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Constellations of the month

 

 
CURRENT MOON

Saturn

Saturn, passed directly behind the Sun on the 13th of January and, as February begins, will rise less than one hour before the Sun. Then, equipped with binoculars and a very low south-eastern horizon, it might be glimpsed at magnitude +0.58 in the pre-dawn sky - but please do not use binoculars after the Sun has risen. As February progresses, its magnitude actually reduces very slightly to +0.66 as it angular size increases from 15.1 to 15.5 arc seconds. Saturn crosses the Ecliptic (the path of the Sun across the heavens) in a southerly direction on the 13th, just 13 days before Jupiter reaches this point whilst Mars reaches it on the 1st of February. (Stellariun shows them beautifully aligned along the ecliptic this month.)

Jupiter

Jupiter. As February begins, Jupiter rises more than 90 minutes before the Sun shining at magnitude of -1.9. During the month it brightens to magnitude -2.0 whilst its angular size increases slightly from 32.5 to 34.1 arc seconds. A low south-eastern horizon will be needed and our views of the giant planet and its Gallilean moons will be hindered by the depth of atmosphere through which it will be observed.

Mars

Mars can be seen towards the southeast in the pre-dawn sky at the start of the month. It then rises some three hours before the Sun and will be best seen at around 7am having an elevation of ~8 degrees. It will have a magnitude of +1.4 and a 4.3 arc second, salmon-pink, disk. By month's end it will be seen further round towards the south before dawn and its magnitude will have increased slightly to +1.1. Its angular size will have increased to 5.5 arc seconds but no markings will be seen unless you have access to the Hubble Space Telescope. Lying along the ecliptic it is moving eastwards above the 'Teapot' of Sagittarius and will lie just above its 'lid' on the 24th.
Venus

Venus is now dominating the south-western twilight sky and appears higher each night, climbing from ~29 degrees above the horizon to more than 38 degrees at sunset. During the month its angular size increases from 15.3 to 18.6 arc seconds but, at the same time, it phase (the percentage of the disk illuminated) decreases from 73% to 63% and so the brightness only increases slightly from -4.1 to -4.3 magnitudes.

Mercury

Mercury passed in front of the Sun (superior conjunction) on the 10th of January and, on the 10th of February, comes to its greatest elongation east, some 18.2 degrees in angle from the Sun. Mercury starts the month at magnitude -1 and dims to magnitude +0.2 by the 14th and will then soon be lost in the Sun's glare. From the 1st to the 14th, its angular size increases from 5.6 to 8.1 arc seconds but its phase (the % illuminated disk) falls from 85% to just 32% - hence the fall in magnitude. On the 1st of the month, it will set about 70 minutes after the Sun and will have an elevation, low in the west-southwest, of ~9 degrees. This will increase until the 10th before it begins to fall back towards the Sun. Binoculars may well be needed, but please do not use them until after the Sun has set.

The Night Sky In and Around Swindon February 2020

SpaceX's Starlink Satellite 'Train'

Not sure if anyone saw it, but the SpaceX Starlink Satellite ''Train' could be seen over Swindon on Monday 27th January. They are 60 satellites launched to aid global broadband internet communication. Whether it can be seen again I don't know?

With thanks to Swindon resident Helen Murphy for spotting this and contacting us.
February 3rd - evening: the Moon between the Hyades and Pleiades Clusters

The Moon within the Hyades Cluster.
Image: Stellarium/IM

Compiled by Prof. Ian Morison
The planets this month
February: find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum

How to find M31
Image: Stellarium/IM
In the evenings when the Moon is not prominent, the galaxy M31 in Andromeda will be visible high in the south The chart provides two ways of finding it:

1) Find the square of Pegasus. Start at the top left star of the square - Alpha Andromedae - and move two stars to the left and up a bit. Then turn 90 degrees to the right, move up to one reasonably bright star and continue a similar distance in the same direction. You should easily spot M31 with binoculars and, if there is a dark sky, you can even see it with your unaided eye. The photons that are falling on your retina left Andromeda well over two million years ago!

