Magnitude +2.9 star Mu (μ) Geminorum, better nown as Tejat in the constellation of Gemini, is occulted (hidden) by the rising 13-day-old waxing gibbous Moon early on the evening of Thursday, 9 January 2020 as seen from the British Isles. This graphic shows the event’s progress as seen from London and Edinburgh, clearly demonstrating the effect of geographical latitude. AN graphic by Ade Ashford.If the early evening sky of Thursday, 9 January is clear, observers in the British Isles get the opportunity to witness a conspicuous naked-eye star slip behind the rising waxing gibbous Moon. Magnitude +2.9 Mu (μ) Geminorum, with the proper name Tejat, lies near the western edge of the constellation Gemini. The precise time and duration of the star’s disappearance behind the Moon – an event known as a lunar occultation, from the Latin occulo, ‘to hide’ – depends on where you live in the UK.
Observers in London will see, weather permitting, Tejat disappear at the darkened limb (edge) of the 13-day-old Moon shortly after 5:05pm GMT (17:05 UT) and reappear at the bright lunar limb 45 minutes later. For a skywatcher in Edinburgh, the star’s corresponding disappearance and reappearance times are a few seconds before 5:17pm GMT (17:17 UT) and 5:52pm GMT, respectively.
Mid-occultation of Tejat takes place with the Moon some 15 degrees (about a span-and-a-half of a fist held at arm’s length) above the UK’s east-northeast horizon. While it is an easy spectacle to follow in a small telescope, the star’s reappearance at the bright lunar limb might be a challenge for binocular users. As with all occultation observations, it pays to be setup and scrutinising the Moon 10 minutes before the predicted times, particularly if you live some distance from either London or Edinburgh.
Now that planet Saturn is effectively lost in the dusk twilight for UK-based observers, you may be wondering what has happened to the other four bright naked-eye planets. Far from disappearing, they have just transferred to the morning sky. From 8—11 October, the waning crescent Moon acts as a guide to Venus, Mars, Jupiter then Mercury in the eastern dawn sky.
A detailed analysis of the flash produced when a meteoroid crashed into the surface of the Moon during January’s lunar eclipse shows the body likely gouged a crater up to 15 metres (49 feet) across.
The serene beauty of the International Space Station sailing silently overhead needs nothing more than the naked eye to appreciate. But when the dazzling ISS is also in conjunction with a pair of prominent Solar System bodies — such at the Moon and Saturn on the night of 2 August 2017 in the UK — you may wish to grab your binoculars and look low in the south-southwest just before 11:20pm BST.
