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« December 2020


The Night Sky January 2021


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 nearly 100 illustrated articles.



Image of the Month

UGC 1810

The 'Antennae' Colliding Galaxies
Image: HST, NASA, ESA.

In the southerly constellation Corvus lie two colliding galaxies some 60 million light years distant. Named NGC 4038 and NGC4039, they are collectivly known as the Antennae galaxies.   This HST image spans 50,000 lights years across but cannot show the extended structures that extend for hundreds of thousand light years.   It is these that give the pair their popular name - The Antennae Galaxies - and are shown in the image lower right. The collision of large clouds of molecular gas and dust trigger extensive star formation shown by the areas of young blue stars that are flung out into space by the gravitational tidal forces.

Antennae
The Antennae Galaxies
Image: Subaru,NASA, ESA ,NAOJ. Roberto Colombari

Highlights of the Month


Early December - still a good time to view Mars.

Mars
Mars imaged by the Hubble Space telescope. NASA, ESA

This is still a reasonable month to observe Mars which had its closest approach to Earth back on October the 6th when it lay 39 million miles from Earth and reached opposition on the 13th.   Wonderfully, at this opposition, Mars has been far higher in the sky than at recent oppositions.   Starting the month in Pisces but moving into Aries on the 5th, Mars, shining at a magnitude of -0.2 at the start of the month, can be seen crossing the meridian at 19:00 GMT.   By month's end it magnitude will have dropped to -0.44 whilst being due south at 18:00 GMT.   Its angular size is just over 10 arc seconds at the start of the month dropping to 7.9 arc seconds by month's end.   Reaching an elevation of ~50 degrees when due south as seen from the UK, at the start of the month amateur telescopes may just be able to see features, such as Syrtis Major, on its surface when the seeing conditions are good.

During this apparition, Mar's southern hemisphere is tipped towards the Earth and so the South Polar Cap should be visible, though much of its frozen carbon dioxide will have vaporised during the Martian summer.   Though the North Polar Cap is beyond our view, one should be able to spot the haze of the North Polar Hood lying above the northern limb of the planet. At 24.6 hours long, the Martian day is similar to ours, so the surface details remain similar at the same time each night.   Mars takes 41 days to make an apparent rotation as seen from Earth.




January - evening: the Double Cluster and the 'Demon Star', Algol.

Algol
Algol and the Double Cluster.
Image: Stellarium/IM

This month, in the evening, is a good time to look high in the south 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
Double Cluster imaged by IM and the Algol Light Curve



January: find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum

M31
How to find M31
Image: Stellarium/IM

In the late 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 (13th January) - 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!






January 1st - after sunset: - Jupiter and Saturn.

Jupiter
Jupiter and Saturn
Image: Stellarium/IM

Given a very low horizon towards the southwest and a clear evening, Jupiter will seen up to the right of Saturn as they come to the end of their apparitions.

January 9th - after sunset: - Jupiter and Saturn are joined by Merury.

Mercury
Jupiter and Saturn are joined by Mercury
Image: Stellarium/IM

Given a very low horizon towards the southwest and a clear evening, Jupiter will seen up to the right of Saturn as they are joined by Mercury lying just above the horizon.

January 11th - before dawn: Venus and a very thin crescent Moon

Venus
Venus and a thin crescent Moon
Image: Stellarium/IM

Before dawn on the 11th of January and given a low horizon towards the southeast you would, if clear, see Venus lying down to the left of a very thin crescent Moon.

January 14th - after sunset: Jupiter, Mercury and a very thin crescent Moon

Mercury
Venus and a thin crescent Moon
Image: Stellarium/IM

After sunset on the 11th of January and given a low horizon towards the southwest you would, if clear, see Mercury, above, and Jupiter lying to th right of a very thin crescent Moon.

January 20th evening: Mars lies above a first quarter Moon

Mars
Mars lies above a first quarter Moon
Image: Stellarium/IM

During the evening, if clear looking south, you will see Mars lying above the first quarter Moon.

January 7th and 22nd/23rd: Two Great Lunar Craters

20thJuly
Tycho and Copernicus: Ian Morison

Two great Lunar Craters: Tycho and Copernicus
These are three great nights to observe two of the greatest craters on the Moon, Tycho and Copernicus, as the terminator is nearby.   Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands.   It is a relatively young crater which is about 108 million years old.  It is interesting in that it is thought to have been formed by the impact of one of the remnents of an asteroid that gave rise to the asteroid Baptistina.   Another asteroid originating from the same breakup may well have caused the Chicxulub crater 65 million years ago.   It has a diameter of 85 km and is nearly 5 km deep.   At full Moon - seen in the image below - the rays of material that were ejected when it was formed can be see arcing across the surface.   Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains.   It is 93 km wide and nearly 4 km deep and is a clasic "terraced" crater.   Both can be seen with binoculars.

Tycho's Rays
Full Moon showing Tycho's rays: Ian Morison

A Messier Object imaged with the Faulkes Telescope: Messier 1 - The Crab Nebula

Messier 1
The Crab Nebula, M1
Image:Nik Szymanik
Faulkes Telescope North.

