Monthly Night Sky Guide February 2023
Compiled by Ian Morison
This page, updated monthly, will let you know some of the things that you can look out for in the night sky. It lists the phases of the Moon, where you will see the naked-eye planets and describes some of the prominent constellations in the night sky during the month.
New(ish)
The author's: Astronomy Digest
which, over time, will provide useful and, I hope, interesting articles for all amateur astronomers. A further aim is to update and add new material to link with the books recently published by Cambridge University Press and which are described on the home page of the digest. It now includes well over 100 illustrated articles.
Image of the Month
Orion Nebula
Image: Ian Morison
The constellation Orion is due south at 21:00 on the first of the month. The lower right image shows the southern part of the constellation containing what is called the 'Sword of Orion'. Within this is the most beautiful object in the northern skies - Messier 42, The Orion Nebula. It is the closest star formation region to our solar system, lying 1,344 light years away and being around 24 light years across. At its heart lie the four young 'Trapezium' stars whose ultraviolet light is exciting the surrounding hydrogen gas which then gives off the deep red H-alpha emission. These stars lie within a diameter of 1.5 light years. With binoculars, the nebula will be seen as a hazy spot, but a small telescope will begin to reveal its beauty. Above lies the 'Running Man' reflection nebula where dust is scattering blue light from the hot stars at its heart,
Sword of Orion Ian Morison
Highlights of the Month
February - a last chance to view Jupiter.
Jupiter imaged by Damian Peach
This is still a reasonable month to observe Jupiter which will be visible in the early evening. It is now moving up the ecliptic and reached an elevations of ~36 degrees when crossing the meridian. An interesting observation is that the Great Red Spot appears to be diminishing in size. At the beginning of the last century it spanned 40,000 km across but now appears to be only ~16,500 km across - less than half the size. It used to be said that 3 Earths could fit within it, but now it is only one. The shrinking rate appears to be accelerating and observations indicate that it is now reducing in size by ~580 miles per year. Will it eventually disappear?
The features seen in the Jovian atmosphere have been changing quite significantly over the last few years - for a while the South Equatorial Belt vanished completely (as seen in Damian's image) but has now returned to its normal wide state. The diagram on right shows the main Jovian features as imaged by the author at the beginning of December 2012.
The image by Damian Peach was taken with a 14 inch telescope in Barbados where the seeing can be particularly good. This image won the "Astronomy Photographer of the Year" competition in 2011.
See more of Damian Peach's images: Damian Peaches Website"
Features in Jupiter's atmosphere - December 2013.
February: find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum
How to find M31
Image: Stellarium/IM
In the earlyevenings when the Moon is not prominent, the galaxy M31 in Andromeda will be visible in the northwest. 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 (20th Febuary) - 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!
February, evening: the Double Cluster and the 'Demon Star', Algol.
Algol and the Double Cluster.
Image: Stellarium/IM
This month is a good time to look high in the Southeast towards the constellations of Cassiopea and Perseus. Perseus contains two interesting objects; the Double Cluster between the two constellations and Algol the 'Demon Star'. Algol in an eclipsing binary system as seen in the diagram below. Normally the pair has a steady magnitude of 2.2 but every 2.86 days this briefly drops to magnitude 3.4.
Double Cluster imaged by IM and the Algol Light Curve
February 3rd - evening: the Moon in Gemini.
The Moon in Gemini.
Image: Stellarium/IM
This evening, if clear, the Moon will be seen close to Pollux in Gemini.
February 22nd - after sunset: Jupiter, Venus and a thin crescent Moon.
Jupiter, Venus and the Moon.
Image: Stellarium/IM
This evening, if clear, one could see a very nice grouping of Jupiter, Venus and a thin crescent Moon.
February 27th - evening: Mars and the Moon.
The Moon and Mars in Taurus.
Image: Stellarium/IM
If clear this evening, the First Quarter Moon will be seen to lie between Mars and the Hyades and Pleaides Clusters..
February 11th and 27th evening: The Hyginus Rille
Hyginus Rille location: IM.
During these evenings the terminator lies close so making it more obvious. For some time a debate raged as to whether the craters on the Moon were caused by impacts or volcanic activity. We now know that virtually all were caused by impact, but it is thought that the Hyginus crater that lies at the centre of the Hyginus Rille may well be volcanic in origin. It is an 11 km wide rimless pit - in contast to impact craters which have raised rims - and its close association with the rille of the same name associates it with internal lunar events. It can quite easily be seen to be surrounded by dark material. It is thought that an explosive release of dust and gas created a vacant space below so that the overlying surface collapsed into it so forming the crater.
Hyginus Crater and Rille
M109 imaged with the Faulkes Telescope
Messier 109
Image: Daniel Duggan
Faulkes Telescope North.
The Galaxy M109, imaged by Daniel Duggan.
This image was taken using the Faulkes Telescope North by Daniel Duggan - for some time a member of the Faulkes telescope team. It shows the barred spiral galaxy M109 that lies at a distance of 83 million light years in the constellation of Ursa Major. It is the brightest galaxy in the Ursa Major group of some 50 galaxies. Our own Milky Way galaxy is now thought to be a barred spiral like M109.
Learn more about the Faulkes Telescopes and how schools can use them: Faulkes Telescope"
The Moon
The Moon at 3rd Quarter. Image, by Ian Morison, taken with a 150mm Maksutov-Newtonian and Canon G7.
Just below the crator Plato seen near the top of the image is the mountain "Mons Piton". It casts a long shadow across the maria from which one can calculate its height - about 6800ft or 2250m.
| new moon |
first quarter |
full moon |
third quarter |
`
| February 20th |
February 27th |
February 5th | February 13th |
Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images
A World Record Lunar Image
The 9 day old Moon.
