Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during May 2014.

Gemini is setting in the west as twilight ends, with Canis Minor and its bright star Procyon to its lower left. Cancer is further to the south, with the Beehive Cluster at its heart. Leo the Lion is even further round, with the star Regulus and some galaxies nearby that are visible with binoculars or a small telescope. Over to the east is Bootes and the star Arcturus, with Corona Borealis beside them. Continuing to move around the sky, the four stars of the Keystone in Hercules can be found, and the globular cluster M13 is two-thirds of the way up its right-hand side. The summer constellations are rising in the north-east, with the stars Vega in Lyra and Deneb in Cygnus. To the south-east, below Bootes, are Virgo and the bright star Spica, as well as Libra, Serpens Caput and the zodiacal constellation of Ophiuchus.

The Planets

• Jupiter is still at 45 degrees' elevation in the west at sunset at the beginning of May, setting around 01:00 BST (British Summer Time, 1 hour ahead of Universal Time). It dims from -2.0 to -1.9 in magnitude during the month, while shrinking from 35 to 33" in angular diameter. It is only 20 degrees above the horizon at sunset by month's end, and sets at around 23:00 BST (although you may see it for up to an hour longer if you have a very low north-western horizon). Jupiter lies in Gemini, moving from beside the fourth-magnitude star Mekbuda towards the bright stars Castor and Pollux, and passing Wasat on the way. You can see the Galilean moons with binoculars, and the Great Red Spot at certain times with a telescope, with the best chance to observe coming early in the month.
• Saturn reaches opposition (opposite the Sun in the sky) on the 10th, so it is in the sky all night. It shines at magnitude +0.1 quite low down in Libra, and its disc is 18.6" in diameter. It is moving west (retrograde) towards the star Alpha Librae. The rings are now 22 degrees from the line of sight and about 43" across, so a small telescope can pick out Cassini's Division.
• Mars is receding from us and dims from -1.2 to -0.5 this month, while shrinking from 14.5 to 11.8" in angular size. It moves little in the sky during May because its retrograde motion ends midway through the month, and it lies close to the star Porrima in Virgo. Mars is best seen early in the month, at around 23:00 BST.
• Mercury has its best apparition of the year this month. It is low in the evening twilight as May begins, but rises higher each evening, appearing 15 degrees above the horizon at sunset in the second half of the month. It reaches elongation (its furthest from the Sun in the sky) on the 25th, shining at magnitude +0.4 and presenting a crescent disc 8" across and 40 percent illuminated. It is visible for 2 hours after sunset at this point, but by the end of May it is only 5 degrees above the horizon 1 hour after sunset, with a brightness of magnitude +1.2.
• Venus lies in Pisces and shines at magnitude -4. It is some 12 degrees above the eastern horizon half an hour before sunrise. Its gibbous disc drops from 17 to 15" in angular size this month, but its illuminated fraction increases from 67 to 77 percent, keeping its brightness almost constant.

Highlights

• It is a good time to observe Mars this month as it appears larger than usual in the sky.
• It is also a good time to observe Saturn this month, since it, too, appears large in the sky and is up throughout the night. It can be located by following the arc of the Plough's handle towards orange Arcturus, then continuing the curve down to white Spica, and finally looking for the slightly brighter yellow object to it's lower left - this is Saturn. As well as its ring system, binoculars or a small telescope allow you to spot its largest moon, Titan, at magnitude 8.2.
• Jupiter is coming to the end of its current apparition, but can still be easily seen this month. It is high in the sky just after sunset, allowing surface features to be seen with a telescope.
• Comet C/2012 K1 (PANSTARRS) passes below the Plough this month. With a magnitude of +7 to +8, it can be seen with binoculars. It is near the leftmost star of the Plough's handle on the 1st and 2nd, passes by Chi Ursae Majoris on the 18th and 19th and approaches Psi Ursae Majoris on the 26th and 27th.
• The Eta Aquariid meteor shower peaks before dawn on the 6th. With a low south-eastern horizon, up to 10 meteors per hour may be visible. The meteors come from dust particles release by Comet Halley when it approached the Sun 4000 years ago.
• Jupiter is near a thin crescent Moon on the 3rd and 4th.
• Mars is near a waxing Moon on the 11th.
Mercury is close to a thin crescent Moon on the 30th.

Southern Hemisphere

John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during May 2014.

Orion the Hunter is low in the west, with three stars forming his Belt. To Maori, they form part of the Bird Snare. The blue star Rigel marks one of Orion's feet, while red Betelgeuse forms one of his shoulders. Above the Belt are the three stars of Orion's Sword, the middle member of which is actually the Orion Nebula. Slightly fuzzy to the naked eye, it is a bat-shaped cloud in binoculars or a small telescope and can be seen to be a beautiful star-forming region with a large telescope. The Belt and Sword are sometimes described as the Pot or the Saucepan by southern hemisphere observers. Following Orion is Canis Major, one of his hunting dogs, with Sirius, the brightest star in the night sky, forming its head. It is commonly known as the Dog Star, but to Maori it is Takarua, the Winter Star, and in Ancient Egypt it was called Sothis, and heralded the annual flooding of the River Nile. Procyon, the brightest start in Canis Minor, is lower down. Both Sirius and Procyon have faint white dwarf companions, but these are not easily observed. Following a line from Rigel through Betelgeuse leads to the planet Jupiter, near to Castor and Pollux, the heads of the Gemini Twins. Bands and belts on Jupiter's surface can be seen on a dark night using a telescope, while binoculars show its four largest moons.

The constellations of Scorpius and Sagittarius are rising in the east in the evening, reaching high into the sky later and showing off many beautiful objects. Crux, the Southern Cross, is high overhead after sunset, and near the star Beta Crucis is a star cluster called the Jewel Box, which appears as a hazy star to the unaided eye and as a pretty group of stars in binoculars or a telescope. Between Crux and Sirius, Carina the Keel and Vela the Sails sit along the Milky Way and contain the asterisms of the False and Diamond Crosses. They contain a wealth of bright stars, clusters and nebulae, many of which can be observed with no equipment. The Carina Nebula is the brightest of these, and appears larger than the Orion Nebula. Binoculars reveal its bright star clusters and glowing clouds of gas, intertwined with dark lanes. Within it, the star Eta Carinae is bright and orange.

The planets Mars and Saturn are in the north and east respectively after sunset. Mars is in Virgo, near the blue-white star Spica, and is now receding from the Earth and shrinking in apparent size. Lying away from the Milky Way, Many galaxies can be spotted in Virgo using a medium-sized telescope. Saturn is a yellowish object in Libra the Scales. It reaches opposition (opposite the Sun in the sky) on the 10th, and is occulted by the nearly-full Moon for observers in New Zealand and Australia at around midnight NZST (New Zealand Standard Time, 12 hours ahead of Universal Time) on the night of the 14th-15th. The event is visible to the unaided eye, but its progress will be spectacular when viewed through binoculars.

Autumn is a prime time to observe the Aurora Australis, or Southern Lights. Caused by the interaction between the solar wind and the Earth's atmosphere, the phenomenon can sometimes be seen from southerly parts of New Zealand, Australia and South America, consisting of a red glow, or even moving sheets of red and green light, on the southern horizon. With a high level of activity on the Sun so far this year, it is worth checking the several websites on which you can find current information and short-term forecasts of aurorae.

The planet Venus is in the morning sky, but rises later each day as it moves closer to the Sun from our perspective.