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Scotland’s Sky in July, 2019

A partial eclipse of the Moon next to Saturn on the 16th

Sky maps looking north and south, showing the position of the main constellations at different times during the month.

The maps show the sky at 01:00 BST on the 1st, midnight on the 16th and 23:00 on the 31st. (Click on map to enlarge)

July brings a slow return to darker and longer nights as the Sun’s trek southwards continues in the wake of our summer solstice.  Until the 12th, the Sun dips no more than 12° below Edinburgh’s northern horizon so that twilight persists through every night. By the month’s end, though, we enjoy almost four hours of effective darkness and, with the Moon out of the way, the fainter stars are once again on show.

The 50th anniversary of Apollo 11’s pioneering lunar landing occurs on the 20th while, for stargazers and the weather permitting, the highlight may be the partial eclipse of the Moon which comes four days earlier on the evening of the 16th, though the Moon rises, and the Sun sets, while the eclipse is already underway.

The event begins at 19:44 BST when the Moon begins to encroach of the edge of the outer shadow of the Earth, the penumbra. Between 21:02 and midnight, part of the Moon lies within the central dark umbra where, in the absence of any direct sunlight, it is illuminated in only a dim reddish glow by sunlight refracting around the edge of the Earth. The Moon rises above Edinburgh’s south-eastern horizon at 21:44 and greatest eclipse occurs at 22:31 when the Moon stands only 8° high in the twilight with its northern 65% covered by the umbra. The eclipse ends when disk exits the penumbra at 01:18.

Sunrise/sunset times for Edinburgh change from 04:31/22:01 on the 1st to 05:14/21:23 on the 31st. New moon on the 2nd brings a total eclipse of the Sun visible along a track that crosses the south-eastern Pacific to Chile and Argentina. Surrounding areas, but not Europe, enjoy a partial eclipse. The Moon reaches first quarter on the 9th, is full at the lunar eclipse on the 16th and at last quarter on the 25th.

Saturn, the fainter of the two bright planets low down in our southern night sky, lies 8° to the right of the Moon and a little higher on the evening of the lunar eclipse. One week earlier, on the 9th, it reaches opposition in the constellation Sagittarius when it lies directly opposite the Sun so that it rises at sunset and is highest in the south in the middle of the night, albeit at an elevation of only 12°. It is also closest to us, 1,351 million km, and at its brightest at magnitude 0.1.

A telescope shows Saturn’s disk to be 18 arcseconds wide while its rings extend across 42 arcseconds and have their northern face tipped Earthwards at 24 degrees. Saturn’s globe is blanketed with clouds of ammonia crystals whose shade varies in bands running parallel to its equator. They appear much less prominent than the equivalent bands on Jupiter and there are few noticeable spots.

Jupiter, itself, lies in southern Ophiuchus some 31° to the right of Saturn and far outshines its neighbour even though it dims slightly in July from magnitude -2.6 to -2.4 as its distance grows from 649 million to 691 million km. It lies just below the bright Moon on evening of the 13th when a telescope shows its disk to be 44 arcseconds wide.

The previous evening, the 12th, would be an opportune time to check out Jupiter’s Red Spot which, as I mentioned last time, appears to have been spooling some of its reddish material into its adjacent cloud belt. It is certainly measurably smaller than it was just a few weeks ago but there are also signs that the disturbance may have subsided.

The other naked eye planets are poorly placed. The brightest, magnitude -3.9 Venus, rises 50 minutes before the Sun and stands less than 5° high in the north-east at sunrise. Mercury stands 4° to the left of Mars in the west-north-west during the hour after sunset on the 1st but both are too dim, at magnitudes of 1.2 and 1.8 respectively, to be glimpsed in our bright twilight.

Mars is edging towards the Sun’s far side and reappears before dawn in October. Mercury reaches inferior conjunction between the Sun and the Earth on the 21st when it passes 5° south of the Sun on its way to our morning sky in August. When Mercury next reaches inferior conjunction, on 11 November, it passes almost centrally across the Sun’s disk in a transit that we hope to witness from Scotland.

Our charts show Jupiter and Saturn low down in our southern sky while the star Vega, only slightly brighter than Saturn, crosses the meridian high above them. Vega, of course, forms the Summer Triangle with Deneb in Cygnus, high in the east, and Altair, lower in Aquila. Our map projection squashes the Triangle somewhat – in fact, Deneb and Vega are closer together in the sky than is either star to Altair. An even larger triangle, this one almost equilateral, fills our south-western sky and has its corners at Vega, Jupiter and Arcturus, which lies due west as the leading star of Bootes.

Capella in Auriga stands at its lowest below Polaris in the north and often features in images of noctilucent clouds or NLCs. Little did I realise when I mentioned these silvery-blue “night-shining” clouds last time that 2019 was to unleash some of our best NLC displays in decades. Formed by ice condensing on high-altitude dust particles, some perhaps debris from meteors, they catch the sunlight when our usual lower-level clouds are in darkness during the middle hours of our nights. Researchers are investigating why this should be such a special year for NLCs but expect the bonanza to continue into August.

Diary for 2019 July

Times are BST

2nd           20h New moon and total solar eclipse

4th           23h Earth farthest from Sun (152,100,000 km)

6th           04h Moon 3° N of Regulus

7th           15h Mercury 4° S of Mars

9th           12h First quarter

9th           18h Saturn at opposition at distance of 1,351 million km

13th         21h Moon 2.3° N of Jupiter

16th         08h Moon 0.2° S of Saturn

16th         23h Full moon and partial lunar eclipse

20th         21h 50th anniversary of first manned lunar landing

21st          14h Mercury in inferior conjunction

24th         00h Mercury furthest E of Sun (25°)

25th         02h Last quarter

28th         02h Moon 2.3° N of Aldebaran

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on June 29th 2019, with thanks to the newspaper for permission to republish here.
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Scotland’s Sky in June, 2019

Is Jupiter’s Great Red Spot unfurling before our eyes?

Sky maps looking north and south, showing the position of the main constellations at different times during the month.

The maps show the sky at 01:00 BST on the 1st, midnight on the 16th and 23:00 on the 30th. (Click on map to enlarge)

The Sun reaches its most northerly point at 16:54 BST on the 21st, marking the summer solstice in our northern hemisphere. Between its setting in the north-west and its rising in the north-east, it follows only a shallow arc below Edinburgh’s horizon and stands, at most, 10.6° below Edinburgh’s due-north horizon at 01:14 BST. As a result, twilight persists throughout our June nights and we must stay up late to glimpse even the brighter stars and planets.

The sunrise/sunset times for Edinburgh change from 04:36/21:46 BST on the 1st, to 04:26/22:03 on the 21st and 04:30/22:02 on the 30th. The Moon is new on the 3rd, at first quarter on the 10th, full on the 17th and at last quarter on the 25th.

At times like these, some stargazers forsake their hobby for a couple of months while others switch to observing the Sun, or, perhaps, noctilucent clouds. This June, though, the giant planet Jupiter is well worth a look as it comes to opposition on the 10th. It is then closest to us (641 million km) and stands directly opposite the Sun, so that it rises in the south-east at sunset and passes (for Edinburgh) less than 12° high in the south in the middle of the night.

