WHAT'S UP THIS MONTH - JANUARY 2022
(Link to What's Up February 2022)
(Link to What's Up December 2021)
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THESE PAGES ARE INTENDED TO HELP YOU FIND YOUR WAY AROUND THE SKY
The chart above shows the whole night sky as it appears on 15 th January at 21:00 (9 o'clock) Greenwich Mean Time (GMT). As the Earth orbits the Sun and we look out into space each night the stars will appear to have moved across the sky by a small amount. Every month Earth moves one twelfth of its circuit around the Sun, this amounts to 30 degrees each month. There are about 30 days in each month so each night the stars appear to move about 1 degree. The sky will therefore appear the same as shown on the chart above at 8 o'clock GMT at the beginning of the month and at 10 o'clock GMT at the end of the month. The stars also appear to move 15º (360º divided by 24) each hour from east to west, due to the Earth rotating once every 24 hours.
The centre of the chart will be the position in the sky directly overhead, called the Zenith. First we need to find some familiar objects so we can get our bearings. The Pole Star Polaris can be easily found by first finding the familiar shape of the Great Bear ‘Ursa Major' that is also sometimes called the Plough or even the Big Dipper by the Americans. Ursa Major is visible throughout the year from Britain and is always quite easy to find. This month it is in the North East. Look for the distinctive saucepan shape, four stars forming the bowl and three stars forming the handle. Follow an imaginary line, up from the two stars in the bowl furthest from the handle. These will point the way to Polaris which will be to the north of overhead at about 50º above the northern horizon. Polaris is the only moderately bright star in a fairly empty patch of sky. When you have found Polaris turn completely around and you will be facing south. To use this chart, position yourself looking south and hold the chart above your eyes.
Planets observable in the evening sky: Jupiter and Neptune (in the early evening), Uranus later.
THE SOUTHERN NIGHT SKY THIS MONTH
The night sky looking south at about 22:00 GMT on 15th January
The chart above shows the night sky looking south at about 21:00 GMT on 15th January. West is to the right and east to the left. The point in the sky directly overhead is known as the Zenith and is shown (in red) at the upper centre of the chart. The curved brown line across the sky at the bottom is the Ecliptic or Zodiac. This is the imaginary line along which the Sun, Moon and planets appear to move across the sky. The brightest stars often appear to form a group or recognisable pattern; we call these ‘Constellations'.
Constellations through which the ecliptic passes this month are: Aquarius (the Water Carrier), Pisces (the Fishes), Aries (the Ram), Taurus (the Bull), Gemini (the Twins), Cancer (the Crab) and Leo (the Lion).
Prominent early in the southern sky is the constellation of Pegasus (the Winged Horse). The main feature of Pegasus is the square formed by the four brightest stars. This asterism (shape) is known as the Great Square of Pegasus. The square is larger than might be expected but once found is easier to find again . There is a very nice Globular cluster in Pegasus it is known as Messier 15 (M15). It is a lovely sight to see in a telescope.
The southern sky is now dominated by the constellation of Taurus (the Bull). The most obvious star in Taurus is the lovely Red Giant Star called Aldebaran. It appears slightly orange to the ‘naked eye' but it is very obviously orange when seen using binoculars or a telescope. Aldebaran is located at the centre of the ‘flattened' X shape formed by the brightest stars in Taurus. At the end of the top right (upper west) arm of the ‘X' is the beautiful ‘naked eye' Open Star Cluster called Messier 45 (M45) also known as the Pleiades (or the Seven Sisters). It really does look magnificent using binoculars.
Following Taurus is the constellation of Gemini (the Twins). The two brightest stars in Gemini are Castor and Pollux and they are named after mythological twins. To the north of Taurus is the odd pentagon shape of Auriga (the Charioteer). Dominating Auriga is the brilliant white star Capella which is almost directly overhead. For those with a telescope there is a line of lovely open clusters to search out in Taurus and Auriga. These are M35 in Taurus and M36, M37 and M38 in Auriga.
To the south of Taurus is the winter constellation of Orion (the Hunter). Orion is easily found by looking for his very obvious three stars of his belt. Orion has his Hunting Dogs Sirius (the big dog) and Procyon (the little dog) to the east (left) and following him.
