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 Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


January 2019 Sky Guide

 

We are now past the winter solstice in the northern hemisphere, so nights are gradually getting shorter.  This certainly won’t be especially noticeable for much of January though.  Of course, conversely, readers in the southern hemisphere are now beginning the long glide towards winter, with gradually lengthening nights.  Although weather in the temperate northern hemisphere at this time of year can be challenging, from an observer’s point of view, the cold conditions often bring us some of the best seeing conditions - especially when it is very cold outside.  Readers experiencing winter are encouraged to get outside and see what January has to offer them - but wrap up warm while doing so.  Wherever you find yourself in the world, we wish you a happy new year and all the best for 2019 - keep looking up, as there’s going to be plenty to see in the skies above us this year.

 

 

The Moon

 

The Moon begins 2019 as a morning object in Libra, sitting a little under 7 degrees to the west of Venus in the same constellation.  As a morning object, rising a little after 3am, the Moon is naturally in the latter part of its monthly cycle and is displaying a very Old Crescent phase of around 20% illumination.  Our natural satellite has a close encounter with the planet Jupiter on the morning of the 3rd, when it can be found a little over 2 1/4 degrees from the solar system’s largest planetary member.

 

The Moon becomes New on the 6th January when it joins the Sun in Sagittarius.  This is the best time of the month for Deep Sky observation and astrophotography, as moonlight won’t affect viewing or images taken of fainter targets.

 

The Moon then re-emerges into the evening sky as a New Crescent, and over the next few days climbs higher and higher in the sky (from a northern hemisphere perspective), passing a little to the south of Neptune in Aquarius on the evening of the 10th and then Mars in neighbouring Pisces a couple of evenings later on the 12th.

 

The Moon reaches First Quarter on the evening of the 14th, while on the Pisces/Cetus  borders, passing south of Uranus, by about 5 1/2 degrees, on the same night.

 

The Moon reaches Full on the 21st, which also gives us observers the added bonus of a lunar eclipse, during a so-called “Supermoon” (more accurately titled “Perigee-Syzygy Moon”), when the Moon is at a close approach to Earth on its slightly elongated orbit.  This is actually the first of three “Supermoons” of 2019, which we’ll cover in due course.  Perigee-Syzygy Moons can occur at any point in the lunar cycle, but the popular “Supermoon” is generally agreed to coincide with a Full Moon. While purists will scoff at the title “Supermoon” - pointing out (quite rightly) that the Full Moon is probably the worst time of the month for lunar observation and that the difference between the moon at its largest angular size in the sky and its smallest is actually only around 7%, the term has inspired plenty of people worldwide to take more notice of the Moon and its cycle, which is something that should be encouraged. 

Montage of the Moon emerging from Total Umbral Phase.  Image Credit, Kerin Smith

 

The Penumbral phase of this total Lunar Eclipse begins at around 2.36am (GMT).  The deepest Umbral part of the eclipse begins a little after 3.30am (GMT) on the 21st and continues until a little before 7am, with the Moon clearing the dissipated Penumbral shadow of the Earth’s atmosphere at about 7.50am - so in Europe and Africa and much of the Middle East and Western Asia, this one is for the early risers!  A Total Lunar Eclipse is one of the most fantastic and eerie sights in nature, so you are encouraged to get an early night and rise to witness it.  The eclipse in its entirety is visible from the Americas, the extreme west of Africa, Iceland, the UK, Portugal, much of Spain and parts of France and Western Scandinavia.  The rest of Europe, Africa and much of Asia will miss the latter stages of the Penumbral phase, or have the Moon set during the Umbral phase.  The further east you are from the western edge of Europe and Africa, the less you will see of the eclipse.  Sadly the Indian Subcontinent, China and much of Australasia won’t see anything of the eclipse at all as the Moon will be set throughout the event.  Naturally the eclipse present some great opportunities for photographic record of the even and you don’t need hugely complicated equipment to capture some really great images.  Combinations of multiple widefield images of the Moon as it tracks through the Earth’s shadow can be very effective.

