The Night Sky December 2011
Compiled by Ian Morison
This page, updated monthly, will let you know some of the things that you can look out for in the night sky. It lists the phases of the Moon, where you will see the naked-eye planets and describes some of the prominent constellations in the night sky during the month.
Image of the Month
Saturn's ring with four moons
Cassini Imaging Team, ISS, JPL, ESA, NASA
This Cassini image shows four of Saturn's Moons. The largest and furthest away is cloud shrouded Titan, which has a dark marking called the north polar shroud near the pole. Closest is Dione showing its craters and ice cliffs. Just outside the outer, F, ring is 80km diameter Pandora - one of the F rings two shepherd moons that keeps it in place. Lying in the Encke gap is Pan - just 35 km across - which helps to keep the gap clear of particles.
Highlights of the Month
December 10th - 15:00 onwards
There is a total eclipse of the Moon on the 10th but, sadly, we will only be able to observe the final part of the partial phase and it will probably only appear as if a "bite" has been taken out of it. Look towards the North-East and the further north and east your location in the UK the better. The Moon rises at 15:24 in Aberdeen, 15:49 in Manchester, 15:51 in London but 16:09 in Exeter. The Earth's shadow finally clears the Moon's surface at 16:18 pm. As should be apparent, this will be the night of the Full Moon. I am not convinced that it is worth travelling to the northern tip of Scotland for this one!
December 14th and 15th after midnight: the Geminid Meteor Shower.
The early mornings of December 14th and 15th will give us the chance, if clear, of observing the peak of the Geminid meteor shower. Sadly, this year,the Full Moon is on the 10th and it will lie close to the radiant this night. This means that you will only see the brighter trails by looking high up away from the glare of the Moon. An observing location well away from towns or cities will also pay dividends though. The relatively slow moving meteors arise from debris released from the asteroid 3200 Phaethon. This is unusual, as most meteor showers come from comets. The radiant - where the meteors appear to come from - is close to the bright star Castor in the constellation Gemini as shown on the chart. If it is clear it will be cold - so wrap up well, wear a woolly hat and have some hot drinks with you.
December 21st - 1 hr before Dawn: Saturn, Spica and a thin waning crescent Moon - and perhaps spot Mercury.
This month Saturn, in the constellation Virgo, is visible in the pre-dawn sky and will make a nice grouping with Spica and a thin waning crescent Moon on the morning of the 21st of December. Given a low eastern horizon, you may also be able to spot Mercury just above the horizon.
December 22nd/23rd - midnight onwards : the Ursid Meteor Shower
Happily, the Moon will not be in evidence on the night of the 22nd/23rd December when the Ursid meteor shower is at its best - though the peak rate of ~10-15 meteors per hour is not that great. The radiant lies close to the star Kochab in Ursa Minor (hence their name), so look northwards at a high elevation. Occasionally, there can be a far higher rate so its worth a look should it be clear.
December 23rd - 1 hr before Dawn: Mercury and a thin crescent Moon
Before dawn on the 23rd of December, you may, given clear skies and a low south-eastern horizon, be able to spot Mercury.
December 27th: Venus and a thin crescent Moon.
After sunset at about 4:40 PM on the 27th, you may, given a low south western horizon and clear skies, be able to spot Venus, at magnitude -3.9 down to the lower right of a thin crescent Moon. Look out for the "earthshine" illuminating the "dark side" of the Moon - often called the "old Moon in the new Moon's arms".
Find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum
In the evening, the galaxy M31 in Andromeda is visible high in the south. The chart provides two ways of finding it:
1) Find the square of Pegasus. Start at the top left star of the square - Alpha Andromedae - and move two stars to the left and up a bit. Then turn 90 degrees to the right, move up to one reasonably bright star and continue a similar distance in the same direction. You should easily spot M31 with binoculars and, if there is a dark sky, you can even see it with your unaided eye. The photons that are falling on your retina left Andromeda well over two million years ago!
2) You can also find M31 by following the "arrow" made by the three rightmost bright stars of Cassiopeia down to the lower right as shown on the chart.
The accompanying image was the first ever taken by the author with a SBIG ST-8300M 8 Mpixel CCD camera mounted on an 80mm Ed refractor from somewhat light polluted and hazy skies near Shrewsbury late November. Perhaps not too bad for a first attempt. M32 is the spherical dwarf elliptical above and M101 the more elongated elliptical below.
