Comet Catalina (C/2013 US10) moves past Kemble's Cascade during the last week of February 2016. Visible with binoculars and small telescopes from northern and tropical latitudes.
Despite moving away from Earth as it heads towards the outer reaches of the Solar System comet Catalina remains well placed from Northern Hemisphere and tropical locations during February. At the start of the month the comet shone at magnitude +6.9 and beyond naked eye visibility but easily within binocular range. Unless something now dramatic happens it's expected to fade by another two magnitudes by months end, becoming increasingly difficult to spot with binoculars. At this level of brightness a small size telescope - preferably larger - is recommended for observing. From mid southern locations Catalina can no longer be seen.
From northern locations, Catalina can be seen high in the sky towards the north after sunset. The comet remains circumpolar from many locations and therefore visible all night long. It spends all of February moving on a southerly path through the dim constellation of Camelopardalis. The highlight of the month occurs on February 22nd and 23rd when Catalina passes close by open cluster NGC 1502. This small cluster shines at magnitude +7.0 and normally would be unremarkable except for a long line of mainly 8th and 9th magnitude stars adjacent to it known as "Kemble's Cascade". This superb asterism was discovered by Father Lucian Kemble who described it as "a beautiful cascade of faint stars tumbling from the northwest down to the open cluster NGC 1502".
The easiest way to find Kemble's Cascade is to imagine a line connection stars Caph (β Cas - mag. +2.3) and epsilon Cas (ε Cas - mag. +3.4) in Cassiopeia. Then extend the line eastwards by the same distance again to reach Kemble's Cascade. The asterism covers about 4 degrees of sky. For imagers a configuration with a large field of view is required to capture both the comet and the Kemble's Cascade in the same shot.
The finder charts below show the positions of Catalina from February 9th to March 8th, 2016.
Jupiter is now an unmistakable dazzling object moving retrograde among the stars of Leo. On March 8th the current apparition peaks when opposition is reached. On this day the "King of the planets" shines brightest for the year attaining its largest apparent size. Visible all night long Jupiter rises in the east at sunset, reaches its highest point in the sky around midnight before setting in the west at sunrise.
The largest of the 8 planets in the Solar System is currently located in southeastern Leo close to the Virgo border. With a declination of 6 degrees north it's best seen from equatorial and tropical latitudes although reasonably well placed from all accessible locations worldwide. From mid-latitude northern or southern locations Jupiter attains a respectable peak altitude of about 45 degrees during the middle of the night.
At opposition this year, Jupiter is located 4.435 AU (663.5 million kilometers or 412.3 million miles) from Earth. Although slightly further away than last year its apparent size is still an impressive 44.4 arc seconds. Of all planets only Venus - on rare occasions - displays a greater apparent size than Jupiter.
Popular 7x50 and 10x50 binoculars show a very small white or creamy coloured planetary disk without detail. Easily seen are Jupiter's four large Galilean moons (Io, Europa, Ganymede and Callisto) which continuously change position as they orbit the giant planet. Sometimes all four are visible at once but on occasions the satellites will be temporarily obstructed as they pass by the planetary disk.
Theoretically all four moons are bright enough to be seen with the naked eye but their close proximity too much brighter Jupiter makes this task virtually impossible. However, a few very keen eyed observers have managed to spot them without optical aid. For comparison, Io shines at magnitude +5.3, Europa magnitude +5.6, Ganymede magnitude +4.9 and Callisto at magnitude +6.0.
Inner planet Mercury reaches greatest western elongation (GWE) on February 7th when it's positioned 26 degrees from the Sun. This apparition offers an excellent opportunity for observers located at southern and tropical latitudes to spot the elusive planet in the morning sky. For those observers, Mercury is visible above the eastern horizon just before sunrise and remains so until the second week of March. From northern temperate latitudes it can also be seen around the time of greatest elongation although much lower down, skirting the horizon.
From latitude 35S (approx. equal to Sydney, Cape Town and Santiago) Mercury appeared 12 degrees above the eastern horizon, 45 minutes before sunrise on February 1st. At magnitude 0.0 it was relatively easy to spot the smallest planet in the Solar System. If you do have trouble locating Mercury, binoculars do greatly assist. Also, much brighter Venus (mag. -3.9) is currently placed just above Mercury and acts as a good marker. After elongation, Mercury appears slightly lower down each subsequent morning until it's finally lost to the bright twilight sky around March 10th. It should be noted the planet steadily increases in brightness and by the end of the visibility period shines at magnitude -0.7.
On February 6th and March 8th the very thin waning crescent Moon passes 4 degrees north of Mercury.
Algol (β Per) is a bright eclipsing binary system located in the northern constellation of Perseus and one of the best-known variable stars in the sky. Often referred to as the "Demon Star" most of the time it shines at magnitude +2.1 but every two days, 20 hours and 49 minutes the star suddenly dips in brightness to magnitude +3.4, remaining dim for about 10 hours before returning to its original state.
Why the change in brightness? The Algol system consists of at least three-stars (β Per A, β Per B and β Per C) with the orbital plane of Algol A and B directly in line with the Earth. The regular dips in brightness occur when the dimmer B star moves in front of and eclipses the brighter A star. There is also an extra dimension in that a secondary eclipse occurs when the brighter star occults the fainter secondary but this results in a very small dip in brightness that can only be detected by those with access to photoelectrical equipment.
Algol is located in Perseus among the stars of the northern Milky Way. It's positioned west of magnitude +0.1 star Capella (α Aur) and southeast of the well known "W" of Cassiopeia. The finder chart below shows the position of Algol along with magnitude data of some surrounding stars for comparative purposes.