Conspicuous at magnitude -2.6 as it creeps westwards against the stars of southern Ophiuchus, Jupiter outshines every other object in our night sky except for the Moon which lies close to it on the night of the 16th-17th. A small telescope or good steadily-held binoculars reveal its four main moons, the Galilean moons, as they orbit from east to west of the planet in periods that range from 1.8 days for Io to 16.7 days for Callisto. Jupiter has more moons, 79 at the latest count, than any other planet, with Saturn’s tally of 62 coming second. Jupiter’s 75 lesser moons, though, are too small and dim to be spotted using any but the largest telescopes.

Jupiter’s globe is shrouded in clouds, mainly of ammonia crystals but tinted red and brown by other compounds which may include hydrocarbons. Telescopes show bands of darker cloud and a plethora of streaks and spots that transit smartly across the disk as the planet rotates in its sub-ten-hour day.

The most famous feature, the Great Red Spot, is an anticyclonic storm that may be more than 300 years old and was once larger than three Earths. It has shrunk significantly over the last century but observations over the past two weeks suggest something startling may be afoot and even that the spot may be disintegrating. It appears that 10,000-km-long streamers of reddish gas, perhaps methane-rich, are peeling away from the spot into the adjacent cloud band, the South Equatorial Belt, that circles the planet. Likened by some to the spot unfurling, nothing on this scale has been seen before so it is just as well that NASA’s Juno probe has a ring-side view as it orbits Jupiter.

Some 30° to the east of Jupiter, below the so-called Teaspoon of Sagittarius, is our Sun’s other gas giant planet, Saturn. Rising in the south-east about one hour before our map times, it brightens slightly from magnitude 0.3 to 0.1 to rival the two brightest stars on our south map – Vega in Lyra which stands very high in the east-south-east and Arcturus in Bootes in the middle of our south-western sky. When Saturn lies just left of the Moon on the night of the 18th, it lies 1,361 million km away and a telescope shows its disk and rings to span 18 and 41 arcseconds respectively.

The constellations of Ophiuchus and Hercules sprawl across the meridian at the map times, though our twilight means that this is not the best month for spotting M13, the Great Globular Cluster in Hercules (see map). Discovered by Edmond Halley of comet fame in 1714, this ball of hundreds of thousands of stars is some 160 light years across, 22,200 light years away and is thought to have formed 11.65 billion years ago. Under the best conditions, binoculars show it as a fuzzy circular patch around two-thirds as wide as the Moon.

Although Venus is brilliant at magnitude -3.9, it rises in the north-east around 40 minutes before the Sun and is unlikely to be noticed in Scotland’s dawn twilight. Mars is now as dim as magnitude 1.8 and becoming much harder to spot low down in our north-western evening twilight. Tracking eastwards in Gemini to pass below Castor and Pollux, it sets for Edinburgh at 00:05 BST on the 5th when it is 4° to the right of the slender young earthlit Moon. Mercury, much easier at magnitude -0.7, lies 11° below-right of Mars at that time and is 4° above the horizon one hour after sunset between the 5th and 19th. Mercury passes 0.2° above Mars on the 18th and stands furthest east of the Sun (25°) on the 24th.

Scotland’s noctilucent cloud season is just beginning and we can look forward to occasional displays of these “night-shining” clouds until August. Often with a bluish-white sheen, they may appear as wisps, streaks and whirls and merge into banks with cirrus-like herring-bone patterns. The clouds are formed when ice crystallises on dust particles in a narrow range of altitudes near 82 km. Here they are high enough to catch the sun’s light when our more typical lower-level terrestrial clouds are in darkness, from, say, one hour after sunset until one hour before sunrise. They rarely reach more than 20° above the horizon and favour directions towards the north-west at nightfall shifting to the north-east before dawn.

Diary for 2019 June

Times are BST

3rd           11h New moon

4th           17h Moon 4° S of Mercury

5th           16h Moon 1.6° S of Mars

7th           09h Moon 0.5° N of Praesepe

8th           21h Moon 3° N of Regulus

10th         07h First quarter

10th         16h Jupiter at opposition at distance of 641 million km

16th         20h Moon 2.0° N of Jupiter

17th         10h Full moon

18th         16h Mercury 0.2° N of Mars

19th         05h Moon 0.4° S of Saturn

21st          16:54 Summer solstice

24th         00h Mercury furthest E of Sun (25°)

25th         11h Last quarter

30th         17h Moon 2.3° N of Aldebaran

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on May 31st 2019, with thanks to the newspaper for permission to republish here.

Scotland’s Sky in May, 2019

Giant world Jupiter becoming obvious in May’s twilit nights

Sky maps looking north and south, showing the position of the main constellations at different times during the month.

The maps show the sky at 01:00 BST on the 1st, midnight on the 16th and 23:00 on the 31st. (Click on map to enlarge)

With its lengthening days and increasingly twilit nights, May is hardly a vintage month for stargazing from Scotland’s latitudes. Official (nautical) darkness for Edinburgh lasts for more than five hours around midnight as the month begins but dwindles to nothing by the start of June and does not return until 12 July

Edinburgh’s sunrise/sunset times change from 05:30/20:51 on the 1st to 04:37/21:45 on the 31st, while the Moon is new on the 4th, at first quarter on the 12th, full on the 18th and at last quarter on the 26th.

Our charts show Leo diving westwards as the Summer Triangle formed by Vega, Altair and Deneb is climbing in the east. After the Moon, our most obvious nighttime object is the planet Jupiter which rises in the south-east 30 minutes before our map times and reaches less than 12° high in the south before dawn. In fact, look for the Moon above-right of Jupiter on the night of the 19th and closer to the planet’s left on the 20th.

The giant world is now edging westwards against the stars of southern Ophiuchus and brightens from magnitude -2.4 to -2.6 as its distance falls from 678 million to 644 million km. The Jovian globe spans 45 arcseconds in mid-May and telescopes show that it is crossed by bands of cloud that lie parallel to its equator. The four principal moons of Jupiter are also easy targets, though sometimes one or more hide from view as they pass in front of, or behind, the disk or are eclipsed in Jupiter’s shadow.

Saturn trails almost two hours behind Jupiter but is fainter at magnitude 0.5 to 0.3. It lies in Sagittarius, below the Teaspoon asterism, where it stands above the Moon but low down in the south-south-east before dawn on the 23rd. Always an impressive sight through a telescope, though not helped by its low altitude, its disk appears 18 arcseconds wide at mid-month, circled by rings that measure 40 by 16 arcseconds.

Mercury and Venus are too deep in the morning twilight to be seen at present, though Mercury slips around the Sun’s far side on the 21st. The morning twilight also hinders views of the Eta-Aquarids meteor shower which peaks around the 6th-7th and brings swift meteors that stream from a point which hovers low in our east-south-eastern sky for two hours before sunrise.

Mars sets a few minutes before our star map times and may be hard to spot low down in our west-north-western evening sky. It stands between the horns of Taurus on the 1st and shines at magnitude 1.6 to rival the star Elnath, which lies 5° above Mars and marks the tip of the Bull’s northern horn.

Mars’ pinkish-orange hue is best appreciated through binoculars as the planet dims further to magnitude 1.8 and speeds 20° eastwards during May, crossing into Gemini at mid-month and sweeping only 0.2° north of the star cluster M35 (use binoculars) on the 19th. It recedes from 335 million to 363 million km during May but, at a mere 4 arcseconds in diameter, is too small to be of telescopic interest. Catch Mars above the slim earthlit Moon on the 7th.