Around the night of new Moon (24th December) you may also be able to spot M33, the third largest galaxy after M31 and our own galaxy in our Local Group of galaxies. It is a face on spiral and its surface brightness is pretty low so a dark, transparent sky will be needed to spot it using binoculars (8x40 or, preferably, 10x50). Follow the two stars back from M31 and continue in the same direction sweeping slowly as you go. It looks like a piece of tissue paper stuck on the sky just a bit brighter than the sky background. Good Hunting!
December: Look for the Great Red Spot on Jupiter
This list gives some the best times during December to observe the Great Red Spot which should then lie close to the central meridian of the planet. The GRS can move in position around the surface and a second set of calculations puts the times of transit a little later than those given.
2nd 21:52 21st 22:33
7th 21:00 24th 20:03
9th 22:38 26th 21:42
12th 20:08 31st 20:51
December: 3/4th and 16/17th: The Alpine Valley
An interesting valley on the Moon: The Alpine Valley
These are good nights to observe an interesting feature on the Moon if you have a small telescope. Close to the limb is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards the upper end you should see the cleft across them called the Alpine valley. It is about 7 miles wide and 79 miles long. As shown in the image a thin rill runs along its length which is quite a challenge to observe. Over the next two nights following the 3rd/4th the dark crater Plato and the young crater Copernicus will come into view. This is a very interesting region of the Moon!
M 109 imaged with the Faulkes Telescope
Spiral galaxy M109, imaged by Daniel Duggan.
This image was taken using the Faulkes Telescope North by Daniel Duggan - for some time a member of the Faulkes telescope team. M 109 is a Barred Spiral some 83 million light years away that lies is a loose collection of Galaxies called the Ursa Major Cloud that may contain over 50 galaxies.
Learn more about the Faulkes Telescopes and how schools can use them: Faulkes Telescope"
Observe the International Space Station
The International Space Station and Jules Verne passing behind the Lovell Telescope on April 1st 2008.
Image by Andrew Greenwood
Use the link below to find when the space station will be visible in the next few days. In general, the space station can be seen either in the hour or so before dawn or the hour or so after sunset - this is because it is dark and yet the Sun is not too far below the horizon so that it can light up the space station. As the orbit only just gets up the the latitude of the UK it will usually be seen to the south, and is only visible for a minute or so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite considerably across the UK. The NASA website linked to below gives details for several cities in the UK. (Across the world too for foreign visitors to this web page.)
Note: I observed the ISS three times recently and was amazed as to how bright it has become.
Find details of sighting possibilities from your location from: Location Index
See where the space station is now: Current Position
The Moon at 3rd Quarter. Image, by Ian Morison, taken with a 150mm Maksutov-Newtonian and Canon G7.
Just below the crator Plato seen near the top of the image is the mountain "Mons Piton". It casts a long shadow across the maria from which one can calculate its height - about 6800ft or 2250m.
|new moon||first quarter||full moon||last quarter|
|Dec 24th||Dec 2nd||Dec 10th||Dec 18th|
Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images
A World Record Lunar Image
To mark International Year of Astronomy, a team of British astronomers have made the largest lunar image in history and gained a place in the Guinness Book of Records! The whole image comprises 87.4 megapixels with a Moon diameter of 9550 pixels. This allows details as small as 1km across to be discerned! The superb quality of the image is shown by the detail below of Plato and the Alpine Valley. Craterlets are seen on the floor of Plato and the rille along the centre of the Alpine valley is clearly visible. The image quality is staggering! The team of Damian Peach, Pete lawrence, Dave Tyler, Bruce Kingsley, Nick Smith, Nick Howes, Trevor Little, David Mason, Mark and Lee Irvine with technical support from Ninian Boyle captured the video sequences from which 288 individual mozaic panes were produced. These were then stitched together to form the lunar image.
Please follow the link to the Lunar World Record website and it would be really great if you could donate to Sir Patrick Moore's chosen charity to either download a full resolution image or purchase a print.
Jupiter will be beautifully seen in the evening sky reaching ~50 degrees above the southern horizon shining at magnitude -2.7 in the constellation of Aries, the Ram. This is one of the best months to view it as it is high in the south at ~8:30 pm mid month. With an angular size of ~46 arc seconds, a small telescope will easily show the equatorial belts (the south equatorial belt has reappeared) and the four Galilean moons. The fact that Jupiter is now high in the sky when due south means that, in contrast to recent years, it is giving us wonderful views this year. Use the details in the highlight above to spot the Great Red Spot (actuall a pale yellow-orange to my eyes) lying in an indentation of the south equatorial belt. Observing it in the last few weeks has shown some prominent dark regions in the north equatorial belt. These are called "barges". If you havn't got a small telescope yet, I cannot think of a better reason for buying one now!See highlight above.