 

The Moon entering Umbral Eclipse Phase January 21st 4am.   Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Once the excitement of the eclipse is over, the Moon reaches Last Quarter phase in Virgo on the 27th January.  It ends the month on the morning of the 31st as a very Old Crescent, about 17% illuminated and is found about equidistant between the dazzling Venus and Jupiter, the three bodies, strung out in a line, forming a loose but extremely striking conjunction before sunrise.

 

 

Mercury 

 

Mercury begins 2019 as a morning object in the non-zodiacal constellation of Ophiuchus, shining at a steady -0.4 mag, being just shy of 90% illuminated.  It’s a relatively tricky spot in the dawn sky as the planet only appears around 7 degrees elevation at sunrise (form 51 degrees N) and is separated from the Sun by just over 16 degrees.  Mercury is heading sunward and increasing its illumination, as it is on the part of its orbit which moves behind the Sun from our perspective here on Earth.  

 

Mercury Sunrise January 1st 2019.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

By mid-month, Mercury has increased its magnitude a little to -0.7, and is now 97% illuminated, but only separated from the Sun by just over 9 degrees, which will make it extremely difficult, if not impossible to spot in the dawn sky.

 

The 30th finds Mercury at Superior Conjunction - behind the Sun from our perspective on Earth.  Subsequently, no more observations can be made until the innermost planet reappears on the evening side of the Sun and has significantly increased its separation from our parent star.

 

Mercury will transit the Sun on November 11th this year, which is worth putting in your diaries now.  If the weather is kind and you have appropriately safe equipment to observe this, it should be a spectacular event to witness.

 

 

Venus

 

Venus stands fairly tall at dawn in Libra at the beginning of the year, shining at a fierce -4.5 magnitude - bright enough to cast clear shadows in darker areas.  Although having faded a little since it reached peak brightness  of -4.7 mag in early December and sitting a tad lower in the sky, the planet still dominates the morning sky.  It’s joined in Libra by the Old Crescent Moon on the 1st and 2nd, the two bodies forming a beautiful pairing in the early morning sky.  At this point, Venus is approaching half phase at just under 26 arc seconds diameter and stands just under 23 degrees high in the south as the sun rises (from 51 degrees N).

 

Venus and the Moon at sunrise January 2nd.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

By mid-month, Venus has sunk a little in height at dawn and degreased brightness a tad to -4.4 mag, but is still unmissable.  Venus makes a brief sojourn in the constellation of Scorpius during the second week of January, until it crosses over to the non-zodiacal constellation of Ophiuchus, where it joins the slightly less brilliant Jupiter.  Both planets come into closest conjunction on the 22nd, when they will be separated by just under 2 1/2 degrees as the Sun rises.

 

By the end of January, the 62% illuminated Venus will stand 15 3/4 degrees high in the SSE at sunrise (from 51 degrees N), shining at -4.3 magnitude.  On the 31st, both Venus, the 18% illuminated old crescent Moon and Jupiter will be strung out in a line in the dawn sky, separated respectively from each other by about 4 degrees.  This will be a lovely sight to witness and photograph.

 

 

Mars 

 

The Red Planet is a +0.5 magnitude target in Pisces at the beginning of January.  Transiting in the late afternoon, at 7.4 arc seconds across, it certainly isn’t a large object when compared with Venus, Jupiter or Saturn, but at reasonably high magnification, some limited surface detail should be visible - particularly as Mars crosses the celestial border into the northern hemisphere, making observation easier for those of us in temperate northern climes.  Elevation from the horizon plays such a crucial role in planetary observation, as those who’ll remember the rather poor Martian viewing during last year’s opposition (which occurred with the planet much further south in the sky) will attest to.

 

The Gibbous Mars at Transit 5.18pm, January 1st.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

By mid-month, Mars has faded a little to +0.7 mag and shrunk to 6.8 arc seconds diameter, though has climbed yet further north in Pisces, standing just over 42 degrees high when it transits at just before 5pm (from 51 degrees N).

