WHAT'S UP THIS MONTH - MARCH 2022

(Link to What's Up April 2022)

(Link to What's Up February 2022)

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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 15th March 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 high 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: Uranus.

British Summer Time (BST) begins on 27th March

 

THE SOUTHERN NIGHT SKY THIS MONTH

The night sky looking south at about 21:00 GMT on 15th March

The chart above shows the night sky looking south at about 22:00 GMT on 15th March. 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) just off the right of the chart, Pisces (the Fishes), Aries (the Ram), Taurus (the Bull), Gemini (the Twins), Cancer (the Crab), Leo (the Lion) and Virgo (the virgin) just coming into view.

In the southern sky is 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) that dominates the southern night sky. Orion is easily found by looking for the very obvious three stars of his belt. As he is so easy to find it is a good place to start exploring the sky. Orion has his Hunting Dogs Sirius (the big dog) and Procyon (the little dog) to the east (left) and following him. Orion was featured as constellation of the month in the January magazine.

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 Spring Equinox (also called Venal Equinox) occurs on 20th March. This means we are half way to summer. British Summer Time (BST) begins on 27th March.

Where to find the planets this month

All the planets, except Uranus are either in or are moving into the early morning sky.

Mercury will be difficult to see low in the east and moving into conjunction on 2nd April.

Venus is very bright in the eastern sky before sunrise and will be at its greatest westerly elongation (furthest from the Sun) on 20th March.

Mars is still close to the Sun and appears very small as it is on the other side of the Sun.

Jupiter will be in conjunction with the Sun on 5th March so will not be observable.

Saturn was in conjunction with the Sun on 4th February so will be difficult to see.

Uranus can be found in the south east in the early evening but really needs a telescope.

Neptune will be in conjunction with the Sun on 15th March so will not be observable.

ORION's INTERESTING STARS

The constellation of Orion and his Dogs

Orion (the Hunter) is one of the best known constellations and one of the easiest to recognise and dominates the southern sky at this time of the year. 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.

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.

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, see the January issue of this magazine for details.

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 Big 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. 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.

We tend to search out Orion to look at the famous object Messier 42 (M42) the Great Nebula. M42 is of great interest and one of the most interesting objects to see. In this article we will be concentrating on some of the very interesting stars in Orion and his Hunting Dogs Sirius and Procyon.

Rigel

We start with Rigel the bright white star at the lower right of the ‘stick' figure depiction shown above. Rigel denotes the bottom right (west) corner of Orion's skirt like tunic. Rigel appears bright to us because it an intrinsically bright giant star. Rigel is a massive, luminous star of the spectral type B8, indicating it is a bright supergiant appearing blue or blue-white in colour.

Rigel has a diameter almost 160 times that of our Sun and has an estimated mass of 21 solar masses. With a temperature of 12,100 K, it shines about 120,000 times brighter than our Sun. It is thought to be about 860 light years away from us.

For those with a telescope Rigel ( a Orionis) can be seen as a double star. The main and brightest star Rigel A is so bright that Rigel B can be difficult to see. Rigel B has an apparent magnitude of 6.7 which would make the star easily visible in small telescopes if it were not so close to Rigel A. As it is about 440 times fainter than its neighbour, Rigel B is difficult to see in telescopes with apertures smaller than 150mm (6").

Rigel A and Rigel B

Betelgeuse

At Orion's left shoulder is the bright orange coloured star Betelgeuse which is much further along its pathway of ‘life'. It is approaching the last phases of its existence as a normal star. It has grown into a (really huge) Red Giant with a diameter greater than the orbit of Jupiter in our Solar System.

Betelgeuse is so big and unstable that it pulsates and wobbles rather like a water filled balloon. By carefully observing the brightness of Betelgeuse it can be seen to brighten and fade. At its brightest it can be as bright as magnitude 0.2 and at its dimmest only magnitude 1.2. It is quite difficult to determine the cycle of the pulsations and brightening because there seems to be a number of intertwined cycles. So it appears to vary at different rates of between 150 to 300 days.

Betelgeuse as seen using a telescope

Betelgeuse appears to be edging towards the end of its life. In fact it is the closest star to us that might explode as a super nova at any time in the near future (astronomically speaking). It could explode and destroy itself sometime in the next million years (maybe as soon as tomorrow). For all we know it may have already exploded but its light will take 650 years to reach us.

