The Telescope

The Telescope

Saturn

Saturn rises at mignight at the beginning of the month, and can be seen due south at an elevation of 31 degrees at around 5:30 am. By the end of February, it rises at 10 pm and will lie in the south at around 3:30 am. It lies in Virgo, shining at magnitude +0.6 (increasing to +0.5 during the month) some 7 degrees slightly up and to the left of the first magnitude star Spica. Sadly, in contrast to Jupiter, Saturn is heading to the more southerly parts of the ecliptic so, for quite some considerable time, will not be seen high above the horizon. However, nicely, the rings are opening out and are now ~15 degrees to the line of sight, so will appear appreciably wider than we have seen during its last apparition. It is now well be worth having a look at its ~18 arc second disk and ring system. With a small telescope on a night of good seeing, you should now be able to easily spot Cassini's Division within the ring system, and given a scope with an aperture of 6 inches or greater and a night of excellent seeing one might even spot Encke's division in the outer A-ring and also the inner, elusive, C-ring.

Jupiter

Jupiter is still beautifully seen in the evening sky transiting due south just half an hour after sunset as February begins. On Febuary 1st it will the lie some ~50 degrees above the southern horizon shining at magnitude -2.4 in Aries close to its boundary with Pisces. With an angular size of ~38.7 arc seconds falling to 36.5 during the month, a small telescope will easily show the equatorial belts (the south equatorial belt has reappeared) and the four Galilean moons. Use the details in the highlight above to spot the Great Red Spot (actually a pale yellow-orange to my eyes) lying in an indentation of the south equatorial belt. Observing it in the last few weeks has shown some prominent dark regions in the north equatorial belt. These are called "barges". I do hope that you will have taken my advice and bought a small telescope to observe it!

Mars

Mars. At the start of February Mars, moving retrograde from Virgo into the southern part of Leo, rises at 8:30 pm and will have risen to an elevation of ~46 degrees due south around 3 am. It brightens from -0.6 to -1.1 during the month, so is becoming more prominent. By month's end it rises at about 6 pm and, more importantly, will transit before 1 am at an elevation of 50 degrees below the lion's hind quarters. Its angular size increases from 12 arc to 14 seconds during the month and so it is now, given good seeing, becoming possible to observe features on the surface of its its salmon-pink disk. Details, such as the V shape of Syrtis Major and the north polar cap (which is tilted towards us), should now be visible. The markings on Mars are quite subtle and it is important that the scope has cooled down to ambient temperature to eliminate tube currents that limit the image quality.

Venus

Venus, prominent in the south-western sky after sunset, is now gradually increasing its angular separation from the Sun and, on Feb 1st, is 39 degreees away from the Sun and will have an elevation of ~30 degrees at sunset. It continues to draw away so that by month's end it will be 44 degrees away and a further 7 degrees above the horizon. Its angular size is increasing - from 15 to 18 arc seconds during the month - but as it does so its phase (the percentage that we see illuminated) is falling from 74 to 64%. One interesting result is that Venus's brightness stays remarkably constant at magnitude -4.1 throughout the month. Observing Venus through a deep blue filter may enable one to see a hint of the cloud structure in its atmosphere, but it is very subtle!

Mercury

Mercury, passes behind the Sun on February 6th (superior conjunction), so will not be visible until it reappears in the sky towards the south-west after sunset in the last week of the month. With a 66% illuminated disk and shining at magnitude -1.1, it will be moving towards the Earth, with an (increasing) angular size of just under 6 arc seconds.

The constellation 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

M101 - The Ursa Major Pinwheel Galaxy

Another, and very beautiful, galaxy is M101 which looks rather like a pinwheel firework, hence its other name the Pinwheel Galaxy. It was discovered in 1781 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).

M51 - The Whirlpool 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

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!)

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 constellations Pegasus and Andromeda

Pegasus

The Square of Pegasus is in the south during the evening and forms the body of the winged horse. The square is marked by 4 stars of 2nd and 3rd magnitude, with the top left hand one actually forming part of the constellation Andromeda. The sides of the square are almost 15 degrees across, about the width of a clentched fist, but it contains few stars visibe to the naked eye. If you can see 5 then you know that the sky is both dark and transparent! Three stars drop down to the right of the bottom right hand corner of the square marked by Alpha Pegasi, Markab. A brighter star Epsilon Pegasi is then a little up to the right, at 2nd magnitude the brightest star in this part of the sky. A little further up and to the right is the Globular Cluster M15. It is just too faint to be seen with the naked eye, but binoculars show it clearly as a fuzzy patch of light just to the right of a 6th magnitude star.

Andromeda

The stars of Andromeda arc up and to the left of the top left star of the square, Sirra or Alpha Andromedae. The most dramatic object in this constellation is M31, the Andromeda Nebula. It is a great spiral galaxy, similar to, but somewhat larger than, our galaxy and lies about 2.5 million light years from us. It can be seen with the naked eye as a faint elliptical glow as long as the sky is reasonably clear and dark. Move up and to the left two stars from Sirra, these are Pi amd Mu Andromedae. Then move your view through a rightangle to the right of Mu by about one field of view of a pair of binoculars and you should be able to see it easily. M31 contains about twice as many stars as our own galaxy, the Milky Way, and together they are the two largest members of our own Local Group of about 3 dozen galaxies.

M31 - The Andromeda Galaxy

February 3rd before dawn: Two Globular Clusters and Comet Garradd

Visible in the east at ~6:30 am will be the bright star Vega in Lyra. Up and a little to the right is the constellation of Hercules whose most prominent stars make up the Keystone - but seen on its side at this time. Just above the line joining the upper two stars of the keystone is the best globular cluster to observe in the northern hemisphere, M13. At magnitude 6, this is easily seen in binoculars. To the left of the keystone when seen at this angle lies M92 at magnitude 6.5. This would be observed far more often if it were not overshadowed by M13! During February, running up to the right of M92 is comet Garradd, expected to be at magnitude ~7, so again, binoculars should be able to pick it out on a dark night. Happily, as it passes closest to M92 on the 3rd of February, the Moon will have set at 3:40 am so its light will not hinder your view.

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: David Malin