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Thursday, 21 June 2018  •  Thursday, 8 Oak Moon 2018

Watching the night sky in Oak Moon 2018

14 June - 12 July 2018

Map of night sky at full moon: 28 June, 04:53 UTC
Northern hemisphere perspective, aligned on the ecliptic. Morning sky to the left, evening to the right.

night sky map for Oak Moon 2018

Venus is the bright evening star in the west after sunset. For northern hemisphere viewers, Venus is highest above the horizon after dark around the start of the lunar month. After that, it continues to pull outwards from the sun, but the solstice is upon us, and the plane of the solar system tilts lower in the south-western sky. As seen from the southern hemisphere, Venus continues to climb for another couple of months. On 15 June, the new crescent moon is near the bright planet.

Mercury rises into the western evening sky from around 19 June, poorly seen at first from the southern hemisphere, but soon well seen from both halves of Earth. For the rest of the lunar month, it lies between Venus and the sunset, making it easy to find, and it is one of these times when you can get a good sense of the inner solar system: the sun just below the horizon, then Mercury, then Venus, and in your mind you may be able to swing the line round to Earth as well, to see us clearly as the third planet. Between 22 and 24 June, Mercury passes south of Castor and Pollux, the bright stars of Gemini, and northern hemisphere viewers may be able to see them with Mercury as the sky darkens. Mercury is brighter than either. On 12 July, Mercury reaches 26.4° east of the sun.

On 9 & 10 July, Venus passes a degree north of Regulus, the bright star of Leo.

Jupiter shines very brightly in the evening and early night sky in the constellation Libra. Mid-month, it sets an hour or two after midnight, depending on your location. On the evening of 23 June, the moon is not so far north of the huge planet.

Saturn is less bright than Jupiter and Mars, but nevertheless shines brightly all night in the constellation Sagittarius. On 27 June, it comes to opposite the sun and nearest to Earth, 1354 million kilometres, or 75 light minutes away. Using binoculars or a small telescope, look for its rings, on fine display this year, and perhaps its bright moons Titan and Rhea.

Although Saturn is at its brightest at this time, the full moon is nearby on the night 27/28 June, and swamps its light somewhat. As seen from Europe, in the early hours of 28 June, the moon comes very close to Saturn, and indeed passes a degree north of the planet just after it has set in the westernmost parts of the continent. [including Cornwall]

Also in Sagittarius is the very faint dwarf planet Pluto, which comes to its own opposition on 12 July, after its closest pass to Earth on 10 July, when it is 4874 million kilometres or 4.5 light hours away. You need a fairly powerful telescope to see it.

Mars rises in the late evening, and brightens considerably during the month. It stops moving eastwards through the stars of Capricornus on 26 June, as Earth catches it up in its orbit, and makes it appear to go backwards against the background, and head that bit further south. On the night of 30 June to 1 July, the moon is north of Mars. By the end of the month, Mars is almost as bright as Jupiter.

At dark moon, there is a minor partial eclipse of the sun visible from Tasmania and the far south of Australia and New Zealand. From Hobart, maximum eclipse is at 13:25 on 13 July (03:25 UTC), when just 3.5% of the sun is covered by the moon.

The month ahead: Holly Moon 2018

13 July - 11 August 2018

Map of night sky at full moon: 27 July, 20:20 UTC
Northern hemisphere perspective, aligned on the ecliptic. Morning sky to the left, evening to the right.

