Jupiter rules our April nights
Venus dominated our evening sky for the first quarter of 2017, but it is now Jupiter’s turn in the spotlight. The conspicuous giant planet lies directly opposite the Sun in the sky on the 7th so that it rises in the east at sunset, reaches its highest point in the south in the middle of the night and sets in the west at sunrise.
Our charts show it in Virgo to the east of south as Taurus and Orion dip beneath the western horizon and the Plough looms overhead, stretched out of its familiar shape by our map projection. Regulus in Leo is in the south-west and almost level with Arcturus in Bootes in the south-east. Vega in Lyra and Deneb in Cygnus are beginning their climb in the north-east.
Sunrise/sunset times for Edinburgh change from 06:43/19:51 BST on the 1st to 05:31/20:50 on the 30th. The Moon is at first quarter on the 3rd, full on the 11th, at last quarter on the 19th and new on the 26th.
Venus rises only a little more than one hour before sunrise and, though brilliant at magnitude -4.2, may be difficult to spot low in the east before dawn. However, the other inner planet, Mercury, remains nicely placed in the evening and stands furthest east of the Sun (19°) on the 1st.
Thirty minutes after Edinburgh’s sunset on that day, Mercury is 12° high in the west and shines at magnitude 0.0. It should be possible to spy it through binoculars and eventually with the unaided eye as the twilight fades and the planet sinks to set another 96 minutes later. By the 8th, though, it is a couple of degrees lower and a quarter as bright at magnitude 1.6 as it is engulfed by the twilight. Inferior conjunction on the Sun’s near side occurs on the 20th.
Mars, magnitude 1.5 to 1.6 and above and to Mercury’s left at present, tracks east-north-eastwards this month to pass 5° below the Pleiades on the 15th and a similar distance left of the star cluster on the 26th. By then it sets late enough to be plotted near our north-western horizon at the star map times.
Its opposition means that Jupiter is at its brightest and closest, shining more brightly than any star at magnitude -2.5 and a distance of 666 million km. It lies 6° north-west (above-right) of Virgo’s leading star Spica as the month begins and tracks 3.7° westwards during April to pass 10 arcminutes or a third of a Moon’s-width south of the fourth magnitude star Theta Virginis on the 5th.
Jupiter lies close to the full Moon on the night of the 10th-11th when the Jovian disk appears 44 arcseconds wide if viewed telescopically, one fortieth as wide as the Moon.
Jupiter’s clouds are arrayed in bands that lie parallel to its equator, the dark ones called belts and the intervening lighter hued ones called zones. There are numerous whirls and spots, the most famous being the Great Red Spot in the southern hemisphere. The planet spins in under ten hours, so a resolute observer might view the entire span of its clouds in a single April night. The four main moons, visible through decent binoculars and easy through a telescope, lie on each side of the disk and change their configuration from night to night.
The beautiful planet Saturn rises in the south-east less than three hours after our map times and is the brightest object (magnitude 0.4 to 0.3) less than 15° above Edinburgh’s southern horizon before dawn. It is a shame that its low altitude means that we miss the sharpest and most impressive views of it rings which span 39 arcseconds in mid-April, and are tilted at 26° around its 17 arcseconds disk. After appearing stationary on the 6th, Saturn begins to creep westwards against the stars of Sagittarius – look for it below and left of the Moon on the 16th and right of the Moon on the 17th.
It is not often that I advertise the annual Lyrids meteor shower. As one of the year’s lesser displays, it yields only some 18 meteors per hour at best, all of them swift and some leaving glowing trains in their wake as they diverge from a radiant point to the right of Vega. The event lasts from the 18th to the 25th and peaks on the 22nd when moonlight should not interfere unduly this year. The Lyrid meteoroids were released by Comet Thatcher, last seen in 1861.
Bright comets have been rare of late, but fainter ones are observed frequently. One such has the jaunty name of comet 41P/Tuttle–Giacobini–Kresák and takes 5.4 years to orbit between the paths of Jupiter and the Earth. It passes within 21 million km of us on the 1st as it nears perihelion, its closest point to the Sun, on the 12th. I glimpsed it through binoculars from a superb dark-sky site at Kielder Forrest, Northumberland, last week when it was a diffuse seventh magnitude smudge close to Merak, the southern star of the Pointers in the Plough.
