The Night Sky This Month

Ian Morison tells us what we can see in the northern hemisphere night sky during February 2012.

The constellation of Orion takes centre stage with its bright stars, Betelgeuse and Rigel. Orion's Sword contains M42, the Orion Nebula, visible as a hazy glow through binoculars. Sirius, our brightest night-time star, is down and to the left; atmospheric scintillation makes it twinkle colourfully. Above and right of Orion is Taurus the Bull, containing the red star Aldebaran as its eye and the Hyades Cluster, which forms its head. The Pleiades, or Seven Sisters, are nearby. Up and left of Orion is Gemini, containing the Heavenly Twins, Castor and Pollux, while Auriga is towards the zenith with its bright star Capella. The Milky Way runs through Auriga and hosts several open star clusters. Leo the Lion rises in the east later in the evening, above the planet Mars.

• Jupiter is at its highest (about 50°) around sunset, shining at magnitude -2.4 in Aries. With an angular size of 38.7", a small telescope will show its equatorial bands and Great Red Spot.
• Saturn is up from late at night until morning, reaching 31° elevation. It brightens from +0.6 to +0.5 during the month and its rings continue to open to our line of sight, reaching 15&#176 from edge-on and allowing the gaps between sets of rings to be seen.
• Mercury passes behind the Sun (superior conjunction) on the 6th, but reappears near month's end, shining at magnitude -1.1 after sunset in the south-western sky. Its angular size is around 6" and is increasing.
• Mars moves westwards in the sky from night to night, contrary to the usual apparent planetary motion; this is called retrograde motion, and results from the Earth overtaking it on the inside track as the two planets orbit the Sun. Its angular diameter is increasing and, at the end of the month, it is 14" in size, rises by 6pm and reaches 50° elevation. Surface features can be seen using a small telescope, including Syrtis Major and the north polar cap.
• Venus is about 30° above the south-western horizon at sunset at the beginning of the month and 37° above by the end, as it increases its angular separation from the Sun. Its angular size increases over the month from 15 to 18" as its illuminated fraction drops from 74 to 64%, giving it a very bright and constant magnitude of -4.1.

• Comet Garradd can be seen in the east before dawn this month. The globular cluster M13 is nearby, above the Keystone, which is the asterism consisting of the four brightest stars in the constellation of Hercules. It is the best-seen globular cluster in the northern hemisphere, and the cluster M92 is not far away, to the left of the Keystone. The two are at magnitudes of +6 and +6.5 respectively, and the magnitude +7 comet makes its closest appearance to M92 on the 3rd, allowing it to be found with binoculars.
• Mars can be seen close to a waning gibbous Moon at around 9pm on the 9th.
• Saturn makes a near-straight line in the sky with a waning Moon and the star Spica before dawn on the 12th.
• Jupiter, Venus, Mercury and a thin crescent Moon are all in close proximity early on the evening of the 25th. You should be able to see Earthshine, otherwise known as 'the old Moon in the new Moon's arms'.
The Hyginus Rille is a nice feature of the Moon to look at around the middle of this month. It appears in the Mare Vaporum as a line with an 11-km crater in the centre, which is probably the result of a volcano during the Moon's early history.

John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during February 2012.

Three planets are visible in the evening sky: Venus, which sets in the west after sunset, Jupiter, which sets in the north-west around midnight, and Mars, which rises red in the north-east after twilight.

The brightest star in the night sky, Sirius, sits high in the north in the constellation of Canis Major, the Large Dog. Towards the northern horizon is Procyon, the eighth-brightest night-time star, in the constellation of Canis Minor, the Little Dog. The two dogs accompany Orion, the Hunter, while between them is Monoceros, the Unicorn. It contains a number of beautiful stars, including the triple system Beta Monocerotis, which can be separated in a telescope, and the double star Epsilon Monocerotis, with its yellow and blue components. The constellation also offers a number of star clusters as it is on the edge of the Milky Way. Between Sirius and Procyon is M50, also designated NGC 2323, a cluster of about 100 stars that is visible in binoculars. To the north-east of Monoceros is NGC 2232, an irregular open cluster, while the bright, scattered cluster NGC 2244 sits in the centre of the Rosette Nebula. Other interesting clusters include NGC 2261, NGC 2301 and NGC 2264, the last of which is also called the Christmas Tree Cluster due to its shape. It contains the Cone Nebula at its tip, which can be seen through a large telescope. Monoceros is also home to the massive 6th-magnitude binary system Plaskett's Star, which has a mass of around 100 times that of our Sun. The 15th-magnitude star V838 Monocerotis has variable brightness, but is usually very faint. Other well-known variable stars include Beta Persei (Algol), which varies because it is an eclipsing binary system, and Betelgeuse, which swells and cools as it nears the end of its life.

In the south-east is Crux, the Southern Cross, and near to that is Musca, the Fly, with the Coalsack Nebula joining the two. The star Alpha Muscae is a double that can be split with a medium-sized telescope. Theta Muscae is also a double, and the brighter of the two partners is a Wolf-Rayet star, meaning that it ejects a lot of material. Nearby are the globular clusters NGC 4372 and NGC 4833 and the 10th-magnitude planetary nebula NGC 5189, which has an S-shaped appearance.

• Two meteor showers, known as the Centaurids, occur in early February, producing 5-25 meteors per hour. The Moon will hamper their observation this year, however.
• The constellations of Orion, Taurus and Gemini are visible this month, but will soon slide away into the twilight sky.
• The Milky Way runs almost from north to the south in the evenings this month, with the constellation of Carina and its bright star Canopus overhead. There are many star clusters and nebulae to be found with binoculars in this region of the sky.

Ian Morison tells us what we can see in the northern hemisphere night sky during January 2012.

There is a lovely sky to start the new year off with. Orion the Hunter is due south in the evening. The three stars of his Belt point down and to the left towards the bright star Sirius in Canis Major. Up to the right we come to Taurus the Bull and the little group of stars called the Hyades, which has an interloper, Aldebaran, a bright orange star that forms the eye of Taurus. Carrying on beyond, we come to the group of stars called the Pleiades, an obvious target for a small telescope. Looking at the two bright stars in the centre of Pleiades, one has a triplet of fainter stars beside it and between it and the other there's a double star, one of which is nice and red. Starting with the central star of Orion's Belt, drop down to the Sword where there is the Orion Nebula, a region of star formation. At its heart is a group of four or five very blue stars called the Trapezium. Up to the left of Orion we have Gemini, with Castor above and Pollux below. Down below them is Procyon, the bright star in Canis Minor. Above Orion is Auriga, coming up towards the zenith, with its bright yellowish star called Capella. The Milky Way runs between Orion and Gemini, above Taurus and through Auriga. There are some very nice little star clusters - M36, M37 and M38 - which can be picked out with binoculars and are nice to observe with a telescope. As the evening goes on, Leo the Lion rises in the south east.

• Jupiter is beautiful in the evening sky. On January 1st, at 7.30pm, it will be at about 50° elevation due south, on the boundary of Pisces and Aries. Its angular size is about 41". The equatorial bands are still easily visible, with the Great Red Spot in the Lower Belt and dark markings called 'barges' currently visible in the North Equatorial Belt.
• Saturn is in the pre-dawn sky. On January 1st it rises at 2am, and by 5am it is about 28° above the horizon. The rings are about 15&#176 from the line of sight, so Cassini's Division can be seen with a small telescope. Its angular size is 17".
• Mercury is also in the pre-dawn sky, towards the south-east, brightening from magnitude -0.4 at the beginning of the month to -0.7 by the end. Its angular size decreases down to 4.8" by the end of the month.
• Mars rises before midnight and before dawn it is about 47° high, due south. It increases in brightness to magnitude -0.4 by month's end, and its angular size increases to 11". It is now possible to see details on the salmon-pink disk, such as the V-shape of Syrtis Major and the North Polar Cap.
• Venus is now gradually increasing its separation from the Sun and reaches 34° away. Its elevation at sunset is about 18°. Its angular size is increasing but the the surface illumination is decreasing, so its magnitude stays constant at -4 throughout the month.