To the east (right) of Taurus is the rather indistinct constellation of Cancer (the Crab). The stars of Cancer are quite faint and can be difficult to discern especially in a light polluted sky. It is really worth searching out Cancer using binoculars or a telescope to see the Open Cluster M44 (the Beehive Cluster). M44 is older and further away than M45 (the Seven Sisters) so is fainter than M45 but still looks lovely. It has a group of stars that resemble an old straw Beehive with bees around it.
The constellation of Leo (the Lion) follows Cancer along the Ecliptic and will be the constellation of the month next month. It does actually look a little like a lion or the Sphinx in Egypt. Around and between Leo and the neighboring constellation of Virgo is a cluster of galaxies. Our Milky Way galaxy and our local group of galaxies are members of this larger group of galaxies called the Virgo Cluster. A medium sized telescope (150mm to 200mm) and a dark sky is required to see these faint objects.
The Ecliptic was low in the sky during the summer months so the Moon and planets appeared close to the southern horizon. Saturn, Jupiter, Neptune and Venus are now moving towards the western horizon and out of view. Uranus is still well placed for those who are fortunate enough to have access to a telescope. Mars is still located on the other side of the Sun so it appears small, close to the Sun and difficult to see.
Where to find the planets this month
Mercury will be at greatest eastern elongation on 7th January is not well placed this month.
Venus will be in Inferior Conjunction with the Sun on 9th January.
Mars is very close to the Sun and appears very small as it is on the other side of the Sun.
Jupiter is very bright in the south west during the early evening but moving towards the west.
Saturn is located to the west of Jupiter and is moving over the western horizon.
Uranus can be found in the south east in the early evening but really needs a telescope.
Neptune is located in the south but will need a telescope to see it.
CONSTELLATION OF THE MONTH – ORION (the Hunter)
The Constellation of Orion photographed by Nicky Fleet
Orion (the Hunter) is one of the best known constellations and one of the easiest to recognise as it begins to dominate the southern sky at this time of the year. There are many depictions of Orion shown on many different star charts. Some old pictures of Orion are very beautifully drawn in fact some are so beautiful that the artists even moved the positions of some of the stars so they would fit the image they had drawn.
Orion the Hunter appears in the winter sky, with his club held over his head and his shield (sometimes shown as a lion's skin) held out in front of him. His hunting dogs, Canis Major (the star Sirius) and Canis Minor (the star Procyon) following behind him.
Greek mythology tells us that Orion was known as a great hunter. He boasted that he could rid the earth of all the wild animals however this angered the Earth goddess Gaia. She sent a scorpion to defeat Orion. Orion tried to battle the scorpion but he quickly realised that he could not shoot his arrow through the creature's armour. To avoid the scorpion he jumped into the sea.
It was then that Apollo (the Greek god of the Sun) decided to take action. He pointed out , to his twin sister Artemis , a small black object in the sea. Claiming it was a horrible villain and he dared her to shoot it with her bow and arrow. Artemis easily hit the target. However when she swam out to retrieve her victim she discovered that the villain was in fact her friend Orion.
Artemis begged the gods to bring Orion back to life but they refused. Instead she put Orion's picture in the sky so she could always see and remember him .
Orion is one of the few constellations that does look (with a little imagination) like what it is named after. The most obvious feature is the line of three stars, called Alnitak, Alnilam and Mintaka that make up Orion's belt. From his belt we can see two bright stars called Saiph and Rigel below. These define the bottom of his ‘skirt like' tunic. Above the belt are two stars Betelgeuse and Bellatrix that denote the position of his shoulders.
Above and between his shoulders is a little group of stars that mark out the head. From his right shoulder (the star Bellatrix) he holds out a shield. From his left shoulder (the star Betelgeuse) a club is held above his head. It almost looks as if Orion is fending off the charge of the great bull Taurus who is located above and to the west (right) of Orion.
Down from Orion's very distinctive belt there is a line of stars, ending at the star Nair al Saif that looks very much like a sword attached to his belt. Here can be found the main interest in Orion, the Great Nebula.
If an imaginary line is traced down from the belt for about six belt length towards the south eastern horizon, a bright twinkling star will be seen. This is Sirius, Orion's Large Hunting Dog in the constellation of Canis Major. It is the brightest and closest star to be seen from the UK at just 8.6 light years from us. See the Orion chart.
To Orion's left (east) of Betelgeuse, a quite bright star in a rather large empty area of sky can be seen. This is Procyon in Canis Minor, Orion's Small Hunting Dog. Coincidentally both of these ‘dog stars' are double stars that have an invisible companion. They were normal stars that had reached the end of their lives and used all their Hydrogen fuel. They have now collapsed to become very compact and dense White Dwarfs stars.
M42 THE GREAT NEBULA IN ORION
Chart showing M42 the Great Nebula in Orion
When we look towards Orion we are looking into one of the nearest spiral arms of our galaxy the Milky Way. Our Sun appears to be located in the area between two spiral arms. Towards the centre of the galaxy from our point of view is the Sagittarius Arm and looking away from the centre is the Orion Arm.
Most of the stars in Orion are located about 900 light years away from us including Rigel but Betelgeuse is much closer at only 310 light years distant. Because the stars of Orion are in a spiral arm there is a lot of gas and dust around the whole area of the constellation. Huge numbers of stars are hidden by the gas and dust .
Below the line of three stars of Orion's belt there is a vertical line of stars forming his sword (hanging below his belt). In the line of stars making up Orion's sword a hazy patch can be seen using binoculars or even with just the naked eye on a clear night. The hazy patch is known as M42 (Messier 42), t he Great Orion Nebula. This Nebula is part of a gigantic cloud of Hydrogen gas mixed with other gases and dust from which new stars are being formed. Through a pair of binoculars the nebula looks like a small fuzzy patch in the line of stars.
An artist impression of our position in the Galaxy
When seen through a telescope the ‘fan shaped' cloud like structure can been made out. Swirls of gas and dust can be seen, some are lit up but some are dark and silhouetted against the illuminated clouds behind .
The Trapezium cluster superimposed on M42
Th is small part of the Nebula is actually illuminated by the young stars forming in it. Most of the energy illuminating this part of the nebula comes from a group of 4 stars known as the Trapezium. These stars have formed out of the gas and dust in the nebula; they are young, hot and very active. The Trapezium can be seen easily using a small telescope. The four stars of the trapezium (there is a fifth fainter star) are just the brightest of what is an Open Cluster in the process of forming. The Orion Nebula actually contains many more very young stars that are still hidden by the gas and dust of the nebula.
Special telescopes that can detect ultraviolet and inferred radiation can be used to penetrate the gas and dust to see the stars forming inside the nebula. The image below shows most of the stars that are normally hidden by the gas and dust clouds.
Stars forming in M42
Gravity draws the atoms of the gas together and as the gas becomes denser it pulls in even more until huge spheres of gas are formed. As the pressure in the core of a sphere increases the temperature rises to tens of millions of degrees and the Hydrogen atoms begin to fuse together to form atoms of Helium. In this process known as Nuclear Fusion a small amount of mass is lost and converted into energy in the form of a powerful flash of X-Rays. This heats the mass of gas of the sphere and it begins to shine as a bright new star.
Much of the gas and dust in the nebula shines by reflecting light from the very young stars of the Trapezium in the centre of the nebula. Some gas also produces its own light because the ultraviolet radiation energy from the powerful young stars excites the gas atoms . This caus es them to glow somewhat like a fluorescent light or the Aurora (Northern Lights) .
When a photon of ultraviolet light from the powerful young stars hits a gas atom it causes an electron to jump from its normal orbit to a higher orbit. After a very short time the electron jumps back to its original orbit and emits a flash of light. The colour of this light is unique to the type of atom that has emitted it. For example Hydrogen always emits red light.
The Orion Nebula can be seen with the naked eye from a dark location on a clear moonless night. It is easily seen using a pair of binoculars. The image below shows the sort of view seen using a pair of 8 x 50 binoculars.
Binocular view of M42 with Orion's belt at the top
A small telescope will show a larger view and some detail in M42. Structure in the nebula can be seen with parts of the nebula illuminated and other parts appearing dark.
The sort of view seen using a small telescope
A larger telescope will show more detail in the structure with the nebula made up of wisps of gas appearing. Photographic images show much more detail including colour in the clouds of gas and dust. The red in the image below is typical of the emissions from excited Hydrogen gas in the nebula.
A photographic image of M42
CANIS MAJOR and CANIS MINOR
The constellations of Orion, Canis Major and Canis Minor
Orion is one of the easiest constellations to recognise and dominates the southern sky at this time of the year. There are many depictions of Orion shown on many different star charts. Orion the Hunter appears in the winter sky, with his club held over his head and his shield (sometimes shown as a lion's skin) held out in front of him. His hunting dogs, Canis Major (the star Sirius) and Canis Minor (the star Procyon) following behind him. See the chart above.
If an imaginary line is traced down from Orion's belt for about six belt lengths towards the south eastern horizon, a bright twinkling star will be seen. This is Sirius, Orion's Large Hunting Dog in the constellation of Canis Major. It is the brightest and closest star to be seen from the UK at just 8.6 light years from us.
Following an imaginary line through the two bright upper stars at Orion's shoulders, Bellatrix and Betelgeuse to Orion's left (east) a quite bright star in a rather large empty area of sky can be seen. This is Procyon in Canis Minor, Orion's Small Hunting Dog.
The chart above shows the location of Sirius and Procyon, Orion's Hunting Dogs. Although the two stars are associated with Orion through their mythological link with the Hunter and their proximity to Orion in the night sky they are actually much closer to us and not associated with the stars of Orion at all.
Sirius is in fact a double star but its companion is quite unusual. The bright star Sirius that we see sparkling close to the horizon is the larger and overall brighter of the pair. We call the visible component of the pair Sirius A (the Dog Star) and the companion star Sirius B (It is sometimes called the Pup).
Sirius is in fact the closest star to Earth that we can see from the Northern Hemisphere and is just 8.6 light years away . It is about twice as massive as our Sun but about 25.4 times brighter. Sirius B is a tiny (in diameter) star about the same volume as Earth but with a mass about the same as our Sun.
An artist's impression of Sirius A and B
Sirius B formed about 230 million years ago as the largest star of the original pair. It was about 5 times the mass of our Sun and fused its Hydrogen fuel into Helium very quickly. It lived out its Main Sequence phase (life as a normal star) much faster than its smaller companion. It is thought Sirius B developed into a Red Giant around 120 million years ago. The Red Giant soon collapsed to form the White Dwarf we see today. It is now a super dense sphere of Carbon and Oxygen about 11,600km in diameter.
Sirius B no longer produces heat through nuclear fusion but is very hot due to the compression when it collapsed from its Red Giant phase. It now has a temperature of 25,000°K and shines brilliantly white. The Pup is thought to be spinning very rapidly and orbits around a common centre of gravity with Sirius A every 50 Earth years. The two very different stars are separated by 20 AU (1 AU ‘Astronomical Unit' is the Earth / Sun distance). This is approximately the same distance as from Earth to Uranus.
Sirius A and B imaged by Hubble.
The picture above was taken by the Hubble Space Telescope with a camera that has a special mask to reduce the glare of Sirius A. Sirius B can be seen to the lower left as a small white dot. Sirius B cannot be seen using any normal amateur's telescope.
An image of Orion and Sirius (lower left)
Sirius is beautiful to look at as it twinkles close to the southern horizon. It can be seen to twinkle to the ‘naked eye' but a pair of binoculars or a telescope will show it flashing brilliantly with all the colours of the rainbow. Sirius the star is not twinkling this is due to atmospheric turbulence. Air close to the horizon is misty, dirty and affected by heat from the ground which causes turbulence that makes the light twinkle.
Sirius will be at its best after the Christmas period and into spring. The Dog Star is just a star but it is definitely one of the most beautiful to look at.
Sirius is the best known ‘Dog Star' but Procyon the Little Hunting Dog is well worth looking out for. Coincidently it is also a double star and the companion is also a White Dwarf. However when the stars are examined more closely they are found to be quite different to the Sirius pair.
Procyon A has a significantly smaller mass than Sirius A (1.5 solar masses compared to 2 for Sirius A) and Procyon A is much further along its life span. Being smaller Procyon A will have a longer active life than the larger and greedier Sirius A. Having said that Procyon A is already a lot older than Sirius A and is already starting its transformation into a Red Giant.