 

At the end of January, Mars is fainter still at +0.9 mag, having shrunk to 6.1 arc seconds diameter.  It now stands just over 47 degrees high in the south as it transits, which occurs at a little after 4.30pm (again from 51 degrees N).  While Mars isn’t anywhere near as spectacular as Venus, Jupiter or Saturn to observe at the current time, if you have a telescope, it’s still worth turning your attention to the Red Planet while you can.  2020’s opposition is in October, so we have a while to wait until Mars gets any better than this.  While Mars is still technically observable up to superior conjunction, which is still some way off in September, Mars will continue to shrink and fade until then.

 


Jupiter

 

Jupiter begins 2019 as a morning object, in Ophiuchus, shining at a steady -1.8 mag.  Rising a little over two hours before the Sun on the 1st (from 51 degrees N), Jupiter will be separated from our parent star by 28 degrees at the month’s beginning.  At 31.8 arc seconds diameter, the King of the Planets is always a rewarding target to observe, but at 14 3/4 degrees from the horizon as the Sun rises, is not fantastically well-placed - particularly for temperate northern hemisphere observers.

 

As the month progresses, Jupiter gains a tiny amount in height as the Sun rises, as it continues to pull further west of the Sun, but the situation remains much the same as far as observing conditions go.

 

As previously reported, Jupiter comes into conjunction with Venus in the latter half of January, with the two coming closest on the 22nd, when they will be separated by under 2 1/2 degrees, which will make for a pretty spectacular sight in the morning sky.

 

At the end of January, again, as previously mentioned, Jupiter is found in looser conjunction with the very Old Crescent Moon and Venus.  Shining at -1.9, it has gained a fraction in brightness, but observing conditions remain unchanged.  The planet stands just over 15 3/4 degrees high in the south as the Sun rises on the 31st.

 

Jupiter, the Moon and Venus in conjunction, sunrise 31st January.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.



Saturn

 

Saturn comes to superior conjunction on the 2nd of January, passing just a little to the north of the solar disk in Sagittarius.  Subsequently, it will be unobservable for the lions share of the month.  

Saturn at Superior Conjunction January 2nd.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


By the end of January, Saturn has re-emerged as a morning object, separated from the Sun by 26 degrees.  However, it is still painfully low on the horizon as the Sun rises, standing just over 8 degrees high at dawn (from 51 degrees N).  There are easier and more rewarding targets to seek out from an observational point of view this month, but as ever, it won’t be too long before Saturn is back to its beautiful best, coming to opposition in early July 2019.

 

 

Uranus and Neptune

 

The two outer giants are to be found either side of Mars in the evening sky: Neptune further towards the west in Aquarius; Uranus towards the east in neighbouring Aquarius.  Of the two, Uranus is undoubtedly the easier to spot.  At +5.8 mag, it is technically naked eye visibility from a very dark site, but binoculars will reveal the tiny 3.6 arc second diameter disk, looking like a slightly defocused star.  Telescopic magnification will reveal Uranus looking akin to a very compact planetary nebulae - its green-grey disk is devoid of features in all but the largest amateur instruments and only under very exceptional circumstances is it easy to make out subtle albeido features.  Sitting above the star Omicron Piscium, by about 1 1/4 degrees on the 1st, Uranus shouldn’t be too challenging to find from a reasonable site. Simply locate Alrischa, Alpha Piscium - the head “point” star in the “V” of Pisces and then trace upwards to Omicron and the planet should reveal itself to the north of this.

 

Uranus and Neptune relative positions, 1st January.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Neptune is a considerably greater challenge and will require powerful binoculars or telescopic magnification to reveal its tiny 2.2 arc second diameter disk.  At +7.9 mag, it’s considerably fainter than its neighbour Uranus.  The area of sky Neptune is in is relatively easily found: if you trace a line south through the western side of the Square of Pegasus (the stars Scheat and Markab), towards the bright southern star in the constellation of Pisces Austrinus, Fomalhaut, or Alpha Pisces Austrini, the location of the planet is within the triangle of stars Phi, Psi and Lambda Aquarii.  Once found, the colour of the planet is pretty unmistakable, even in smaller instruments - Neptune is definitely a blue planet.  Neptune’s more compact size tends to emphasise its colour much more than Uranus.  As with its neighbour, the joy of finding Neptune is the observational reward for most observers.  Some vague markings can occasionally be made out when narrowband imaging the outer planets at high power with larger instruments, particularly in the CH4 band.

