This looping movie shows the position of Mercury some 14 degrees above the eastern horizon one hour before sunrise as seen from Sydney, New South Wales from 26 April to 10 May 2018. The innermost planet attains a favourable elongation of 27 degrees west of the Sun on the last morning of April in Australasia, meaning that it can be seen in a dark sky before the onset of astronomical dawn throughout the period of this animation. For scale, the view is 80 degrees wide, or four times the span of an outstretched hand at arm’s length. AN graphic by Ade Ashford.Have you ever seen the closest planet to the Sun? If you wish to tick Mercury off your to-see list, particularly if you live in the Southern Hemisphere, now’s the time to be scrutinising the eastern sky shortly before sunrise for the planet’s rosy glow. On 29 April (30 April in Australasia), Mercury attains a greatest westerly elongation of 27 degrees from the Sun – just 4 percent short of the farthest it can ever appear from our parent star.
Observing conditions for Mercury under southern skies are so good over the next fortnight (weather permitting) that skywatchers in Australia and New Zealand can comfortably view the planet in a truly dark sky from a viewing location that offers an unobstructed view of the east-northeast horizon about 1½ hours before sunrise.
Mercury’s magnitude grows from +0.7 to zero over the next two weeks, but atmospheric dimming close to the horizon will make it appear up to a magnitude fainter. Even so, the innermost planet will be a conspicuous dawn object for Southern Hemisphere observers through to the middle of May.
The old Moon gets close to Mercury and UranusObservers in Australasia looking low in the eastern sky an hour before sunrise on Monday, 14 May 2018 can see an attractive conjunction between magnitude -0.2 Mercury and the slim crescent of a 27-day-old Moon in the constellation of Pisces. In this simulated seven-degree 7×50 binocular view from Sydney, New South Wales, there’s the added incentive of glimpsing magnitude +5.9 planet Uranus in the same field of view. Uranus lies just over the constellation border into Aries, one-fifth of a degree from a similar brightness star known as HIP 8588. Don’t confuse Uranus with magnitude +4.3 star omicron (ο) Piscium above in the same binocular field. AN graphic by Ade Ashford.Mercury crosses the constellation border from Cetus into Pisces on 1 May and has a close encounter with an old crescent Moon on 14 May. On this date, observers in Australasia should look low to the east-northeast horizon an hour before sunrise to see the 27-day-old Moon just 2 degrees to the right of the magnitude -0.2 planet. Small telescopes and binoculars magnifying 20× or less will show the pair in the same field of view. And as a bonus for owners of binoculars, magnitude +5.9 planet Uranus also lies 2¼ degrees to the left of Mercury on this morning!
Early risers in the UK with an unobstructed horizon from southeast through south can see the old crescent Moon close to dazzling Venus in Libra then Jupiter in Ophiuchus over three consecutive mornings starting New Year’s Day around 7am GMT. The brightest and largest planets lie little more than the span of an outstretched hand at arm’s length apart at this time.
Observers with a clear sky to the south as darkness falls on Sunday 7 May can see the 12-day-old waxing gibbous Moon and planet Jupiter separated by little more than twice the width of a full Moon. For telescope owners in the UK, this is a night where you can also see Jupiter’s Great Red Spot and the planet’s four large Galilean moons.
On the night of 12-13 December, the waxing gibbous Moon glides in front of the loose open star cluster known as the Hyades in the constellation of Taurus, culminating in the occultation of bright star Aldebaran around 5:24am GMT for observers in the British Isles. In North America, the event occurs at a more sociable hour late into the evening of 12 December.
