WHAT'S UP THIS MONTH - MARCH 2017

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THESE PAGES ARE INTENDED TO HELP YOU FIND YOUR WAY AROUND THE SKY

Click HERE for a downloadable white chart

The chart above shows the night sky as it appears on 15th March at 21:00 (9 o'clock) in the evening 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 10 o'clock GMT at the beginning of the month and at 8 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 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: Uranus, Mars, Venus and Jupiter (later in the evening until dawn).

EXPLORING THE NIGHT SKY THIS MONTH

The early night sky looking south on 15th March at 18:30

The chart above shows the night sky looking south at about 18:30 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 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 constellations through which the ecliptic passes are known as the constellations of the ‘Zodiac'.

Constellations through which the ecliptic passes this month are: Pisces (the Fishes), Aries (the Ram), Taurus (the Bull), Gemini (the Twins), Cancer (the Crab), Leo (the Lion) and Virgo (the Virgin) just appearing over the eastern horizon.

The Milky Way (our Galaxy) appears to rise up from the south eastern horizon. It continues up through the constellations of Monoceros, Orion, Gemini, Auriga, Perseus and into Cassiopeia at the top right of the chart.

Venus is in the constellation of Pisces and is very bright and high in the west in the evening as the Sun sets. Mercury is just visible very low in the west just after the Sun has set. Mars (the Red Planet) has moved from Pisces into Aries and is still visible in the south west in the evening twilight. Neptune has now moved over the western horizon and is no longer observable. Uranus is in Pisces and still in a good position for telescopic observation in the west early in the evening. Saturn is now in a good position for observation close to the eastern horizon in the early morning before the Sun rises. Jupiter rises in the east later in the evening. It is very bright and easy to find in the south until the sky brightens at about 6 o'clock in the morning.

Orion is still dominating the evening sky and is easy to find in the south western sky. The familiar shape of Orion the Hunter is followed across the sky by his hunting dogs Sirius and Procyon.

To the north of Orion are the fairly obvious constellations of Taurus and Gemini. To the north west and sitting astride the ecliptic is the constellation of Taurus (the Bull). The Taurus asterism (shape) looks like a squashed cross ‘X'. At the centre of the cross is a large, faint Open Cluster called the Hyades. It has the bright Red Giant star Aldebaran in the centre. The real beauty of Taurus is the naked eye Open Cluster M45 the Pleiades.

To the north of M45 (the Pleiades cluster in Taurus) is a line of stars defining the constellation of Perseus. The whole asterism (shape) of Perseus looks like a horse rider's stirrup. At the top of the line of stars is the beautiful object ‘the Double Cluster' best seen using binoculars.

Following Taurus along the ecliptic is Gemini (the Twins). The twin stars Pollux and Castor are easy to find. There is a lovely Messier Open Cluster M35 in Gemini just off the end of the line of stars emanating from the bright star Castor. Castor is a double star when seen in a telescope.

To the east of Gemini is the faint and rather indistinct constellation of Cancer (the Crab). The asterism (shape) of Cancer looks quite uninteresting but the Open Cluster Messier 44 (M44) Praesepe or the Beehive Cluster looks beautiful and like a swarm of bees around an old style hive when seen using binoculars. Following Cancer is Leo (the Lion) the constellation of the month this month.

CONSTELLATION OF THE MONTH – Leo (the Lion)

The constellation of Leo (the Lion)

Leo is quite distinctive with the ‘Sickle ' (a curved tool for cutting straw) shaped pattern of stars looking much like the head of the lion that Leo represents. In fact the traditional ‘stick figure' shape of Leo as shown on the chart above does look rather like the lion's body or the Sphinx in Egypt. The ‘ Sickle' is also described as looking like a backwards question mark (?).

A classical illustration of Leo (the Lion)

Leo does look unexpectedly large in the sky and may be a little difficult to find for the first time but once found it is easy to recognise and find again .

Regulus is a large blue / white star approximately 160 times brighter than our Sun and lying at a distance of 69 light years.

When viewed through a small telescope a smaller companion star can be seen close by making Regulus a double star. Regulus sits virtually on the ecliptic line (the brown line shown on the chart above) . This is the imaginary line along which the Sun, Moon and planets appear to move across the sky. Leo is therefore one of the twelve constellation s of the Zodiac. Every eighteen years Regulus is ‘occulted' by the Moon every month for a period of eighteen months. An occultation occurs when the Moon passes in front of the star so the star disappears behind the Moon. The last series of occultations occurred around 2007 and the next series will be around 2024. The Moon does however pass close to Regulus every month.

The star Algieba, located above Regulus on the ‘Sickle', is a very nice double star about 75 light years from us. The two stars orbit each other around their common centre of gravity every 620 years and have magnitudes of +2.2 and +3.5 which give them a combined magnitude of +1.98.