NASA’s InSight lander used its sensitive French-built seismometer to detect its first likely marsquake on 6 April. The faint vibrations are now being studied for clues as to Mars’ interior. Another instrument, a German heat probe designed to drill up to five metres into the surface, seems to have encountered a rock and is currently stalled well short of its target depth.

The Plough looms directly overhead at nightfall and stands high in the west by our map times. If we extend a curving line along its handle, we reach the prominent star Arcturus which, at magnitude -0.05, is the brightest of all the stars in the sky’s northern hemisphere and, after Sirius, the second brightest (nighttime) star visible from Scotland, although both Vega and Capella come close.

Classed officially as a red giant star, though more yellow-orange in hue, Arcturus is slightly more massive than our Sun and perhaps 50% older. As such, it has depleted the hydrogen used to power its core through nuclear fusion, progressed to fusing helium instead and inflated to 25 times the Sun’s radius and 170 times its luminosity. Eventually, after shedding its outer layers, it will settle down as a dim white dwarf star comparable in size to the Earth.

At present, though, we admire it as the leading star in the constellation of Bootes which has been likened to a pale imitation of Orion or even an ice-cream cone. Bootes takes its name from the Greek for herdsman or plowman, apparently in relation to the seven stars of the Plough which were also known as the “Seven Oxen” in early times.

Arcturus’ own name comes from the Greek for “guardian of the bear”, another reference to its role in following Ursa Major across the sky. In truth, it is something of a temporary guardian since it is rushing past our solar system at 122 km per second at a distance of 36.7 light years and will likely fade from naked-eye view within (only) half a million years as it tracks south-westwards in the direction of Virgo and the bright star Spica.

It is in the north of Virgo, and roughly coincident with the “D” of the label for Denebola on our south star map, that we find the galaxy M87, the owner of the supermassive black hole whose image was released a few weeks ago. M87 is 54 million light years away and visible as a smudge in small telescopes.

Diary for 2019 May

Times are BST

5th           00h New moon

6th           15h Peak of Eta-Aquarids meteor shower

6th           23h Moon 2.3° N of Aldebaran

8th           01h Moon 3° S of Mars

11th         03h Moon 0.3° N of Praesepe

12th         02h First quarter

12th         16h Moon 3° N of Regulus

18th         22h Full moon

19th         18h Mars 0.2° N of star cluster M35 in Gemini

20th         18h Moon 1.7° N of Jupiter

21st          14h Mercury in superior conjunction

22nd         23h Moon 0.5° S of Saturn

26th         18h Last quarter

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on April 30th 2019, with thanks to the newspaper for permission to republish here.

Scotland’s Sky in April, 2019

Galaxy clusters of interest in April’s southern evening sky

The maps show the sky at midnight BST on the 1st, 23:00 on the 16th and 22:00 on 30th. An arrow depicts the motion of Mars. (Click on map to enlarge)

The maps show the sky at midnight BST on the 1st, 23:00 on the 16th and 22:00 on 30th. An arrow depicts the motion of Mars. (Click on map to enlarge)

Orion stands in the south-west at nightfall as the sparkling skies of winter give way to the less flamboyant constellations of spring, led by Leo and Virgo. By our map times, Orion has mostly set the west and the Milky Way arcs only some 30° above Edinburgh’s north-western horizon as it flows between Auriga and the “W” formation of Cassiopeia.

The Milky Way, of course, marks the plane of our disk-shaped galaxy, itself dubbed the Milky Way, around which our Sun orbits every 240 million years. If we look along it, we encounter numerous distant stars but countless more are forever hidden from sight behind intervening clouds of gas and dust – the raw material from which new stars and planets may eventually coalesce. If we gaze in directions away from the plane of the Milky Way, though, the star numbers fall away and there is negligible gas and dust to hide our view of galaxies far beyond our own.

It follows that we might expect our best view of the distant universe to be in directions at right angles to the plane, towards the galactic poles. Regions around the North Galactic Pole are ideally placed in our April evening sky and host some of the most interesting clusters of galaxies in the entire sky.

The pole itself lies in the less-than-startling Coma Berenices which is approaching the high meridian at our map times. As the only modern constellation named for a historic person, this celebrates Queen Berenice II of Egypt who is said to have sacrificed her long hair as an offering to Aphrodite. Her tresses are represented by a cascade of stars that spill southwards through the “M” of “COMA” on the chart. These make up a dispersed but nearby star cluster at a distance of about 280 light years – the second closest star cluster after the Hyades in Taurus.

Roughly coincident with the “C” of “COMA” is another cluster, but this one of more than 1,000 galaxies at a distance of some 320 million light years. The Coma Cluster’s brightest galaxies are only around the twelfth magnitude and, as such, a challenge for many amateur telescopes. It was by studying this cluster that the Swiss astronomer Fritz Zwicky uncovered evidence as long ago as 1933 for the existence of what we now call dark matter. He found its galaxies were simply moving too fast to be held together unless addition material was present to supply an extra gravitational pull. Now we suspect that up to 90% of the Coma Cluster consists of this still-mysterious dark matter.

Lying south of Coma Berenices, and about 9° to the east (left) of Leo’s star Denebola, is the closer Virgo Cluster of galaxies. This sprawls across 8° of sky and holds about 1,500 galaxies at a distance of 54 million light years or so. Small telescopes show several, though we’d struggle to locate them without a better chart than I can supply here. In fact, The Virgo Cluster lies at the heart of a much larger family of galaxies and galaxy clusters dubbed the Virgo Supercluster which includes the so-called Local Group of galaxies in which the Milky Way is a major player. The Coma Cluster rules another supercluster.

Edinburgh’s sunrise/sunset times change from 06:44/19:50 BST on the 1st to 05:32/20:49 on the 30th as the Moon stands at new on the 5th, first quarter on the 12th, full on the 19th and last quarter on the 26th. As I mentioned last time, satellites may now be spotted at any time of night though the current spell of evening passes by the International Space Station ends on or about the 5th.

Mars stands some 30° high and alongside the Pleiades in our western sky as our nights begin at present. The planet, though, is tracking east-north-eastwards against the stars and passes north of Taurus’ main star, Aldebaran, to lie between the Bull’s horns later in the month. The young earthlit Moon is an impressive sight 9° below Mars on the 8th and stands above Aldebaran and to the left of Mars on the 9th.

Mars no longer glares like an orange beacon in our sky and is now only half as bright as Aldebaran. As its distance grows from 302 million to 335 million km in April, it dims a little more from magnitude 1.5 to 1.6. Even large telescopes reveal little detail on its small ochre disk, less than 5 arcseconds in diameter, and viewing conditions can only deteriorate as it sinks towards the north-western horizon where it sets in the middle of the night.

There are two brighter planets in our predawn sky, both of them low in the south to south-east as the Summer Triangle formed by Vega, Deneb and Altair climbs through the east.

Jupiter, conspicuous at magnitude -2.2 to -2.5, rises in the south-east less than three hours after our map times and stands 11° above Edinburgh’s southern horizon before dawn. Slow-moving in southern Ophiuchus, it reaches a stationary point on the 10th when its motion appears to reverse from easterly to westerly as it begins to be overtaken by the Earth. Saturn, rather fainter at magnitude 0.6 to 0.5 and at its own stationary point on the 30th, lies in Sagittarius some 25° to Jupiter’s left. Catch the Moon near Jupiter on the 23rd and Saturn on the 25th.