night sky map for Holly Moon 2018

At full moon on 27 July, there is a total eclipse of the moon, visible from Europe, Africa, Australasia and much of Asia and South America. As seen from NW Europe and SE South America, the moon rises in total eclipse. It is a deep eclipse, with the moon near the middle of Earth’s shadow, and the moon is dark red with the small amount of sunlight refracted through Earth’s atmosphere. As seen from the moon, Earth is a ring of fire. The eclipse starts at 18:14 (17:14 UTC) when the moon enters the partial shadow of Earth, and a partial eclipse starts on the moon. At first, the change is hard to see, but gradually the moon’s eastern limb darkens (the top of the moon as it rises over eastern Europe and down across Africa to Nigeria), and the full shadow touches the edge of the moon at 19:24 (18:24 UTC). The full shadow covers the moon completely, and total eclipse starts, at 20:30 (19:30 UTC). Over London, the moon rises at 20:48, and the sun sets at 20:55. The corresponding times for Glasgow are 21:25 and 21:32 and for Penzance 21:05 and 21:11. The darkest part of the eclipse is at 21:21 (20:21 UTC), and may well be hard to see until the sun sets and the sky itself darkens. Totality ends at 22:13 (21:13 UTC), and the moon leaves the full shadow at 23:19 (22:19 UTC) and the partial (penumbral) shadow at 00:28 (23:28 UTC). As seen from Australasia and eastern Asia, the moon sets and the sun rises during the eclipse, on the morning of 28 July. This is an especially red eclipse, as the very bright red Mars is nearby, to the south of the eclipsed moon. As seen from most of Britain & Ireland, Mars rises below the totally eclipsed moon. [From Cornwall, Mars rises below the moon just before the total eclipse ends.]

The evening sky is full of bright planets, especially after Mars rises and before Venus sets.

Venus shines brightly in the western evening sky all month, albeit low down as seen from the north. At the start of the lunar month, Mercury is in the evening sky too, easily seen below Venus. On 14 July, the new crescent moon is close to Mercury, with Venus above the pair. On 15 July, the moon is between the two, nearer to Venus, and also close to Regulus, the bright star of Leo. As seen from the west coast of North America, the moon passes very close north of Venus that evening. As seen from the northern hemisphere, Mercury slips quickly into the twilight over the next few days. Southern hemisphere viewers can see Mercury above the sunset until about 29 July. Mercury passes this side of the sun on 9 August.

Round to the south, as seen from the northern hemisphere, is bright Jupiter in the constellation Libra. On the evening of 20 July, the moon is close by.

Much further round is the less bright Saturn in the constellation Sagittarius, setting in the early hours. On the night of 24/25 July, the moon is near Saturn, with the west of North America again being especially favoured with a close pass while they are above the horizon.

Mars shines very brightly in the night sky, moving westwards through the southern stars of Capricornus. On 4 July, it surpasses the brightness of Jupiter. On 27 July, it reaches opposition, rising at sunset, and on the night of 30-31 July, it is nearest to Earth, 57.6 million kilometres or 3.2 light minutes away. It is brightest on 27 or 28 July, when it is opposite the sun. The full moon is nearby on the night 27/28 July. Look for Mars during the lunar eclipse, if you’re in the right place, and see it shining red to the south of the deep red moon. After the eclipse is over, the full moon will dampen Mars’ brilliance somewhat. This is one of Mars’ closer passes to Earth. Its oppositions can come at any time of the Earth year, and the nearest ones are when it falls around 27 August on Earth, as in 2003. This is because Mars’ orbit is relatively eccentric, and a 27 August opposition coincides with Mars’ perihelion, its nearest point to the sun.

At dark moon on 11 August, there is a partial eclipse of the sun over the Arctic, much of north and NE Asia, Greenland, Iceland, most of Scandinavia and the far north of Scotland. From Reykjavík, 10% of the sun is covered at 08:46, Lerwick 1.6% and Thurso 0.3% at 09:50 (08:50 UTC), Longyearbyen 35% at 11:18 (09:18 UTC), Stockholm 0.9% at 11:10 (09:10 UTC), Moscow 0.4% at 12:35 (09:35 UTC), Yakutsk 58% at 19:15 (10:15 UTC) and Ulaanbaatar 30% at 18:40 (10:40 UTC). As seen from Beijing, the sun sets during the eclipse.

Look out for the Delta Aquarid meteors on the night 28/29 July, especially after midnight.

William Morris
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