Intresting object in the southern sky Chart for the southern sky in January
Interesting objects in Orion and Taurus Chart for the northern sky in January
The brightest stars and Mars are in the east half of the sky at dusk. They are spread from Taurus and Orion in the north, through Canis Major and around to Crux and the Pointers in the south. Canopus, the second brightest star, is southeast of overhead. Mercury, the closest planet to the sun and the smallest, makes a rare evening sky appearance on its own in the southwest.
Sirius is the first star to appear at dusk, high in the east. Orange Mars appears about the same time low in the northeast. Left of Sirius, as the sky darkens, are Rigel and Betelgeuse the brightest stars in Orion. Between them, but fainter, is a line of three stars: Orion's belt. To southern hemisphere star watchers, the line of three make the bottom of 'The Pot'. Orion is directly above Mars. Left of Mars and Orion is the V-shaped pattern of stars making the face of Taurus the Bull. Left again, toward the north and lower, is the Pleiades/Matariki star cluster, also known as the Seven Sisters and Subaru. From northern New Zealand the bright star Capella is on the north skyline.
Mars appears in the northeast at dusk and is due north by midnight. It is orange coloured and nearly as bright as Sirius. We passed it by in mid-December and are now leaving it behind. Mars is tiny in a telescope, being half the diameter of Earth and 100 million km away.
Sirius, 'the Dog Star', marks the head of Canis Major the big dog. A group of stars to the right of it make the dog's hindquarters and tail, upside down just now. 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 white Sirius often twinkles like a diamond. Procyon, in the northeast below Sirius, marks the smaller of the two dogs that follow Orion the hunter across the sky.
Rigel, directly above Orion's belt, is a bluish supergiant star, 70 000 times brighter than the sun and much hotter. It is 800 light years away. Orange Betelgeuse, below the line of three, is a red-giant star, cooler than the sun but hundreds of times bigger: a ball of extremely thin hot gas.
The V-shaped group making the face of Taurus the bull is called the Hyades cluster. It is 150 light years away. Orange Aldebaran, Arabic for 'the eye of the bull', is not a member of the cluster but on the line of sight, half the cluster's distance. The Pleiades/ Matariki cluster, pretty to the eye and impressive in binoculars, is 400 light years from us.
Low in the south are Crux, the Southern Cross, and 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 stars orbiting each other. Beta Centauri, like most of the stars in Crux, is a blue-giant star hundreds of light years away. Canopus is also very luminous and distant.
The Milky Way is in the eastern sky, brightest in the southeast toward Crux. It can be traced along the eastern sky towards the north but becomes faint below Orion. The Milky Way is our edgewise view of the galaxy, the pancake of billions of stars. The thick hub of the galaxy, 30 000 light years away, is hidden by the sun at this time of year. The nearby outer edge is the faint part below Orion. Binoculars show many star clusters and a few glowing gas clouds in the Milky Way.
The Clouds of Magellan, LMC and SMC are high in the southern sky. They are easily seen by eye on a dark moonless night. They are two small galaxies about 160 000 and 200 000 light years away. The larger cloud is about 5% the mass of the Milky Way galaxy, the smaller cloud 3%.
Venus (not shown) is the brilliant 'Morning Star' rising in the southeast two hours before the sun. Saturn (not shown) rises in the northeast about 11 pm and is due north at dawn. It is the right-hand 'star' of a similar pair of widely spaced stars in an otherwise empty area of sky.
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 is the brightest star in the evening sky, high in the east at dusk. Mars is low in the north, bright and orange coloured. Canopus, the second brightest star, is southeast of the zenith. Orion, containing 'The Pot', is in the northeast with Taurus and the Pleiades/Matariki toward the north. Crux, the Southern Cross, and the Pointers are low in the south. Mercury is very low in the southwest; setting in the late twilight. Saturn rises in the northeast later.
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 stars seen as patches of light in binoculars and telescopes. Both clouds are about 160 000 light years away, very close by for galaxies. (1 light year is about 10 000 billion km.)
47 Tucanae,looks like a faint fuzzy star on the edge of the SMC. It is a globular cluster, a ball of millions of stars. A telescope is needed to see a peppering of stars around the edge of the cluster. Though it appears on the edge of the SMC it is one-tenth the distance, 15 000 light years away, and is has no connection to the Small Cloud. Globular clusters are mostly very old, 10 billion years or more; at least twice the age of the sun.
