Interesting object in the southern sky Chart for the southern sky in May
Interesting objects in the northwest Sky Chart for the northwest sky in May
Sirius and the bright stars of Orion light up the western sky. Canopus is in the southwest sky. Crux, the Southern Cross, and the Pointers are southeast of overhead. Lower in the southeast the Scorpion is rising, upside down with Sagittarius below it. Jupiter appears below Sagittarius in the later evening. Saturn, midway up the north sky, makes an eye-catching pair with Regulus, the head star of Leo the lion. Mars, now distant -- 300 million km away -- and faint, is above Castor and Pollux, the head stars of Gemini the twins, low in northwest.
Sirius is the first star to appear at dusk, midway down the western sky. Below, near the western skyline, it Rigel and Betelgeuse become visible. They are the brightest stars in Orion. Rigel is bluish-white and Betelgeuse orange. Between Rigel and Betelgeuse is a vertical line of three stars, Orion's belt. To southern hemisphere star watchers, the line of three makes the bottom of 'The Pot'.
Sirius, 'the Dog Star', marks the head of Canis Major the big dog. A group of stars above it make the dog's hindquarters and tail. Sirius is the brightest star in the sky both because it is relatively close, nine light years away, and 23 times brighter than the sun. Being bright and low, Sirius often twinkles like a diamond as the air breaks up its white light. Procyon, right of Sirius, marks the other dog following Orion the hunter down the sky.
Crux, the Southern Cross, is southeast of the zenith. Below it are Beta and Alpha Centauri, often called 'The Pointers'. Alpha Centauri is the closest naked-eye star, 4.3 light years away. A telescope shows it is a binary star: two suns orbiting each other in 80 years. Beta Centauri and many of the stars in Crux are hot, extremely bright blue-giant stars hundreds of light years away. Canopus is also a very luminous and distant, 13 000 times brighter than the sun and 300 light years away.
Scorpius is midway up the southeast sky, below the Pointers. Its brightest star is orange Antares, marking the scorpion's heart. Antares is a red giant star: 600 light years away and 19 000 times brighter than the sun. Red giants are much bigger than the sun but much cooler, hence the red colour. They are dying stars; wringing the last of the thermo-nuclear energy from their cores. Antares and Betelgeuse will end in spectacular supernova explosions in a few million years.
The Milky Way is brightest and broadest in the southeast toward Scorpius and Sagittarius. It remains bright but narrower across the zenith but fades in the western sky. The Milky Way is our edgewise view of the galaxy, the pancake of billions of stars of which the sun is just one. The thick hub of the galaxy, 30 000 light years away, is in Sagittarius. A scan along the Milky Way with binoculars will find many clusters of stars and some glowing gas clouds. Relatively nearby dark clouds of dust and gas make holes and slots in the Milky Way.
The Clouds of Magellan, LMC and SMC are midway down the southern sky, easily seen by eye on a dark moonless night. They are two small galaxies about 160 000 and 200 000 light years away. The LMC is about 5% the mass of the Milky Way galaxy; the SMC around 3%; but that's still billions of stars in each galaxy.
Arcturus, in the northeast, twinkles red and green as the air disperses its orange colour. It is 120 light years away and 37 times brighter than the sun.
Saturn rings and its largest moon, Titan, are visible in small telescopes. The rings are 'closing' now and will be edge-on in 2009. Saturn is around 1400 million km away. Jupiter rises in the southeast around 9 p.m.; a very bright golden 'star'. Binoculars show it as a small disk. A telescope will reveal its four big moons strung out on either side of the planet. It is 700 million km away.
To use the chart, hold it up to the sky. Turn the chart so the direction you are looking is at the bottom of the chart. If you are looking to the south then have 'South horizon' at the lower edge. As the earth turns the sky appears to rotate clockwise around the south celestial pole (SCP on the chart). Stars rise in the east and set in the west, just like the sun. The sky makes a small extra rotation from night to night as we orbit the sun.
Sirius the brightest star, is midway down the western sky. Directly below it, setting early, is Orion with 'the Pot', on its side, at its centre. Canopus, the second brightest star, is southwest of overhead. Saturn makes an eye-catching pair with Regulus in Leo, midway up the northern sky. Mars, orange and faint, is low in the northwest. Crux, the Southern Cross, and the Pointers are high in the southeast sky. The Scorpion, on its back, is below them. Jupiter, very bright and golden, rises in the southeast about 9 pm.
Centaurus, with the bright 'Pointers', and Crux, the Southern Cross are south-east of overhead, the tightest grouping of bright stars in the sky. Originally Crux was the hind legs of the Centaur, the horse-man of Greek mythology. The complete Centaur, with bow, is outlined at left. It was only in the 17th Century that Crux was split off as a separate constellation. The slow wobble of Earth's axis allowed this part of the sky to be seen from more northerly places in ancient times. The fainter Pointer and the three bluish-white stars of the Crux are all super-bright stars hundreds of light years away. Alpha Centauri is just 4.3 light years away and the reddish top star of Crux is 90 light years from us.
Omega Centauri, also southeast of the zenith, is a globular cluster, a ball-shaped cluster of millions of stars. Its total mass is six million times the sun's. It is 17 000 light years away and 200 light years across. Globular clusters are very ancient, around 10 billion years old, twice the age of the sun. Omega Centauri is the biggest of the hundred-odd globulars randomly orbiting our galaxy. It may originally have been the core of a small galaxy that collided with the Milky Way and was stripped of its outer stars.