For those new to variable star observing, Algol is an excellent first choice target. It dims quite dramatically and the regular brightness changes are obvious to the naked eye. The table below contains date and time information of Algol's minima for February 2016 for various World time zones that cover most regions of Europe, America, China and Australia. For time zones not listed, local eclipse times can be calculated by adjusting the table to fit to the observers local time.
Algol Minima for February 2016
|Date||Time (UT - GMT)||Time (CET - Europe)||Time (EST - N America)||Time (PST - N America)||Time (CST - China)||Time (AEDT - Australia)|
|Feb 02||00:52||01:52||19:52 (Feb 1)||16:52 (Feb 1)||08:52||11:52|
|Feb 04||21:41||22:41||16:41||13:41||05:41 (Feb 5)||08:41 (Feb 5)|
|Feb 07||18:30||19:30||13:30||10:30||02:30 (Feb 8)||05:30 (Feb 8)|
|Feb 10||15:20||16:20||10:20||07:20||23:20||02:20 (Feb 11)|
|Feb 19||05:47||06:47||00:47||21:47 (Feb 18)||13:47||16:47|
|Feb 22||02:36||03:36||21:36 (Feb 21)||18:36 (Feb 21)||10:36||13:36|
|Feb 24||23:26||00:26 (Feb 25)||18:26||15:26||07:26 (Feb 25)||10:26 (Feb 25)|
|Feb 27||20:15||21:15||15:15||12:15||04:15 (Feb 28)||07:15 (Feb 28)|
Mercury reaches greatest elongation west on February 7th when it's positioned 26 degrees from the Sun. The planet is not well placed for observation at northern temperate locations but from southern latitudes this happens to be the most favourable morning apparition of the year. With an extended period of visibility, the nearest planet to the Sun can be seen in the morning skies until the second week of March.
From latitude 35S (approx. equal to Sydney, Cape Town and Santiago) Mercury appears 12 degrees above the eastern horizon, 45 minutes before sunrise on February 1st. At magnitude 0.0 it should be relatively easy to spot. If you're having trouble finding the planet binoculars do greatly assist, as does brilliant Venus a good placed marker just above Mercury. For the rest of the month, the planet remains well placed for observation. During February its brightness increases from magnitude 0.0 to -0.3.
From northern temperate latitudes Mercury can also be seen for a short while around the time of greatest elongation. However, it's always low down and at best just a few degrees above the horizon.
On February 6th, the very thin waning crescent Moon passes 4 degrees north of Mercury and Venus.
The latest morning apparition of Venus is now fast coming to an end from mid-northern temperate latitudes. From such locations our inner planetary neighbour remains a brilliant object at the start of the month, rising 90 minutes or so before sunrise but by months end it will be difficult to spot against the bright morning twilight sky. Further south the period of visibility is noticeably better with Venus visible throughout February.
As the month progresses the phase of the planet increases from 85% to 91%. Its apparent size stands at about 12 arc seconds. As mentioned previously, Mercury remains close to Venus this month and on February 6th, the very thin waning crescent Moon passes 4 degrees north of the pair.
Mars continues to gain in brightness and apparent size as it heads towards opposition in May. The planet is moving direct through Libra and increases from magnitude +0.8 on February 1st to magnitude +0.3 on the last day of the month. Its apparent size increases from 7 to 9 arc seconds.
Mars is currently moving relatively quickly eastwards in relation to the "fixed" background stars. From northern locations the "Red planet" can be seen from around 1am improving by 45 minutes by months end. For those living at tropical and southern latitudes it can be seen two hours earlier than that.
It's now possible to start serious telescopic observations of the famous planet. However, the apparent size remains small compared to Jupiter and Saturn and therefore good seeing, high magnifications and access to at least a medium sized (200mm - 8 inch) scope are needed to tease out surface markings.
On February 1st, the last quarter Moon passes 3 degrees north of Mars. It again passes north of the planet on February 29th, separation 4 degrees. At months end, Mars has moved to within 18 degrees of Saturn.
Jupiter is a brilliant object moving retrograde in southeastern Leo close to the Virgo border. At the start of the month the master planet rises a few hours after sunset but by months end it's visible practically all night as it closes in on a March 8th opposition date. Due to its current declination of a few degrees north of the celestial equator, Jupiter is reasonably well placed for observers worldwide.
The "King of the Planets" brightens from magnitude -2.4 to -2.5 as the month progresses with its apparent size increasing from 42.5 to 44.3 arc seconds. It easily outshines all night-time stars.
A pair of binoculars is all that's required to reveal the planets four largest moons Io, Europa, Ganymede and Callisto. Sometimes all four are visible at once but on occasions satellites are obstructed and hidden from view as they pass behind or in front of Jupiter's disk. Telescopically the planet is a gem. Even small instruments show the main cloud belts with medium or larger scopes revealing a wealth of finer detail including smaller belts, ovals, festoons and of course the famous "Red Spot".
The waning gibbous Moon passes 1.7 degrees south of Jupiter on February 24th.
Saturn, mag. +0.6, remains an early morning object moving direct among the stars of Ophiuchus. By months end the planet rises around midnight from southern temperate locations although up to three hours later for those located further north. To the naked eye it appears creamy or off-white in colour.
Located west of Saturn is Mars which moves nearer to the "Ringed planet" as the month progresses. Even closer to Saturn is first magnitude star Antares - often called the "Rival of Mars" due to its striking deep orange/red colour - which is 8 degrees southwest of the planet.