Although Venus is brilliant at magnitude -4.0, it rises in the east less than 38 minutes before sunrise and is unlikely to be noticed. Mercury is furthest west of the Sun (28°) on the 11th but is much fainter and lower still in the morning twilight.

Diary for 2019 April

Times are BST

2nd           05h Moon 2.7° S of Venus

3rd            00h Moon 4° S of Mercury

5th           10h New moon

9th           08h Moon 5° S of Mars

9th           17h Moon 2.1° N of Aldebaran

10th         18h Jupiter stationary (motion reverses from E to W)

11th         21h Mercury furthest W of Sun (28°)

12th         20h First quarter

13th         22h Moon 0.1° N of Praesepe

15th         10h Moon 2.8° N of Regulus

16th         23h Mars 7° N of Aldebaran

19th         12h Full moon

23rd         00h Uranus in conjunction with Sun

23rd         13h Moon 1.6° N of Jupiter

25th         15h Moon 0.4° S of Saturn

26th         23h Last quarter

30th         03h Saturn stationary (motion reverses from E to W)

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on March 30th 2019, with thanks to the newspaper for permission to republish here.

Scotland’s Sky in March, 2019

Watch earth satellites transit our vernal equinox sky

The maps show the sky at 23.00 GMT on the 1st, 22.00 GMT on the 16th and 21.00 GMT (22.00 BST) on the 31st. Summer time begins at 01.00 GMT on the 31st when clocks go forward one hour to 02.00 BST. An arrow depicts the motion of Mars from the 7th. (Click on map to enlarge)

The maps show the sky at 23.00 GMT on the 1st, 22.00 GMT on the 16th and 21.00 GMT (22.00 BST) on the 31st. Summer time begins at 01.00 GMT on the 31st when clocks go forward one hour to 02.00 BST. An arrow depicts the motion of Mars from the 7th. (Click on map to enlarge)

The Sun climbs northwards at its fastest for the year in March and crosses the sky’s equator at 21:58 on the 20th, the time of our vernal or spring equinox. As the days lengthen rapidly, the stars in the evening sky appear to drift sharply westwards so that Orion, which is astride the meridian as the night begins on the 1st, stands 45° over in the south-west by nightfall on the 31st.

Another consequence of the Sun’s motion is that the Earth’s shadow, on the night side of the planet, is tilting increasingly southwards so that it no longer reaches so far above Scotland at midnight. Indeed, by the end of March the shadow is shallow enough that satellites passing a few hundred kilometres above our heads may be illuminated by the Sun at any time of night. This allows them to appear as moving points of light against the stars as they take a few minutes to cross the sky. Some are steady in brightness while others pulsate or flash as they tumble or spin in orbit.

Dozens of satellites are naked-eye-visible every night, while many times this number may be glimpsed through binoculars. Predictions of when and where to look, including plots of their tracks against the stars, may be obtained online for free, or example from heavens-above.com, or via smartphone apps. Of particular interest are the so-called Iridium satellites which can outshine every other object in the sky, bar the Sun and Moon, during brief flares when their orientation to the Sun and the observer is just right. Although online predictions also include these, Iridium flares are falling rapidly in frequency since the satellites responsible are being deorbited as they are replaced by 2nd generation (and non-flaring) craft.

The most obvious steadily-shining satellite is, of course, the International Space Station which can outshine Sirius as it transits up to 40° high from west to east across Edinburgh’s southern sky. As it orbits the Earth every 93 minutes at a height near 405 km, it is visible before dawn until about the 15th and begins a series of evening passes a week later.

Sunrise/sunset times for Edinburgh change from 07:05/17:46 GMT on the 1st to 05:47/18:48 GMT (06:47/19:48 BST) on the 31st which is the day that we set our clocks to British Summer Time.

The Moon is new on the 6th and spectacular over the following days as its brightly earthlit crescent stands higher each evening in the west-south-west. Catch the Moon 12° below Mars on the 10th and 6° below and left of the planet on the 11th. Mars itself stands around 30° high in the west-south-west at nightfall and is well to the north of west when it sets before midnight. This month it dims from magnitude 1.2 to 1.4 as it speeds more than 20° north-eastwards from Aries into Taurus to end the period only 3° below-left of the Pleiades.

Mercury has been enjoying its best spell of evening visibility this year, but is now fading rapidly and may be lost from view by the 7th. Binoculars show it shining at magnitude 0.1 on the 1st as it stands 10° directly above the sunset position forty minutes after sunset.

The Moon and planets never stray far from the ecliptic, the line around the sky that traces the apparent path of the Sun during our Earth’s orbit. The ecliptic slants steeply across our south-west at nightfall towards the Sun’s most northerly point which it reaches to the north of Orion at our summer solstice in June.

Given a clear dark evening, this is the best time of year to spy a broad cone of light stretching along the ecliptic from the last of the fading twilight. Dubbed the zodiacal light, this glow comes from sunlight scattering from interplanetary dust particles and was the subject on which Brian May, the lead guitarist of Queen, gained his doctorate.

As the Moon continues around the sky, it reaches first quarter on the 14th and passes just north of the star Regulus in Leo on the night of the 18/19th. Regulus, 45° high on Edinburgh’s meridian at our map times, lies less than a Moon’s breadth above the ecliptic and marks the handle of the Sickle of Leo.

Algieba in the Sickle is a splendid binary whose contrasting orange and yellow component stars lie 4.7 arcseconds apart and may be separated telescopically as they orbit each other every 510 years or so. The larger of the pair has at least one companion which may be a planet much larger than Jupiter or, perhaps, a brown dwarf star.

Between full moon on the 21st and last quarter on the 28th, the Moon passes very close to the conspicuous planet Jupiter on the 27th. The giant planet rises in the south-east in the small hours and is unmistakable at magnitude -2.0 to -2.2 low in the south before dawn where it is creeping eastwards against the stars of southern Ophiuchus.

The red supergiant star Antares in Scorpius lies some 13° to the right of Jupiter while Saturn, fainter at magnitude 0.6, is twice this distance to Jupiter’s left and lower in the twilight. Look for Saturn to the Moon’s left on the 1st and just above the Moon on the 29th.

Venus is brilliant (magnitude -4.1) but becoming hard to spot very low down in our morning twilight. More than 10° to the left of Saturn as the month begins and rushing further away, it rises in the south-east 81 minutes before sunrise tomorrow and only 39 minutes before on the 31st.

Diary for 2019 March

1st           18h Moon 0.3° N of Saturn

2nd          21h Moon 1.2° S of Venus

6th           16h New moon

7th           01h Neptune in conjunction with Sun

11th         12h Moon 6° S of Mars

13th         11h Moon 1.9° N of Aldebaran

14th         10h First quarter

15th         02h Mercury in inferior conjunction

17th         13h Moon 0.1° S of Praesepe

19th         00h Moon 2.6° N of Regulus

20th         21:58 Vernal equinox

21st         02h Full moon

27th         02h Moon 1.9° N of Jupiter

28th         04h Last quarter

29th         05h Moon 0.1° S of Saturn

30th         10h Mars 3° S of Pleiades

31st         01h GMT = 02h BST Start of British Summer Time

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on February 28th 2019, with thanks to the newspaper for permission to republish here.

