This looping animation depicts a southwesterly view one hour after sunset from 13–31 January 2020 at two-day intervals as seen from the heart of the UK. At magnitude -4.0 or slightly brighter, dazzling Venus exceeds the brightness of distant planetary sibling Neptune 63,000 fold! Venus passes just 4 arcminutes (one-fifteenth of a degree) south of Neptune at 8pm GMT on Monday, 27 January 2020, so both planets will fit in the same high-power telescope view from 6pm GMT until they set. Note magnitude +4.2 naked-eye star Phi (φ) Aquarii that lies within 0.9° east of magnitude +7.9 Neptune throughout the period. AN animation by Ade Ashford.Even casual skywatchers cannot fail to notice brightest planet Venus currently hanging like a lantern above the southwest horizon at nautical dusk, around 90 minutes after sunset for the centre of the British Isles. On 11 January, Venus crossed the constellation border into Aquarius where it resides for the remainder of the month. Between now and the beginning of February, observers can also see Venus close the gap on its most distant planetary sibling, Neptune, until the pair reach a close conjunction on 27 January 2020.Venus passes one-twentieth of a degree south of Neptune at 8pm GMT at 27 January 2020, but the pair will be very low in the UK sky. Observers in the British Isles are advised to look at 6pm GMT around the onset of nautical twilight when the two planets are about 19° high in the southwest. Their separation is slightly more than 7 arcminutes at this time. In this simulated one-degree telescope field of view the magnification is 40-50×. AN graphic by Ade Ashford.While there will no difficulty in identifying Venus in your telescope on the evening of 27 January, Neptune may prove a little more difficult to see in the glare of its planetary sibling. Their difference amounts to a whopping 12 magnitudes, which is another way of saying that Venus is 63,000 times brighter than Neptune! If the outermost planet is lost in Venus’ dazzle, try to spot magnitude +4.2 star Phi (φ) Aquarii in the same field of view shown above. Neptune passes just 2¼ arcminutes north of the star at 8:15pm GMT (20:15 UT) on 10 February 2020, but I’ll cover that in more detail nearer the time.
If you do succeed in viewing Venus and Neptune in the same telescope field of view, do bear in mind that their apparent proximity is merely a line of sight effect. On the evening of 27 January, Venus lies a little more than 167 million kilometres (or 1.117 astronomical units) from Earth, but outermost planet Neptune is a staggering 4,590 million kilometres (or 30.683 astronomical units) distant.