The waning crescent Moon passes 4 degrees north of Saturn on February 3rd.
Uranus, mag. +5.9, remains an early evening binocular object during February, moving slowly direct in Pisces. At the beginning of the month the planet is visible as soon as it's dark towards the west. For those located at mid-northern latitudes Uranus can be seen for some 5 hours on February 1st, reducing to around 3 hours by months end. From southern locations its visibility period is only about half as long.
On February 12th, the thin waxing crescent Moon passes 2 degrees south of Uranus.
Neptune reaches solar conjunction on February 29th. The distant planet is positioned inconveniently close to the Sun and therefore not suitably placed for observation this month.
The "Winter Circle" or "Winter Hexagon" is a bright asterism that's best seen during the months from December to March. The group consists of a large circle of stars or more actually a hexagon shape loosely centred on red supergiant Betelgeuse (mag. +0.42). All stars are bright. Starting from the most northerly point and moving in a clockwise direction they are as follows: Capella (mag. +0.1), Aldebaran (mag. +0.9), Rigel (mag. +0.1), Sirius (mag. -1.4), Procyon (mag. +0.3), and Pollux (mag. +1.1). It's possibly the largest of the well-known asterisms.
What is an asterism?
An asterism is a recognised pattern of stars in the night sky. It may be part of one of the 88 official constellations or it may be composed of stars from many constellations. Anyone can make his or her own asterism and if many people use it often enough it can find its way into Astronomy vocabulary. In the case of the Winter Circle it's no accident it's so large, the six stars come from six different constellations (Auriga, Taurus, Orion, Canis Major, Canis Minor and Gemini).
The Winter Circle is so named because it appears above the southern horizon during the dark Northern Hemisphere winter nights, although it can actually be seen from all over the World. The exceptions are far southerly locations such as the South Island of New Zealand and the south of Chile and Argentina. At tropical latitudes the asterism is visible almost overhead. From southern locations it's towards the northern part of the sky appearing inverted to the Northern Hemisphere view. From the Southern Hemisphere it's called the "Summer Circle" as Summer time is in swing at the time of year.
How to spot Mercury, Venus, Mars, Jupiter and Saturn in the morning sky during the last week of January 2016
Normally a few of the bright planets, Mercury, Venus, Mars, Jupiter and Saturn, are visible in night sky but it's rare to be able to see all of them at the same time. The good news is that over the next few weeks it's possible to spot all five "naked eye" planets in the morning sky just before sunrise. Such an alignment last occurred at the end of 2004 and the next opportunity will not take place until October 2018.
Venus is the brightest planet at magnitude -4.0 followed by Jupiter at magnitude -2.3. Saturn (mag. +0.6) and Mars (mag. +0.8) are roughly equal in brightness although impossible to confuse; Mars has a deep red hue and Saturn off white in colour. Mercury shines at magnitude +0.8 on January 24th, increasing in brightness to magnitude +0.0 at months end.
With clear skies observers will have no problem spotting Venus, Mars, Jupiter and Saturn. The difficult one is Mercury. It appears low down and requires a clear view of the eastern horizon to glimpse it. The planet is better placed from southern latitudes and next month will reach greatest western elongation (February 7th). In addition, this will be the most favourable time of the year to spot the planet in the morning sky from southerly locations.
The illustrations below show the positions of the five planets from mid-latitude northern locations and mid-latitude southern locations one hour before sunrise on January 24th and January 31st. The northern illustrations cover areas such as Europe, United States, Canada, China, Japan and Russia. The southern illustrations are valid from regions such as Australia, New Zealand, South Africa and South America. Depending on the exact observers location, the view may be slightly different to those shown below.
Comet Catalina (C/2013 US10) now fading as it recedes from Earth. Currently moving through the far northern constellations. Remains visible with binoculars and small telescopes.
It's now time for the final swan song for comet Catalina as it heads into deep space and not to be seen for a very long time again, if ever. On January 17th, the comet made its closest approach to Earth and was easily visible with binoculars in the constellation of Ursa Major more commonly known as the Plough or Big Dipper. At magnitude +6.2, it appeared as a fuzzy smudge of light and was clearly non-stellar in nature.
Although now fading, Catalina will remain within the range of telescopes for a few more weeks to come. It may also be seen with binoculars although for a shorter time period. The advantage for most living in the Northern Hemisphere is that the comet is now circumpolar and therefore visible all night long. It can be seen towards the northern part of the sky during early evenings close to Ursa Major. On January 25th, Catalina passes close by elliptical galaxy NGC 4589. This galaxy shines at magnitude +10.7 and therefore requires a medium or large size scope to be seen. For comparison, the comet will be 40x brighter than the galaxy. During the last week of January the bright Moon will somewhat interfere with viewing. Catalina then heads southwards spending all of February moving through the faint constellation of Camelopardalis. It remains well placed in the evening sky from northern latitudes although from mid southern locations it can no longer be seen.
The finder charts below show the positions of Catalina from January 9th to February 12th, 2016.
The waxing gibbous Moon moves through the Hyades followed by an occultation of bright star Aldebaran
On the evening of January 19th / 20th observers in the USA, Canada, Western Europe and South Greenland will be able to watch the 10-day-old waxing gibbous Moon occult first-magnitude orange giant star Aldebaran in Taurus. Before that the Moon will pass in front of one of the best naked eye and binocular open clusters in the sky, the Hyades.
The first bright lunar occultation of 2016 starts around 19:00 UT (19:00 GMT - 14:00 EST) on January 19th with the Moon positioned at the edge of the very large and loose Hyades open cluster. Spanning 5.5 degrees of sky the Hyades apparent diameter is equivalent to 11 times that of the full Moon. It's also the nearest open cluster to us.