 

 

New Horizons reaches 2014/MU69

 

The New Horizons probe will rendezvous with 2014/MU69 on January 1st 2019.  After the probe’s initial (and very successful) encounter with Pluto in July 2015, the search was on for a suitable candidate object for a follow on mission.  This is the first example of a probe having been redirected to an as-yet undiscovered object during the lifetime of its mission.  The Hubble Space Telescope was tasked with observing an area of sky a degree wide around the path of New Horizons, in order to seek out potential targets for the probe.  After three potential targets were discovered, 2014/MU69 was singled out as being potentially different enough in colour to Pluto and also being one of the more efficient objects of the three from a fuel point of view for New Horizons to fly by.  This conservation of onboard Hydrazine fuel would open up the possibility of the probe having more encounters in the future, if suitable targets further out are discovered.

 

2014/MU69 - an artist's impression.  Image credit: Kerin Smith

 

Initial observations of 2014/MU69 - also unofficially nicknamed “Ultima Thule” - suggest that it is a tiny (30km) object, which is irregular in shape (possibly double-lobed, or a very close binary).  However, its light curve is very shallow, meaning it is quite uniform in surface brightness, or being approached by New Horizons at (or close to) the objects’ polar axis.  It has been suggested that 2014/MU69 may be surrounded by a debris field or rings, but observations by the HST of the second of two occultation events, visible from Earth, seems to have ruled this out above around 1500km from the object.  This bodes well for New Horizon’s survival of the encounter, as the probe will pass around 3500km from 2014/MU69 at closest approach.  Of course in spaceflight nothing is certain - especially when we remember that New Horizons is one of the fastest objects ever launched and that even a tiny collision with a very small piece of debris could spell the end of the probe. 

 

Whatever happens during the encounter, we stand a very good chance of making some very interesting discoveries regarding the nature of variety in the Kupier belt.  2014/MU69 may be very small in comparison to Pluto, but it represents a pristine piece of the early solar system, so doubtless there will be much to learn from it.  The transmission bandwidth rates from New Horizons are very low, due to the immense distance of the probe from us on Earth, so data will trickle back from the probe for months after the encounter.  As with New Horizons at Pluto, we hope the wait will be well worth it.  

 

Beyond 2014/MU69, New Horizons will examine the “Hydrogen Wall” of the outer Solar System in much more detail than has been possible with instrumentation on the Voyager probes.  Even if another suitable flyby candidate doesn’t materialise, the probe will continue to explore the outer solar system and its boundary with interstellar space for some years to come.  The probe is estimated to have enough power to keep up observations until the mid-to-late-2030s.

 

 

Comets

 

Comet 46/P Wirtanen will still be visible in the evening skies during January, though fading as it recedes from the inner solar system.  As the comet moves away from us, its enormous angular speed across the sky, which has been so noticeable during closest approach to Earth in mid-December, truncates quite significantly.  Found in Lynx on the 1st of the month, the comet may still technically be within naked eye visibility from a dark site, but in all likelihood (barring outburst), its large and diffuse nature will need binoculars or telescopes to see it at all.  The comet hasn’t shown much signs of a tail when observed from Earth, but this doesn’t mean it’s not got one.  The comet’s tail is largely hidden behind its coma from our perspective on Earth, as the solar wind “blowing” the tail is meeting the comet almost head-on as we view it.  As the month progresses, this angle between the Earth and the comet will change subtly and we may see more of Wirtanen’s tail, though this probably won’t become too noticeable until the month’s end, when the angular relation between the comet’s path and Earth causes the comet to appear to almost “dog leg” and start to sink towards the south.  By this point Wirtanen will have faded further still, so early observations will be easier and potentially more rewarding.