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. It is 14 000 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.
Alpha Centauri is the closest naked-eye star, 4.3 light-years away. Alpha Centauri is a binary star: two stars about the same size as the sun orbiting around each other in 80 years. A telescope that magnifies 30x shows the pair. (A very faint and slightly closer star, Proxima Centauri, probably orbits the Alpha pair.)
Omega Centauri is a globular cluster like 47 Tucanae but bigger. Its total mass is six million times the sun's. It is 17000 light years away and 200 light years across. Omega Centauri is the biggest globular cluster in our galaxy. It may have once been the core of a small galaxy that was captured by the Milky Way.
The Coalsack nebula, in Crux, is a cloud of dust and gas about 300 light years away, dimming the more distant stars in the Milky Way. Many similar 'dark nebulae' can be seen, appearing as slots and holes in the Milky Way. These clouds of dust and gas eventually coalesce into clusters of stars.
The Jewel Box also in Crux, is a compact cluster of young luminous stars about 7000 light years away. The cluster formed less than 10 million ago. To the eye it looks like a faint star.
Eta Carina
nebula is a glowing gas cloud about 8000 light
years away. The golden star in the cloud, visible in
binoculars, is Eta [Greek η] Carinae. It is estimated
to be to be 60 times heavier than the sun and a million
times brighter but is dimmed by dust clouds around it. It
is expected to explode as a supernova "soon", that is in
the next few thousand years.
Many star clusters are found in this part of the Milky Way.
Sirius and Mars are eye-catching objects in the north sky in January 2008: Sirius high up; Mars low down. Between them is Orion the Hunter marked by prominent Rigel and Betelgeuse with the well-known 'pot' or 'saucepan' pattern between them. Below and left of Orion is Taurus the Bull with Aldebaran being one of Taurus's eyes. The V-shaped Hyades cluster outlines the bull's head. (All these pictures were thought up by north hemisphere cultures so are upside down to us.) The Pleiades or Matariki star cluster rides on the Bull's back, left of Aldebaran. Low in the northeast are Castor and Pollux marking the heads of Gemini the Twins. Right of them, rising later in the evening, is the Praesepe star cluster making the shell of Cancer the Crab.
The Pleiades / Seven Sisters / Matariki / Subaru, and many other names, is a cluster of stars well known in both hemispheres. Though often called the Seven Sisters, most modern eyes see only six stars. Dozens are visible in binoculars. The cluster is about 440 light years away. Its brightest stars are around 200 times brighter than the sun.
The Hyades cluster is 150 light years away. Its brightest stars (not Aldebaran!) are about 70 times brighter than the sun. Aldebaran is not a member of the cluster but simply on the line of sight. It is 65 l.y. away and 150 times brighter than the sun. Aldebaran is a giant star about 25 times bigger than the sun though only five times heavier. Its orange colour is due to its temperature, around 3500° C. The sun is 5500° C.
Orion, in the northern hemisphere view, has a shield raised toward Taurus and a club ready for action. The line of three stars makes Orion's Belt. The line of faint stars above the belt form Orion's Sword in the northern view, dangling from his belt. To most southern hemisphere sky watchers the belt and sword form The Pot, or the Saucepan.
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 may be less than 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.
Rigel is a blue 'supergiant' star around 40,000 times brighter than the sun and 800 l.y. away. Its surface temperature is around 20,000°C, giving it a bluish colour.
Betelgeuse is a red giant star 250 times bigger than the sun -- wider than earth's orbit! -- but only around 20 times heavier. It is mostly very thin gas surrounding a hot dense core. It is around 10,000 times brighter than the sun, about 400 light years away, and has a surface temperature around 3000°.
Sirius is the brightest star, though the planets Venus and Jupiter, and sometimes Mars, are brighter. Sirius appears bright because it is both brighter than the sun and relatively a close 8.6 l.y. 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.
Mars, though bright, is disappointing in a telescope. It is around 100 million km from us in January and shows only a tiny disc. Mars remains in our evening sky for most of the year, but fades.