Over the following few hours the Moon will then pass in front of a number of stars in the cluster. The event can be followed with the naked eye and even better with a pair of binoculars or a small telescope. In Europe the sky will already be dark but from the United States and Canada it will still be daytime. By the time of sunset from eastern US and Canadian locations the occultation of the Hyades will be already underway.
The highlight of the evening occurs when the Moon occults Aldebaran (α Tau - mag. +0.9) with the exact timing depending on the observer's location. For example, from London, England the star disappears behind the advancing lunar limb at 03:24 GMT (Jan 20). The Moon then re-appears about 20 minutes later. From New York City, the occultation begins at 21:31 EST ending at 22:43 EST (Jan 19). From Los Angeles, the occultation begins around sunset at 17:03 PST and finishes at 18:14 PST (Jan 19).
Gemini is a northern zodiac constellation and one of the 48 constellations described by second century astronomer Ptolemy. Its name is Latin for the twins and it's one of the few constellations in the sky that actually looks like what it represents. This bright grouping contains two-standout stars, Castor (α Gem) and Pollux (β Gem). At mag. +1.16 Pollux is the brighter while multiple system Castor shines at mag. +1.58. Surprisingly Pollux was assigned "beta Geminorum" by Johann Bayer, the German astronomer who labelled the stars with Greek letters in 1603, even though it easily outshines Castor. Some astronomers have suggested that maybe Pollux has since brightened or Castor faded but both possibilities seem extremely improbable. The likelihood is that Bayer simply made a mistake and didn't carefully distinguish which was the brighter star.
In Greek mythology, Castor and Pollux were twin brothers whose mother was Queen Leda although Castor was the mortal son of King Tyndareus and Pollux the divine son of Zeus. Together the twins were known as the Dioscuri, which means the "sons of Zeus". However, in most versions of the myth only Pollux was Zeus's child. The twins were the patron saints of mariners appearing in ships rigging as the St Elmo's fire phenomena. When Castor died Pollux begged Zeus to give Castor immortality which he did thereby uniting the twins together in the heavens.
In Babylonian astronomy the twins were regarded as minor gods. In Chinese astronomy part of Gemini represented the White Tiger of the West and another part the Vermillion Bird of the South. In more modern times, William Herschel discovered Uranus in 1781 near eta Geminorum (η Gem). In 1930, Clyde Tombaugh discovered Pluto on photographic plates centered on Wasat (δ Gem). Project Gemini was also the name of NASA's second human spaceflight program during the 1960's.
Gemini occupies 514 square degrees of sky and is partly located among the rich star fields of the Milky Way. The constellation is positioned high in the sky for Northern Hemisphere observers during the winter months. It's less well placed from southern locations but nevertheless can still be seen at latitudes as far as 60 degrees south. Deep sky objects within amateur range include fine open clusters, planetary nebulae, a reflection nebula and a supernova remnant. In addition there are many nice double stars. Gemini contains only one Messier object, open cluster M35.
The Sun passes through Gemini from late June to late July. The constellation is also the radiant for the Geminids, a rich December meteor shower and highlight of the annual meteor calendar.
Bright Star, Multiple Star
Castor (alpha Geminorum - α Gem) - is one of the finest multiple stars in the sky. The brightest components, Castor A and Castor B, shine at magnitudes +1.9 and +3.0 respectively. With a current separation of 5.0 arc seconds a small 80mm (3.1-inch) refractor at about 100x power will comfortably split the pair into two white components. In the 1960s this was a much more difficult task; at closest they were only 1.8 arc seconds apart. Since then the stars have widened slightly and will continue to do so until about 2100 after which they start to close up again. The orbital period is 445 years.
A third much fainter red dwarf companion, Castor C (mag. +9.8) is positioned 71.0 arc seconds from the main pair. In addition, each star itself is a spectroscopic binary making a sextuple system in total!
Castor has a combined magnitude of +1.58 and is 51 light years distant.
Pollux (beta Geminorum - β Gem) - mag. +1.16, is a type K0 orange giant star that's 34 light years away. It's the brightest star in Gemini and is believed to have been originally a blue white A-type main sequence star. It's since exhausted the hydrogen at its core and evolved into the orange giant we see today.
Alhena (gamma Geminorum - γ Gem) - mag. +1.93, is a hot blue-white type A1 star that's located 109 light years from Earth.
Multiple Stars, Double Stars
Wasat (delta Geminorum - δ Gem) - is a challenging double star for small scopes due to the brightness difference of the two components. The primary is a magnitude +3.6 white main sequence star separated by 5.8 arc seconds from its magnitude +8.2 orange K class companion. A quality 80mm (3.1-inch) refractor on good nights should split them. The separation is within this scope's reach, the problem is the secondary often gets lost in the glare of the main star. A magnification of about 150x is recommended.
Wasat is also a spectroscopic binary making this a triple star system. It lies 60 light years from Earth.
Mebsuta (epsilon Geminorum - ε Gem) - is a nice wide double star. Any size telescope or large binoculars will reveal a main yellow star of magnitude +3.1 alongside a fainter companion (mag. +9.7) separated by 111 arc seconds. The star achieved much publicity on April 8, 1976 when it was occulted by Mars allowing measurements of the planet's atmosphere. The next occultation will take on September 3, 2015 when asteroid Iphigenia moves in front of the star.
The Mebusta system is 840 light years from Earth.
