the spring equinox of 2019, the security fencing around it has at last been removed and it will be possible to see the midsummer Sun rise over the marker stone, though midsummer sunset will be behind the new houses in the former Sighthill Park.

The planet Mercury is not visible this month, still too far south in the morning sky for us, although it’s at greatest western elongation at the beginning of the month.

Venus remains very bright in the evening sky, setting around midnight.  At the beginning of June Venus is near Castor and Pollux in Gemini, and is at its greatest elongation from the Sun on the 4th.  On the 12th to the 14th it brushes the open cluster Praesepe, the Beehive, in Cancer.  On the 21st Venus lies almost on the line between Mars and the waxing crescent Moon, and is to the right of the Moon the following night.  Venus will be gone by July 10th, and at inferior conjunction with the Sun on 13th August.

On June 1st to 6th Mars passes through the Beehive, best seen through a telescope or binoculars.  Mars is passed by the Moon as it crosses into Leo on June 22nd, and sets soon after midnight.

Not long after it ‘bit the dust’, literally, succumbing to the buildup of dust on its solar panels, results from NASA’s Insight lander have finally succeeded in mapping the interior of the Red Planet  (Vishwam Sankaran, ‘NASA Mars lander study reveals ‘main source of heat’ on Red Planet’,The Independent, 18th May 2023), never achieved since the Viking landers failed to do it in 1976  (one seismometer detected nothing, the other failed to deploy).  In the last months while it was still active, Insight’s readings were boosted by the seismic waves from two distant meteorite impacts.  Now the findings have been analysed, a paper in Geophysical Research Letters reveals that the Mars crust is 42-56 km deep  (26-35 miles, twice Earth’s (21-27 km).  The density is similar in the northern lowlands and the southern highlands, but the crust is thicker in the southern highlands, like Earth’s below the continents, which supports the idea that the whole northern hemisphere was originally ocean.  The planet’s internal heat comes from radioactive decay, but 50-70% of it is in the crust, so present-day melt-zones are still forming – that ties in with the finding from orbiting probes that Mars is gravitationally ‘lumpy’, like the Moon.

The United Arab Emirates’ Hope probe has achieved a first in photographing the side of the outer moon Deimos which faces away from Mars, and found a deep cleft in it which was previously unknown.  Infrared data appears to confirm the hypothesis that the moons of Mars are agglomerations of rock ejected from the surface of Mars in big impacts.  NASA has seconded 10 of its top planetary scientists to Japan’s Martian Moons Exploration mission, which is intended to launch in 2024 and to return samples from Phobos, the inner moon.  Russia has previously attempted that three times, without success.

On May 24th Europe’s Trace Gas Orbiter, which has been orbiting Mars since 2016, sent a coded message to Earth, received by the Allen Telescope Array, the Green Bank Telescope and the Medicina Radio Astronomical Station in Italy.  The signal was broadcast worldwide and the object of the exercise is to see how successful the international community would be at decoding a message from another civilisation.

Jupiter now rises about 3.30 a.m. in Aries, and is passed by the Moon on June 14th.  There’s very good news about the European Space Agency’s Jupiter Icy Moons Explorer, which was launched in April.  All of its experiments were successfully deployed except RIME, the deep penetrating radar, but after two weeks of effort mission controllers succeeded in freeing it on May 12th.  JUICE will reach the Jupiter system in 2031 after multiple slingshots of Earth, the Moon and Venus.

On May 16th, on its 51st orbit of Jupiter, NASA’s Juno probe approached the volcanic moon Io, taking visual and infrared images at 22,000 miles.  The closest approach will be in December, when Juno will pass Io at 1500 miles and the images should be spectacular.  These close approaches are only possible because of the evolution of the spacecraft’s orbit during its extended mission, originally to have ended in 2016 but now continuing till 2025 at least.

Saturn in Aquarius rises about 1 a.m., before midnight by the end of the month, and is near the waning crescent Moon on the 10th.  As the Earth catches up with it, on June 18th Saturn appears to come to a halt and then reverse its motion among the stars.  Saturn has been in the news twice lately, first with the discovery of 62 previously unknown moons, giving a total of 145 – far ahead of Jupiter’s known total of 95.  (Kelly Kizer Whitt, ‘Saturn’s moon count grows by 62 for a record 145 satellites’, EarthSky, 17th May 2023.)  As the late Carl Sagan pointed out, Saturn has ‘billions and billions’ of moons if you count all the particles in the rings.  New calculations of the rings’ age suggest that they might have formed, by satellite collision or breakup, within the last 400,000 years, possibly 100,000, which would be within the timespan of the human race.  (Paul Scott Anderson, ‘Saturn’s Rings Much Younger than Saturn Itself’, EarthSky, 17th May 2023.)  The figure has been reached by comparing the brightness of the ring particles with the amount of dust detected in the Saturn system by the Cassini orbiter on its 14-year mission. 

The confirmation that the rings are dimmed by dust sticking to the ice particles is not particularly good news.  In the discussions which led to my book Man and the Planets  (Ashgrove Press, 1983), after a lecture by the late A.T. Lawton on interstellar dust, it was suggested that the rings might have swept up large quantities of it, rich in heavy and exotic elements from nearby supernovae over their history.  I was surprised to find that some of the young Turks in the group were quite happy to contemplate the extraction of it by lasers and ion scoops, inevitably stripping off the ice cover or evaporating ice particles completely.  As the process continued, the Irish fiddle tune The Frost Is All Gone would change from a gay jig to a lament.  When challenged, “Why do you want to preserve the rings?”, I replied “They’re pretty”, and was told, “That’s not a very good reason”.  The argument was finally won with the statement that the rings are ‘the best advertisement spaceflight ever had’, and when it was suggested that photos of how they used to look would suffice, the artist Gavin Roberts invoked the Trades Descriptions Act.

Uranus in Aries reappears towards the end of June, rising at 2.30 a.m., near the Moon on June 15th.  A re-evaluation of images taken by Voyager 2 in 1986 appears to confirm that there are liquid water oceans inside four of Uranus’s moons, with a frozen one inside Miranda, making a new expedition to the planet much more likely.  With Uranus’s north pole now turned towards us, because of its side-on rotation, the James Webb Space Telescope has discovered a large polar vortex among the bright clouds covering most of the northern hemisphere.  When Voyager 2 passed Uranus in 1986 the south pole was facing the Sun, and there were indications of a similar vortex, though the spacecraft cameras weren’t able to resolve it.

Neptune rises about 1.30 a.m. in Pisces, and is near the Moon on the 11th.

June and July are the months in which to look for noctilucent clouds in the evening and morning sky, after sunset and before dawn.  These ‘night-glowing’ clouds are about 50 miles up and reflect sunlight so well that they appear to be ice crystals, though it’s not clear how ice can remain aloft and react to high winds at such a height.

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

map of the night sky for June 2023

Categories: Science

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