Although its path is not depicted on our chart, the comet is poised to sweep close to three of the stars identified in Draco, between the Plough and Polaris, the Pole Star. It passes 0.6° north of Thuban on the night of the 2nd-3rd, 1.5° south-west of Eta on the 11th (sadly, in full moonlight) and 0.6° west of Beta on the 18th-19th. During past perihelia, it has been seen to flare by several magnitudes for a few days at a time, so, if we are lucky, it may reach naked-eye visibility.
This is a slightly-revised version of Alan’s article published in The Scotsman on March 31st 2017, with thanks to the newspaper for permission to republish here.
Moon between Venus and Mars on the 2nd
The new year opens with the Moon as a slim crescent in our evening sky, its light insufficient to hinder observations of the Quadrantids meteor shower.
Lasting from the 1st to the 6th, the shower is due to reach its maximum at about 15:00 GMT on the 3rd. Perhaps because of the cold weather, or a lingering hangover from Hogmanay, this may be the least appreciated of the year’s top three showers. It can, though, yield more than 80 meteors per hour under the best conditions, with some blue and yellow and all of medium speed. It can also produce some spectacular events – I still recall a Quadrantids fireball many years ago that flared to magnitude -8, many times brighter than Venus.
Although Quadrantids appear in all parts of the sky, perspective means that their paths stream away from a radiant point in northern Bootes. Plotted on our north map, this glides from left to right low across our northern sky during the evening and trails the Plough as it climbs through the north-east later in the night. The shower’s peak is quite narrow so the optimum times for meteor-spotting are before dawn on the 3rd, when the radiant stands high in the east, and during the evening of that day when Quadrantids may follow long trails from north to south across our sky.
Mars and Venus continue as evening objects, improving in altitude in our south-south-western sky at nightfall and, in the case of Venus, becoming still more spectacular as it brightens from magnitude -4.3 to -4.6. Mars, more than one hundred times fainter, dims from magnitude 0.9 to 1.1 but is obvious above and to Venus’ left, their separation falling from 12° to 5° during the month as they track eastwards and northwards from Aquarius to Pisces.
On the evening of the 1st, Mars stands only 18 arcminutes, just over half a Moon’s breadth, above-left of the farthest planet Neptune though, since the latter shines at magnitude 7.9, we will need binoculars if not a telescope to glimpse it. At the time, Neptune, 4,556 million km away, is a mere 2.2 arcseconds wide if viewed telescopically and Mars appears 5.7 arcseconds across from a range of 246 million km. On that evening, the young Moon lies 8° below and right of Venus, while on the 2nd the Moon stands directly between Mars and Venus. The pair lie close to the Moon again on the 31st.
As its distance falls from 115 million to 81 million km this month, Venus swells from 22 to 31 arcseconds in diameter and its disk changes from 56% to 40% sunlit. In theory, dichotomy, the moment when it is 50% illuminated like the Moon at first quarter, occurs on the 14th. However, the way sunlight scatters in its dazzling clouds means that Venus usually appears to reach this state a few days early when it is an evening star – a phenomenon Sir Patrick Moore named the Schröter effect after the German astronomer who first reported it. Venus stands at its furthest to the east of the Sun, 47°, on the 12th.
The Sun climbs 6° northwards during January and stands closer to the Earth in early January than at any other time of the year. At the Earth’s perihelion at 14:00 GMT on the 4th the two are 147,100,998 km apart, almost 5 million km less than at aphelion on 3 July. Obviously, it is not the Sun’s distance that dictates our seasons, but rather the Earth’s axial tilt away from the Sun during winter and towards it in summer.
Sunrise/sunset times for Edinburgh change from 08:43/15:49 on the 1st to 08:09/16:44 on the 31st. The Moon is at first quarter on the 5th, full on the 12th, at last quarter on the 19th and new on the 28th.
The Moon lies below the Pleiades on the evening of the 8th and to the left of Aldebaran in Taurus on the next night. Below and left of Aldebaran is the magnificent constellation of Orion with the bright red supergiant star Betelgeuse at his shoulder. Soon in astronomical terms, but perhaps not for 100,000 years, Betelgeuse will disintegrate in a supernova explosion.
The relics of a supernova witnessed by Chinese observers in AD 1054 lies 15° further north and just 1.1° north-west of Zeta Tauri, the star at the tip of Taurus’ southern horn. The 8th magnitude oval smudge we call the Crab Nebula contains a pulsar, a 20km wide neutron star that spins 30 times each second.
The conspicuous planet in our morning sky is Jupiter which rises at Edinburgh’s eastern horizon at 01:27 on the 1st and at 23:37 on the 31st. Creeping eastwards 4° north of Spica in Virgo, it brightens from magnitude -1.9 to -2.1 and is unmistakable in the lower half of our southern sky before dawn. Catch it just below the Moon on the 19th when a telescope shows its cloud-banded disk to be 37 arcseconds broad at a distance of 786 million km. We need just decent binoculars to check out the changing positions of its four main moons.
Saturn, respectable at magnitude 0.5, stands low in our south-east before dawn, its altitude one hour before sunrise improving from 3° to 8° during the month. Look to its left and slightly down from the 6th onwards to glimpse Mercury. This reaches 24° west of the Sun on the 19th and brightens from magnitude 0.9 on the 6th to -0.2 on the 24th when the waning earthlit Moon stands 3° above Saturn.
This is a slightly-revised version of Alan’s article published in The Scotsman on December 31st 2016, with thanks to the newspaper for permission to republish here.
Mercury joins two brightest planets in evening sky
Spring may have arrived, but the leading constellation of our winter sky, Orion, is still on view in our early evening sky, if not for very much longer. Look for it in the south-west at nightfall, with the three stars of his Belt lying almost parallel to the horizon. Stretch their line to the left to reach Sirius in Canis Major, our brightest nighttime star, and to the right towards Taurus, with its bright star Aldebaran and the Pleiades star cluster. High in the south-south-west is Gemini, with the twins Castor and (slightly brighter) Pollux.
To the south of Gemini is Procyon, the Lesser Dog Star in Canis Minor. Together with the true Dog Star, Sirius, and the distinctive red supergiant Betelgeuse at Orion’s top-left shoulder, Procyon completes an almost-isosceles triangle which we dub “The Winter Triangle”. At present, in fact, it forms a similar but smaller triangle with Pollux and the conspicuous planet Jupiter which dominates our southern sky at nightfall. Leo stands to the left of Jupiter with its leading star, Regulus, in the handle of the Sickle.
As April’s days lengthen, our whole sky-scape shifts further westwards each evening until, by the month’s end, Orion is setting in the west as the sky darkens
The Sun climbs more than 10° northwards during April and sunrise/sunset times for Edinburgh change from 06:44/19:50 BST on the 1st to 05:32/20:49 on the 30th. Meanwhile, the duration of nautical twilight at the start and end of the night stretches from 84 to 105 minutes.
The Moon is full on the 4th when a total lunar eclipse is visible from the Pacific and surrounding areas but not from Europe. In fact, totality, with the moon just inside the northern part of the Earth’s dark umbral shadow lasts for a mere 4 min 34 sec centred at 13:00 BST, making this the briefest total lunar eclipse for 486 years. By comparison, totality lasts for 72 minutes during the next total lunar eclipse which is visible from Scotland on the morning of 28 September this year. The Moon’s last quarter on the 12th is followed by new moon on the 18th and first quarter early on the 26th.
By nightfall on the 26th, that first quarter Moon lies 6° below Jupiter in the south-south-west. Jupiter, itself, dims a little from magnitude -2.3 to -2.1 and is slow-moving in Cancer 5° to the left of the Praesepe cluster in Cancer. The star cluster is best seen through binoculars which also show the changing positions of the four main Jovian moons as they swing from side to side of the planet. The giant planet progresses into the south-west by our star map times and sets in the north-west more than five hours later.
Even though Jupiter is twice as bright as Sirius, it pales by comparison with the evening star Venus which blazes brilliantly in the west at nightfall, and sets at Edinburgh’s west-north-western horizon by 23:38 BST on the 1st and in the north-west as late as 01:08 on the 30th. This month Venus approaches from 180 million to 150 million km and swells in diameter from 14 to 17 arcseconds, its dazzling disk appearing gibbous through a telescope as its phase changes from 78% to 67% illuminated.
Venus also speeds eastwards during the period, moving from Aries to Taurus where it passes 2.7° south of the Pleiades on the 11th to end April 3° south of Elnath at the tip of the Bull’s northern horn. There should be an impressive sight on the evening of the 21st when Venus lies 7° above-right of the earthlit crescent Moon which, in turn, is 2.5° above-left of Aldebaran.
Mars, magnitude 1.4, is low and hard to spot in our western evening twilight, becoming lost from view later in the month as it tracks towards the Sun’s far side. However, after passing beyond the Sun at superior conjunction on the 10th, Mercury emerges in our twilight to begin the innermost planet’s best evening apparition of the year.
On the 19th, Mercury shines at magnitude -1.3 and stands 4° high in the west-north-west forty minutes after sunset. Mars lies 2.8° above and to its left while the sliver of the earthlit Moon is 12° high and to their left. By the month’s end Mercury is 10° high forty minutes after sunset and shines at magnitude -0.4 22° below and to the right of Venus and only 1.7° below-left of the Pleiades. Binoculars may help to pick it out at first but it should emerge as a naked-eye object as the twilight fades and it sinks to the north-western horizon by 23:00.
Saturn is on show during the second half of the night though it does not climb far above our horizon so is not well placed for the sharpest views of its stunning ring system. For Edinburgh, it rises in the south-east at 00:46 on the 1st and by 22:40 on the 30th, reaching its highest point of 15° in the south four hours later before dawn.
Shining at magnitude 0.3 to 0.1, Saturn lies in Scorpius where it creeps 1.5° westwards above the double star Graffias. As it lies below and left of the Moon on the 8th, a telescope shows the planet’s rotation-flattened disk to be 18 arcseconds wide, within rings that span 41 arcseconds and have their northern face tilted Earthwards at 25°. Although they show an amazing complexity on the small scale, the main rings, dubbed A and B, are separated by the relatively empty dark arc of the Cassini Division. B, the brightest of the rings, has A outside it and the dusky C ring within.
This is a slightly-revised version of Alan’s article published in The Scotsman on March 31st 2015, with thanks to the newspaper for permission to republish here.
Jupiter at its conspicuous best as Comet Lovejoy recedes
The prize for venturing outside after nightfall in February is a view of our most stunning evening sky of the year. Venus, now closing in on Mars, blazes low in the west-south-west as the twilight dwindles while the conspicuous planet Jupiter is climbing in the east and the glorious shape of Orion is unmistakable in the south-east.
By our star map times, Orion has progressed into the south-south-west and it is Jupiter that dominates in the south-east. The line of Orion’s Belt slants towards Sirius which twinkles furiously on the meridian and westwards towards Aldebaran and on to the Pleiades in Taurus. Extend it still further, and across onto the western side of our northern map, to locate the area where we now find Comet Lovejoy.
The comet has been an easy binocular object during January, appearing as a fuzzy ball of light climbing to the west of Orion and below the Pleiades. Indeed, it was visible to the naked eye in a dark sky while photographs brought out its long tail with several fast-changing spokes, kinks and knots and the striking green hue of its head, due to fluorescence from cyanogen and diatomic carbon. It peaked near magnitude 3.8 after passing closest to the Earth on 7 January and reaches its closest point to the Sun, perihelion, on 30 January.
Our north map shows it approaching the star Almach, the upper (eastern) bright star of Andromeda, and it passes less than 0.7° above it on the night of Wednesday, 4 February. In fact, we will find the comet and the star within the same binocular field until the 12th or so. Now receding and fading, it is closer to magnitude five at present and may be magnitude 6.5 by the month’s end as it heads towards the familiar W-shaped pattern of Cassiopeia.
Jupiter stands to the right of Leo’s Sickle and near the full Moon on Tuesday, 3 February as it edges westwards from Leo into Cancer. It reaches opposition in Cancer on the 6th when it stands opposite the Sun so that it rises in the east-north-east at sunset, is highest in the south around midnight and sets in the west-north-west at dawn. It is then at its closest (650 million km) and brightest (magnitude -2.6), and shows a 45 arcseconds disk through a telescope.
Its four main moons are visible through binoculars, unless, that is, they are in transit across the disk or hidden beyond it. With their orbits still edge on to us and to the Sun, they also eclipse each other occasionally.
The obvious surface features on Jupiter are the bands of dark and light clouds running parallel to its equator, but peppering these are streaks and spots that drift across the disk to betray the planet’s rotation in just under ten hours. Since it is observable throughout our long night, we might inspect its entire meteorology in a single session if we had the dedication and enough cups of coffee.
February sees the Sun climbs 9.5° northwards in the sky as the sunrise/sunset times for Edinburgh change from 08:08/16:45 on the 1st to 07:07/17:44 on the 28th. The duration of nautical twilight at dawn and dusk shrinks from 86 to 80 minutes. The Moon is full on the 3rd, at last quarter on the 12th, new on the 18th and at first quarter on the 25th as it passes just above Aldebaran.
Venus is now established as an brilliant evening star of magnitude -3.9, its altitude above Edinburgh’s south-western horizon at sunset increasing from 16° to 23° during February so that by the month’s end it is visible for more than three hours after sunset. Viewed telescopically, its dazzling and almost-full gibbous disk swells from 11 to 12 arcseconds in diameter.
Mars lies 10° above and to the left of Venus on the 1st, but is more than 100 times fainter at magnitude 1.2 and distinctly reddish in appearance. It is also a good deal smaller at 4 arcseconds and we will struggle to glimpse any of its surface detail. Both planets are more distant than the Sun at present, but while Venus is sliding closer to the Earth in its orbit, we are leaving Mars behind as it slips towards the Sun’s far side.
The two are also drawing closer together in our sky so that Venus lies 0.8° below Mars on the 20th with the slender young earthlit Moon 4° away, below and to their right. Venus lies only 0.5° (one Moon-breadth) below-left of Mars on the 21st when their distances from the Earth are 212 million and 330 million km respectively and they lie 10° below-right of the Moon. By the 28th, Venus stands 3° above-left of Mars.
Mercury remains hidden in our pre-dawn twilight but Saturn is a morning planet in Scorpius. Rising in the east-south-east at about 03:35 on the 1st and 01:55 on the 28th, it climbs almost 15° high into the south-south-east to south before dawn. As the brightest object low down in that part of the sky, it shines at magnitude 0.5 and surpasses the red supergiant Antares 9° below and to its left.
Saturn is tracking slowly eastwards but is at present just 1° north of the star Graffias which appears double through a small telescope but really has many stellar components. The planet lies 4° to the right of the waning Moon on the morning of the 13th when a telescope shows its disk to be 16 arcseconds wide, while its rings span 37 arcseconds and have their northern face tipped 25° towards us.
This is a slightly-revised version of Alan’s article published in The Scotsman on January 31st 2015, with thanks to the newspaper for permission to republish here.
Comet Lovejoy heralds an exciting year in astronomy
The coming year promises to be an exciting one in astronomy and space research. NASA’s New Horizons mission is due to make the first flyby visit to Pluto in July while Comet Churyumov–Gerasimenko is nearest the Sun a month later, hopefully with Europe’s Rosetta probe still alongside and in prime position to observe the comet in full flow. Whether we hear again from the Philae lander remains to be seen, but its controllers are hopeful that it may come back to life in the spring.
Closer to home, the highlight is surely the solar eclipse on the morning of 20 March. This is total for the Faroe Islands and Svalbard while from Scotland the Moon hides all but a thin sliver around the Sun’s lower limb. From Edinburgh 94% of the Sun is obscured but for observers in Kirkwall, Lerwick and Stornoway this jumps to 97%.