• Early morning on January 3rd/4th is the Quadrantid meteor shower. The radiant is between Boötes and the handle of the Plough. There can be up to 200 meteors per hour, but they are not very bright and visibility is hampered by a first-quarter Moon in the sky. The Moon sets at 3.30am, so from 1-2am its light should not be too much of a problem.
• Looking south west on January 10th, Asteroid Vesta is about 3' up to the left of the star Tau Aquarii in Aquarius. It is at magnitude +8, so binoculars should pick it out.
• On January 12th/13th/14th, Neptune is just above and to the right of Venus, shining at magnitude +8. On January 13th, use binoculars to centre Venus in the field of view and Neptune should be up and to the right, about a third of the way to the edge of the field of view.
• There is a nice skyscape on January 16th, about an hour before dawn, with Saturn close to a third-quarter Moon and Spica, the brightest star in Virgo.
• On January 26th, just after sunset, at about 4.40pm, there is a chance to spot Venus and a thin crescent Moon. It should be possible to see Earthshine, or "the old Moon in the new Moon's arms".

John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during January 2012.

January finds the planets Venus and Jupiter in the evening sky. Venus is low down in the west, setting about two hours after sunset. Jupiter is higher in the north and will set around midnight. In early January, Jupiter moves from the constellation of Pisces the Fish into the constellation of Aries the Ram. Aries is a faint constellation containing a number of double stars, but larger telescopes are needed to easily observe them.

In sharp contrast to faint Aries, Orion the Hunter has a large number of bright stars and sights for binoculars and any size of telescope. Orion's brightest stars, Rigel, Betelgeuse and Bellatrix - along with the three stars of his Belt - form an easily seen pattern in the evening sky. Well placed for viewing is the Orion Nebula, which can be found in the middle of Orion's Sword. To the unaided eye, this nebula appears to be a fuzzy star. If you have binoculars or a small telescope, you will see a bat-shaped cloud. A telescope with an aperture of 100mm or more will reveal a number of stars in and around the nebula, including a tight group of four stars called the Trapezium. Marking Orion's left foot is Rigel, the brightest star in Orion, shining at magnitude +0.18.

Running from a star nearby to Rigel and across the sky to Achernar is the long and rambling constellation of Eridanus, the River. Epsilon Eridani is a magnitude +3.7 dwarf star. Theta Eridani (Acamar) is a pair of blue-white stars of magnitudes +3.2 and +4.4, separated by just over 8", that are easily seen through a telescope. 32 Eridani is a beautiful double star for small telescopes, consisting of a magnitude +5 yellow star and a blue-green magnitude +6.3 companion separated by just under 7". 40 Eridani is a remarkable triple star system: small telescopes will reveal a magnitude +4.4 yellow star; nearby is a widely separated magnitude +9.6 white dwarf companion, the most easily seen white dwarf star in the sky. Large telescopes will show that the white dwarf has an 11th magnitude red dwarf companion. Also along the river is NGC 1535, a small planetary nebula appearing in a nice field of scattered stars.

Returning to the northern sky, we find Taurus, along with the Pleiades (Matariki to the Māori) to the west of Orion, which sets around midnight. To the east of Orion are his two hunting companions Canis Major, the Larger Dog, and Canis Minor, the Smaller Dog. The brightest star in our night sky, Sirius, marks the collar of Canis Major.

For those staying out later, Mars rises after midnight in the constellation of Leo. It appears as a reddish coloured star and is brighter than any of the other nearby stars. Later, Saturn will rise in Virgo, its rings slowly tilting towards us, which will lead to better views of them later this year.

