Looking Forward; The Planets Feb/March 2019.
Alan Clitherow is the Planetary Section Director of the Society for Popular Astronomy and an active member of DAS, and writes regularly on planetary observations. This article is reproduced from the Society For Popular Astronomy and with the kind permission of Mr Clitherow.
© Alan Clitherow. All rights reserved
Society for Popular Astronomy
Mercury puts on its best evening apparition of the year for Northern Hemisphere observers in late February; however the separation from the Sun at greatest eastern elongation is only 18 degrees so the best viewing window is quite narrow. Maximum elongation occurs on the 27th of the month so look for mercury appearing at around 10 degrees of elevation, a little south of due-west, shortly after sunset from around the 22nd of February to the 3rd of March. After this Mercury is rapidly lost, moving between the Earth and the Sun (inferior Conjunction), on the 15th of March. Its reappearance in the morning sky of late March will be barely visible in the north and much better seen from the southern hemisphere.
Venus dominates the pre-dawn sky in this period as a brilliant morning 'star' shining brighter than magnitude -4 until the very last days of March. Its separation from the Sun is steadily decreasing as it moves away from the Earth on its faster, inner orbit and its visible phase grows while its apparent size falls noticeably. On the 18th of February Venus passes one degree above much fainter Saturn with their planetary discs being 17 and 15 arcseconds in size respectively. This event can only be seen at very low altitude in darkness but the pair can easily be followed into full daylight making an interesting photo opportunity for suitably equipped observers. By late March the visible phase of Venus rises to 81% illuminated with an apparent size just less than 14 arcseconds from pole to pole. Throughout this period observers using ultra violet photographic or deep-purple optical filters should look for subtle darker cloud features in the atmosphere of the planet.
Mars seems to have put on a very long show during its current apparition and it remains visible in the evening sky throughout February and March. Its apparent size is now small, falling below 5 arc seconds in late March, so only the major surface features will be visible and good seeing needed to tease out detail, however this effort is helped by the good altitude of the planet as seen from the UK. In the darkening skies of early evening it will appear a little west of due south above 40 degrees of elevation in early February, its prograde motion helping to maintain this elevation as evening falls a little later, night-on-night, throughout the period. By early March it will have moved around to the south-west on first appearance and nearly due west by the end of the month but, even then, its elevation will be around 35 degrees up and it can be followed until after 2300 hours UT. In the second week of February, Mars and Uranus keep close company and on the 13th they are just one degree apart and visible together in a low power eyepiece in most amateur instruments.
After Venus, Jupiter is the next most prominent planet appearing in the morning skies of early February. It rises in the south-east around 0450 UT on the first then steadily earlier, rising at around 0130 UT by late March, and it can then be followed easily through morning twilight and into full daylight. On the first of February Jupiter, Venus, a very narrow crescent Moon and Saturn form an obvious descending line in the south-eastern sky. Jupiter will show a disc more than 33 arcseconds in apparent size and this will grow throughout the period to nearly 40 arcseconds by late March; considerable detail in its ever changing belt structure should be on view although the elevation of the planet will be disappointingly low, as seen from the UK, during much of its upcoming apparition.
Saturn follows Jupiter in this period, appearing late in morning twilight initially and then rising in full darkness by the third week of February. Like Jupiter, Saturn reaches only relatively low altitudes as it moves into daylight however its rings are still tilted towards the Earth by some 24 degrees so presenting themselves well for our observations. On the 2nd of February Saturn rises in occultation behind the moon, moving back into visibility from around 0625 UT and this may be visible depending on your location; the more southerly your location the better the chance with observers at mid-UK latitudes just catching the event as the Moon breaks the south-easterly horizon.
Of the outer 'Ice-Giant' planets, Uranus is the most observable, staying close to Mars for most of February therefore remaining well up in the south-western sky as night falls. Visible against the background stars of Pisces, its tiny 3.5 arcsecond disc hangs on the edge of naked eye visibility and appears as an unfocussed green or blue-green 'star' in binoculars. Telescopes reveal its obvious planetary nature and large-aperture telescopes will show subtle shading from equator to pole. Its relatively high elevation in mid evening will help with observation through February but by March the planet starts to subside noticeably to the West, evening on evening, so it is best observed early in the period. Neptune reaches conjunction with the Sun on the 7th of March so is not observable in this period.