WHAT'S UP THIS MONTH - FEBRUARY 2019
(Link to What's Up January 2019)
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THESE PAGES ARE INTENDED TO HELP YOU FIND YOUR WAY AROUND THE SKY
The chart above shows the night sky as it appears on 15th February 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 .
EXPLORING THE NIGHT SKY THIS MONTH
The Southern Night Sky during January 2019 at 21:00 GMT
The chart above shows the night sky looking south at about 20:00 GMT on 15th February. West is to the right and east to the left. The point in the sky directly overhead is known as the Zenith or Nadir and is shown at the 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'. See page 4.
Constellations through which the ecliptic passes this month are: Piscis (the Fishes), Aries (the Ram), Taurus (the Bull), Gemini (the Twins), Cancer (the Crab), Leo (the Lion) and Virgo, rising over the eastern horizon.
The Milky Way (our Galaxy) flows up from the south horizon through Orion and Gemini . It continues up through Perseus and Cassiopea and on to Cygnus which is on the northern horizon.
Mars is still in a reasonable position, for observing during the early evening but is looking small now, in the constellation of Piscis. Uranus is just to the south of Mars but will need a good pair of binoculars or better still a telescope to find it.
Along the Ecliptic is the constellation of Taurus (the Bull). The stick figure representation of Taurus resembles a squashed ‘X' with the bright orange coloured Red Giant star Aldebaran at its centre. This is a lovely star to look at especially using binoculars or a telescope and does look noticeably orange in colour.
Following the North western (upper right) arm of the ‘X' shape of Taurus guides us to the beautiful Pleiades ‘naked eye' Open Star Cluster. This bright Open Cluster with its seven brightest stars is known as Messier 45 (M45), the Pleiades or ‘Seven Sisters'.
Attached to the upper left star of Taurus called ‘Elnath' is the constellation of Auriga the Charioteer. Auriga appears like an odd shaped pentagon the beautiful bright white star Capella on the opposite side to Elnath.
To the east of Taurus along the Ecliptic is the constellation of Gemini (the Twins). The twin stars Castor and Pollux are easy to identify. Taurus is the constellation of the month.
Below Gemini is Orion the constellation of the month, in December. Orion is depicted as a hunter with two hunting dogs called Sirius and Procyon. The two stars that represent Orion's hunting dogs are also called Sirius and Procyon. Sirius and Procyon are the brightest stars in the constellations of Canis Major (the great dog) and Canis Minor (the little dog). These were the constellations of the month last month.
Further to the east (left) of Gemini is the constellation of Leo (the Lion). Leo is quite distinctive with the ‘Sickle' 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' shape is also described as looking like a backwards question mark (?).
CONSTELLATIONS OF THE MONTH – AURIGA, GEMINI AND CANCER
The constellations of Auriga, Gemini and Cancer
The chart above shows the winter constellations of Auriga (the Charioteer), Gemini (the Twins) and Cancer (the Crab). These are interesting constellations to search out and have some very interesting objects to see even when using just a pair of binoculars. Gemini and Cancer are located on the Ecliptic and therefore are occasional hosts to the Sun, Moon and Planets as they appear to move along this imaginary line.
Capella is the brightest star in the constellation of Auriga, the sixth-brightest star in the night sky, and the forth-brightest in the northern celestial hemisphere after Sirius, Arcturus and Vega. A prominent object in the northern winter sky, it is circumpolar to observers north of 44°N. Its name means "little goat" in Latin. Capella is depicted as the goat Amalthea that suckled Zeus in classical mythology. The Capella system is relatively close, at only 42.9 light-years (13.2 pc) from the Sun.
Although it appears to be a single star to the naked eye, Capella is actually a quadruple star system with two binary pairs made up of the stars Capella Aa, Capella Ab along with Capella H and Capella L.
The first pair, Capella Aa and Capella Ab is composed of two bright yellow giant stars, both of which are around 2.5 times as massive as the Sun. The second pair, Capella H and Capella L is positioned around 10,000 astronomical units (AU) from the first pair and are two faint, small and relatively cool red dwarfs.
Auriga has three Messier Open Clusters that can be seen using binoculars. These are M36, M37 and M38. See the chart above. Open Clusters are groups of stars that have formed from the gas and dust in a Nebula (large cloud of gas and dust). These clusters look like small smudges of light using binoculars. They are best seen using a telescope which will show many of the individual stars in the clusters.
During the midwinter months Capella is almost directly overhead which makes it very easy to find. During the summer months it can be seen close to the northern horizon. The Milky Way (our galaxy) passes through Auriga and can be seen on the chart above. The three open clusters are seen against the dense star fields of the Milky Way.
The constellation of Auriga is joined to the constellation of Taurus at the most southerly star of Auriga called Elnath. Oddly Elnath is actually included in the lists of the stars belonging to both constellations.
There is a fourth Open Cluster that appears to be in the same line as M36, M37 and M38 over the border in the constellation of Gemini, this is Messier 35 (M35). Gemini is named after the mythical twins Pollux and Castor from Greek mythology.
The recognised shape of Gemini is in the form of a rough rectangle with Pollux and Castor at the eastern short side. A line of stars runs south west from Castor to the star Tejat Posterior. The line from Pollux takes a diversion south through kappa (?) then south west through Wasat to Alhena and Alzirr.
The two brightest stars in Gemini are Castor and Pollux which look quite similar and represent the twins. Castor and Pollux were the children of Leda. However Pollux was actually the son of Zeus who seduced Leda but Castor was the son of Tyndareus, King of Sparta and Leda's husband.