47 Tucanae, by the SMC, is a similar sort of cluster 16 000 light years. Though it appears near the SMC it has no connection, being 15 000 light years away.
The Coalsack nebula, left of Crux, looks like a hole in the Milky Way. It is a cloud of dust and gas 300 light years away, dimming the distant stars in the Milky Way. Many "dark nebulae" can be seen along the Milky Way, appearing as slots and holes. These clouds eventually form new stars.
The Jewel Box is a compact cluster of young bright stars about 7000 light years away. The cluster formed less than 10 million years ago. To the eye it looks like a faint star close by the second-brightest star in Crux. A telescope is needed to see it well.
Eta Carina nebula, a luminous spot in the Milky Way to the right of Crux, is a glowing gas cloud about 8000 light years from us. The thin gas glows in the ultra-violet light of nearby hot young stars.
The golden star in the cloud, visible in binoculars, is η [Greek 'e'] Carinae. It is estimated to be to be 60 times heavier than the sun. It is a million times brighter than the sun but is dimmed by dust clouds around it. It is expected to explode as a supernova in the next few thousand years. Many star clusters are found in this part of the sky.
The Large & Small Clouds of Magellan (LMC and SMC) appear as two luminous patches, easily seen by eye in a dark sky. They are two galaxies like the Milky Way but much smaller. Each is made of billions of stars. The Large Cloud contains many clusters of young luminous bright stars seen as patches of light in binoculars and telescopes. Both clouds are about 160 000 light years away, very close by for galaxies.
Tarantula nebula is a glowing gas cloud in the LMC. The gas glows in the ultra-violet light from a cluster of very hot stars at centre of the nebula. The cloud is about 800 light years across. It is easily seen in binoculars and can be seen by eye on moonless nights. This nebula is one of the brightest known. If it was as close as the Orion nebula then it would be as bright as the full moon.
Canopus is the second brightest star in the sky. It is 13 000 times brighter than the sun and 300 light years away. Sirius, low in the east on spring evenings, is the brightest star in the sky.
Orion, the Hunter is prominent in the western evening sky, below Sirius the brightest star. Sirius marks the head of one of the two dogs following the hunter down the sky. Procyon marks the lesser dog. Well to the right of Orion are the pair of stars making Gemini the Twins with Mars, similar in brightness but orange in colour, above them. Above and right of Castor and Pollux is the Praesepe star cluster marking the shell of Cancer the Crab
Sirius is the brightest star, though star-like Venus and Jupiter, and sometimes Mars, are brighter. Sirius appears bright because it is both brighter than the sun -- 23 times brighter -- and relatively a close 8.6 light years* away. Sirius was often called 'the dog star' being the brightest star in Canis Major, one of the two dogs that follow Orion across the sky. Canis Major is heading down the western sky; the dog's hindquarters are marked by four bright stars above Sirius. Sirius, being bright, often twinkles like a diamond when low, as the air breaks its light into separate colours.
Orion the Hunter, or warrior, is now upside down in the west in our southern hemisphere view. The line of three stars makes Orion's Belt. The line of faint stars above and left of the belt form Orion's Sword in the northern view, hanging from his belt. To most southern hemisphere sky watchers the belt and sword form The Pot or The Saucepan, now lying on its side. In early June Orion can be seen both in the west at dusk and in the east at dawn.
The Orion Nebula is visible in binoculars as a misty glow around the middle stars of Orion's Sword or the handle of The Pot. It is a vast cloud of dust and gas about 1270 l.y. away and nearly 20 l.y. across. Ultra-violet light from a massive, extremely hot star in the cloud causes it to glow. Some stars in this region are around a million years old. The sun, by contrast, is 4.6 billion years old. Stars continue to form in a giant cloud behind the glowing nebula. There are many bright and dark nebulae in this region. The Horsehead nebula, a favourite of astronomy books, is beside the right-hand star of Orion's Belt, but too faint to be seen in small telescopes.
The Milky Way is faint in this region as we are looking toward the nearby edge of the disk. Several star clusters visible in binoculars or small telescopes are marked with asterisks. The numbers beside them are from a catalogue complied by Charles Messier, an 18th Century French comet searcher. M47 is visible to the naked eye as a fuzzy spot though it is 1600 light years away. M41, M50 and M93 are best seen in a telescope. Messier also catalogued the Orion Nebula (M42) and the Praesepe cluster (M44).
Pollux and Castor mark the heads of the Gemini, the twins. Though paired in myths, the two stars are not related at all. Castor is a hot white star like Sirius but 52 light years away. Golden Pollux is bigger and brighter but cooler than Sirius and 34 light years away.
Mars is moving up and to the right against the background stars on the chart. At the beginning of the month it is directly above Castor and Pollux, making a line with them. Its position on the chart is marked for mid month. On May 23 it crosses the Praesepe star cluster. In reality, Mars is staying in the same place night-to-night while the stars slip past due to the earth orbiting the sun.
The Praesepe cluster marks the shell of Cancer the crab. To the eye, in a dark sky, it is a spot of light bigger than the full moon. It is also known as the Beehive and binoculars show how it got that name: dozens of stars are seen like bees around a hive. The cluster is some 500 light years from us. It formed in a gas cloud about 700 million years ago.
