Planetary Notes
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Society for Popular Astronomy
Looking Forward; February & March 2023
A period with a number of close planetary conjunctions.

Mercury starts February as a morning object, its own orbit moves below that of the ecliptic early in the month meaning it will be seen very low down from UK latitudes; but Mercury is certainly visible, at least for the first three weeks of February. Look for it rising in the south-east around 0645UT in early February and only minutes later by the start of March; by then it will be hard to spot in a rapidly brightening sky. After this Mercury rises with the Sun and is unobservable in twilight from the UK. On 02 March Mercury sits very close to Saturn but since Saturn is fainter than Mercury you are unlikely to see either.
Mercury passes behind the Sun (Superior Conjunction) on 17 March and ends the month just appearing in the evening sky, close to Jupiter on 28 March, by which time its orbit is moving above the ecliptic such that Mercury will go on to give an excellent evening apparition in the next period.

Venus is a lovely and improving evening object. It is, itself, just below the ecliptic and ascends above it on 14 March. Brightening slowly from magnitude -3.9 to -4.0, Venus will be the first ‘star’ visible as twilight falls in the western sky. Initially Venus will show a 90% illuminated phase, some 11 arcseconds (11”) from pole to pole; the illuminated phase falls and the apparent size increases steadily through the period being respectively 77% and 14” by the end of March, by which time Venus will be very obvious, some 30 degrees up in the west, shortly after sunset.

Venus has an extremely close conjunction with Neptune on 15 February with Neptune a little below and to the right of the glare of Venus; an interesting if very challenging observing or imaging project. Venus is close to Jupiter on 02 March and this will be much easier to observe. On 30 March Uranus will sit 1.2 degrees below and to the left of Venus but, like Neptune, will be much harder to catch due to the huge disparity in brightness between them. This is a good period to image Venus in the near ultra-violet.

Mars fall below 10” in apparent size in early February but the planet will be at excellent elevations for much of the evening. South transit will be around 1955UT at the start of the month and more than 60 degrees up for most of the UK. At that time Mars will sit directly above Aldebaran in Taurus with the red planet noticeably the brighter of the pair. Mid period, south transit will be around 1845UT, towards the end of twilight and with the same excellent elevation. By late March south transit is in daylight but Mars will be obvious, sitting between Betelgeuse and Capella, from around 1915UT, somewhat west of due south and only a little below 60 degrees up; by then Mars will be setting around 0200UT so it can still be followed for many hours. In March Mars starts to show an obvious gibbous phase and falls in apparent size to just over 6”; catch it earlier in the period for the best views of its dusky surface features.

Jupiter is definitely best seen early in this period as it is rapidly sinking into the west during evening twilight. Start looking for it from around 1715UT, about 35 degrees up in the south-west in early February. Venus will be the first thing you see but Jupiter will be noticeable, higher and further south. A telescopic view will still show a large 36” disc and the cloud features should be well on show in the steady air of early evening. As the period progresses Jupiter and Venus will draw closer together until 01 and 02 March when the pair are around half a degree apart; they will appear from 1800UT with Venus, again, the most obvious. By late March Jupiter sets around 1900UT so is effectively lost for most UK observers by the middle of the month.

Saturn is in conjunction, hidden behind the Sun, on 16 February and thereafter moves into the morning sky but at very low altitude. Mid-period Saturn rises only shortly before the Sun and in late March only 45 minutes before, so observation is difficult. On 02 March Saturn rises in close company with Mercury but, as already mentioned, this conjunction is unlikely to be visible from the UK unless the pair are caught and followed into daylight.

Of the ice-giants, Neptune is low in the western evening sky and will be lost to observation first. It has a very close conjunction with Venus on 15 February which will be interesting to watch telescopically. This can be followed from twilight into darkness when blue-green Neptune will be more noticable close to the dazzling glare of Venus.

Uranus is best seen at the beginning of January when it transits around 1810UT, at the end of twilight. At some 55 degrees of elevation at that time Uranus will sit above the head of Cetus, the whale. Shining with a visual magnitude of +5.7 it is unlikely to be glimpsed without visual aid but is easy in binoculars. As the period progresses Uranus sinks slowly into the west with each new sunset but can still be found and followed in darkness. On 30 March Uranus has its own close meeting with Venus, passing to the left and then below Venus for a couple of nights around this date. Yet another fascinating observing event to finish the period off.