We have a visitor to the inner Solar System that may be visible in early January. Comet Lovejoy made a close approach to the Sun on December 15th 2011, and by late December it was visible throughout the night in the south. This comet may now have dropped in brightness as it moves away from the Sun, and might only be visible through telescopes.

Ian Morison tells us what we can see in the northern hemisphere night sky during December 2011.

The summer constellations of Cygnus and Lyra are still visible high in the north-west in the evening, with their bright stars Deneb and Vega. The Milky Way arcs overhead from Cygnus. The Square of Pegasus is in the south, while the winter constellations of Taurus and Orion follow from the east. The Pleiades star cluster lies in Taurus, and in the centre a telescope reveals a triplet of stars and a double star system nestled among the brighter members. Below Orion's Belt, the nebula M42 makes up part of Orion's Sword. The stars of the Trapezium can be seen within the nebulosity using a telescope. Sirius, the brightest star in the sky, rises to the lower left of Orion later in the evening. Above and left of Orion and Taurus is Gemini with its twin bright stars Castor and Pollux. Leo rises late in the night.

• Jupiter dominates the night sky, reaching an elevation of 50° for observers in the UK. Its height means observations of detail on its surface is less hampered by atmospheric scintillation.
• Saturn rises before dawn, reaching an elevation of about 20° when the Sun comes up at the beginning of the month. It is a few degrees from the star Spica at this time, in the constellation of Virgo. By the end of the month it is at a height of 27° in the south at dawn. Its maximum elevation will get lower over the next few months, but its rings continue to open out from our point of view and are now at 13.5° to the line of sight. The planet's disc spans 16.5".
• Mercury passes in front of the Sun (inferior conjunction) on the 4th, but reappears before dawn in the south-eastern sky near the end of the month, shining at magnitude -0.4. It is near to a thin crescent Moon and the star Antares on the 23rd.
• Mars reaches an angular diameter of 9" by month's end, allowing surface detail to be seen with a telescope. It also brightens from +0.7 to +0.2 during December, but only rises towards midnight.
• Venus is quite low in the south-west at sunset, but reaches 18° elevation by the time the Sun goes down at the end of the month. Its angular size is 13° and it is now waning in phase, but remains at a magnitude of about -3.9 all month.

• A partial lunar eclipse is visible in the UK from around 3pm GMT (Greenwich Mean Time) on the 10th, although the Moon will only be up for an hour or so before it begins to leave the Earth's shadow.
• The Geminid meteor shower peaks in the early mornings of the 14th and 15th. The Moon will obscure some of the shower, however. The meteors come from the asteroid 3200 Phaeton, rather than from a comet as is more common.
• Saturn, the star Spica and a thin, waning crescent Moon are close together an hour before dawn on the 21st. Mercury may also be visible, very low in the east.
• The Ursid meteor shower is visible on the morning of the 23rd, unhampered by the Moon's glare. 10-15 meteors per hour may be observed, but occasionally more are seen. The radiant, from where the meteors appear to originate, is near the star Kochab in Ursa Minor
• Mercury and a thin crescent Moon appear together before dawn on the 23rd.
• Venus and a thin cresent Moon are close together after sunset on the 27th.
• Our neighbouring galaxy, Andromeda, also known as M31, is visible this month. With a large angular size of around 3°, it is best viewed through binoculars or a small telescope.

John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during December 2011.

The constellations of Taurus, Orion, Canis Major and Canis Minor are in the northern sky in the evening. The fainter summer constellations of Hydrus, Mensa and Volans cluster around the south celestial pole. The ninth-brightest night-time star, a blue giant named Achernar, is high in the winding constellation of Eridanus, the River. It is not spherical, but is flattened by its high rotational speed. Hydrus, the Water Snake, contains three bright stars, each of around magnitude +3, in a triangle which crosses the constellation of Tucana and the Small Magellanic Cloud. Pi Hydri is a double star of magnitude +5.5, consisting of unconnected red and yellow stars. Mensa, the Table, contains no stars brighter then magnitude +5, but it is home to part of the Large Magellanic Cloud, the most massive dwarf satellite galaxy of the Milky Way, in which star clusters and nebulae can be seen with binoculars or a small telescope. The star Pi Mensae is orbited by a planet of around 10 times the mass of Jupiter. Volans, the Flying Fish, contains a double star called Gamma Volantis in a field of scattered stars.