Scotland’s Sky in February, 2019

Orion and Winter Hexagon in prime-time view

The maps show the sky at 22:00 GMT on the 1st, 21:00 on the 15th and 20:00 on the 28th. An arrow depicts the motion of Mars. (Click on map to enlarge)

The maps show the sky at 22:00 GMT on the 1st, 21:00 on the 15th and 20:00 on the 28th. An arrow depicts the motion of Mars. (Click on map to enlarge)

Even though the two brightest planets, Venus and Jupiter, hover low in the south-east before dawn, the shortest month brings what many consider to be our best evening sky of the year. After all, the unrivalled constellation of Orion is in prime position in the south, passing due south for Edinburgh one hour before our star map times. Surrounding it, and ideally placed at a convenient time for casual starwatchers, are some of the brightest stars and interesting groups in the whole sky.

I mentioned some of the sights in and around Orion last time, including the bright stars Procyon, Betelgeuse and Sirius which are prominent in the south at the map times and together form the Winter Triangle.

Like the Summer Triangle, this winter counterpart is defined as an asterism which is a pattern of stars that do not form one of the 88 constellations recognised by the International Astronomical Union. Both triangles are made up of stars in different constellations, but we also have asterisms that lie entirely within a single constellation, as, for example, the Sickle of Leo which curls above Regulus in the east-south-east at our map times, and the Plough which comprises the brighter stars of the Ursa Major, the Great Bear, climbing in the north-east.

Yet another asterism, perhaps the biggest in its class, includes the leading stars of six constellations and re-uses two members of the Winter Triangle. The Winter Hexagon takes in Sirius, Procyon, Pollux in Gemini and Capella in Auriga which lies almost overhead as Orion crosses the meridian. From Capella, the Hexagon continues downwards via Aldebaran in Taurus and Rigel at Orion’s knee back to Sirius.

Edinburgh’s sunrise/sunset times change from 08:08/16:45 on the 1st to 07:07/17:44 on the 28th. The Moon is new on the 4th and at first quarter on the 12th when it stands 12° below the Pleiades in our evening sky. The 13th sees it gliding into the Hyades, the V-shaped star cluster that lies beyond Aldebaran. Both the Pleiades and the Hyades are open clusters whose stars all formed at the same time. Another fainter cluster, Praesepe or the Beehive in Cancer, is visible through binoculars to the left of the Moon late on the 17th. Full moon is on the 19th with last quarter on the 26th.

A number of other open star clusters lie in the northern part of the Hexagon, two of them plotted on our chart. At the feet of Gemini and almost due north of Betelgeuse is M35, visible as a smudge to the unaided eye but easy though binoculars and telescopes which begin to reveal its brighter stars. It lies 3,870 ly (light years) away, as compared with 440 ly for the Pleiades and 153 ly for the Hyades. Further north in Auriga is the fainter M37 (4,500 ly) which binoculars show 7° north-east of Elnath, the star at the tip of the upper horn of Taurus. M36 (4,340 ly) and M38 (3,480 ly) lie from 4° and 6° north-west of M37.

Mars dims a little from magnitude 0.9 to 1.2 but remains the brightest object near the middle of our south-south-western evening sky, sinking westwards to set before midnight. Mars is 241 million km distant when it stands above the Moon on the 10th, with its reddish 5.8 arcseconds disk now too small to show detail through a telescope. As it tracks east-north-eastwards against the stars, it moves from Pisces to Aries and passes 1° above-right of the binocular-brightness planet Uranus (magnitude 5.8) on the 13th.

The usually elusive planet Mercury begins its best evening apparition of 2019 in the middle of the month as it begins to emerge from our west-south-western twilight. Best glimpsed through binoculars, it stands between 8° and 10° high forty minutes after sunset from the 21st and sets itself more than one hour later still. It is magnitude -0.3 on the 27th when it lies furthest from the Sun in the sky, 18°, and its small 7 arcseconds disk appears 45% illuminated.

Venus, brilliant at magnitude 4.3, rises for Edinburgh at 05:11 on the 1st and stands 8° high by 06:30 as twilight begins to invade the sky. That morning also finds it 6° above and right of the waning earthlit Moon. A telescope shows Venus to be 19 arcseconds in diameter and 62% sunlit.

Jupiter is conspicuous 9° to the right of, and slightly above, Venus on the 1st though it is one ninth as bright at magnitude -1.9. Larger and more interesting through a telescope, its 34 arcseconds disk is crossed by bands of cloud running parallel to its equator while its four main moons may be glimpsed through binoculars. Edging eastwards (to the left) in southern Ophiuchus, it is 9° east of the celebrated and distinctly red supergiant star Antares in Scorpius, a star so big that it would engulf the Earth and Mars if it switched places with our Sun.

Our third predawn planet, Saturn rises at 06:38 on the 1st and is more of a challenge being fainter (magnitude 0.6) in the twilight. One hour before Edinburgh’s sunrise on the 2nd, it lies only 2° above the horizon and less than 10 arcminutes above-right of the Moon’s edge. Watchers in south-eastern England see it slightly higher and may glimpse it emerge from behind the Moon at about 06:31.

Venus speeds eastwards through Sagittarius to pass 1.1° north of Saturn on the 18th and shine at magnitude -4.1 even lower in the morning twilight by the month’s end. By then, the Moon has come full circle to stand above-right of Jupiter on the 27th and to Jupiter’s left on the 28th.

Diary for 2019 February

2nd          07h Moon 0.6° N of Saturn

4th           21h New moon

10th         16h Moon 6° S of Mars

12th         22h First quarter

13th         20h Mars 1.1° N of Uranus

14th         04h Moon 1.7° N of Aldebaran

18th         03h Moon 0.3° S of Praesepe

18th         14h Venus 1.1° N of Saturn

19th         13h Moon 2.5° N of Regulus

19th         16h Full moon

26th         11h Last quarter

27th         01h Mercury furthest E of Sun (18°)

27th         14h Moon 2.3° N of Jupiter

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on January 31st 2019, with thanks to the newspaper for permission to republish here.

Scotland’s Sky in January, 2019

Rise early for a total lunar eclipse on the 21st

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 31st. An arrow depicts the motion of Mars. (Click on map to enlarge)

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 31st. An arrow depicts the motion of Mars. (Click on map to enlarge)

Any month that has the glorious constellation of Orion in our southern evening sky is a good one for night sky aficionados. Add one of the best meteor showers of the year, a total eclipse of the Moon, a meeting between the two brightest planets and a brace of space exploration firsts and we should have a month to remember

Orion rises in the east as darkness falls and climbs well into view in the south-east by our star map times. Its two leading stars are the blue-white supergiant Rigel at Orion’s knee and the contrasting red supergiant Betelgeuse at his opposite shoulder – both are much more massive and larger than our Sun and around 100,000 times more luminous.

Below the middle of the three stars of Orion’s Belt hangs his Sword where the famous and fuzzy Orion Nebula may be spied by the naked eye on a good night and is usually easy to see through binoculars. One of the most-studied objects in the entire sky, it lies 1,350 light years away and consists of a glowing region of gas and dust in which new stars and planets are coalescing under gravity.

The Belt slant up towards Taurus with the bright orange giant Aldebaran and the Pleiades cluster as the latter stands 58° high on Edinburgh’s meridian. Carry the line of the Belt downwards to Orion’s main dog, Canis Major, with Sirius, the brightest star in the night sky. His other dog, Canis Minor, lies to the east of Orion and is led by Procyon which forms an almost-equilateral triangle with Sirius and Betelgeuse – our so-called Winter Triangle.