Mu Geminorum - mag. +2.9, is the fourth brightest star in Gemini. It has a faint wide companion (mag. +9.4) that appears deep red in colour. Any telescope will easily split this wide pair of 122 arc seconds separation.
Kappa Geminorum - 143 light years distant is a challenging double for small scopes consisting of magnitudes +3.7 and +8.2 stars, separated by 7.2 arc seconds. Like Wasat the extreme brightness difference of the components posses problems for anything less than a 100mm (4-inch) scope. High powers and steady seeing conditions are a must.
Nu Geminorum - is a blue-white star of magnitude +4.1 with a wide magnitude +8.0 companion visible with binoculars. Separation is 112 arc secs.
38 Geminorum - is a beautiful double star for small telescopes. It consists of a magnitude +4.8 yellow-white F0 star and a fainter white secondary star of magnitude +7.8. They are separated by 7 arc seconds. A small 80mm (3.1-inch) scope at 100x power will split this delightful pair.
20 Geminorum - positioned midway between nu (ν) Gem and gamma (γ) Gem is 20 Gem, an easily resolvable pair of white magnitudes +6.3 and +6.9 components. A nice target for small scopes, the separation is 20 arc seconds.
15 Geminorum - looks like a fainter version of Albireo in Cygnus. The two stars are yellow and blue in colour shining at magnitudes +6.7 and +8.2. They appear attractive together and are easily split in any scope. The separation is 25 arc seconds. Also visible in the same low power field of view is 16 Gem.
Double Stars, Variable Stars
Mekbuda (zeta Geminorum - ζ Gem) - is both a variable star and a binocular double. The primary is of the Cepheid variety that fluctuates between magnitudes +3.6 and +4.2 every 10.2 days. Binoculars and small telescopes reveal an unrelated companion (mag. +7.7) separated by 101 arc seconds.
Eta Geminorum (η Gem) - is another double variable. The primary is a semi-regular red giant star whose brightness varies between magnitude +3.15 and +3.9 over a period of 234 days. It has a close 9th magnitude companion - separation 1.8 arc seconds - that requires a larger scope to distinguish it from the glare of the primary.
U Geminorum - is the prototype dwarf nova star. It's a binary system consisting of a white dwarf closely orbiting a red dwarf every 4 hours and 11 minutes. Consequently, due to transits and eclipses its magnitude varies between +14.0 and +15.1. At this brightness the star is extremely faint and requires a 250mm (10-inch) scope and dark skies to be seen. However, roughly once ever 100 days it undergoes a significant outburst and brightens to 9th magnitude and within the range of binoculars and small scopes. The star then stays bright for a couple of weeks before fading down. The burst in activity is believed to result from instability in the accretion disk. When gas reaches a critical temperature it collapses onto the white dwarf releasing massive amounts of energy.
Unfortunately the 100 day period is also extremely irregular and has been known to vary between 62 days and 257 days. U Geminorum is estimated to be 270 light years distant.
BU Geminorum - is a semi-regular variable star that varies between magnitudes +5.7 and +7.5 over a period of 325 days. At brightest it's just about visible to the naked eye.
R Geminorum - is a Mira type variable star 1900 light-years from Earth that varies between magnitudes +6.0 and +14.0 over a period of 370 days. When at brightest it's easily visible with 7x50 or 10x50 binoculars.
M35 (NGC 2168) - is the most striking deep sky object in Gemini. It's a magnitude +5.2 open cluster that appears to the naked eye as a misty patch of light. When seen through binoculars, M35 is a fantastic sight with many bright stars visible superimposed on a hazy background. A medium size 150mm (6-inch) scope at low power reveals a field full of stars arranged in curves with a brighter orange member towards the centre.
M35 is 2,800 light years distant and spans 28 arc minutes, similar to that of the full Moon. It's estimated to contain up to 200 stars. Located about 15 arc minutes southwest of M35 is another fainter open cluster NGC 2158, which can be glimpsed with binoculars.
NGC 2158 - mag. +8.6, is located 15 arc minutes southwest of much closer cluster, M35. It's 11,000 light years distant and therefore appears smaller, fainter and more difficult to resolve than its apparent neighbour. On nights of good seeing NGC2158 can be spotted with binoculars appearing as a faint circular smudge of light. Small telescopes fare better while a 250mm (10-inch) scope at high power reveals many stars distributed across 5 arc minutes of sky. Such a view gives a real sense of looking deep into interstellar space.
NGC 2158 is an old cluster of some 2 billion years that contains 10,000 stars in total. The brightest individual members are of 12th magnitude. The cluster is very compact and appears not unlike a loose globular cluster.
NGC 2129 - like NGC 2158 is another distant open cluster in Gemini although that's where the similarity ends. NGC 2129 is about 10 million years old and therefore much younger than NGC 2158. It shines at magnitude +6.7 primarily because of three 8th and 9th magnitude stars positioned at the group's centre. The remaining stars in the group are fainter, in total about 50 members brighter than 15th magnitude. The cluster spans 5 arc minutes in diameter.
A small 80mm (3.1-inch) scope reveals the bright stars at the centre surrounded by an irregular misty haze of partly resolved fainter stars. Larger scopes at higher powers reveal many more stars.
NGC 2129 is 7,200 light years away.
NGC 2420 - located 4 degrees east of Wasat is NGC 2420, a group of 30 stars packed into a 7 arc minute diameter. The cluster shines at a collective 9th magnitude but all members are faint. The brightest individual components are of 11th magnitude.
Small scopes show a hazy patch with some brighter members resolvable. Through larger scopes at medium to high powers it shows more character including a nice curved chain of stars around the centre.
