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Royal Astronomical Society of New Zealand

The Evening Sky in February 2012 - what you can see.

Notes by Alan Gilmore, University of Canterbury's Mt John Observatory, www.canterbury.ac.nz

Chart for the whole sky in February      Stars and planets in the February evening sky

Chart for the southern sky in February      Interesting objects in the February southern sky

Chart for the north sky in February      Interesting objects in the Summer North Sky


The Evening Sky in February 2012

February evening sky

Chart produced by Guide 8 software; www.projectpluto.com.

The Evening Sky in February 2012 - using the chart

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.

Venus and Jupiter, low in the west, are the first 'stars' to appear after sunset. They are later joined by Mars rising on the opposite horizon. Sirius, the brightest star, appears north of overhead at dusk. Canopus, the second brightest star, is south of the zenith. Orion, containing 'The Pot' is midway up the north sky with Taurus and the Pleiades/Matariki toward the northwest. The Southern Cross and Pointers are midway up the southeast sky. The Clouds of Magellan, LMC and SMC, are high in the south sky. Saturn rises due east in the late evening.


The Evening Sky in February 2012

Whole sky chart for February 2012

Three planets are bright 'stars' in a rich evening sky. Venus and Jupiter appear in the west soon after sunset as Mars rises in the east. North of the zenith is Sirius, the brightest true star. South of overhead is Canopus, the second brightest star.

Brilliant silver Venus appears low in the west soon after sunset. Though bright it is of little interest in a telescope being covered in white cloud. It looks like a tiny gibbous moon. It is slowly catching us up but is still around 150 million km away. It sets around 10 pm. Venus is the same size as Earth.

Jupiter, also in the west, shines with a steady golden light. A telescope will easily show the four bright moons first seen by Galileo in 1610. Binoculars, steadily held, often show one or two. Jupiter is 780 million km from us now. The planet is 11 times Earth's diameter and 320 times Earth's mass.

Orange-red Mars rises around 10:30 at the beginning of February. By the end of the month it is up at dusk. We pass it by at the beginning of March at a distance of 100 million km. That's nearly twice as far away as it was at the close 'opposition' of 2003. (It's called an opposition because the planet is opposite the sun when closest to Earth.) So Mars appears small in a telescope: one-third the size of Jupiter. Mars is half the diameter of Earth and one-tenth Earth's mass. (Mass = weight, sort of.)

Saturn (not shown) rises in the east around midnight at the beginning of the month. It is up at 10 pm by the end of February. It is below and left of Spica, a star a little fainter than Saturn.

Sirius, 'the Dog Star', marks the head of Canis Major the big dog. A group of stars above and right of it make the dog's hindquarters and tail. Procyon, in the northeast below Sirius, marks the smaller of the two dogs following Orion the hunter across the sky. Sirius is eight light years away.

Below Sirius, and a bit to the left, are Rigel and Betelgeuse, the brightest stars in Orion. Between them is a line of three stars: Orion's belt. To southern hemisphere star watchers, the line of three makes the bottom of 'The Pot'. The handle of "The Pot" is Orion's sword. It has the Orion Nebula at its centre; a glowing gas cloud many light-years across and around 1300 light years away.

Orion's belt points down and left to a V-shaped pattern of stars making the face of Taurus the Bull. The V-shaped group is called the Hyades cluster. It is 130 light years away. Orange Aldebaran, Arabic for 'the eye of the bull', is not a member of the cluster but merely on the line of sight, half the cluster's distance from us.

Left again, toward the northwest and lower, is the Pleiades or Matariki star cluster, also known as the Seven Sisters and Subaru. Six stars are seen by most eyes. Dozens are visible in binoculars. The cluster is 400 light years from us. Its stars formed around 100 million years ago. From northern New Zealand the bright star Capella is on the north skyline. It is the sixth brightest star in the sky.

Crux, the Southern Cross, is in the southeast. Below it are Beta and Alpha Centauri, often called 'The Pointers'. Alpha Centauri is the closest naked-eye star, 4.3 light years away. Beta Centauri, like most of the stars in Crux, is a blue-giant star hundreds of light years away. Canopus is also a very luminous distant star; 13 000 times brighter than the sun and 300 light years away.

The Milky Way is brightest in the southeast toward Crux. It can be traced up the sky, fading where it is nearly overhead. It becomes very faint east or right of Orion. The Milky Way is our edgewise view of the galaxy, the pancake of billions of stars of which the sun is just one.

The Clouds of Magellan, LMC and SMC are high in the south 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 Southern Sky in February

Southern evening sky in February

Chart produced by Guide 8 software; www.projectpluto.com. Labels and text added by Alan Gilmore


Interesting Objects in the Southern Sky

Chart for the Southern Sky in February

Large and Small Clouds of Magellan (LMC and SMC) appear as two luminous clouds, easily seen by eye in a dark sky. They are galaxies like the Milky Way but much smaller. Each is made of billions of stars. The Large Cloud contains many clusters of young bright stars seen as patches of light in binoculars. Both clouds are about 160 000 light years away, very close by for galaxies.

47 Tucanae 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. Omega Centauri, very low in the south, is a similar cluster.

 


Tarantula Nebula
The 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 (in The Pot's handle) then it would be as bright as the full moon and look bigger than the whole constellation of Orion.


Canopus is the second brightest star. It is 13 000 times brighter than the sun and 300 light years away. Sirius, north of Canopus on autumn evenings, is the brightest star in the sky.

Alpha Centauri the brighter pointer, 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 50x shows the pair. (A very faint star, Proxima Centauri, orbits a quarter of a light-year, or 15 000 Sun-earth distances, from the Alpha pair.)

Coalsack nebula, is a cloud of dust and gas about 600 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 is a compact cluster of young bright stars about 7000 light years away. The cluster formed less than 10 million 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

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 any time in the next few thousand years.
Many star clusters are found in this part of the sky.


The Southern Pleiades is a newish name for a cluster of stars at one point of the 'Diamond Cross'. It is formally the Theta Carina cluster after its brightest star but is also known as the 'Five of Diamonds' cluster, the reason obvious when it is seen in a telescope. It is much fainter and smaller than the real Pleiades in Taurus but a nice sight in binoculars. The cluster is about 500 light years away and is around 10 million years old.


The Northern Evening Sky in February

Northern evening sky in February

Chart produced by Guide 8 software; www.projectpluto.com. Labels and text added by Alan Gilmore


Interesting Objects in Orion and Taurus

Chart for the February Northern evening Sky

Taurus the Bull and Orion the Hunter are constellations recognised by most northern hemisphere cultures. To see the northern hemisphere pictures turn the chart upside down. The face of Taurus is outlined by the V-shaped Hyades cluster. The brightest star in this group is orange Aldebaran, the name meaning 'the eye of the bull' in Arabic. Taurus's long horns extend down our sky. The Pleiades cluster rides on the Bull's back.

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 and left of 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, The Iron Pot, or The Saucepan.

The Pleiades



The Pleiades / Seven Sisters / Matariki / Subaru, (left) 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 400 light years away. Its brightest stars are around 200 times brighter than the sun. It formed about 100 million years ago.


The Hyades cluster is 160 light years away. Its brightest stars (not Aldebaran!) are about 70 times brighter than the sun. The cluster is about 700 million years old. 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.



The Orion Nebula
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 1300 l.y. away and more than 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 two 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, so it is mostly very thin gas. It is around 10 000 times brighter than the sun, about 400l.y. away, and has a surface temperature around 3000°C.

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 a relatively 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.


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