Saturn passed behind the Sun on the 18th of October(called superior conjunction) and can now be seen in the pre-dawn sky. As December begins it will lie in the south-east at an elevation of ~20 degrees when dawn breaks. It lies in Virgo, shining at magnitude +0.8 just a few degrees from the first magnitude star Spica. By month's end it will be visible some 27 degrees above the horizon just east of South as dawn breaks. Sadly, Saturn is heading to the more southerly parts of the ecliptic so, for quite some considerable time, will not be seen high above the horizon however, nicely, the rings are opening out and are now 13.5 degrees to the line of sight, so will appear appreciably wider than we have seen during its last apparition. So, given a good low horizon in the south-east, it could well be worth having a look at its ~16.5 arc second disk and ring system. With a small telescope on a night of good seeing, you should now be able to spot Cassini's Division within the ring system.
Mercury. This month, Mercury passes in front of the Sun on December 4th so will not be visible until late in the month when it will reappear before dawn in the south-eastern sky. Shining at magnitude -0.4 it will be well seen on the 23rd when it lies above a thin crescent Moon and, further down to the right, the star Antares.See highlight above.
Mars. By month's end it rises before midnight and will have risen to an elevation of ~45 degrees an hour before sunrise so can be easily seen in the pre-dawn sky towards the East. It brightens from +0.7 to +0.2 during the month, so is becoming more prominent. Its angular size reaches nearly 9 arc seconds by the end of the month and so it is now, given good seeing, becoming possible to observe features on the surface of its its salmon-pink disk. By month's end it will have already reached an elevation of 15 degrees just south of East by midnight and will lie due south at an elevation of 43 degrees before dawn on New-Years morning - you might still be up! Details, such as the V shape of Syrtis Major and the north polar cap, should now just be visible, but observers will have to wait until early next year for its angular size to exceed 10 arc seconds when these suface details should be readily apparent. (This is providing, of course, that Mars does not suffer a major dust storm!)
Venus, is now gradually increasing its angular seperation from the Sun so can be seen for longer after sunset, but as the ecliptic makes quite a shallow angle to the horizon at this time of the year it will only have an elevation of ~5 degrees at Sunset so very hard to see. But, during the month, our view improves and by its end, Venus lies some 18 degrees above the horizon just south of where the sun sets at sunset. Its angular size is increasing - from 12 to 13 arc seconds - but as it does so its phase (the percentage that we see illiminated) falls from 89 to 83%. One interesting result is that Venus's brightness stays remarkably constant at -3.9 throughout the month.
See highlight above.
Find more planetary images and details about the Solar System: The Solar System
The Early Evening December Sky
The Late Evening December Sky
This maps shows the constellations seen towards the south in early and late evening. Setting towards the west in early evening is the beautiful region of the Milky Way containing both Cygnus and Lyra. Below is Aquilla. The three bright stars Deneb (in Cygnus), Vega (in Lyra) and Altair (in Aquila) make up the "Summer Triangle". East of Cygnus is the great square of Pegasus - adjacent to Andromeda in which lies M31, the Andromeda Nebula. To the north lies "w" shaped Cassiopeia and Perseus. The lower map shoesthe constellation Taurus, with its two lovely clusters, the Hyades and the Pleaides, and is also described in more detail below. as the evening draws on, Orion, the Hunter, follows Taurus into the eastern sky with the constellations Auriga, above, and Gemini, to the upper left. Later Sirius, in Canis Major will be seen to the lower left of Orion. Due to its brightness and scintillations caused by the atmosphere it often appears as a rainbow of colours flashing in the sky.
The constellations Lyra and Cygnus
This month the constellations Lyra and Cygnus are seen almost overhead as darkness falls with their bright stars Vega, in Lyra, and Deneb, in Cygnus, making up the "summer triangle" of bright stars with Altair in the constellation Aquila below. (see sky chart above)
Lyra is dominated by its brightest star Vega, the fifth brightest star in the sky. It is a blue-white star having a magnitude of 0.03, and lies 26 light years away. It weighs three times more than the Sun and is about 50 times brighter. It is thus burning up its nuclear fuel at a greater rate than the Sun and so will shine for a correspondingly shorter time. Vega is much younger than the Sun, perhaps only a few hundred million years old, and is surrounded by a cold,dark disc of dust in which an embryonic solar system is being formed!
