Interesting objects in the southern sky Chart for the southern sky in June
Interesting objects in the eastern Sky Chart for the eastern sky in June
Sirius the brightest star, appears low in the western sky at dusk before it sets early. Canopus is in the southwest sky, circling lower into the south later on. Crux, the Southern Cross, and Beta and Alpha Centauri are south of overhead. Scorpius, upside down, is midway up the eastern sky. Below it is Sagittarius; its brighter stars making 'the teapot'. Midway down the northwest sky is Saturn with Regulus below it. Orange Arcturus in the north often twinkles red and green.
Sirius when low in the sky often twinkles like a diamond as the air breaks up its white light. It is the brightest star both because it is relatively close, nine light years away, and 23 times brighter than the sun.
Crux, the Southern Cross, is south of the zenith. Beside it, and brighter, Beta and Alpha Centauri, often called 'The Pointers' because they point at Crux. Alpha Centauri is the closest naked-eye star, 4.3 light years away. A telescope shows it is a binary star: two sun-sized stars orbiting each other in 80 years. Beta Centauri, and many of the stars in Crux are hot, extremely brihgt blue-giant star hundreds of light years away. Canopus is also very luminous and distant.
Scorpius is midway up the eastern sky, lying on its back. Its brightest star is orange Antares, marking the heart of the Scorpion. 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 will end in a spectacular supernova explosion in a few million years.
The Milky Way is brightest and broadest in the southeast toward Scorpius and Sagittarius. It remains bright but narrower through Crux and Carina. 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 in the lower 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. They are only a fraction the mass of our galaxy but still contain billions of stars.
Arcturus, toward the north, often twinkles red and green as the air disperses its orange light. It is 120 light years away and 37 times brighter than the sun.
Saturn's rings are almost edge-on to us now. They look like a narrow spike through the globe of Saturn. In steady conditions a telescope shows the shadow of the rings as a dark line on Saturn. In June Saturn is around 1440 million km away. The shadow of Titan, Saturn's biggest moon, crosses the planet on the evening of June 16. Titan emerges from Saturn's shadow on the evenings of June 8 at 11:31, and on June 24 at 10:53.
Jupiter (not shown) rises due east in the later evening. It is the brightest star-like object in the night sky till brilliant Venus rises around 4 a.m. Binoculars show the disk of Jupiter. A small telescope easily shows Jupiter's four big moons lined up on either side of the planet. Jupiter is 12 times wider than the earth and 320 times heavier. In June it is around 680 million kilometres away. By the morning hours Jupiter is north of overhead and Venus is in the northeast sky. Below Venus is Mars, looking like Antares. Antares is Greek for 'Rival to Mars.' Ares was the Greek name for Mars.
Sirius twinkles colourfully in the west before setting in the mid evening. Canopus is in the southwest swinging down to the south through the night. South of overhead are Alpha and Beta Centauri, with the Southern Cross (Crux) to their right. Further to the right are the Diamond Cross and False Cross, with a bright region of the Milky Way above them. Regulus, Saturn and Spica make a widely spaced line up the northwest sky. Orange Arcturus in the north often twinkles red and green. The Scorpion is on its back midway up thee astern sky with Sagittarius below it. Jupiter (not shown) rises in teh east in the late evening. It is the brightest 'star' in the night sky till brilliant Venus rises near dawn.
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.
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. The Large Cloud is 160 000 light years away, the Small Cloud 200 000 light years, 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.
Antares is the brightest star in the region. It is orange coloured; being a 'red giant' star. (The 'red' of red giants is usually more an orange tint.) It is 600 light years away, 19 000 times brighter than the sun, and big enough to fill Earth's orbit. Its mass or weight is about 20 times that of the sun, so most of the star is very thin gas spread around a hot dense core. Red giants are the last stage in the evolution of stars. The dense core of the star has shrunk and heated. The outer regions of the star have expanded to a very spread-out gas. The core is wringing the last of the thermo-nuclear energy out of elements like helium, carbon, oxygen and neon. In about two million years the core of Antares will run out of energy and collapse, triggering a spectacular supernova explosion. (The sun will become a red-giant in about seven billion years time but it ends up as a white dwarf star, not a supernova.)
Antares marks the heart of Scorpius. In the evening at this time of year the Scorpion is on its back with its tail on the right, curving upward then turning down and curling clockwise. The sting is the horizontal line of bright stars pointing toward Antares. In Maori star lore the tail's hook is the 'fish hook of Maui'. By midnight the scorpion's tail is directly overhead.
Antares marks the heart of Scorpius. In the evening at this time of year the Scorpion is on its back with its tail on the right, curving upward then turning down and curling clockwise. The sting is the horizontal line of bright stars pointing toward Antares. In Maori star lore the tail's hook is the 'fish hook of Maui'. By midnight the scorpion's tail is directly overhead.
At the right-angle bend in the tail is a large and bright cluster of stars, NGC 6231, looking like a small comet. It is around 6000 l.y. away. Its brightest stars are 60 000 times brighter than the sun. The cluster is about 8 light years across, similar in size to the Pleiades/Matariki cluster in our summer sky. Were it as close at the Pleiades (400 l.y.) then its brightest stars would be as bright as Sirius. Below the Scorpion's sting is M7 a cluster obvious to the eye and nicely seen in binoculars. M7 is about 800 l.y. away and around 260 million years old. (The older a star cluster, the fewer bright stars it has.)
Below M7 and fainter is M6, the 'butterfly cluster'. M6 is around 1300 l.y. away and is half the age of M7. Other clusters worth a look in binoculars are M21, M23, NGC 6167, and NGC 6193. The 'M' objects were listed by the 18th Century French astronomer Charles Messier. He hunted comets, so made a catalogue of fuzzy objects that could be mistaken for comets. The NGC (New General Catalogue) objects shown are bright to enough to have been seen by Messier but are too far south to be seen from Paris.
Left of the Sagittarius 'Teapot' is the glowing gas cloud M8, the 'Lagoon Nebula'. It is a star-forming region where gas and dust have recently gathered into new stars. ('Recently' = the past million years or so.) Ultraviolet light from one particularly hot star is lighting up the leftover gas, making it glow. On colour photos it appears pink due to hydrogen atoms fluorescing in the UV light. Below M8 is M20, the Trifid Nebula, small glowing patch in binoculars, also a pink hydrogen region in photos. Right alongside it is a blue reflection nebula where starlight is scattered by dust. Other nearby nebulae (gas and dust clouds) are M16 and M17.
Globular clusters, spherical clusters of ancient stars, are found throughout the region. The brightest is M4 by Antares. It is also one of the closest at 10 000 l.y. away. In binoculars and small telescopes 'globs' appear as round fuzzy spots. Others marked on the chart are M9, M10, M12, M14, M19, M22, M55, M54, M62, M80 and NGC 6541 . The concentration of globular clusters in this area was an early clue that the centre of the galaxy lay in this direction.
This part of the Milky Way is broad and bright as we are looking to the centre of the galaxy. The actual centre, 27 000 light years away, is hidden from our view by intervening dust clouds. The nearer clouds make gaps and slots along the Milky Way. The hub of the galaxy is a great sphere of stars, called the 'central bulge'. Some of the central bulge is glimpsed in gaps between the dust clouds. At the very centre lies a black hole three million times the sun's mass but only the size of our solar system. Infra-red telescopes, peering through the dust, show stars orbiting the invisible black hole at high speed. By plotting the movements of these stars over the past two decades, astronomers have been able to deduce the mass of the central black hole and its distance. All big galaxies have a massive black hole at their centre.