NGC 2266 - is a compact 9th magnitude cluster located just north of Mebsuta and near the border with Auriga. It's a fairly rich compact object with about 50 stars spread across 4 arc minutes of sky. The individual stars are faint, the brightest being of 11th magnitude but the cluster offers nice views through medium and large size scopes.
NGC 2395 - mag. +8.0, a large open cluster positioned at the northwest corner of Abell 21, the Medusa Nebula. Up to about 40 stars can be seen in this 15 arc minute diameter elongated shape. Through a 200mm (8-inch) scope at 100x power it appears loose with most stars between 10th and 13th magnitude.
NGC 2392 - mag. +9.1, is the constellations brightest planetary nebula. Resembling a person's head surrounded by a parka hood it's also known as the "Eskimo Nebula" or "Clown Face Nebula". The planetary is a challenging binocular object appearing faint and stellar like although it may be possible to notice a twinkling effect when switching between normal and averted vision, hinting at the object's true nature.
The Eskimo Nebula's small apparent size of 48 arc seconds - no larger than Jupiter at opposition - means that when searching with small scopes at low powers it's easily missed. The planetary appears as a tiny out of focus star with a noticeable bluish-green tint. It's positioned about 100 arc seconds from a magnitude +8.2 yellow white star. Once you have identified NGC 2392 switch to higher powers to reveal the 10th magnitude central star and the fuzzy encircling disk.
The Eskimo Nebula takes magnification well. When viewed through medium size scopes intrigue details can be seen including dark arcs and mottling. As is common with objects of this type the planetary appears to often blink on and off. It's estimated to be 2900 light-years distant, which corresponds to a spatial diameter of 0.68 light years.
In January 2000, the Hubble Space Telescope (HST) captured an iconic image of the Eskimo Nebula.
NGC 2371/2372 - is a faint 13th magnitude dual lobed planetary nebula positioned a few degrees from Castor and Pollux. Its structure is reminiscent of the Dumbbell Nebula (M27) in Vulpecula and the little Dumbbell Nebula (M76) in Perseus. NGC 2371/2372 appears like two separate objects hence the double NGC notation given to it by William Herschel.
On good nights the planetary can be seen with a 250mm (10-inch) telescope appearing as two fuzzy almost touching semi-circles. It measures 44 arc seconds in diameter and has a magnitude +12.5 central star. Narrow-band filters in particular those of the O III variety can help.
Abell 21 - the Medusa Nebula is a large planetary nebula in the southern part of Gemini close to the Canis Minor border. It was discovered in 1955 by American astronomer George Abell who originally classified it as an old planetary nebula. Also known as Sharpless 274 the object was later thought to be a supernova remnant until scientific investigations indicated it was likely a planetary nebula after all.
The Medussa nebula is a challenging amateur object due to its large apparent size and low surface brightness. Under dark skies and with the aid of an O III filter it can be spotted with a 200mm (8-inch) scope but normally a larger instrument is required.
It's estimated to lie 1,500 light years from Earth.
Comet PanSTARRS (C/2013 X1) a possible naked eye comet later this year now visible with binoculars in the evening sky
Comet PanSTARRS (C/2013 X1) after a recent outburst of activity can now be seen in the evening sky with binoculars and small telescopes. At the beginning of the year it had reached magnitude +8.6 and if keeps brightening as predicted, could reach fourth magnitude in June and early July.
Comet PanSTARRS was discovered on December 4, 2013 using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) located on the island of Maui in Hawaii. At discovery, the comet was extremely faint with an apparent magnitude of +20.2.
The Pan-STARRS project is in its infancy and eventually will use an array of four 1.8m astronomical telescopes to survey the sky continuously in the hunt for moving objects. Although there are current funding issues and only two of the four telescopes are completed, the project is producing good results and already numerous asteroid and comet discoveries have been made.
Location and star charts
Throughout January, PanSTARRS is well placed for observation from northern locations as it moves through the constellation of Pegasus. The comet is visible with binoculars towards the western horizon after sunset, although many observers may require the extra aperture offered by telescopes to spot it. To find PanSTARRS, first locate the four stars that form the "Great Square of Pegasus". The comet slowly cuts through the south-eastern side of the square during January, heading in the direction of Pisces.
In the Northern Hemisphere, it will remain visible until late February. It then passes through perihelion on April 20th before returning very low down in the pre-dawn sky towards the end of May. It remains low down during the peak period. For Southern hemisphere observers the comet is low down during January but they will be favoured when it reaches peak brightness in June / July.
The finder charts below show the positions of PanSTARRS from December 25, 2015 to February 26, 2016.
It's generally regarded that when one of outer planets - Mars, Jupiter, Saturn, Uranus or Neptune - reaches its first stationary point it signals the beginning of the next opposition period. The planet then commences retrograde motion, eventually culminating on the day of opposition. A second stationary point follows later signalling the end of the opposition period and a return to direct motion.
When seen from Earth the planets move in either direct or retrograde motion. The direct motion is eastwards compared to the "fixed" background stars. Retrograde motion is when the planet moves westwards. In the case of the outer planets this occurs when the Earth, on its faster inner orbit, catches up and then overtakes the outer planet. It's most noticeable with Mars.
On January 8th, Jupiter reached its first stationary point and the start of the 2016 opposition period. On March 8th, the giant planet reaches opposition when it will shine at magnitude -2.5 and be visible all night. Two months later on May 9th it reaches its second stationary point and the opposition period is over.