Procyon B is also smaller than Sirius B at just 0.6 Solar masses compared to Sirius B at 1.0 Solar mass. It has a larger diameter than Sirius B at 17,200km compared to 11,600km. This is due the additional super gravity of the more massive Sirius B pulling its material into an even more compact sphere.
The comparative size of Procyon B and Earth
White Dwarfs are created when a star, normally up to about 5 times the mass of our Sun, collapse after completing their Red Giant phase. White Dwarfs can exist up to a mass of 1.44 times the mass of our Sun where further collapse is prevented by a process called ‘ electron degeneracy pressure ' .
Smaller stars tend to produce a White Dwarf comprised of a core of highly compressed Carbon and Oxygen surrounded by a shallow but extremely dense atmosphere of Hydrogen. Some large White Dwarfs are thought to be composed of Carbon so compressed it has been turned to Diamond.
If a Red Giant star collapses and the resulting White Dwarf has a mass greater than 1.44 solar masses it will continue to collapse. The ‘ electron degeneracy pressure ' resistance will be overcome and the core will collapse to form an even denser ‘Neutron Star'.
A Neutron Star has a diameter of about 25 km but can have a maximum mass up to between 3 and 5 Solar Masses, depending on the chemical composition of the original star. Up to this absolute upper mass limit further collapse can be halted by a process called ‘Neutron degeneracy pressure ' .
If this upper mass is exceeded then the star core will overcome the ‘Neutron degeneracy pressure ' and collapse even further to create a ‘Stellar Black Hole'. A Stellar Black hole is a very small object that has such powerful gravity that to escape from its gravity would require an escape velocity faster that light so nothing can escape (not even light itself).
THE SOLAR SYSTEM - JANUARY 2022
The planets at 17:00 GMT on 1st January 2022
The chart above shows the location of the planets along the Ecliptic. The sky has been darkened to make the planets visible. The visible planets are: Venus, Mercury, Saturn, Jupiter, Neptune and Uranus. They are visible along the Elliptic from the West (right) to East (left). The planets appear low in the sky and are not well positioned for observing.
MERCURY will be very close Saturn the just after sunset early in the month in the west but will be difficult to see. It will be at its Greatest Easterly Elongation (apparent furthest point from the Sun) on 7th and will then move back into conjunction with the Sun on 23rd January.
Mercury Greatest Elongation 23rd and Venus in Conjunction on 9th January
VENUS will be moving into inferior conjunction on 9th January, when it will pass between Earth and the Sun (but above the Sun). It will be at its largest diameter but as its narrowest crescent. Venus will reappear in the early morning sky near the Sun in the east at sunrise next month. At this stage it is often called the Morning Star.
MARS is on the other side of the Sun (so appears very small) and is still very close to the Sun so will be difficult to see. Mars has moved out of conjunction with the Sun and into the early morning sky but will not appear in the evening sky again until September 2022.
Mars and Venus at sunrise on 15th January
JUPITER will be visible in the south west as the sky darkens before sunset. It will be at its rather poor best in the south at about 17:00 but it will be moving towards the western horizon to set at about 20:30. It will start to be visible in the early morning sky in the next few months.
SATURN is now bidding us goodbye until next year. It will be difficult to see in the turbulent air close to the south western horizon after sunset. Saturn will set over the western horizon at 18:30.
URANUS will be observable this month and will be best at 21:00 when it will be due south and at its highest point above the horizon but is small and faint at +5.7.
NEPTUNE will be just visible to the east of Jupiter and will be at its best at 16.30 as the sun sets. It is small a difficult to see at only 2.9 arc-seconds in diameter and at magnitude +7.7.
The Sun rises at about 08:10 at the beginning of the month and 07:45 by the end. It sets at 16:00 at the beginning of the month and 16:40 at the end of the month. It was at its lowest point in the sky on 21st December and at the Winter Solstice. That was the longest night at 16 hours and shortest day at just 8 hours long. There have been a few small Sunspots recently.
Sun spots imaged by SOHO on 27th December 2021
THE MOON PHASES DURING JANUARY
New Moon will be on 2nd January
First Quarter will be on 9th January
Full Moon will be on 17th January
Last Quarter will be on 25th January
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