The Moon stands about 15° above Procyon when it is eclipsed during the morning hours of the 21st. The event begins at 02:36 when the Moon lies high in our south-western sky, to the left of Castor and Pollux in Gemini, and its left edge starts to enter the lighter outer shadow of the Earth, the penumbra.

Little darkening may be noticeable until a few minutes before it encounters the darker umbra at 03:34. Between 04:41 and 05:46 the Moon is in total eclipse within the northern half of the umbra and may glow with a reddish hue as it is lit by sunlight refracting through the Earth’s atmosphere. The Moon finally leaves the umbra at 06:51 and the penumbra at 07:48, by which time the Moon is only 5° high above our west-north-western horizon in the morning twilight.

This eclipse occurs with the Moon near its perigee or closest point to the Earth so it appears slightly larger in the sky than usual and may be dubbed a supermoon. Because the Moon becomes reddish during totality, there is a recent fad for calling it a Blood Moon, a term which has even less of an astronomical pedigree than supermoon. Combine the two to get the frankly ridiculous description of this as a Super Blood Moon.

Sunrise/sunset times for Edinburgh change from 08:44/15:49 on the 1st to 08:10/16:43 on the 31st. New moon early on the 6th, UK time, brings a partial solar eclipse for areas around the northern Pacific. First quarter on the 14th is followed by full moon and the lunar eclipse on the 21st and last quarter on the 27th.

The Quadrantids meteor shower is active until the 12th but is expected to peak sharply at about 03:00 on the 4th. Its meteors, the brighter ones leaving trains in their wake, diverge from a radiant point that lies low in the north during the evening but follows the Plough high into our eastern sky before dawn. With no moonlight to hinder observations this year, as many as 80 or more meteors per hour might be counted under ideal conditions.

Mars continues as our only bright evening planet though it fades from magnitude 0.5 to 0.9 as it recedes. Tracking through Pisces and well up in the south at nightfall, it stands above the Moon on the 12th. Our maps show it sinking in the south-west and it sets in the west before midnight.

Venus, its brilliance dimming only slightly from magnitude -4.5 to -4.3, stands furthest west of the Sun (47°) on the 6th and is low down (and getting lower) in our south-eastern predawn sky. Look for it below and left of the waning Moon on the 1st with the second-brightest planet, Jupiter at magnitude -1.8, 18° below and to Venus’s left. As Venus tracks east-south-eastwards against the stars, it sweeps 2.4° north of Jupiter in an impressive conjunction on the morning of the 22nd while the 31st finds it 8° left of Jupiter with the earthlit Moon directly between them.

Saturn, magnitude 0.6, might be glimpsed at the month’s end when it rises in the south-east 70 minutes before sunrise but Mercury is lost from sight is it heads towards superior conjunction on the Sun’s far side on the 30th.

China hopes that its Chang’e 4 spacecraft will be the first to touch down on the Moon’s far side, possibly on the 3rd. Launched on December 7 and named for the Chinese goddess of the Moon, it needs a relay satellite positioned beyond the Moon to communicate with Earth.

Meantime, NASA’s New Horizons mission is due to fly within 3,500 km of a small object a record 6.5 billion km away when our New Year is barely six hours old. Little is known about its target, dubbed Ultima Thule, other than that it is around 30 km wide and takes almost 300 years to orbit the Sun in the Kuiper Belt of icy worlds in the distant reaches of our Solar System.

Diary for 2019 January

1st            06h New Horizons flyby of Ultima Thule

1st            22h Moon 1.3° N of Venus

2nd          06h Saturn in conjunction with Sun

3rd           05h Earth closest to Sun (147,100,000 km)

3rd           08h Moon 3° N of Jupiter

4th           03h Peak of Quadrantids meteor shower

6th           01h New moon and partial solar eclipse

6th           05h Venus furthest W of Sun (47°)

12th         20h Moon 5° S of Mars

14th         07h First quarter

17th         19h Moon 1.6° N of Aldebaran

21st         05h Full moon and total lunar eclipse

21st         16h Moon 0.3° S of Praesepe

22nd        06h Venus 2.4° N of Jupiter

23rd         02h Moon 2.5° N of Regulus

27th         21h Last quarter

30th         03h Mercury in superior conjunction

31st         00h Moon 2.8° N of Jupiter

31st         18h Moon 0.1° N of Venus

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on December 31st 2018, with thanks to the newspaper for permission to republish here.

Scotland’s Sky in December, 2018

Comet sweeps near Earth as meteors streak from Gemini

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 31st. Also indicated are the motions of both Mars and Comet Wirtanen. (Click on map to enlarge)

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 31st. Also indicated are the motions of both Mars and Comet Wirtanen. (Click on map to enlarge)

December brings our longest and perhaps most interesting nights of the year. The two stand-out planets are Mars in the evening and Venus before dawn, the latter now as brilliant as it ever gets and the source of a flurry of recent UFO reports. We may also enjoy the rich and reliable Geminids meteor shower and Comet Wirtanen looks set to be the brightest comet of the year.

The comet’s progress is plotted on our charts, beginning low in the south near the Cetus-Eridanus border on the 1st and sweeping northwards and eastwards through Taurus to Auriga and beyond. A small comet with an icy nucleus possibly less than 1 km wide, Wirtanen was discovered in 1948 and orbits the Sun every 5.4 years between the Earth and Jupiter. It was the original destination of the European Space Agency’s Rosetta mission before delays forced the probe to target Comet Churyumov–Gerasimenko instead.

Comet Wirtanen reaches perihelion, its closest to the Sun and just beyond the Earth’s orbit, on the 12th. It is nearest the Earth on the 16th, passing only 11.6 million km away in the tenth closest approach of any observed comet since 1950. On that evening it lies 4° east (left) of the Pleiades and may appear as a large fuzzy ball lacking any obvious tail.

Predictions of its appearance at that time vary, but I suspect that its total brightness may be around the fourth magnitude, a little brighter than the fainter stars plotted on our charts. While this would normally put it well within naked-eye range, the fact that it is so close to the Earth is likely to mean that its light is spread out over an area even wider than the Pleiades. Unless we have a good dark sky, we may struggle to see its extended glow, and it is a pity that the gibbous Moon (63% sunlit) will also hinder observations before midnight. Only a week later, on the evening of the 23rd, it lies only 1° east-south-east of the bright star Capella but will be fading in still brighter moonlight.

The Sun reaches its most southerly point at the winter solstice at 22:23 GMT on the 21st as sunrise/sunset times for Edinburgh change from 08:19/15:44 GMT on the 1st to 08:42/15:40 on the 21st and 08:44/15:48 on the 31st. The Moon is new on the 7th, at first quarter on the 15th, full on the 22nd and at last quarter on the 29th.

Our charts show Andromeda and its Galaxy high in the south as Orion stands proudly in the south-east below Taurus and the Pleiades. Castor lies above Pollux in Gemini in the east and is close to the point in the sky that marks the radiant of the Geminids meteor shower.