The position of Jupiter during January and the path of the planet against the background stars of Leo and Virgo from November 2015 to September 2016 are shown below:
The long cold nights of the Northern Hemisphere winter months are populated with some of the finest constellations in the sky. During the months of December, January and February many celestial gems are visible in the evening sky. They include spectacular open clusters, stunning nebulae as well as numerous bright stars. Below is a list of five of the best open clusters visible at this time of year; all of which can be spotted with the naked eye and each one a superb binocular object.
We start the countdown with the faintest and smallest cluster on our list, M35 in Gemini. At mag. +5.2 it appears to the naked eye as a somewhat misty patch of light. Surprisingly it wasn't discovered until 1745-46. When seen through binoculars M35 is a fantastic sight with the brightest dozen or so stars resolvable. Enhancing the view is a hazy glow surrounding the stars. Telescopes reveal many more stars but the glow effect disappears. M35 is 2,800 light years distant and spans 28 arc minutes which is similar to the full Moon diameter. It's estimated to contain up to 200 stars.
Located about 15 arc minutes southwest of M35 is open cluster NGC 2158, which at mag. +8.6 is faintly visible with binoculars.
The Double cluster consists of two bright open clusters, NGC 869 and NGC 884, separated by just half a degree in the constellation of Perseus. They are easily visible to the naked eye and through binoculars and telescopes are a wonderful sight. The Double Cluster has been known since antiquity and early celestial cartographers named them as stars "h Persei" (NGC 869) and "χ Persei" (NGC 884).
To the naked eye it appears like a large detached unresolved part of the Milky Way. Of the two clusters, NGC 869 is marginally the brighter at mag. +4.3 while NGC 884 glows at mag +4.4. Through binoculars the view is superb with many bright blue and white stars visible in a hazy mist. The increased aperture and magnification offered by telescopes reveal dozens more stars that fill the eyepiece field of view. A gem of a cluster.
NGC 884 and NGC 869 are located at distances of 7600 and 6800 light-years from Earth respectively. Each cluster is estimated to contain a few hundred stars.
The Hyades is the perfect binocular open cluster due to its brightness and large apparent size. Spanning 5.5 degrees of sky it's equivalent to 11 times the diameter of the full Moon. When seen through 7x50 or 10x50 binoculars it fills the complete field of view and can even over-spill in some models. Easily found since it surrounds first magnitude orange giant Aldebaran (α Tau - mag. +0.87) in Taurus, at least 20 stars are visible to the naked eye with the number rising to above 100 with binoculars. The cluster is notably "V" shaped. Of interest Aldebaran is only a foreground star and not a true member.
At a distance of 153 light-years the Hyades is the nearest open cluster to us. Located 12 degrees to the northwest is another open cluster on our list, M45 the brilliant Pleiades.
Comet Catalina (C/2013 US10) remains visible with binoculars and small telescopes at it moves northwards. This month offers the last good chance to catch a glimpse before it fades significantly.
Comet Catalina is now an evening object that's well placed throughout January for observers at northern locations. For some weeks now the comet has shone between 6th and 7th magnitude; not quite bright enough to be seen with the naked eye but within the range of binoculars and telescopes. On January 17th, it makes its closest approach to Earth at 0.72 AU (108 million kilometres or 67 million miles). It's a shame it's not nearer but nevertheless a peak magnitude of +6.2 is predicted. After that Catalina will continue on its long journey to the far reaches of the Solar System. Although remaining superbly placed from Northern latitudes, its best days are then behind it. Catch it soon before it disappears forever!
Location and star charts
At the start of the year, Catalina passed less than a degree west of bright orange star Arcturus (mag. -0.04). On January 8th it moves into Canes Venatici, rising before 11pm from northern temperate locations. Continuing on its almost direct northerly trajectory the comet's visibility continues to improve for northern based observers; from the middle of the month it's visible practically all night and even circumpolar from many locations. Just west of the comet on January 14th is one of the most famous galaxies in the sky, M51 the Whirlpool Galaxy (mag. +8.4). It will be interesting to compare the appearance of the two objects. Through a small scope they both should look hazy although it's predicted Catalina will be 5 times brighter.
Next stop for Catalina is Ursa Major, the Great Bear. Such a well know constellation will aid in locating the comet. On January 17th, the date of closest approach to Earth it passes between star 83 UMa (mag. + 4.6) and M101 the Pinwheel galaxy (mag. +7.9). Following that, Catalina moves through Draco and Ursa Minor before ending the month in Camelopardalis. From southern latitudes it's visible low down in morning twilight for the first half of the month, not anymore after that.
The finder charts below show the positions of Catalina from January 1st to January 22nd, 2016.
Almach (γ And) is one of the finest colour contrast double stars in the sky. To the naked eye it appears as a single bright star of mag. +2.10 but scopes resolve it into an outstanding double consisting of a bright yellow or slightly orange primary and a fainter deep blue secondary. It's widely regarded as the second best colour contrast double in the sky, surpassed only by Albireo (β Cyg) in Cygnus.
Almach is located in the eastern part of Andromeda. It's the the 3rd brightest star in the constellation and is comparable in magnitude to Polaris and the main stars of Ursa Major. To locate Almach the Great Square of Pegasus is a good starting point and in particular its northeastern star Alpheratz (α And). With an apparent magnitude of +2.07, Alpheratz is marginally brighter than Almach. From Alpheratz imagine a line moving in a northeastern direction towards Perseus. The line first passes through delta And (δ And - mag. +3.3) followed by Mirach (β And - mag. +2.1) and then onto Almach.