Spring time is regarded as the season of galaxies and Leo is on the edge of a large group of galaxies. The main group is located in the neighbouring constellations of Virgo and Coma Berenices to the east (left) of Leo. However Leo does have f our lovely relatively bright galaxies of its own, these are known as: M65, M66, M95 and M96. They are marked in yellow on the chart above just below the ‘lion'.

The galaxies labelled on the previous chart are shown in detail below. A 100mm to 150mm aperture telescope and a clear sky at a dark location will be required to see the faint ‘misty' outline of these galaxies. There is a third galaxy close to M65 and M66 called NGC3628 these three are known as the Leo Triplet.

The Leo Triplet M65, M66 and NGC 3628

Messier 66 (also known as NGC 3627) is a barred spiral galaxy located about 36 million light-years away in the constellation Leo. M66 has an apparent magnitude of +8.9. It was discovered by Charles Messier in 1780. M66 is about 95 thousand light-years across with striking dust lanes and bright star clusters along sweeping spiral arms.

M66 showing the Spiral Arms at the end of a bar

Messier 65 (also known as NGC 3623) and is a spiral galaxy located about 35 million light-years away in the constellation Leo. We see it slightly tilted away from us. It was also discovered by Charles Messier in 1780.

M65 showing a dust lane in the Spiral Arms

There is another beautiful pair of galaxies M95 and M96 further to the west (right) of M65 and M66 below Leo.

Galaxies M96 and M95 in Leo

Messier 96 (also known as M96 or NGC 3368) is a spiral galaxy located about 31 million light-years away in the constellation Leo. M95 and M96 were discovered by Pierre Méchain in 1781 and catalogued by Charles Messier four days later.

M96 has a deformed arm (top)

Messier 95 (also known as M95 or NGC 3351) is a barred spiral galaxy located about 38 million light-years away in the constellation Leo.

M95 is seen almost ‘face on' to us

 

WHAT ARE GALAXIES?

It is likely that all stars formed in galaxies. In the beginning of the universe all the matter that existed was closer together but expanding. Gravity pulled the newly formed atoms (mainly comprised of Hydrogen gas) together to form denser areas. On a smaller scale dense clouds of Hydrogen formed where stars were created like we can see in Messier 42 (M42) the Great Nebula in the constellation of Orion. On the largest scale the gas was drawn by gravity into gigantic filaments that left great voids of empty space between the filaments. Within these filaments giant accumulations of gas clouds, containing developing stars, created the galaxies.

A computer simulation showing the formation of filaments of galaxies

The galaxies we have looked at in Leo are all spiral galaxies but there are other types.

The first galaxies to form were closer together than galaxies we see around us today and they were subtly different. The theories of galaxy formation that we use at the moment suggest that galaxies were smaller when they first formed but larger galaxies may have grown through the merging of smaller ones into larger ones.

Galaxies are classified into four types, these are: Elliptical, Spiral, Barred Spiral, and Irregular. Elliptical galaxies are generally the largest and Irregular Galaxies the smallest. The great American astronomer Edwin Hubble (whom the Hubble Space Telescope is named after) devised a theory about how galaxies formed. The ‘Y' shaped diagram that Hubble produced to demonstrate his theory is still used today to classify galaxies and is shown below.

Edwin Hubble's classification of galaxies

ELLIPTICAL GALAXIES

These are huge balls of stars that do not have spiral arms and are elliptical (egg shaped). Many of these Elliptical Galaxies are the largest of all star groups with some having thousands of billions (trillions) of stars. Elliptical Galaxies are classified according to how flattened they are, nearly round ones are known as E0 and sausage shaped ones E7. Most Elliptical Galaxies are far away and therefore appear very faint and need a fairly large telescope to see them. There are many indications that the giant elliptical galaxies grew from the collision of two or more smaller galaxies. There are indeed some galaxies which can be seen to be in the process of colliding and combining.

Messier 87 (M87) the giant Elliptical Galaxy in Virgo surrounded by Spiral Galaxies

IRREGULAR GALAXIES

These galaxies are , as the name implies , large groups of stars but with no classifiable shape, in other words they may be any shape. Our spiral galaxy and the other close large spiral known as M31, or The Great Andromeda Galaxy, have smaller irregular galaxies associated with them as satellite galaxies. Two of the irregular galaxies associated with our galaxy can be seen from the southern hemisphere as islands broken off the Milky Way. These are known as the Large and Small Magellanic Clouds. There are other small galaxies within our spiral galaxy that have been pulled in by gravity and are in the process of being absorbed by our giant spiral galaxy. We can also see the same process occurring in M31 the Great Spiral Galaxy in Andromeda.