The Geminids always produce an abundance of slow bright meteors which streak in all parts of the sky as they diverge from the radiant. The latter climbs to pass high in the south at around 02:00 and sinks into the west before dawn. The shower is active from the 8th to the 17th with the night of 13th-14th expected to be the best as meteor rates build to a peak at around dawn. An observer under an ideal dark sky with the radiant overhead may count upwards of 100 meteors per hour making the Geminids the highest-rated of our annual showers, though most of us under inferior skies may glimpse only a fraction of these.

Mars shines brightly some 25° high in the south as night falls for Edinburgh at present and is almost 10° higher by the month’s end after moving east-north-eastwards from Aquarius into Pisces. Our maps have it sinking in the south-west on its way to setting in the west before midnight. Although the brightest object in its part of the sky, it dims from magnitude 0.0 to 0.5 as it recedes from 151 million to 189 million km. When Mars stands above the Moon on the 14th, a telescope shows its ochre disk to be only 8 arcseconds across.

Saturn, magnitude 0.6, hangs just above our south-western horizon at nightfall as December begins but is soon lost in the twilight. Our other two evening planets, Uranus and Neptune, are visible through binoculars at magnitudes of 5.7 and 7.9 in Pisces and Aquarius respectively. Mars acts as an excellent guide on the evening of the 7th when Neptune stands about one quarter of a Moon’s breadth below-right of Mars.

Venus, now at its best as a dazzling morning star, rises in the east-south-east four hours before the Sun and climbs towards the south by dawn. This month it dims slightly from magnitude -4.7 to -4.5 as it tracks away from Virgo’s brightest star Spica in Virgo into the next constellation of Libra. Telescopes shows its crescent shrink from 40 to 26 arcseconds in diameter. Look for Venus below-left of the Moon on the morning of the 3rd and to the Moon’s right on the 4th.

Mercury is set to become as a morning star very low in the south-east and is soon to be joined by the even brighter Jupiter. Mercury rises more than 100 minutes before the Sun from the 5th to the 24th and stands between 5° and 9° high forty minutes before sunrise. It shines at magnitude 0.8 when it lies 7° below-left of the impressively earthlit Moon on the 5th, and triples in brightness to magnitude -0.4 by the 24th.

Jupiter, conspicuous at magnitude -1.8, emerges from the twilight and moves from 9° below-left of Mercury on the 11th to pass 0.9° south of Mercury on the 21st.

Diary for 2018 December

3rd            19h Moon 4° N of Venus

5th            21h Moon 1.9° N of Mercury

7th            07h New moon

7th           15h Mars 0.04° N of Neptune

9th           06h Moon 1.1° N of Saturn

12th         23h Comet Wirtanen closest to Sun (158m km)

14th         08h Peak of Geminids meteor shower

14th         23h Moon 4° S of Mars

15th         11h Mercury furthest W of Sun (21°)

15th         12h First quarter

16th         13h Comet Wirtanen closest to Earth (11.6m km) and 3.6° SE of Pleiades

20th         02h Jupiter 5° N of Antares

21st         08h Moon 1.7° N of Aldebaran

21st         15h Mercury 0.9° N of Jupiter

21st         22:23 Winter solstice

22nd        18h Full moon

23rd         18h Comet Wirtanen 0.9° SE of Capella

25th         05h Moon 0.3° S of Praesepe in Cancer

29th         10h Last quarter

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on November 30th 2018, with thanks to the newspaper for permission to republish here.

Scotland’s Sky in November, 2018

InSight probe to land on bright evening planet Mars

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 30th. An arrow depicts the motion of Mars. (Click on map to enlarge)

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 30th. An arrow depicts the motion of Mars. (Click on map to enlarge)

The Summer Triangle, still high in the south at nightfall, shifts to the west by our map times as our glorious winter constellations climb in the east. Taurus with the Pleiades and its leading star Aldebaran (close to the Moon on the 23rd) stands well clear of the horizon while Orion is rising below and dominates our southern sky after midnight.

In the month that should see NASA’s InSight lander touch down on its surface, the planet Mars continues as a prominent object in the south at nightfall. Venus springs into view as a spectacular morning star but we must wait to see whether the Leonids meteor shower, which has produced some storm-force displays in the past, gives us any more than the expected few meteors this year.

InSight is due to land on the 26th on a broad plain called Elysium Planitia that straddles Mars’ equator. There it will place an ultra-sensitive seismometer directly onto the surface and cover it with a dome-like shell to shield it from the noise caused by wind and heat changes. This should be able of detect marsquakes and meteor impacts that occur all around Mars. Other InSight experiments will hammer a spike up to five metres into the ground to measure Mars’ heat flow, and further investigate the planet’s interior structure by using radio signals to track tiny wobbles in its rotation.

Until recently, Mars has remained low down as it performed a loop against the stars in the south-western corner of Capricornus. That loop, resulting entirely from our changing vantage point as the Earth overtook Mars and came within 58 million km on 31 July, took Mars more than 26° south of the sky’s equator and 3° further south than the Sun stands at our winter solstice.

Now, though, Mars is climbing east-north-eastwards on a track that will take it further north than the Sun ever gets by the time it disappears into Scotland’s night-long twilight next summer. One by-product of this motion is that Mars’ setting time is remarkably constant over the coming months, being (for Edinburgh) within 13 minutes of 23:42 GMT from now until next May.

This month sees Mars leave Capricornus for Aquarius and shrink as seen through a telescope from 12 to 9 arcseconds as it recedes from 118 million to 151 million km. Its path, indicated on our southern chart, carries it 0.5° (one Moon’s breadth) north of the multiple star Deneb Algedi, the goat’s tail, on the 5th. It almost halves in brightness, from magnitude -0.6 to 0.0, but its peak altitude above Edinburgh’s southern horizon early in the night improves from 16° to 25°, though by our map times it is sinking lower towards the south-west.

Mars is not our sole evening planet since Saturn shines at magnitude 0.6 low down in the south-west at nightfall. It is only a degree below-right of the young Moon on the 11th and sets more than 90 minutes before our map times. The two most distant planets, Neptune and Uranus, are also evening objects and may be glimpsed through binoculars at magnitudes 7.9 and 5.7 in Aquarius and Aries respectively.

Edinburgh’s sunrise/sunset times vary from 07:19/16:32 on the 1st to 08:17/15:45 on the 30th. The Moon is new on the 7th, at first quarter and below-right of Mars on the 15th, full on the 23rd and at last quarter on the 30th.

Jupiter is hidden in the solar glare as it approaches conjunction on the Sun’s far side on the 26th. Mercury stands furthest east of the Sun (23°) on the 6th but is also invisible from our northern latitudes.

Venus, though, emerges rapidly from the Sun’s near side into our morning twilight where it stands to the left of the star Spica in Virgo. Shining brilliantly at magnitude -4.1, the planet rises in the east-south-east only 29 minutes before the Sun on the 1st. By the 6th, though, it rises 80 minutes before sunrise and stands 8° below and right of the impressively earthlit waning Moon. Venus itself is 58 arcseconds wide and 4% illuminated on that morning, its slender crescent being visible through binoculars. By the 30th, Venus rises four hours before the Sun, climbs to stand 23° high in the south-south-east at sunrise and appears as a 41 arcseconds and 25% sunlit crescent.

It is just as well that my previous note led on the usually neglected Draconids meteor shower because observers, at least those under clear skies, were thrilled to see it provide perhaps the best meteor show of 2018. For just a few hours around midnight on 8-9th October, the sky became alive with slow meteors at rates of up to 100 meteors per hour or more.