There is a lovely double star called Epsilon Lyrae up and to the left of Vega. A pair of binoculars will show them up easily - you might even see them both with your unaided eye. In fact a telescope, provided the atmosphere is calm, shows that each of the two stars that you can see is a double star as well so it is called the double double!
Between Beta and Gamma Lyra lies a beautiful object called the Ring Nebula. It is the 57th object in the Messier Catalogue and so is also called M57. Such objects are called planetary nebulae as in a telescope they show a disc, rather like a planet. But in fact they are the remnants of stars, similar to our Sun, that have come to the end of their life and have blown off a shell of dust and gas around them. The Ring Nebula looks like a greenish smoke ring in a small telescope, but is not as impressive as it is shown in photographs in which you can also see the faint central "white dwarf" star which is the core of the original star which has collapsed down to about the size of the Earth. Still very hot this shines with a blue-white colour, but is cooling down and will eventually become dark and invisible - a "black dwarf"! Do click on the image below to see the large version - its wonderful!
M56 is an 8th magnitude Globular Cluster visible in binoculars roughly half way between Alberio (the head of the Swan) and Gamma Lyrae. It is 33,000 light years away and has a diameter of about 60 light years. It was first seen by Charles Messier in 1779 and became the 56th entry into his catalogue.
Cygnus, the Swan, is sometimes called the "Northern Cross" as it has a distinctive cross shape, but we normally think of it as a flying Swan. Deneb,the arabic word for "tail", is a 1.3 magnitude star which marks the tail of the swan. It is nearly 2000 light years away and appears so bright only because it gives out around 80,000 times as much light as our Sun. In fact if Deneb where as close as the brightest star in the northern sky, Sirius, it would appear as brilliant as the half moon and the sky would never be really dark when it was above the horizon!
The star, Albireo, which marks the head of the Swan is much fainter, but a beautiful sight in a small telescope. This shows that Albireo is made of two stars, amber and blue-green, which provide a wonderful colour contrast. With magnitudes 3.1 and 5.1 they are regarded as the most beautiful double star that can be seen in the sky.
Cygnus lies along the line of the Milky Way, the disk of our own Galaxy, and provides a wealth of stars and clusters to observe. Just to the left of the line joining Deneb and Sadr, the star at the centre of the outstretched wings, you may, under very clear dark skys, see a region which is darker than the surroundings. This is called the Cygnus Rift and is caused by the obscuration of light from distant stars by a lane of dust in our local spiral arm. the dust comes from elements such as carbon which have been built up in stars and ejected into space in explosions that give rise to objects such as the planetary nebula M57 described above.
There is a beautiful region of nebulosity up and to the left of Deneb which is visible with binoculars in a very dark and clear sky. Photographs show an outline that looks like North America - hence its name the North America Nebula. Just to its right is a less bright region that looks like a Pelican, with a long beak and dark eye, so not surprisingly this is called the Pelican Nebula. The photograph below shows them well.
Brocchi's Cluster An easy object to spot with binoculars in Gygnus is "Brocchi's Cluster", often called "The Coathanger",although it appears upside down in the sky! Follow down the neck of the swan to the star Albireo, then sweep down and to its lower left. You should easily spot it against the dark dust lane behind.
The constellations Pegasus and Andromeda
The Square of Pegasus is in the south during the evening and forms the body of the winged horse. The square is marked by 4 stars of 2nd and 3rd magnitude, with the top left hand one actually forming part of the constellation Andromeda. The sides of the square are almost 15 degrees across, about the width of a clentched fist, but it contains few stars visibe to the naked eye. If you can see 5 then you know that the sky is both dark and transparent! Three stars drop down to the right of the bottom right hand corner of the square marked by Alpha Pegasi, Markab. A brighter star Epsilon Pegasi is then a little up to the right, at 2nd magnitude the brightest star in this part of the sky. A little further up and to the right is the Globular Cluster M15. It is just too faint to be seen with the naked eye, but binoculars show it clearly as a fuzzy patch of light just to the right of a 6th magnitude star.
The stars of Andromeda arc up and to the left of the top left star of the square, Sirra or Alpha Andromedae. The most dramatic object in this constellation is M31, the Andromeda Nebula. It is a great spiral galaxy, similar to, but somewhat larger than, our galaxy and lies about 2.5 million light years from us. It can be seen with the naked eye as a faint elliptical glow as long as the sky is reasonably clear and dark. Move up and to the left two stars from Sirra, these are Pi amd Mu Andromedae. Then move your view through a rightangle to the right of Mu by about one field of view of a pair of binoculars and you should be able to see it easily. M31 contains about twice as many stars as our own galaxy, the Milky Way, and together they are the two largest members of our own Local Group of about 3 dozen galaxies.