 

 Comet Wirtanen's path through January 2019.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Meteors

 

The Quadrantids are the major shower of January and are normally fairly numerous in ZHR, yet rather muted brightness-wise in comparison with the major showers of the year.  The Quadrantids emanate from the northern polar region of the sky around Bootes, Draco and Hercules.  Possibly seeded by Minor Planet 2003 EH1, which may well be an extinct comet, the Quadrantids are numerous at their peak, sometimes reaching a Zenithal Hourly Rate of approaching 200 (though of course not all of these will be seen from a given location).  This year, the peak date of the Quadrantids  - January 3rd/4th - coincides with a very Old Crescent Moon, which rising at 6.30am GMT (from 51 degrees N), won’t really be around to spoil the shower at all.  The Quadrantids sometimes peak with major storms, but the cloud of debris that seeds it is often perturbed by the passage of the major planets, which can't be easily predicted.  With the Moon out of the way, the Quadrantids will have a good chance to fulfil their potential this year.

 

 Quadrantids Radiant location.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Deep Sky Delights in Auriga and Taurus

 

Last month, we covered some of the more obscure objects in the winter skies, with a look at the many Caldwell objects observable at this time of year.  This month we return to two well-known winter constellations, Taurus and neighbouring Auriga, which are home to some of the best-known of this season’s deep sky treasures.

 

Taurus and Auriga.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

The zodiacal constellation of Taurus, The Bull, is home to some of the most outstanding deep sky objects in the sky, the most notable of these is perhaps M45, the Pleiades, or the Seven Sisters.  At collective magnitude of +1.5, M45 is easily seen with the naked eye and has been recorded by numerous cultures throughout the world.  The ancients knew the Pleiades by different names: Subaru in Japanese, Krittika in Hindi, Soraya in Persian amongst many others.  The Pleiades are mentioned in Homer's Odyssey and Iliad, the Bible and the Quran.  It is known that cultures as far apart as the Maori and Aborigines and the Native Plains Tribes of North America had knowledge of this star cluster - which makes it pretty well-known worldwide!

 

M45 presents its nine major members, (named after siblings from classical Greek mythology), the "sister" stars of Merope, Sterope, Electra, Maia, Tygeta, Celaeno and Alcyone - along with the "parent" stars Altas and Pleione - to the naked eye from a very dark location, but most people with reasonable eyesight can split six under average skies.  Telescopes and binoculars reveal many more of the 1000-or so members of the cluster and larger instruments and photography can pick up blue-hued reflection nebulosity surrounding the cluster - particularly around Maia and Merope.  This nebulosity is caused by illumination of left-over material from the cluster's formation.  The view of M45 with a widefield, low power eyepiece is one of the most glorious sights in any telescope, though at 2 degrees in diameter, one has to be careful about eyepiece choice in order to get the outlying members in a useable field of view.

 

M45, The Pleiades.  Image credit: Kerin Smith

 

The Pleiades are thought to be around 100 million years old and lie between 430 and 440 light years away.

 

Next door - though not cosmically speaking - to the Pleiades, is the older and more spread-out Hyades cluster.  Its major naked eye members are arranged in a V-shape which marks the head of Taurus.  Again, similarly to M45, the Hyades have been known since antiquity and were traditionally seen by the Ancient Greeks as being the sisters of the Pleiades - via their shared father Atlas.

 

The Hyades lie 152 light years away, and as such are nearest star cluster to us on Earth (though arguably the stars in the Plough or Big Dipper in Ursa Major can actually be thought of as a cluster and are closer).  The Hyades consist of over 300 individual stars and modern estimates put its age at around the 600+ million year mark - making it markedly older than the Pleiades.  The Hyades share a galactic trajectory with M44, the Beehive in nearby Cancer, again suggesting a common origin point in space.  However, the Beehive appears to be slightly older at 600-730 million years.

 

Line of sight puts Taurus' principle Alpha star Aldebaran - the eye of the Bull - within the boundaries of the Hyades, though this Red Giant is unrelated and distinctly closer to us at 65 light years.   

 

Reaching East down the Southerly "horn" of the Bull, we come to the +3 mag star Zeta Tauri.  This star is a convenient location point for another jewel of the night sky - the Crab Nebula, M1 on Messier's List.

