By Duncan Lunan

The Moon will be Full on August 13^th, which will be a Supermoon, at Full when at its nearest to Earth  (perigee), unfortunately right at the peak of the Perseid meteor shower.  The Moon will be New on August 27^th.

On August 6^th at approximately 9.40 p,m,  (depending on the observer’s location)  the Moon occults the eruptive variable star Dschubba  (delta Scorpii).  Dschubba is a very hot giant star, 13 times the mass of the Sun, 491 light-years away, and its small variations in brightness may be due to spots on its surface.  But every so often it brightens dramatically as it throws off material to form a disc around the star, raising it briefly to 1^st magnitude in 1937.  These events may or may not be connected to close passages of a companion star, which has an orbital period of 10.8 years, during which it travels out to a distance equivalent to Saturn’s from our Sun.  The latest close passage was three months ago, so it will be very interesting to see what’s revealed as the edge of the Moon passes over it.  

The planet Mercury is not visible in August or September, though it will be at its greatest separation from the Sun on August 27^th,  and south of the Moon on the 29^th.

Venus is brilliant in the morning sky, in Gemini, rising at 4 a.m. in August, with the waning crescent Moon nearby on August 26^th.  By then Venus has moved through Cancer into Leo, passing the Beehive cluster in Cancer on the 18^th, though the stars will be hard to see near sunrise.  As always when using optical instruments, beware the rising Sun  (5.58 a.m. in Troon, 5.39 a.m. in Orkney.)

Mars is near Uranus at the beginning of August, in Aries, rising just before midnight and moving into Taurus on August 10^th, passing the Pleiades on the 21^st, approaching and making an interesting contrast with the red star Aldebaran by the end of the month.  The Moon is nearby on August 20^th.  Europe’s Rosalind Jackson Mars rover, named after the crystallographer whose work led to the mapping of the DNA molecule, was to have been launched by a Russian booster in August, but cooperation with Russia in space has now been officially terminated. 

We hoped for better news of the US probe to the metallic asteroid Psyche, which was also due for launch in August, to arrive in 2026.  All the previously visited asteroids have been rocky, so this will be the first visit to the core of one of the parent bodies of the Asteroid Belt.  However, due to late delivery of guidance software and test equipment, the launch was postponed to September, then to 2023 or 2024, meaning that the probe will not reach Psyche until 2029 or 2030.

Jupiter rises at 10.30 p.m. in August, in Pisces, making a welcome return to our maps along with Neptune and Saturn.  Jupiter is near the Moon on August 15^th.

Saturn in Capricornus is visible all night in August, coming to opposition on August 14^th.  The Moon is near Saturn on August 11^th.  The August issue of Astronomy Now has two detailed lists of phenomena to be expected with Saturn and its moons around opposition, many of them visible even in small telescopes.

Uranus in Aries rises at 11 p,m, in August, near Mars on 1^st and near the Moon on the 18^th, occulted by it on the 18^th as seen from Iceland to Hawaii.   Uranus reaches its ‘stationary point’ on the 24^th, before reversing its apparent movement in the sky as the Earth begins to overtake it.

Neptune in Aquarius rises at 9.30 p.m. in August, and is near the Moon on the 14^th.

The New Horizons spacecraft is being used increasingly for deep sky surveys, after its successful flybys of Pluto and Arrokoth in the Kuiper Belt.  It has discovered that in both visible and ultraviolet light the background sky is brighter than expected, for reasons not yet understood.  Long-distance studies of Uranus and particularly Neptune are also on the cards.  The probe’s productive lifetime looks likely to continue to 2040, rather than 2030 as planned, so it’s possible than more flyby targets will be found and reached before the power supply finally fails.

Events have gone very fast during the final phases of testing the James Webb Space Telescope, which has now been officially commissioned for work.  After checking out how the telescope functioned in various positions, all four of the main scientific instruments were brought to operating temperatures and turned on.  Trial images showed much better quality than the images achieved by previous space telescopes such as Spitzer, WISE and even the Hubble, and in a spectacular moment, a trial image taken by the JWST’s Canadian finder telescope proved to be deeper than the HST’s Ultra Deep Field.  Positioning by Europe’s Ariane V booster has proved to be so good that the JWST’s probable lifetime has increased from 10 to 20 years, so it too should be with us till 2040.  Less good news was that the C3 mirror segment was hit by a meteoroid, bigger and also sooner than had been thought likely.  But although both factors are worrying, so early in the mission, the damage can mostly be compensated for and there’s no discernible effect on the six images released so far, covering Jupiter, an exoplanet, targets throughout the Milky Way, the distant colliding galaxies of Stephan’s Quintet, and a gravitationally lensed starfield which may extend back to within 200 million years of the Big Bang.  And that’s just from the telescope’s first week’s work!

Duncan Lunan’s most recent books, From the Moon to the Stars and The Other Side of the Interface, were published by Other Side Books in 2019 and 2021, and are available through Amazon or through bookshops, or from the publishers.  For details and for his other books see Duncan’s website, www.duncanlunan.com.

You can download a copy of the August Star Map here: