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Scotland’s Sky in November, 2016

Nights begin with Venus and end at Jupiter

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 after the first week of the month. (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 after the first week of the month. (Click on map to enlarge)

The end of British Summer Time means that we now enjoy six hours of official darkness before midnight, though I appreciate that this may not be welcomed by everyone. The starry sky as darkness falls, however, sees only a small shift since a month ago, with the Summer Triangle, formed by the bright stars Vega, Deneb and Altair, now just west of the meridian and toppling into the middle of the western sky by our star map times.

Those maps show the Square of Pegasus high in the south. The star at its top-left, Alpheratz, actually belongs to Andromeda whose other main stars, Mirach and Almach, are nearly equal in brightness and stand level to its left. A spur of two stars above Mirach leads to the oval glow of the Andromeda Galaxy, M31, which is larger than our Milky Way and, at 2.5 million light years, is the most distant object visible to the unaided eye. It is also approaching us at 225 km per second and due to collide with the Milky Way in some 4 billion years’ time.

Binoculars show M31 easily and you will also need them to glimpse more than a handful of stars inside the boundaries of the Square of Pegasus, even under the darkest of skies. In fact, there are only four such stars brighter than the fifth magnitude and another nine to the sixth magnitude, close to the naked eye limit under good conditions. How many can you count?

Mars is the easiest of three bright planets to spot in tonight’s evening sky. As seen from Edinburgh, it stands 11° high in the south as the twilight fades, shining with its customary reddish hue at a magnitude of 0.4, and appearing about half as bright as the star Altair in Aquila, 32° directly above it.

Now moving east-north-eastwards (to the left), Mars is 5° below-right of the Moon on the 6th and crosses from Sagittarius into Capricornus two days later. Soon after this, it enters the region covered by our southern star map, its motion being shown by the arrow. By the 30th, Mars has dimmed slightly to magnitude 0.6 but is almost 6° higher in the south at nightfall, moving to set in the west-south-west at 21:00. It is a disappointingly small telescopic sight, though, its disk shrinking from only 7.5 to 6.5 arcseconds in diameter as it recedes from 188 million to 215 million km.

We need a clear south-western horizon to spy Venus and Saturn, both low down in our early evening twilight. Venus, by far the brighter at magnitude -4.0, is less than 4° high in the south-west thirty minutes after sunset, while Saturn is 4° above and to its right, very much fainter at magnitude 0.6 and only visible through binoculars. The young earthlit Moon may help to locate them – it stands 3° above-right of Saturn on the 2nd and 8° above-left of Venus on the 3rd.

Mercury is out of sight in the evening twilight and Saturn will soon join it as it tracks towards the Sun’s far side. However, Venus’ altitude thirty minutes after sunset improves to 9° by the 30th when it sets for Edinburgh at 18:30 and is a little brighter at magnitude -4.1. Viewed telescopically, Venus shows a dazzling gibbous disk that swells from 14 to 17 arcseconds as its distance falls from 178 million to 149 million km.

Sunrise/sunset times for Edinburgh change from 07:20/16:31 on the 1st to 08:18/15:44 on the 30th. The Moon reaches first quarter on the 7th, full on the 14th, last quarter on the 21 and new on the 28th.

The full moon on the 14th occurs only three hours after the Moon reaches its perigee, the closest point to the Earth in its monthly orbit. As such, this is classed as a supermoon because the full moon appears slightly (7%) wider than it does on average. By my reckoning, this particular lunar perigee, at a distance of 356,509 km, is the closest since 1948 when it also coincided with a supermoon.

Of the other planets, Neptune and Uranus continue as binocular-brightness objects in Aquarius and Pisces respectively in our southern evening sky, while Jupiter, second only to Venus in brightness, is now obvious in the pre-dawn.

Jupiter rises at Edinburgh’s eastern horizon at 04:28 on the 1st and stands more than 15° high in the south-east as morning twilight floods the sky. It outshines every star as it improves from magnitude -1.7 to -1.8 by the 30th when it rises at 03:07 and is almost twice as high in the south-south-east before dawn.

Currently close to the famous double star Porrima in Virgo, Jupiter is 13° above-right of Virgo’s leader Spica and draws 5° closer during the period. Catch it less than 3° to the right of the waning earthlit Moon on the 25th. Jupiter’s distance falls from 944 million to 898 million km during November while its cloud-banded disk is some 32 arcseconds across.

The annual Leonids meteor shower has produced some stunning storms of super-swift meteors in the past, but probably not this year. Active from the 15th to 20th, it is expected to peak at 04:00 on the 17th but with no more than 20 meteors per hour under a dark sky. In fact, the bright moonlight is likely to swamp all but the brightest of these this year. Leonids diverge from a radiant point that lies within the Sickle of Leo which climbs from low in the east-north-east at midnight to pass high in the south before dawn.

Alan Pickup

This is a slightly-revised version of Alan’s article published in The Scotsman on November 1st 2016, with thanks to the newspaper for permission to republish here.
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Scotland’s Sky in November, 2014

Europe’s Philae probe to attempt first touchdown on comet

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 30th. (Click on map to englarge)

The maps show the sky at 21:00 GMT on the 1st, 20:00 on the 16th and 19:00 on the 30th. (Click on map to englarge)

In an exciting month in astronomy and space exploration, November should bring the first soft landing on a comet when the European Space Agency’s Philae craft detaches from the Rosetta probe and drops gently onto the icy nucleus of Comet Churyumov-Gerasimenko.

Our sky at nightfall s similar to that of a month ago although, with our return to GMT, darkness arrives more than two hours earlier in the evening. Mars continues as the only bright planet at these times, visible low in Edinburgh’s south-south-western sky and fading only a little from magnitude 0.9 to 1.0 as it tracks eastwards above the Teapot of Sagittarius.

However, even though Mars is drawing closer to the Sun, its altitude at the end of nautical twilight improves from 5° to 9° during November as the Sun plunges more than 7° southwards in the sky and Mars edges almost 3° northwards. This also means that Mars-set in the south-west occurs at about 19:05 throughout the period. It stands below the young crescent Moon on the 26th.

Sunrise/sunset times for Edinburgh change from 07:19/16:33 GMT on the 1st to 08:17/15:45 on the 30th as the duration of nautical twilight at dawn and dusk extends from 83 to 93 minutes. The Moon is full on the 6th, at last quarter on the 14th, new on the 22nd and at first quarter on the 29th.

Comet Churyumov-Gerasimenko lies 6° south-east of Mars on the 12th but is a very dim telescopic object some 450 million km from the Sun. On that day Philae is due to unlatch from Rosetta and take about seven hours to fall 22.5km, coming to rest on tripod legs at about 16:00 GMT atop the head of the comet’s strange “rubber-duck” shape. To stop itself bouncing off into space in defiance of the comet’s feeble gravitational pull, it should then fire a tethered harpoon to anchor itself to the surface.

The comet’s 6-year orbit is carrying it closer to the Sun, eventually to reach perihelion at a distance of 186 million km next August. Meantime, its activity is picking up and Rosetta is imaging jets of dust and gas emerging, mainly from the duck’s neck region at present. With Philae in position to also monitor conditions at the surface, and even below the crust using sonar, seismographs and permittivity probes, our knowledge of what makes comets tick should soon be transformed.

The Summer Triangle of Vega, Deneb and Altair, lies in the west at our map times as Orion rises in the east below Taurus and the Pleiades. The Square of Pegasus stands high on the meridian with the three main stars of Andromeda, Alpheratz, Mirach and Almach, leading off from its top-left corner. The Andromeda Galaxy, M31, could hardly be better placed, being visible to the naked eye in a decent sky and not difficult at all through binoculars. It stands 2.5 million light years (ly) away and appears as an oval smudge some 8° above Mirach.

A line through the Square’s two right-hand stars points the way to Fomalhaut, bright but very low in the south. I mentioned last time that it may have at least a couple of planets. In fact, the first so-called extrasolar planet circling a solar-type star was discovered in 1995 and is about half the size of Jupiter yet orbits in only 4.2 days at a distance only one seventh of that of Mercury from the Sun. The star concerned is 51 Pegasi, magnitude 5.5 and 50 ly distant, which is unmistakable through binoculars just 1.5° or 3 Moon-widths to the right of the Scheat-Markab line.

Of the 1,800-plus extrasolar planets now known, no less than four orbit Upsilon Andromedae, a fourth magnitude star at 44 ly that stands between Mirach and Almach (see chart).

Jupiter, is creeping eastwards to the right of the famous Sickle of Leo. Rising in the east-north-east at about 23:20 on the 1st and as early as 21:40 on the 30th, it is prominent until dawn as it climbs through our south-eastern sky to pass about 50° high on our meridian before dawn. The Jovian disk is 38 arcseconds across when Jupiter lies near the Moon on the night of 13/14th.

The annual Leonids meteor shower lasts from the 15th to the 20th, building to a sharp peak on the morning of the 18th. Its super-swift meteors flash in all parts of the sky, though their paths radiate from a point in the Sickle. There is little moonlight interference this year, but meteor rates may be well down on what they were a few years ago when the shower’s parent comet was in the vicinity.

Venus sets too soon after the Sun to be seen, and with Saturn reaching conjunction on the Sun’s far side on the 18th, our only other observable bright planet is Mercury, fortunately putting on its best morning show of 2014.

On the 1st Mercury rises two hours before the Sun and shines at magnitude -0.5 as it climbs to an altitude of 10° in the east-south-east forty minutes before sunrise. Although it soon brightens to magnitude 0.8, it also slips back towards the Sun, so that by the 14th it rises 89 minutes before the Sun and is 6° high forty minutes before sunrise. Given a clear horizon, though, binoculars should show it easily and it should be a naked-eye object until it is swamped by the brightening twilight. Look for Virgo’s leading star, Spica, climbing from below Mercury to pass 5° to its right on the 7th.

Alan Pickup

This is a slightly-revised version of Alan’s article published in The Scotsman on October 31st 2014, with thanks to the newspaper for permission to republish here.