Betelgeuse looks red (orange) because it is more advanced in its life cycle than Rigel and has moved into its Red Giant Phase. The nuclear fusion process is fusing the heaver atoms it has produced into even heavier elements, with each fusion stage contributing additional energy to power the star. All this additional energy pushes out against the force of gravity pulling inwards. The additional energy has forced the outer regions of the star to expand outwards to produce this huge (in volume) bloated and unstable Red Giant Star.

Meissa

Meissa is one of the stars in the small group of stars that define Orion's head. It is one of a group of very hot Blue Super Giants. Meissa really is a giant star with a stellar classification of O8 III and has an apparent magnitude +3.54. It is actually an enormous star with about 28 times the mass of the Sun and 165,000 times brighter. It has a surface temperature of around 35,000 K, giving it a characteristic blue glow of a hot O-type star.

The giant star Meissa

Saiph

Saiph is located at the lower left (east) Orion's tunic. It is of a similar distance and size to Rigel but appears much fainter. This is because it has a very high surface temperature (26,000°K) that causes it to emit most of its light in the ultraviolet region of the spectrum. Our eyes are not sensitive to ultraviolet wavelengths so it appears fainter than would be expected.

The super giant star Saiph

There are many other interesting stars in Orion beside the more well known stars like Rigel and Betelgeuse. It is always interesting to ponder about the true nature of these specks of light that are so far away. The stars of Orion's belt are very easy to see with our naked eyes and the distinctive line of the three stars is one of the most recognised star formations so we should consider what interesting features they may be hiding from us.

The stars of Orion's belt Alnitak (marked), Alnilam and Mintaka

Alnitak

Alnitak - Zeta Orionis ( ? Ori) is the brightest O class star in the sky and is 250,000 times brighter than our Sun. The star is located at the east (lower left) of Orion's belt and is actually a triple star system. The system is comprised of a pair of stars (Alnitak Aa, Ab) that are magnitude 1.9 and 5.5 and orbiting around a common centre of gravity. They appear to be separated by 2.6" (arc-seconds). The third star (Alnitak B) is a fainter magnitude 10 companion orbiting 57.6" from Aa - Ab pair. This triple star system is thought to be about 820 light years away.

Alnita with the Flame Nebula and the Horsehead Nebula imaged by Marc Charron Reading AS

Adjacent to Alnitak is the beautiful Flame Nebula known as NGC 2024 which is shown to the left of Alnitak in the image above. Just below Alnitak is the famous Horse Head Nebula. These nebulae are difficult to see even using a large telescope.

Alnilam

Alnilam is the middle star of Orion's belt and is the 29th brightest star in the sky (the 4th brightest in Orion). It is a blue-white supergiant with a mass 34.6 times that of the Sun, it has a radius 24 times that of the Sun and 275,000 times more luminous than our Sun. It is estimated to be 2000 light years from us and relatively young with an estimated age of only 5.7 million years. It is expected to develop into a Red Giant within the next million years.

Mintaka

Mintaka is the western (right) star in Orion's belt and is a multiple star system with an overall magnitude of +2.23 but can vary between + 2.50 and +3.90. This is because a 7 th magnitude star that is currently about 52 arc-seconds away from the main component sometimes eclipses the main star. There is an even fainter star in between these two stars. The main component itself is triple star system comprised of a bright giant and a rare B class main sequence star orbiting every 5.73 days and another B class sub-giant 0.2 arc-seconds away.

ORIONS HUNTING DOGS

In mythology, Orion the Hunter has two hunting dogs so the constellation of Orion also has two hunting dogs following him in the sky. These are the stars Sirius, in the constellation of Canis Major (the large dog) and Procyon in the constellation of Canis Minor (the little dog). Sirius can be found by following a line down from Orion's belt and Procyon can be found to the left (east) of Betelgeuse.

The chart of Orion 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 the brightest star in the small constellation of Canis Major (Orion's Large Dog) and in Canis Minor is Procyon (Orion's Little Dog).

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. It has a companion called ‘Sirius B' that 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 (The Pup)

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. It is very close to the brighter component (Sirius A) but is much smaller. Sirius B is considerably smaller and fainter and yet it is one of the more massive white dwarfs ever discovered.