The Crab Nebula, M16, imaged by Nik Szymanek.
This image was taken using the Faulkes Telescope North by Nik Szymanek - one of the UK's leading astro-photograpers.   The Crab nebula - the first entry in Charles Messier's catalogue - is the remnant of a supernovae that was seen to explode in the year 1054.   It is visible as the lower right of the pair of stars at the centre of the nebula and is a "neutron star" just 30km across but weighing more than our Sun!   Under the intense pressure of gravity, the protons and electrons fused to form neutrons and the compact object became stable as gravity was opposed by "neutron degeneracy pressure" - a quantum mechanical force.   It is now spinning just under 30 times a second and emitting two opposed beams of light and radio waves which pass across our location in space.   We thus detect very regular pulses and so objects like this are called pulsars.   At 8.4 magnitudes it is easily seen in a small telescopes under dark transparent skies appearing as a smudge of light which is a little underwhelming to see!

Learn more about the Faulkes Telescopes and how schools can use them: Faulkes Telescope"

Observe the International Space Station

The International Space Station
The International Space Station and Jules Verne passing behind the Lovell Telescope on April 1st 2008.
Image by Andrew Greenwood

Use the link below to find when the space station will be visible in the next few days. In general, the space station can be seen either in the hour or so before dawn or the hour or so after sunset - this is because it is dark and yet the Sun is not too far below the horizon so that it can light up the space station. As the orbit only just gets up the the latitude of the UK it will usually be seen to the south, and is only visible for a minute or so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite considerably across the UK. The NASA website linked to below gives details for several cities in the UK. (Across the world too for foreign visitors to this web page.)

Note: I observed the ISS three times recently and was amazed as to how bright it has become.

Find details of sighting possibilities from your location from: Location Index

See where the space station is now: Current Position


The Moon

3rd Quarter 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
January 13th January 20th January 28th January 6th

Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images

A World Record Lunar Image

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
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

Lunar Image
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
A montage of the Solar System. JPL / Nasa

Jupiter

Jupiter
A Cassini image of Jupiter . Nasa

Jupiter, along with Saturn, remains just visible as January begins low in the sky at at elevation of ~5 degrees in the southwest when darkness falls at around 17:00 GMT and sets some 40 minutes later.   Following their close conjunction on the 21st of December, they are still just 1.25 degrees apart on the 1st and remain within 2 degrees of each other until the 8th.   Its magnitude remains at -2.0 during the month whilst its angular diameter falls from 32.9 to 32.5 arc seconds.   Sadly, even when first seen after sunset, the atmosphere will limit our view.   Jupiter will disappear into the Sun's glare by the middle of the month as it moves towards superior conjunction (behind the Sun) on the 28th.  Due its position in the most southerly part of the ecliptic this has been a very poor apparition for those of us in the northern hemisphere.



Saturn

Saturn
The planet Saturn. Cassini - Nasa

Saturn just precedes Jupiter into the sky, some 1.25 degrees ahead at the start of the month and, as with Jupiter, can be seen very low in the southwest as January begins but will soon be lost in the Sun's glare.   Its magnitude remains steady at +0.6 whilst its angular size remaisn at 15.2 arc seconds.   The rings span some 35 arc seconds across and, at ~22 degrees to the line of sight, show up well.   Saturn, along with Jupiter, lies in Capricornus.   Sadly again, its low elevation of ~5 degrees when first visible in the evening on the first will limit our views of this most beautiful planet.




Mercury

Mercury.
Messenger image of Mercury Nasa

Mercury appears in the southwest after sunset around the 7th of the month shining at magnitude -0.6 and quickly rises into the evening sky.   It reaches greatest elongation east of the Sun on the 23rd and will then have an elevations of ~8 degrees 45 minutes after sunset having an angular size of ~7 degrees and a magnitude of +0.68.   By month's end it will be lost in the Sun's glare. [See highlights above.]






Mars

Mars showing Syrtis major.
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa

Mars. We have just witnessed the best apparition of Mars for some years and, for the first time since June, it angular size falls below 10 arc seconds on the 4th of January.   Below this angular size, features on the surface become hard to see with moderate sized telescopes.   As January begins, Mars at magnitude -0.2, is just 1/10th as bright as at its peak last October.   Its magnitude falls to +0.4 by the end of the month then having an angular diameter of 7.9 arc seconds.   However, Mars will still be visible in the evening sky until August and passes behind the Sun in October.




Venus

Venus
Venus showing some cloud structure

Venus, rises in the southeast over an hour before the Sun at the start of January but will be lost in the Sun's glare by month's end.   Its magnitude remains at -3.86 throughout the month whilst its angular size reduces from 10.7 to 10.1 arc seconds.   At the same time its phase, the percentage illuminated disk, increases from 94% to 98% which explains why its magnitude remains constant.   It is heading towards superior conjunction on the 27th of March so will remain hidden from our view for some time.

Radar Image of Venus
Radar image showing surface features









The Stars

The Mid to Late Evening January Sky

JanuarySky
The January Sky in the south - mid to late evening.

This map shows the constellations seen in the south around midnight.   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.   Finally, up and to the left of Sirius is Procyon in Canis Minor.   There is also information about the constellation Ursa Major, seen in the north,in the constellation details below.

The constellation Taurus

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.

The Pleiades
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!)

The Crab Nebula
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.

The Crab Nebula
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

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 Orion Nebula
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 Ursa Major

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
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
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
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.



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