The rich star fields of Carina, along the Milky Way, contain the asterism of the Diamond Cross and the open cluster IC 2602, known as the Southern Pleiades. The cluster contains over 30 stars, the brightest of which is Theta Carinae at magnitude +2.8. On the other side of the Diamond is another open cluster, NGC 3532, or the Wishing Well Cluster, which spans twice the area of the full Moon. The Carina Nebula, at the heart of which is the immense star system of Eta Carinae, is in the same constellation. Crux, the Southern Cross, is further south along the Milky Way, small but very visible. The dark and dusty cloud of the Coalsack Nebula runs alongside, and is a place where stars of the future will be born.

• Venus is low in the west after sunset, in a gibbous phase similar in shape to an almost-full Moon.
• Jupiter is high in the northern sky in the evening, allowing telescopes to make out its disc and larger moons.

• A total lunar eclipse is visible throughout Australia and New Zealand, with the Moon completely within the Earth's shadow on the 11th from 03:06 to 03:58 (New Zealand Daylight Savings Time, 13 hours ahead of GMT)

Ian Morison tells us what we can see in the northern hemisphere night sky during November 2011.

The Square of Pegasus is in the south-east after sunset. An arc of stars forms the mane and head of Pegasus, the Winged Horse. The globular cluster M15 is up and right of Enif, the nose of the Horse. The top-left of the Square is the star Alpheratz, from which your unaided eye can locate 2.5-million-year-old photons coming from the Andromeda Galaxy. Under a dark sky, the Triangulum Galaxy, our smaller neighbour, can also be found. The w-shaped constellation of Cassiopeia is high in the sky, with Perseus slightly lower to the north-east. Between them, where the Milky Way runs, the Perseus Double Cluster can be made out with binoculars or a telescope. Taurus, the Bull, is lower in the east, containing the Pleiades Cluster. The V-shaped Hyades Cluster marks the head of the Bull. The Bull's eye is the bright red giant star Aldebaran, which is not part of the Hyades. Orion rises in the east later in the evening, and moves across the southern sky during the night.

• Jupiter is just past opposition (when it is on the opposite side of the Earth to the Sun) and so is close to us. It is in Aries, the Ram. As well as getting high in the sky, it is close to perihelion, giving it an angular size of almost 50", which is near the maximum possible. You can make out its Great Red Spot at certain times using a telescope.
• Saturn has now passed superior conjunction (when it was behind the Sun in the sky) and reappears in the pre-dawn sky this month. It has a magnitude of +0.8 and lies in Virgo, a few degrees from the first-magnitude star Spica. By month's end, it is at 20° elevation at dawn. The rings are 13.5° from edge-on and continue to open out, with the Cassini Division easily visible with a telescope.
• Mercury is about 2° below Venus in the first half of the month and shines at magnitude -0.3. Its low elevation at sunset means that binoculars are needed to see it (be sure not to look or point a telescope towards the Sun). As the month progresses, Venus climbs higher each night while Mercury drops down out of view.
• Mars resides in Leo at magnitude +1, and passes close to the Lion's brightest star, Regulus, on the 10th and 11th. By the end of the month, it is visible by midnight each night and reaches 40° above the horizon by dawn. With an angular diameter of 7", surface features are now becoming visible, and it will increase to 10" after Christmas.
• Venus has emerged from superior conjunction and has an 11" disc which is 90% illuminated. It can be seen just above the south-western horizon at sunset at the start of the month, with a magnitude of -3.8. By the end of the month it is up for a little longer after sunset.