Any small scope will split Almach. For example, a 80mm (3.1 inch) refractor at 75x will easily transform the star into two colourful Suns separated by 9.4 arc seconds. The colour contrast is stark, the brighter star is a K3 type giant that shines orange yellow while its companion is a hot blue B9 type main-sequence star. Depending on your eyes and seeing conditions you may perceive slightly different colors. It was German physicist and astronomer Johann Tobias Mayer who first identified the star as a double in 1778.
The blue secondary star is actually a triple star and through large amateur scopes on night of good seeing can be split into components of magnitude +5.1 and +6.3. The separation is a measly 0.3 arc seconds and requires apertures of at least 250mm (10-inch) to accomplish. German astronomer Wilhelm Struve in October 1842 discovered it was a double star. In addition, the brighter member of the pair is also a spectroscopic double making this a four star system in total. It's located 358 light years distant.
Almach is a wonderful double star for all types of telescopes. It's best seen from northern latitudes during the months of October, November and December.
The second closest planetary conjunction of 2016 occurs on the morning of January 9th when Venus passes just 5 arc minutes north of Saturn. The time of minimum separation occurs at 03:57 UT when the two planets will be only 1/6 of the apparent diameter of the Moon apart. The brightness difference and closeness of the pair means it's unlikely - but not impossible - they can be split with the naked eye and therefore a pair of binoculars will probably be required.
Both planets will rise above the southeastern (Northern Hemisphere) / eastern (Southern Hemisphere) horizon about two hours before the Sun. At magnitude -4.0, Venus is brilliant and unmistakable with only the Sun and Moon brighter. Saturn (mag. +0.6) is much fainter and 70x less brighter than Venus. For observers, the separation of the planets on the morning of the 9th will depend on location. For those in Europe, Africa, Middle East and western Asia, Venus and Saturn will be very close together just before sunrise. For those at other locations such as USA, Canada, Mexico, South America, China and Australia the planets will be slightly further apart. Regardless of location, this will be a nice visual event for all. Of note, in the same region sky located 6 degrees south of Venus and Saturn is red supergiant Antares (α Sco - mag. +1.0).
If you look an hour or so before sunrise towards the southeastern (Northern Hemisphere) / eastern (Southern Hemisphere) horizon this month the planets Venus and Saturn are currently visible. Brilliant Venus is by far the brighter of the pair. It shines at magnitude -4.0 and is unmistakable, a dazzling beacon of light hovering above the horizon. Saturn at mag. +0.6 is 70x fainter than the much closer Venus but nevertheless easily found. Venus also acts as a useful guide in locating the more distant planet. Positioned 6 degrees further south is red supergiant Antares (α Sco - mag. +1.0).
A good time to look is on the morning of January 7th when the thin 10% illuminated waning crescent Moon forms a nice pairing with the two planets.
Although Coma Berenices is a small constellation it does contains one of the densest concentrations of external galaxies in the sky. However its most outstanding feature is not a galaxy but an extremely large and loose naked eye open cluster called Mel 111 or the Coma Star Cluster. In total, Mel 111 contains about 50 stars spread over 6 degrees of apparent size at a distance of 280 light-years.
Although conspicuous and easily visible to the naked eye the cluster was not included in both the Messier or NGC catalogues due to its loose nature, large apparent size and unproven status as a genuine open cluster. It was in 1938 that Swiss-American astronomer Robert J. Trumpler identified 37 stars as cluster members, establishing its true nature. Before that in 1915, British astronomer Philibert J. Melotte included it as number 111 in his catalogue of star clusters, hence the name Melotte 111 or Mel 111.
Mars starts the New Year in Virgo as a mag. +1.2 morning object that rises between 2am and 3am local time from northern temperate latitudes. Even better for observers further south, the planet rises slightly earlier than this. At this time of morning, the view towards the east / southeast has first magnitude star Spica (α Vir - mag. +1.0) positioned 7 degrees southwest of Mars with brilliant Jupiter (mag. -2.2) located higher up in the sky. Later in the night - but before sunrise - even brighter Venus (mag. -4.0) along with Saturn (mag. +0.6) both rise above the eastern horizon.
On January 3rd, the waning crescent Moon passes 5 degrees north of Spica at 4 UT then passes 1.5 degrees south of Mars at 19 UT. The trio form a wonderful pairing on the mornings of January 3rd and 4th.
The Earth and all other planets in the Solar System orbit the Sun in slightly elliptical orbits and therefore the distance of each planet varies somewhat. Venus is the planet with the most circular orbit and Mercury the most eccentric. Orbital eccentricity is the parameter that describes the amount by which an orbit around another body deviates from a perfect circle. For Venus the value is 0.0068 which is close to a perfect circle. Mercury has a much more eccentric orbit at 0.2056 while the Earth has a value of 0.0167.
For our planet this means that the distance from the Sun varies between 0.9832899 AU at perihelion (closest) to 1.0167103 AU at aphelion (most distant). This corresponds to minimum and maximum distances of 147,098,074 kilometres (91,402,330 miles) and 152,097,701 kilometres (94,508,948 miles) respectively. However, the story is not so simple. Due to gravitational perturbations of the Moon and to a lesser extent the planets, the Earth's distance at perihelion and aphelion is not fixed and varies by up to 30,000 kilometres or 18,640 miles. The date of perihelion occurs between January 2nd and 5th. In 2016, the Earth reaches perihelion on January 2nd at a distance of 0.9833039 AU (147,100,170 kilometres or 91,403,632 million miles). This is slightly more than the mean value.
The diagram below shows the orbit of the Earth. Note that the elliptical form is strongly exaggerated for display purposes.