Leonid meteors arrive this month between the 15th and 20th, with the shower expected to hit its usually-brief peak at around 01:00 on the 18th. Although they flash in all parts of the sky, they diverge from a radiant point in the so-called Sickle of Leo which rises in the north-east before midnight and climbs high into the south before dawn. No Leonids appear before the radiant rises, but even with the radiant high in a dark sky we may see fewer than 20 per hour – all of them very swift and many of the brighter ones leaving glowing trains in their wake.

Leonid meteoroids come from Comet Tempel-Tuttle which orbits the Sun every 33 years and was last in our vicinity in 1998. There has not been a Leonids meteor storm since 2002 and we may be a decade or more away from the next one, or are we?

Diary for 2018 November

2nd           05h Moon 2.1° N of Regulus

6th            16h Mercury furthest E of Sun (23°)

7th            16h New moon

11th         16h Moon 1.5° N of Saturn

15th         15h First quarter

16th         04h Moon 1.0° S of Mars

18th         01h Peak of Leonids meteor shower

23rd         06h Full moon

23rd         22h Moon 1.7° N of Aldebaran

26th         07h Jupiter in conjunction with Sun

26th         20h InSight probe to land on Mars

27th         09h Mercury in inferior conjunction on Sun’s near side

27th         21h Moon 0.4° S of Praesepe

30th         00h Last quarter

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on October 31st 2018, with thanks to the newspaper for permission to republish here.

Scotland’s Sky in October, 2018

Draconid meteors glide away from the Dragon’s head

The maps show the sky at 23:00 BST on the 1st, 22:00 BST (21:00 GMT) on the 16th and at 20:00 GMT on the 31st. An arrow depicts the motion of Mars. Summer time ends at 02:00 BST on the 28th when clocks are set back one hour to 01:00 GMT. (Click on map to enlarge)

The maps show the sky at 23:00 BST on the 1st, 22:00 BST (21:00 GMT) on the 16th and at 20:00 GMT on the 31st. An arrow depicts the motion of Mars. Summer time ends at 02:00 BST on the 28th when clocks are set back one hour to 01:00 GMT. (Click on map to enlarge)

Mars dominates our southern evening sky but most of the other bright planets are poorly placed this month. Even so, our October nights are full of interest, from the Summer Triangle in the evening to the star-fest around Orion before dawn.

Although Mars dims from magnitude -1.3 to -0.6, its reddish light remains prominent as it moves from low in the south-south-east at nightfall to the south-south-west at our map times and onwards to set in the south-west a little before 01:00 BST (midnight GMT). As its distance grows from 89 million to 118 million km, and its diameter shrinks from 16 to 12 arcseconds, the planet speeds through Capricornus to climb 6° northwards and that much higher in our sky. Catch it to the left of the Moon on the 17th and below-right of the Moon on the 18th.

The Sun tracks 11° southwards as Edinburgh’s sunrise/sunset times change from 07:15/18:48 BST (06:15/17:48 GMT) on the 1st to 07:17/16:35 GMT on the 31st. The Moon is at last quarter on the 2nd, new on the 9th, at first quarter on the 16th, full (the Hunter’s Moon) on the 24th and back at last quarter on the 31st.

Our charts show the Plough in the north as it moves below Polaris, the Pole Star. Mizar, in the Plough’s handle, forms a famous double star with the fainter Alcor – the pair being separated by about one third the diameter of the Moon. Once held as a (not very rigorous) test of eyesight, they were dubbed “The Horse and Rider”.

Both lie 83 light years (ly) from us although we can’t be certain that they are tied together by gravity. In any case, we are not talking about just two stars, for Alcor has a faint companion and most telescopes show Mizar to be a binary star – the first to be discovered telescopically in the 17th century. Spectroscopes reveal that each of Mizar’s components is itself binary, so Mizar and Alcor, if they are truly associated, together form a sextuplet star system.

Mizar is the same brightness, magnitude 2.2, as Eltanin which lies 14° to the right of Vega and very high in the west at nightfall, falling into the north-west overnight. It is the brightest star in Draco and a member of a quadrilateral that marks the head of the Dragon whose body and tail twist to end between the Plough and Polaris. It lies 154 ly away but is approaching the Sun and will pass within 28 ly in another 1.5 million years to become the brightest star in Earth’s night sky.

Meteors from the Draconids shower diverge from a radiant point that lies close to Draco’s head (see our north map) between the 7th and 10th. Don’t expect a major display – perhaps no more than 10 meteors per hour, though all of them are very slow as they glide away from the radiant. The shower’s peak is due in a moonless sky around midnight on the 8th-9th and is worth checking because some years surprise us with strong displays and the shower’s parent comet, Comet Giacobini-Zinner, was visible through binoculars when it swept within 59 million km last month.

A better-known comet, Halley, is responsible for the meteors of the Orionids shower which lasts from the 16th to the 30th and has a broad but not very intense peak of fast meteors between the 21st and 24th. The radiant point, between Orion and Gemini, rises in the east-north-east soon after our map times and passes high in the south before dawn. Sadly, the peak coincides with the full moon, so don’t expect much of a show.

From high in the south at nightfall, the Summer Triangle (Vega, Deneb and Altair) tumbles into our western sky by the map times. By then, the less impressive and rather empty Square of Pegasus is in the south and Taurus and the Pleiades star cluster are climbing in the east. Orion rises below Taurus over the next two hours and crosses the meridian as the night ends.

Neptune and Uranus, now well placed in the evening, may be located through binoculars using better charts than I can provide here. A web search, for example for “Neptune finder chart”, should help. Neptune shines at magnitude 7.8 and lies in Aquarius at a distance of 4,342 million km on the 1st. Uranus is 2,824 million km away in Aries, near its border with Pisces, when it stands opposite the Sun in the sky (opposition) on the 24th. Although the full Moon stands close to it on that day, its magnitude of 5.7 makes it just visible to the unaided eye under a good dark and moonless sky.

October should see the launch of the European Space Agency’s BepiColombo mission to Mercury, but the planet itself is too low in our evening twilight to be seen. Venus sweeps around the Sun’s near side at inferior conjunction on the 26th and remains hidden in the Sun’s glare.

Jupiter is bright (magnitude -1.8) but less than 8° high in the south-west at sunset as the month begins. One of our last chances of spotting it in our bright evening twilight comes on the 11th when it lies 4° below-left of the young earthlit Moon.

Saturn, magnitude 0.5 and edging eastwards in Sagittarius, stands less than 10° high above Edinburgh’s south-south-western horizon as the sky darkens and sets in the south-west some 45 minutes before our map times. Look for it to the left of the Moon on the 14th.

Diary for 2018 October

Times are BST until the 28th

2nd           11h Last Quarter

9th            00h Peak of Draconids meteor shower

9th            05h New moon

11th         22h Moon 4° N of Jupiter

15th         04h Moon 1.8° N of Saturn

16th         19h First quarter

18th         14h Moon 1.9° N of Mars

21st – 24th         Peak of Orionids meteor shower

24th         02h Uranus at opposition at distance of 2,824m km

24th         18h Full moon

26th         15h Venus in inferior conjunction on Sun’s near side

28th         02h BST = 01h GMT End of British Summer Time

31st         17h GMT Last quarter

Alan Pickup

This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on September 29th 2018, with thanks to the newspaper for permission to republish here.