• Mars is 1.3° from Leo's brightest star, Regulus, an hour before dawn on the 11th, remaining close by for five days.
• The Leonid meteor shower peaks on the night of the 16th-17th. The best time to view it is around midnight, when the Moon is not nearby in the sky. The meteors are the dust of Comet Tempel-Tuttle, which orbits the Sun every 33 years, and appear to originate from the from the Lion's head (also known as the Sickle) in the constellation of Leo.
• Saturn is close to the star Spica and a thin, waning crescent Moon before dawn on the 22nd.
• Venus appears near the thin crescent Moon at sunset on the 27th, also giving a chance to spot 'the Old Moon in the New Moon's Arms'.
• Neptune can be found using binoculars or a telescope from the 20th to the 27th, when the Moon is not washing it out. It is near the star Iota Aquarii in Aquarius. On the 22nd, it is in the same position in the sky as it was when it was discovered.
• Comet Garradd is visible this month at magnitude +6 using binoculars in the constellation of Hercules, to the left of the Keystone, near the star Alpha Hercules. The Hercules Globular Cluster is not far away, to the right of the Keystone.
• The asteroid Eunomia can be viewed with binoculars towards the end of the month at magnitude +8, as it passes high to the east through Perseus. It is almost overhead on the 28th, lying in front of the California Nebula, which is a reddish region of excited hydrogen gas.
• Uranus can just be made out with the naked eye in a dark sky at magnitude +5.8 this month. It is in Pisces, about 15° below the eastern side of the Square of Pegasus.

John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during November 2011.

The winter constellations of Scorpius and Sagittarius are descending towards the western horizon, while the rise of Taurus, Orion and Canis Major in the east heralds the arrival of summer. Early in the month, Mercury and Venus are close together in the west after sunset, and by the middle they approach to the red star Antares, the heart of the Scorpion. Jupiter rises high in the northern sky by midnight, appearing at its brightest as it is close to the Earth, having just passed opposition (when it was on the opposite side to the Sun in the sky). Binoculars or a small telescope reveal its four largest moons, which change position from night to night. Banding on its surface is also visible, as is its Great Red Spot at certain times. Jupiter's rapid rotation and fluid composition make it appear wider than a sphere at its equator.

The three brightest stars in the night sky - Sirius, Canopus and Alpha Centauri - line the south-eastern horizon near the Milky Way. The brightest is Sirius in upside-down Canis Major (the Great Dog), which shines at magnitude -1.46 and is intrinsically around 26 times more luminous than our Sun. The second-brightest star in Canis Major is Adhara, at magnitude +1.5, which is intrinsically some 20,000 times more luminous than the Sun and one of the brightest ultraviolet sources in the sky. The Great Dog's third-brightest star is at the Wezen, at the tip of its tail; it is a yellow supergiant 50,000 times more luminous than the Sun. The open star cluster M41 is in the belly of the Dog, and can be seen with the naked eye or resolved into individual stars using binoculars or a telescope.

Crux, the Southern Cross, is in the south-west after sunset and descends during the night but never sets. Taurus the Bull and Orion the Hunter stand to the north-east of Sirius, with the Hyades Cluster forming the Bull's head. The brightest star in this region is Aldebaran (the Follower), which lies between Earth and the Hyades, and is named for following the Pleiades Cluster across the sky. The Pleiades are part of the Bull's back, and are also known as the Seven Sisters in Greek mythology, as Matariki to the Māori and as Subaru to the Japanese. Near to where the Bull's horns point to the northern horizon is the Crab Nebula, an expanding cloud of gas and dust resulting from a supernova observed in 1054. Orion has his shield and sword raised, and a Belt of three aligned stars with a fainter Sword slightly higher in the sky. A faint haze in the Sword marks the Orion Nebula, a star-forming region 1200 light-years from us. To most southern hemisphere observers the Belt and Sword are called the Pot, the Iron Pot or the Saucepan, while to M&#257 they are Tautoru. The Maya visualised Orion as a turtle with three stone glyphs on its back, while they saw the stars Alnitak, Rigel and Saiph as a triangular hearth from which the Orion Nebula was rising smoke.