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Constellations of the month

 

 

Saturn

Saturn will be seen down to the right of Jupiter in the southwest at nightfall. It then shines with a magnitude of +0.71 with its disk 15.46 arc seconds across and the rings spanning some 36 arc seconds. By month's end, it will be lost in the Sun's glare. Sadly, its very low elevation will hinder our view of this most beautiful planet.

Jupiter

Jupiter. As darkness falls at the start of January, Jupiter, having a magnitude of -2.13 and an angular size of 35.36 arc seconds, may be seen low in the southwest. By month's end its magnitude will have reduced slightly to -2.05 and its angular size to 33.65 arc seconds. Sadly, its very low elevation will hinder our view of the solar system's giant planet.


Mars

This month, Mars continues to climb out of the Sun's glare in the pre-dawn sky having a magnitude of +1.53 on the first with an angular size of 4 arc seconds. It will then be best seen before sunrise in the southeast. By month's end it will have an elevation of ~10 degrees at sunrise and its magnitude will have slightly increased to +1.41. Binoculars may well be needed to spot it, but please do not use them after the Sun has risen.

Venus

Venus passes behind the Sun on the 5th of January, but, by around the 16th of the month, appears again in the pre-dawn sky with a magnitude of -4.4. It will then show a thin crescent disk about 1 minute of arc across. Binoculars may well be needed to spot it, but please do not use them after the Sun has risen.

Mercury
Mercury. At the start of the month, Mercury can be seen low in the southwest below Saturn. It will have a magnitude of ~-0.72 and an angular size of ~6 arc seconds. By mid month it will be lost on the Sun's glare but, having passed through inferior conjunction on the 23rd, will appear in the pre-dawn sky by month's end Binoculars may well be needed to spot it, but please do not use them until after the Sun has set (early January) or risen (end January).

The Night Sky in and around Swindon - January 2022
January - still worth observing Jupiter

Jupiter imaged by Damian Peach

This is still not a bad month to observe Jupiter which will be visible in the south after sunset. It lies in the southern part of the ecliptic and, sadly, will only reach an elevations of ~22 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 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

Compiled by Prof. Ian Morison
The planets this month
January 13th evening: - the Moon between the Hyades and Pleaides

The Moon and two clusters in Taurus
Image: Stellarium/IM

If clear in the late evening of the 13th, one could observe the 11 day old Moon lying between the Hyades and Pleiades clusters in Taurus.

January 13th evening: - Mercury and Saturn

Jupiter, Saturn and Mercury
Image: Stellarium/IM
If clear after sunset on the 13th, one could observe Mercury lying just down to the right of Saturn as it reaches greatest elongation east from the Sun.
January 4th - after sunset: Three planets and a crescent Moon

Three planets and a 2.2 day old crescent Moon
Image: Stellarium/IM

If clear after sunset on the 4th, there will be lovely line up of Jupiter, Saturn and Mercury along with a very thin crescent Moon. Binoculars may well be needed to cut through the Sun's glare, but please do not use them until after 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
January 31st - before dawn: Venus, Mars and Mercury

Venus, Mars and Mercury
Image: Stellarium/IM
If clear, and given a low horizon towards the southeast, Venus should be very prominent with Mercury to its lower left and Mars to its lower right. Mercury had pased between the Sun and Earth (Inferior Conjunction) on the 23rd of the month having been seen in the evening sky at the start of January.
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