January should be interesting in its own right. Not only are all the planets on view, but the constellations centred on Orion dominate our evening hours and we have the prospect that Comet Lovejoy may be a naked-eye object as it climbs to the right of Orion.
The year begins with the Quadrantids meteor shower which is active from the 1st to the 6th but reaches a rather sharp peak at around midnight on the 3rd/4th when as many as 80 medium-speed meteors per hour might be seen under ideal conditions from a dark location. Sadly, the Moon is full on the 5th so all but the brighter meteors will be swamped in the moonlight this year. Quadrantids appear in all parts of the sky but their paths trace back to a radiant point that is plotted low in the north at our star map times. Later in the night the radiant follows the Plough as it climbs through our north-eastern sky.
You may find it surprisingly that the Earth is at perihelion, our closest to the Sun, at 06:36 on the 4th. The centre of our planet then lies 147,096,204 km from the Sun, 5 million km closer than it does at aphelion on 6 July. Sunrise/sunset for Edinburgh change from 08:44/15:49 on the 1st to 08:10/16:43 on the 31st as the duration of nautical twilight at each dawn and dusk shrinks from 96 to 85 minutes. That full moon on the 5th is followed by last quarter on the 13th, new moon on the 20th and first quarter on the 27th.
As the Moon climbs in the east on the evening of the 1st, it stands below the Pleiades and above-right of Aldebaran, the eye of Taurus. By 19:00 the whole of Orion is unmistakable in the east-south-east, moving into the south-south-east by our map times as the Pleiades glimmer on the meridian.
Our chart traces the path of Comet Lovejoy as it climbs from Lepus the Hare, at Orion’s feet, through Eridanus the River and Taurus as it approaches the star Almach in Andromeda as the month ends. Discovered in August by the Australian amateur astronomer Terry Lovejoy, the comet has brightened more than most people expected and reached the threshold of naked-eye visibility, the sixth magnitude, in mid-December.
During January I expect it to shine at around the 4th or 5th magnitude, fainter than the stars on our chart but perhaps similar in brightness to the Orion Nebula. As such, it should be visible easily through binoculars as a hazy smudge, probably smaller than the Moon and with brighter core around its nucleus. Indeed, it should be a naked-eye object in a dark sky once the current moonlight has subsided. Photographs show a greenish hue and a narrow striated tail more than 5° long pointing up and to the left, away from the Sun.
Comet Lovejoy takes about 13,500 years to orbit the Sun and reaches perihelion on 30 January at a distance of 193 million km. It comes closest to the Earth, 70 million km, on the 7th.
Jupiter remains our pre-eminent planet as it rises in the east-north-east some 90 minutes before our map times. Blazing at magnitude -2.5 to -2.6, it is now creeping westwards to the west (right) of the Sickle of Leo and crosses the meridian in the early hours. A telescope shows it to be 44 arcseconds wide when it stands above the Moon on the morning of the 8th.
Venus is a brilliant magnitude -3.9 evening star very low in the south-west as the night begins. It sets for Edinburgh at 17:07 on the 1st and at 18:58 by the 31st. Use it (and binoculars) to locate Mercury which shines at magnitude -0.8 as it moves from 3° below-right of Venus on the 1st to lie less than 0.7° to the right of Venus on the 11th. It then tracks to the right of Venus and lies 7° away by the 22nd when it is a difficult magnitude 0.9 object in the twilight. On that evening, the thin earthlit Moon lies 9° above Venus and 7° to the right of the orange-hued planet Mars (magnitude 1.2) which otherwise remains the brightest object low in the south-west at nightfall.
The other naked-eye planet, Saturn, rises in the south-east at about 05:20 on the 1st and almost two hours earlier by the month’s end, becoming the brightest object low in the south-south-east to south before dawn. This month it tracks eastwards from Libra to pass 1° north of the star Graffias in Scorpius. Look for Saturn 2.6° below-left of the waning Moon on the 16th when a telescope shows its globe to be 16 arcseconds wide within rings that span 36 arcseconds and have their north face tipped 25° towards the Earth.