 

The Crab Nebula is the remnant of a star which went Supernova in the year 1054 (to us here on Earth).  This event was recorded throughout the world, from New Mexico to China.  It would have been a dazzling sight, peaking at -6 mag, brighter than the planet Venus and visible in daylight.  After it faded, the event receded from popular consciousness and it was nearly 700 years later, in 1731, that the object than would become known as the Crab was discovered by Astronomer John Bevis.  Messier rediscovered it when searching for the return of Halley's Comet 27 years later in 1758.  First thinking the object was a comet, it was the Crab that prompted Messier to compile his list, so other comet-hunters would not be confused by these static, cloud-like objects when searching the heavens.

 

Lord Rosse, observing the Crab with what was then the largest telescope in the world at his Birr Castle Observatory in Ireland, in 1844, made a sketch that showed claw-like protrusions - presumably the filament structure of the outer lying regions.  The object was nicknamed the Crab - and the moniker stuck.

 

Early both Century photographic observations of M1 showed that the object was expanding rapidly.  This expansion was extrapolated backwards and it was noted that the object should have started its expansion around 900 years previously.  A little bit of astronomical detective work ensued and the events of 1054 and the Crab were tied together.

 

Although a hardly dazzling +8.39 mag, the Crab's is quite well condensed and as such its surface brightness is fairly high.  It can be found as a misty patch with ordinary binoculars, though larger binoculars reveal it as a definite elongated, round-edged feature.  Telescopically, the texture of the Crab becomes evident in refractors of 4-inches aperture or reflectors of the 6-8-inch class.  Reflectors of 16+ inches in aperture and dark skies are needed to glimpse the filament structures of M1's outlying regions and real striation in its core.  Filtration will help with this object, especially in small instruments where it can sometimes be difficult to isolate the nebulosity of the object from the rich background of the Milky Way.

 

Photographically, the Crab Nebula is a rewarding target, with the "Hubble Palette" of H-Alpha, OIII and SII being particularly useful in bringing out the tangled, chaotic structure of the object's core.  Though it can be very effectively recorded with single shot colour cameras, as displayed by Mark Blundel's picture below, which was taken with a Canon 1100D via a Meade 6000 Series Triplet Refractor on a Skywatcher HEQ5 Pro mount, guided via the Orion Magnificent Mini Autoguider package.

 

M1, The Crab Nebula.  Image credit: Mark Blundell.

 

No-one with any form of optical equipment should ignore the Crab Nebula. While not as spectacular is the neighbouring Orion Nebula, it is the only easily-observed remnant of a Supernova that humans have actually observed in relatively recent history.  Given the dearth of Supernovae in our galaxy in recent times, the Crab remains a special object to us.

 

Moving northwards into Auriga, the Charioteer, following straight line from Zeta Tauri, the more southerly tip of the Bull's two horns, through Elnath, one of the few stars in the sky that is shared between two constellations, giving it the classification of both Beta Tauri and Gamma Aurigae, we come to the Flaming Star Nebula, IC405.  Found 6 degrees north of Elnaith, this object is a partial emission, partial reflection nebula, meaning that one  part of its structure glows under excitement from radiation, whereas the other part merely reflects light from the stars imbedded in the object.  Measuring around 30 x 19 arc minutes, IC405 is centred around the star AE Aurigae, a star which was ejected from the nearby Orion Nebula under 3 million years ago.  At +10 mag, it is not an intrinsically bright object, but condensed enough to be seen in small telescopes from a decent location.  It is unsure if any of the material that makes up the Flaming Star Nebula was once a part of the Orion Molecular Cloud - it is more likely that it is material that the star is merely passing through.  As previously mentioned, this is an area rife with gas and other star forming material.  IC405 lies some 1500 light years from Earth.

 

IC405, the Flaming Star Nebula.  Image credit: Mark Blundell.