Gemini is easy to find because its two brightest stars are quite close together and similar in appearance. The two brightest stars are called Pollux (ß) and Castor (a) and are known as the Gemini Twins. Although Castor has been given the Greek letter designation a (alpha), which is normally given, to the brightest star in a constellation, Castor is not actually the brightest Pollux is in fact the brighter of the two.
The open Clusters in Auriga and Gemini
Messier 36 (M36)
Messier 37 (M37)
Messier 38 (M38)
Messier 35 (M35) and NGC2158
Pollux is brighter at magnitude +1.59 compared to the +1.9 of Castor. However Castor is a double star with a fainter companion that has a magnitude of +2.9 and separated by 6 arc-seconds. The two stars, known as Castor A and Castor B, orbit their common centre of gravity every 467 years. The pair can be separated in a 75mm aperture telescope on a good clear night.
Messier 35 (M35) is located at the end of the upper of the two lines of stars that emanate from Pollux and Castor. It is the most spectacular of the four Open Clusters and is shown above.
Cancer is a faint and rather indistinct constellation but it does have a rather nice Open Cluster called Messier 44 (M44) Praesepe or ‘the Beehive Cluster'. The stick figure shape of Cancer is an up-side-down letter ‘Y'. Although M44 is large, the stars are dispersed and fairly faint. It is quite difficult to find in a light polluted area so will require binoculars to see it.
Messier 44 (M44) Praesepe the Beehive Cluster in Cancer
Open Star Clusters are listed in Charles Messier's Catalogue along with other objects of interest to amateur astronomers. Messier listed these objects along with Globular Clusters, Nebulae and Galaxies so they would not be mistaken for the comets he was searching for. Many of the brighter open clusters do look quite comet-like when viewed through binoculars. They are as the name suggests clusters of related stars and many are very beautiful to look at.
It is thought all stars form in vast clouds of gas and dust known as Nebulae (singular Nebula). Gravity pulls the atoms together into denser clumps until the gas and dust is compressed into very dense spheres. The temperature and pressure in the centre of the spheres rises until Nuclear Fusion begins. The Nuclear Fusion in the core produces an enormous amount of energy and the spheres begin to shine as stars and an Open Star Cluster is formed.
The brightest and most easily seen Open Cluster is Messier 45 (M45). See the constellation chart above. This is a cluster of about 300 stars in the constellation of Taurus. The cluster is known as the Pleiades but even more widely known as the Seven Sisters.
Messier 45 (M45) in the constellation of Taurus
Six or possibly seven of the brightest stars in M45 are easily visible to the naked eye in a clear dark sky. They occupy an area of sky about the same size as the full Moon. Using a pair of 10 x 50 binoculars another thirty or so fainter stars can be seen embedded within the Seven Sisters.
The clusters M35, M36, M37 and M38 are further away so appear smaller and fainter. They can just about be seen using binoculars but a telescope is required to see them well. M35 is particularly lovely as it has a spectacular string of stars that appear to cascade through its centre. To the lower right of M35 is another Open Cluster called NGC2158 which is even further away and consequently appears much smaller and fainter. NGC2158 does need a larger telescope to see any detail. .
THE SOLAR SYSTEM FEBRUARY 2019
MERCURY sets over the western horizon soon after the Sun so it is just above the horizon and best placed low in the west in the evenings at the end of the month.
VENUS was at its Furthest Western Elongation from the Sun on 6 th January. It now rises over the eastern horizon at about 05:00 and will be very bright in the south east even at 06:30 as the sky brightens at dawn. Venus is very bright and always remains about the same brightness because as the diameter increases or decreases the phase narrows or widens. When it is on the other side of its orbit (far side of the Sun) it appears smaller but has a full phase. As it moves around and towards us it appears larger but develops into a narrow crescent therefore remaining at about the same overall brightness. See the Jupiter and Saturn chart below.
How Venus will appear using a telescope
MARS is still well placed in the early evening. It is low over the southern western horizon in turbulent and smoggy air. The Red Planet is moving away from Earth and looking smaller at 6.0 arc-seconds in diameter but still bright at magnitude +1.0. See the Uranus and Neptune chart below.
JUPITER is moving away from the Sun before sunrise. It now rises over the eastern horizon around 03:30 about 3 hours before sunrise. It is now becoming well worth getting up early to see. See the chart below.
Saturn, Venus and Jupiter at sunrise 07:00
SATURN is moving away from the Sun before sunrise and will be close to Venus. It will be observable but difficult to find in the brightening sky however nearby Venus will help. See the chart above.
URANUS will be in an observable position in the south west in the early evening but is moving towards the south western horizon. A good pair of 9x50 binoculars will reveal a slightly fuzzy blue, magnitude +5.8, star like, object. A telescope at a magnification of 100x will show it as a small blue/green disc. See the chart below.
Uranus, Neptune and Mars at 18:30 on 15 th January
NEPTUNE is now close to the western horizon as the Sun sets but it is small and difficult to find.
The Sun has been very quiet over the last few months as can be expected in its inactive phase. There have been no significant sunspots. The Sun rises at 07:30 at the beginning of the month and at 06:50 by the end of the month. It will be setting at 16:50 at the beginning and 17:30 at the end of the month.
THE MOON PHASES IN FEBRARY
The ‘New Moon' will always be seen in the west after the Sun has set over the western horizon. At this phase the Moon will be emerging from conjunction with the Sun (passing between Earth and the Sun). The Moon orbits Earth once a month (Moonth). The cardinal phases listed below occur every seven days. Full Moon will always appear in the East as the Sun is setting in the West.
New Moon will be on the 4th February
First Quarter will be on 12th February
Full Moon will be on 19th February
Last Quarter will be on 26th February
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