M33 in Triangulum
If, using something like 8 by 40 binoculars, you have seen M31 as described above, it might well be worth searching for M33 in Triangulum. Triangulum is
the small faint constellation just below Andromeda. Start on M31, drop down to Mu Andromedae and keep on going in the same direction by the same distance as you have moved from M31 to Mu Andromedae. Under excellent seeing conditions (ie., very dark and clear skies) you should be able to see what looks like a little piece of tissue paper stuck on the sky or a faint cloud. It appears to have uniform brightness and shows no structure. The shape is irregular in outline - by no means oval in shape and covers an area about twice the size of the Moon. It is said that it is just visible to the unaided eye, so it the most distant object in the Universe that the eye can see. The distance is now thought to be 3.0 Million light years - just greater than that of M31.
The constellation Taurus
Taurus is one of the most beautiful constellations and you can almost imagine the Bull charging down to the left towards Orion. His face is delineated by the "V" shaped cluster of stars called the Hyades, his eye is the red giant star Aldebaran and the tips of his horns are shown by the stars beta and zeta Tauri. Although alpha Tauri, Aldebaran, appears to lie amongst the stars of the Hyades cluster it is, in fact, less than half their distance lying 68 light years away from us. It is around 40 times the diameter of our Sun and 100 times as bright.
More beautiful images by Alson Wong : Astrophotography by Alson Wong
To the upper right of Taurus lies the open cluster, M45, the Pleiades. Often called the Seven Sisters, it is one of the brightest and closest open clusters. The Pleiades cluster lies at a distance of 400 light years and contains over 3000 stars. The cluster, which is about 13 light years across, is moving towards the star Betelgeuse in Orion. Surrounding the brightest stars are seen blue reflection nebulae caused by reflected light from many small carbon grains. These relfection nebulae look blue as the dust grains scatter blue light more efficiently than red. The grains form part of a molecular cloud through which the cluster is currently passing. (Or, to be more precise, did 400 years ago!)
Close to the tip of the left hand horn lies the Crab Nebula, also called M1 as it is the first entry of Charles Messier's catalogue of nebulous objects. Lying 6500 light years from the Sun, it is the remains of a giant star that was seen to explode as a supernova in the year 1056. It may just be glimpsed with binoculars on a very clear dark night and a telescope will show it as a misty blur of light.
Its name "The Crab Nebula" was given to it by the Third Earl of Rosse who observed it with the 72 inch reflector at Birr Castle in County Offaly in central Ireland. As shown in the drawing above, it appeared to him rather lile a spider crab. The 72 inch was the world's largest telelescope for many years. At the heart of the Crab Nebula is a neutron star, the result of the collapse of the original star's core. Although only around 20 km in diameter it weighs more than our Sun and is spinning 30 times a second. Its rotating magnetic field generate beams of light and radio waves which sweep across the sky. As a result, a radio telescope will pick up very regular pulses of radiation and the object is thus also known a Pulsar. Its pulses are monitored each day at Jodrell Bank with a 13m radio telescope.
The constellation Orion
Orion, perhaps the most beautiful of constellations, will be seen in the south at around 11 - 12 pm during January. Orion is the hunter holding up a club and shield against the charge of Taurus, the Bull up and to his right. Alpha Orionis, or Betelgeuse, is a read supergiant star varying in size between three and four hundred times that of our Sun. The result is that its brightness varies somewhat. Beta Orionis, or Rigel, is a blue supergiant which, at around 1000 light years distance is about twice as far away as Betelgeuse. It has a 7th magnitude companion. The three stars of Orion's belt lie at a distance of around 1500 light years. Just below the lower left hand star lies a strip of nebulosity against which can be seen a pillar of dust in the shape of the chess-board knight. It is thus called the Horsehead Nebula. It shows up very well photographically but is exceedingly difficult to see visually - even with relativly large telescope.
Beneath the central star of the belt lies Orion's sword containing one of the most beautiful sights in the heavens - The Orion Nebula. It is a region of star formation and the reddish colour seen in photographs comes from Hydrogen excited by ultraviolet emitted from the very hot young stars that make up the Trapesium which is at its heart. The nebula, cradling the trapesium stars, is a beautiful sight in binoculars or, better still, a telescope. To the eye it appears greenish, not red, as the eye is much more sensitive to the green light emitted by ionized oxygen than the reddish glow from the hydrogen atoms.