 

Just under 3 degrees to the NE of the Flaming Star lies the first of Auriga's three great open star clusters, the lovely M38, otherwise known as the Starfish Cluster.  It's difficult to see exactly what resemblance this +6.4 mag, 20 arc minute diameter collection of stars has to the titular marine invertebrate, but it is certainly a pretty sight in any sort of optical instrument.  M38 was first recorded by the preeminent Sicilian astronomer Giavanni Batista Hordierna in 1654 and re-squired much later by French observer Le Gentil in 1749.  Le Gentil's observations alerted Charles Messier to M36's location and it was included in his original list in 1764.

 

M38, the Starfish Cluster.  Image credit: Miguel Garcia, Creative Commons.

 

At over a third of a degree angular diameter, M38 is ripe for observation in most telescopes and binoculars.  Observers will note long chains of stars, many of which are blue, but there are also some lovely contrasting yellow and gold-coloured members.  In total, M38 has around 100 stars as members and lies around 4200 light years from us.  It is thought to be around 200-225 million years old.

 

2 and 1/3 degrees to the SE of M38 we come to the second of Auriga's great clusters, M36.  This cluster is a good deal more compact than its neighbour at 10 arc minutes diameter and slightly brighter as a resultant +6 mag.  Through a telescope, this collection of hot white stars can appear quite brilliant in comparison to M38 - indeed, it is said that if M36 were placed in the position of the Pleiades, it would outshine them by a factor of three.  M36 was again discovered by Hordierna, in 1654, rediscovered by Le Gentil and added to the Messier list in 1764.  

 

M36.  Imge credit: Ole Neilsen, Creative Commons.

 

This cluster is a good deal younger than its neighbour and contains many young hot blue main sequence stars, of spectral type B2 and B3.  There are no older population stars to speak of in M36, so it is thought to be just 25 million years old.  Lying at around 4300 light years hence, M36 is one of the many objects that share the moniker "The Pinwheel" - though apart from a circular collection of stars to the NE side of the cluster, it is difficult to see why it has picked up such a name - especially in the light of the other "Pinwheels" in the sky.  Perhaps we should come up with a new more original nickname for this great cluster - it deserves better.

 

The last of Auriga's fine open clusters is its best - the spectacular M37.  There are many great clusters in this area of sky: the much nearer Hyades, Pleiades, Beehive, the nearby M35 in Gemini and the Double Cluster in Perseus - but M37 is one the most beautiful of these and is a lovely sight is any telescope or binoculars.  At a quarter of a degree in diameter, M37 is about the same angular size as the Full Moon in the sky.  It is also the brightest of Auriga's "Trio" at +5.59 mag and the oldest at an estimated 300 million years of age.  Like its neighbours, M37 contains many hot blue stars, but also significantly many more mature yellow, orange and red giant stars.  This more evolved stellar population makes for some fine viewing for we astronomers here on Earth as the blues of the newer, hotter population contrast superbly with the warmer tones of the older stars.

 

M37.  Image credit: Ole Neilsen, Creative Commons.


M37 was again discovered by Hodierna, though almost inexplicably was missed by Le Gentil - Messier himself found it again at catalogued it in 1764.  M37's total stellar population is thought to number in the 500+ levels, of which maybe 150-or-so are observable in amateur telescopes.  It is the furthest lying of Auriga's clusters at 4500 light years distance and the largest at 25 light years across.

 

Sitting astride (from a northern hemispherical perspective) this rich are of sky is Auriga's principle star, Capella.  At +0.08 mag, Capella is the sixth brightest star in the night sky, being a shade fainter than Vega.  It is comprised of two large G-type stars - roughly the same temperature as our Sun - but these are much larger in mass and diameter and have already begun to exhaust their nuclear fuel.  Despite being a little over 42 light years away, this system is not split-able (as yet) with even the largest of Earth-bound telescopes, as the two main component stars orbit a common centre of gravity which keeps them around 60 million miles apart, roughly 2/3rds of the distance between the Earth and Sun.  There is a much fainter outlying star system which is gravitationally bound to the main Capella pairing, though this comprises itself of two faint M-class dwarf stars, making the whole system technically a Quadruple star.

 

Text: Kerin Smith

 

 

 

 

 

 

Text: Kerin Smith