Sirius B (also called the Pup) has a mass slightly more than the Sun's but its radius is only 0.0084 solar radii. In other words, it has the mass of the Sun packed into the size of Earth. The star's estimated surface temperature is about 25,200 K and it will continue to gradually cool over the next 2 billion years. Sirius B is a stronger X- Ray source than Sirius A so appears brighter when using a telescope that is sensitive to X-Rays.

Procyon is the brightest star in the small constellation of Canis Minor (Orion's Small Dog) . Strangely and coincidently Procyon also has a tiny White Dwarf companion just like Sirius. Procyon A has a mass of 1.499 solar masses and a radius twice that of the Sun. With an effective temperature of 6,530 K, it shines with 6.93 solar luminosities. The star will continue to expand until it is 80 to 150 times its current size and turn orange or red at some point in the next 10 to 100 million years. It will end its life as a white dwarf not unlike its companion Procyon B. Procyon B is also fainter and significantly less massive than S irius B , even though it has a larger estimated radius (8,600 km) than that of its neighbour Sirius B (5,800 km).

THE SOLAR SYSTEM - MARCH 2022

The location of the planets at 07:30 GMT on 15th March 2022

The chart above shows the location of the planets along the Ecliptic after sunrise in the east. The sky has been darkened to make the planets visible. The planets are: Mercury, Venus, Mars, Jupiter, Saturn and Neptune. They are visible along the Elliptic from the West (right) to East (left). The planets appear low in the sky, in the bright morning sky and are not well positioned for observing.

MERCURY will be very close to Saturn before sunrise in the east but will be difficult to see this month. It will be in the early morning sky throughout March.

VENUS rises about two hours before the Sun climbs over the eastern horizon. It is looking very bright in the east before sunrise. It will show a large diameter but it will be getting smaller and will appear as a widening crescent, see the computer generated images below. Venus is often called the ‘Morning Star' at this time.

Venus as it will appear on 1st March

Venus as it will appear on 31st March

MARS is on the other side of the Sun (so appears very small) and still appears 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.

JUPITER will appear to be approaching the Sun at the beginning of March. It will pass below the Sun on 5th March but will actually be on the far side of the Sun from our point of view. After its conjunction with the Sun on 5th March it will begin to move away from the Sun and to the west. Jupiter will then continue to move westward through the daytime sky until it eventually appears in the evening sky before midnight in August.

Jupiter in Conjunction and passing the Sun on 5th March

SATURN has now moved away from the Sun after its conjunction on 4th February so will be appearing in the morning sky about one hour before sunrise. It will be very low over the eastern horizon in the brightening sky and will be moving into the evening sky later in the year.

Planets in the east at sunrise 15th March

URANUS will be observable this month and will be best seen at 19:00 when it will be due south west and at its highest point above the horizon but it is small and faint at +5.7.

Uranus in the evening sky at about 19:00

NEPTUNE will be in conjunction with the Sun on 13th March so will not be visible this month.

 

THE SUN

The Sun rises at about 06:40 at the beginning of the month and 05:50 by the end of the month. It sets at 17:45 at the beginning of the month and 18:30 at the end of the month. It will be half way to midsummer on 20th March when it will be the spring (Vernal) equinox. On this date the night and day will be of equal length and exactly 12 hours long.

Midsummer will be on 21st June (Summer Solstice) when it will be the longest day at 16 hours and the shortest night at just 8 hours long. The Sun is starting to climb higher in the sky now. It will be half way between its lowest point (Winter Solstice) on 21st December 2021 and its highest on 21st June 2022 (Summer Solstice).

There have been a few nice Sunspots recently as we move into the Sun's more active phase. Sunspots and other activity on the Sun can be followed live and day to day by visiting the SOHO website at: http://sohowww.nascom.nasa.gov/ .

Sunspots are caused by the magnetic field of the Sun. Magnetic lines of force cause a depression on the surface that can expose a cooler and darker layer below the very bright visible surface (Photosphere).

 

THE MOON PHASES DURING MARCH

New Moon will be on 2nd March

First Quarter will be on 10th March

Full Moon will be on 18th March

Last Quarter will be on 25th March .

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