2) You can also find M31 by following the "arrow" made by the three rightmost bright stars of Cassiopeia down to the lower right as shown on the chart.

Around new Moon (23rd February) - and away from towns and cities - you may also be able to spot M33, the third largest galaxy after M31 and our own galaxy in our Local Group of galaxies. It is a face on spiral and its surface brightness is pretty low so a dark, transparent sky will be needed to spot it using binoculars (8x40 or, preferably, 10x50). Follow the two stars back from M31 and continue in the same direction sweeping slowly as you go. It looks like a piece of tissue paper stuck on the sky just a bit brighter than the sky background. Good Hunting!

The Moon and the Hyades
In the evening one could see the waxing Moon, moving towards full, lying to the right of the Hyades Cluster. Aldeberan is a red giant star far closer to us than the Hyades.
February 7th - after sunset: Venus lies above Mercury

Venus lies above Mercury
Image: Stellarium/IM

After sunset, low in the southwest, Venus will lie above Mercury. Venus will not be missed, but to spot Mercury which lies down to its lower right, a low horizon just south of west and perhaps binoculars will be needed - but please do not use them until the Sun has set.

The constellation Taurus
Taurus is one of the most beautiful constellations and you can almost imagine the Bull charging down to the left towards Orion. His face is delineated by the "V" shaped cluster of stars called the Hyades, his eye is the red giant star Aldebaran and the tips of his horns are shown by the stars beta and zeta Tauri. Although alpha Tauri, Aldebaran, appears to lie amongst the stars of the Hyades cluster it is, in fact, less than half their distance lying 68 light years away from us. It is around 40 times the diameter of our Sun and 100 times as bright.
To the upper right of Taurus lies the open cluster, M45, the Pleiades. Often called the Seven Sisters, it is one of the brightest and closest open clusters. The Pleiades cluster lies at a distance of 400 light years and contains over 3000 stars. The cluster, which is about 13 light years across, is moving towards the star Betelgeuse in Orion. Surrounding the brightest stars are seen blue reflection nebulae caused by reflected light from many small carbon grains. These relfection nebulae look blue as the dust grains scatter blue light more efficiently than red. The grains form part of a molecular cloud through which the cluster is currently passing. (Or, to be more precise, did 400 years ago!)

VLT image of the Crab Nebula
Close to the tip of the left hand horn lies the Crab Nebula, also called M1 as it is the first entry of Charles Messier's catalogue of nebulous objects. Lying 6500 light years from the Sun, it is the remains of a giant star that was seen to explode as a supernova in the year 1056. It may just be glimpsed with binoculars on a very clear dark night and a telescope will show it as a misty blur of light.

Lord Rosse's drawing of M1
Its name "The Crab Nebula" was given to it by the Third Earl of Rosse who observed it with the 72 inch reflector at Birr Castle in County Offaly in central Ireland. As shown in the drawing above, it appeared to him rather lile a spider crab. The 72 inch was the world's largest telelescope for many years. At the heart of the Crab Nebula is a neutron star, the result of the collapse of the original star's core. Although only around 20 km in diameter it weighs more than our Sun and is spinning 30 times a second. Its rotating magnetic field generate beams of light and radio waves which sweep across the sky. As a result, a radio telescope will pick up very regular pulses of radiation and the object is thus also known a Pulsar. Its pulses are monitored each day at Jodrell Bank with a 13m radio telescope
February 29th - before Dawn: a lineup of Saturn, Jupiter and Mars