To mark International Year of Astronomy, a team of British astronomers have made the largest lunar image in history and gained a place in the Guinness Book of Records! The whole image comprises 87.4 megapixels with a Moon diameter of 9,550 pixels. The resolution of ~0.4 arc seconds allows details as small as 1km across to be discerned! The superb quality of the image is shown by the detail below of Plato and the Alpine Valley. Craterlets are seen on the floor of Plato and the rille along the centre of the Alpine valley is clearly visible. The image quality is staggering! The team of Damian Peach, Pete lawrence, Dave Tyler, Bruce Kingsley, Nick Smith, Nick Howes, Trevor Little, David Mason, Mark and Lee Irvine with technical support from Ninian Boyle captured the video sequences from which 288 individual mozaic panes were produced. These were then stitched together to form the lunar image.
Plato and the Alpine Valley.
Please follow the link to the Lunar World Record website and it would be really great if you could donate to Sir Patrick Moore's chosen charity to either download a full resolution image or purchase a print.
The 8 day old Moon
The 8 day old Moon imaged by Ian Morison.
This image was taken by the author on a night in March 2018 when the Moon was at an elevation of ~52 degrees and the seeing was excellent. This enabled the resolution of the image to be largely determined by the resolution of the 200 mm aperture telescope and the 3.75 micron pixel size of the Point Grey Chameleon 1.3 megapixel video camera. The use of a near infrared filter allowed imaging to take place before it was dark and also reduced the effects of atmospheric turbulence. The 'Drizzle' technique developed by the Hubble Space Telescope Institute (HSTI) was used to reduce the effective size of the camera's pixels to allow the image to be well sampled. Around 100 gigabytes of data, acquired over a 2 hour period, was processed to produce images of 54 overlapping areas of the Moon which were then combined to give the full lunar disk in the free 'stitching' program Microsoft ICE. A further HSTI development called 'deconvolution sharpening' was then applied to the image. The Moon's disk is ~6,900 pixels in height and has a resolution of 0.6 to 0.7 arc seconds. Interestingly, as seen in the inset image, the rille lying along the centre of the Alpine Valley is just discernable and this is only ~0.5 km wide! [Due to size limitations the large image is 2/3 full size.]
The Planets
A montage of the Solar System. JPL / Nasa
Jupiter
A Cassini image of Jupiter . Nasa
Jupiter. As darkness falls at the start of the month Jupiter is seen in the Southwest, shining at magnitude -2.19 and having an angular size of 36 arc seconds. It elevation will be ~30 degrees, so details on the surface should still be seen. By the end of the month, its magnitude will have dropped a little to -2.1 and its angular size to 34 arc seconds and will be seen in the West-southwest as darkness falls. See highlight above - a day before a very close conjunction with Venus on the first of March.
Saturn
The planet Saturn. Cassini - Nasa
Saturn lies too close to the Sun to be seen this month.
Mercury
Messenger image of Mercury Nasa
Mercury. On the first of the month Mercury might just be glimpsed shining at a magnitude 0.16 just before sunrise in the southeast. Binoculars or a small telescope will be needed to cut throught the Sun's glare - but please do not use them after the Sun has risen. Mercury will then rapidly disappear from view as it moves beyond the Sun when it will reach superior conjunction on the 17th of March. It will not been seen again until it reappears in the evening sky in mid April.
Mars
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa
As darkness falls at the start of the month, Mars will seen in the south having a magnitude of -0.24 and an angular size of 10.61 arc seconds. It will then transit the meridian at 21:00 GMT at an elevation of ~61 degrees. As the month progresses its magnitude reduces to 0.42 with a reduced angular size of 8.2 arc seconds. Under good seeing conditions, details on the surface should still be visible during the month.
Venus
Venus showing some cloud structure
Venus. As darkness falls at the beginning of the month, Venus will be seen very low in the west-southwest shining at magnitude -3.87 at an elevation of ~9 degrees which, of course, varies from south to north across the UK - a variation of 7 degrees in latitude. By the end of the month, its elevation as darkness falls, will have increased to ~16 degrees whilst it magnitude stays almost constant at -3.91 See highlight above - a day before a very close conjunction with Jupiter.
The Stars
The Mid Evening February Sky
The February Sky in the south-east - mid evening.
This map shows the constellations seen in the south during the evening. The brilliant constellation of Orion is seen in the south. Moving up and to the right - following the line of the three stars of Orion's belt - brings one to Taurus; the head of the bull being outlined by the V-shaped cluster called the Hyades with its eye delineated by the orange red star Aldebaran. Further up to the right lies the Pleaides Cluster. Towards the zenith from Taurus lies the constellation Auriga, whose brightest star Capella will be nearly overhead. To the upper left of Orion lie the heavenly twins, or Gemini, their heads indicated by the two bright stars Castor and Pollux. Down to the lower left of Orion lies the brightest star in the northern sky, Sirius, in the consteallation Canis Major. Up and to the left of Sirius is Procyon in Canis Minor. Rising in the East is the constellation of Leo, the Lion, with the planet Saturn up and to the right of Regulus its brightest star. Continuing in this direction towards Gemini is the faint constellation of Cancer with its open cluster Praesepe (also called the Beehive Cluster),the 44th object in Messier's catalogue. On a dark night it is a nice object to observe with binoculars. There is also information about the constellation Ursa Major,seen in the north, in the constellation details below.
The constellation Taurus
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.
AAO Image of the Pleiades, M45, by David Malin
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.
The constellation Orion
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: David Malin
The constellation Ursa Major
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
