Planetary Notes
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Looking Forward; April & May 2022
Greatest elongation to the east of the Sun happens on 29 April but the planet will be easily found for more than 10 days either side of this date from some 40 minutes after sunset. For mid UK latitudes Mercury will sit around 13 degrees above the western horizon on the 29th at 2000 UT shining at magnitude +1. After this Mercury moves steadily back towards the Sun, reaching inferior conjunction on May 21.

Venus dominates the morning sky, initially with Saturn and Mars close by in early April, all three rising at around the same time in the east-south-east. Look for Venus first from around 0430 UT at a brilliant magnitude -4.3 and Saturn and Mars will be a little further south. At the same time each subsequent morning all three planets will appear a little higher but from 10 Apr the orbit of Venus passes from above to below the ecliptic through its ‘descending node’ so, thereafter, it suffers in altitude above the horizon when compared with Saturn and Mars. Venus also draws further east each morning as its tight inner orbit moves it ever closer to the Sun.

At the end of April Venus moves into a close line-of-sight conjunction with Jupiter; on the morning of 01 May they will sit one-third of a degree (20 minutes of arc) apart with Venus below Jupiter. At magnitude -4.1 and -2.1 respectively Venus will be much more obvious but the pair will sit comfortably together in a low or medium powered eyepiece in telescopes up to at least 1000mm focal length and can easily be followed into full daylight as long as all sensible precautions are taken to keep the Sun well clear of the field of view. Do be warned, if you don’t take such precautions you may end up permanently blind! By late May Venus rises from 0245UT, has fallen to just below -4 in magnitude and will show a 78% illuminated phase some 14 arcseconds in size from pole to pole. Venus (and Jupiter) have close conjunctions with Neptune but these are described at the end of this report when discussing the ice-giants.

As mentioned Mars rises with Saturn in early April and both may be easily found by looking a little south of brilliant Venus. At magnitude +1 and 5 arcseconds in size Mars will be hard to observe in the bright early morning skies of springtime but steadily improves and is worth seeking out. Saturn sits very close by and on 05 April the pair have their own close conjunction, this one being also one-third of a degree apart with Mars sitting a little below Saturn. Look for them at 6 or 7 degrees of elevation in the south-east on that date from 0500UT and follow them as long as possible to see them at higher altitudes.

After this Mars draws steadily away from Saturn, moving a little further north with each sunrise following Venus towards its own rendezvous with Jupiter. On 18 May Mars actually sits half a degree below tiny Neptune and the pair may be spotted a little south of due-east from 0300UT for perhaps 15 minutes before Neptune is washed out by the brightening sky. This conjunction will only be properly observed from much closer to the equator. Mars catches up with Jupiter on 29 May and sits half a degree below it on that morning. This pairing can be observed from at least 0225UT, as long as you have a low easterly horizon, and can be followed for at least an hour or more at more sensible altitudes.

Jupiter itself rises around 0530UT in early April so is best seen later in the period. It rises (with Venus) on 01 May at 0340UT for mid UK latitudes and at 0150UT by the end of May, in company with Mars. In the period Jupiter brightens slightly from magnitude -2.0 to -2.2 and grows in apparent size from 33.4 to 37.3 arcseconds. Follow it (carefully) into brighter skies and higher altitudes. There is currently a suggestion that the North Equatorial Belt is undergoing an outbreak, darkening and thickening, and it would be good to confirm this if possible.

The position of Saturn has already been discussed; it rises around 0430UT in early April, 0235UT mid-period and 0044UT in late May. The planet shines at magnitude +0.9 for most of this period with the rings well-presented, tilted some 13 degrees towards us with the northern hemisphere on view. Saturn is improving as it moves towards opposition in early August and its visible size is growing steadily if slowly during April and May; take the opportunity for some early observations of this beautiful planet.

Both of the ‘ice giant’ outer planets are hard to observe with Uranus perhaps being just visible soon after sunset low in the west. Your best opportunity is to use Mercury as a marker on 18 April as described above; after this Uranus moves into solar conjunction on 05 May and is then lost for the rest of the period. Neptune is a morning object but its faintness makes it very hard to find. There are some close planetary conjunctions but only the one with Mars on 18 May will help UK observers. On 12 Apr Neptune sits ridiculously close to Jupiter, passing one-tenth of a degree below it. Sadly this is extremely unlikely to be seen from the UK due to the brightness of the sky. The same is true of its conjunction with Venus 0n 27 Apr when the pair are just (read this carefully!) one-hundredth of a degree apart. This pairing happens at 1910UT so is invisible to us! C’est la vie.

I did say there were a lot of conjunctions in this period.
In this period Mercury has its best eastern (evening) apparition of the year for UK observers and the ongoing dance of planets in the morning sky gives us a number of beautiful close conjunctions to observe.

Mercury starts the period in superior conjunction with the Sun, emerging from behind it and into the evening sky from as early as the 10th of April. It will be seen very low initially, soon after sunset and around 15 degrees north of due-west. As the month progresses Mercury may be found higher in the sky after sunset, slowly growing in size and reducing in visible phase. On the 18th, Mercury sits a little less than 2 degrees above Uranus; look for Mercury shining at just brighter than zero magnitude around 1935 UT, 10 degrees above the horizon on a compass bearing of 285degrees then, with binoculars or a small telescope, you may catch distant faint Uranus a little below it as the sky continues to darken.