Saturn, Jupiter and Mars in the predawn sky
Image: Stellarium/IM
If clear around 6:30 am on the 29th, one will see a nice lineup of, from left to right, Saturn, Jupiter and Mars. A low horizon towards the southeast will be needed to spot Saturn.
The constellation Orion
Orion, perhaps the most beautiful of constellations, will be seen in the south at around 11 - 12 pm during January. Orion is the hunter holding up a club and shield against the charge of Taurus, the Bull up and to his right. Alpha Orionis, or Betelgeuse, is a read supergiant star varying in size between three and four hundred times that of our Sun. The result is that its brightness varies somewhat. Beta Orionis, or Rigel, is a blue supergiant which, at around 1000 light years distance is about twice as far away as Betelgeuse. It has a 7th magnitude companion. The three stars of Orion's belt lie at a distance of around 1500 light years. Just below the lower left hand star lies a strip of nebulosity against which can be seen a pillar of dust in the shape of the chess-board knight. It is thus called the Horsehead Nebula. It shows up very well photographically but is exceedingly difficult to see visually - even with relativly large telescope.

The Horsehead Nebula: Anglo Australian Observatory
Beneath the central star of the belt lies Orion's sword containing one of the most beautiful sights in the heavens - The Orion Nebula. It is a region of star formation and the reddish colour seen in photographs comes from Hydrogen excited by ultraviolet emitted from the very hot young stars that make up the Trapesium which is at its heart. The nebula, cradling the trapesium stars, is a beautiful sight in binoculars or, better still, a telescope. To the eye it appears greenish, not red, as the eye is much more sensitive to the green light emitted by ionized oxygen than the reddish glow from the hydrogen atoms.
The Orion Nebula

The Orion Nebula: David Malin
The constellation of Ursa Major

The stars of the Plough, shown linked by the thicker lines in the chart above, form one of the most recognised star patterns in the sky. Also called the Big Dipper, after the soup ladles used by farmer's wives in America to serve soup to the farm workers at lunchtime, it forms part of the Great Bear constellation - not quite so easy to make out! The stars Merak and Dubhe form the pointers which will lead you to the Pole Star, and hence find North. The stars Alcor and Mizar form a naked eye double which repays observation in a small telescope as Mizar is then shown to be an easily resolved double star. A fainter reddish star forms a triangle with Alcor and Mizar.

Ursa Major contains many interesting "deep sky" objects. The brightest, listed in Messier's Catalogue, are shown on the chart, but there are many fainter galaxies in the region too. In the upper right of the constellation are a pair of interacting galaxies M81 and M82 shown in the image below. M82 is undergoing a major burst of star formation and hence called a "starburst galaxy". They can be seen together using a low power eyepiece on a small telescope.


M81 and M82

Another, and very beautiful, galaxy is M101 which looks rather like a pinwheel firework, hence its other name the Pinwheel Galaxy. It was discovered in1781 and was a late entry to Messier's calalogue of nebulous objects. It is a type Sc spiral galaxy seen face on which is at a distance of about 24 million light years. Type Sc galaxies have a relativly small nucleus and open spiral arms. With an overall diameter of 170,000 light it is one of the largest spirals known (the Milky Way has a diameter of ~ 130,000 light years).


M101 - The Ursa Major Pinwheel Galaxy
Though just outside the constellation boundary, M51 lies close to Alkaid, the leftmost star of the Plough. Also called the Whirlpool Galaxy it is being deformed by the passage of the smaller galaxy on the left. This is now gravitationally captured by M51 and the two will eventually merge. M51 lies at a distance of about 37 million light years and was the first galaxy in which spiral arms were seen. It was discovered by Charles Messier in 1773 and the spiral structure was observed by Lord Rosse in 1845 using the 72" reflector at Birr Castle in Ireland - for many years the largest telescope in the world.

M51 - The Whirlpool Galaxy
Lying close to Merak is the planetary nebula M97 which is usually called the Owl Nebula due to its resemblance to an owl's face with two large eyes. It was first called this by Lord Rosse who drew it in 1848 - as shown in the image below right. Planetary nebulae ar the remnants of stars similar in size to our Sun. When all possible nuclear fusion processes are complete, the central core collpses down into a "white dwarf" star and the the outer parts of the star are blown off to form the surrounding nebula.

M97 - The Owl Planetary Nebula & Lord Rosse's 1848 drawing of the Owl Nebula