The Magellanic Clouds seen from the southern hemisphere

SPIRAL GALAXIES

Like our galaxy the Milky Way, many galaxies , are disc shaped with spiral arms. Some have arms like curved spokes in a wheel, some gently curved, some tightly wrapped around the central ‘bulge' . The class is preceded by S' for Spiral and ‘SB' for Spiral Barred. Spiral and Barred Spiral galaxies are further divided into three subdivisions a, b and c depending on how tightly the arms are wound. They are therefore referred to as Sa, Sb and Sc or SBa, SBb and SBc. The Great Andromeda Galaxy is our closest spiral neighbour and can even be seen with the naked eye on a very clear night and from a dark location.

Messier (M33) a face on spiral Galaxy in Triangulum

BARRED SPIRAL GALAXIES

Some Spiral Galaxies have what looks like a straight bar of stars extending out from the central b ulge with the spiral arms attached to ends of the bar, these are called Barred Spiral Galaxies. It was originally thought that the ‘Bar' naturally formed as normal spiral galaxies matured. However this theory is now in question and it has been suggested that the bar is formed by gravitational forces in some spiral galaxies. It is now thought that our own galaxy, the Milky Way, is a Barred Spiral Galaxy.

An artist's impression of how our galaxy the Milky Way may look

Spiral Galaxies generally have star formation in the spiral arms and this can be seen as blue and pink colours in the arms of our galaxy in the image above. Spiral galaxies rotate as a solid disc and not faster towards the centre due to the influence of huge amounts of invisible dark matter surrounding the galaxy. The spiral arms are actually more like shock waves moving through the disc. As the shock wave passes through the disc, gas is compressed and stars are formed. The star formation then adds to the shock wave. The cores of Spiral Galaxies and the whole of Elliptical Galaxies have little or no current star formation.

Our Milky Way has more than 200 billion stars and the Andromeda galaxy may be up to twice the size with up to 400 billion stars. All the other members of our ‘Local Group ' are smaller with many of them located like satellites around the two large spiral galaxies.

 

THE PLANETS THIS MONTH

MERCURY will be in superior conjunction on 7th March but will rapidly then move away from the Sun through the rest of the month. The smallest planet will be at its elusive best on 23rd March but will still be low over the western horizon after sunset.

Mercury, Venus and Mars in the west soon after sunset

VENUS is very well positioned in the south west as the Sun sets and very bright at magnitude -4.3. The telescopic view is now very good because Venus getting closer to us and appearing larger. The crescent is getting noticeably bigger but narrower. It still requires a Moon filter to reduce the dazzling effect and improve the view. See the chart above.

MARS will be in the south west as the Sun is setting and the sky begins to darken. The Red Planet appears small at just 4.5 arc-seconds in diameter and is fading to magnitude +1.4. Mars is getting low in the turbulent air near the horizon and will set at 21:45. Mars is now on the opposite side of the Sun to us on Earth. See the Mercury and Venus chart above.

JUPITER is now a good late evening object. It rises over the eastern horizon at 21:00 at the beginning of March and at 19:30 by the end of the month. It will be observable by mid evening towards the end of the month.

The position of Jupiter at 22:00 on 16th March

Jupiter is the most detailed planet to look at using a telescope and therefore the most interesting. There is always something different to see. Even a good pair of binoculars will show the four brightest moons changing position as they orbit the giant planet. A small telescope will allow the moons to be seen very clearly. A computer planetarium application will show the positions of the moons and help identify them.

Jupiter with its four brightest moons imaged by Steve Harris

A small telescope will show the two equatorial cloud belts and a larger telescope will reveal the other fainter belts. On a clear night a larger telescope will allow the Great Red Spot to be seen. However the spot is often difficult to make out as it is usually pink in colour rather than red.

Jupiter imaged by Newbury's own John Napper

SATURN will be visible in the brightening dawn sky close to the south eastern horizon. The ringed planet rises at about 02:00 this month, this about 4 hours before the Sun. The view of Saturn will not be good as it is still quite close to the Sun and rather low. It is observable in the south east from 04:00 until the sky begins to brighten before sunrise.

Saturn in the south east at about 04:00

It will also be close to the south eastern horizon in turbulent and dirty air. Saturn will remain low in the sky this year so the views will not be perfect but the rings are nearly wide open and should still look very impressive.

URANUS will still be observable this month. It will be moving towards the south western horizon as the sky darkens. Uranus may just be visible using a good pair of binoculars but a telescope at a magnification of 100x or higher will be needed to see it as a small blue/green disc. See the chart above.

Uranus close to Mars and Mercury in the west at 19:00

NEPTUNE will not be visible as it has now moved over the western horizon.

 

THE SUN

There are still occasional sunspots to see even though the active phase of the Solar Cycle is all but over.

The Sun rises at 06:40 at the beginning of the month and at 05:45 by the end of the month. It will be setting at 17:45 at the beginning and 18:30 at the end of the month. 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/ .

 

THE MOON PHASES IN MARCH

First Quarter will be on 5th March

Full Moon will be on 12th March

Last Quarter will be on 20th March

New Moon will be on 28th March

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