February Night Sky Wonders

While the winter sky may be the ‘Aladdin’s cave’ for skywatchers, and we may already have plundered deeply one of its greatest celestial treasures, the constellation of Orion, we forge ahead undeterred as February reveals yet another vault of celestial wonders awaiting exploration…

No northern stargazer would wish to run too long with their expanding sky-viewing portfolio still missing the ‘canine collection’ from their personal list of recognised star patterns. This pleasing celestial set is fairly readily identifiable in dark skies thanks to each pattern containing at least one bright star and its close proximity to the constellation of Orion. The latter point also ties in nicely with Greek myth as the Hunter was in fact the owner of these two ‘hunting dogs’. So if you look to the south and target your gaze on the star-marked ‘signpost’ at the centre of the constellation of Orion and slide your eyes down the three stars of Orion’s belt towards the horizon, with comparatively little effort you should find yourself staring at one of the brightest stars of the night sky.

Looking south, mid-month, 10pm: Below and a little left of the constellation Orion’s bottom stars Saiph and Rigel can be seen one of the most life-like constellations invented by the ancient Greeks, that of Canis Major, The Great Dog.
(Image credit: Nick Parke/Stellarium)

Although you may note that we have used the phrase “one of the brightest” while discussing stars on perhaps seemingly numerous occasions before now, this time there is a special difference. (I wonder can you guess what it is?) Yes, this month dear reader we celebrate a significant milestone in our cumulative journey across space, for in gazing on Sirius, ‘the Dog Star’, our eyes are receiving light from none other than what looks to be the most radiant star in all of the heavens! While other more powerful stars in the Universe such as Rigel may in fact illuminate their distant corners of the Cosmos with greater intensity (luminosity), to the eyes of any observer on Earth, the much closer Sirius will ‘appear’ to be the brightest.  Oh, and for the record, where lower numbers equate to greater radiances, our ‘apparent magnitude’ champion takes this particular stellar podium with a brightness rating of -1.4. Canis Major, the constellation who triumphs with this star, was said to be associated with the mythological dog ‘Laelaps’ who could “outrun anything” and appears to be chasing Lepus, the star pattern of the Hare that is springing over the celestial ground beneath his master’s feet.

A view from Sirius: This exceptionally detailed artist’s impression reveals the ‘double star’ or binary system encapsulated within the single object image seen from Earth. Where blue equals hotter, Sirius A, the star whose Greek name means “scorched” is about 20 times brighter than our Sun, but its companion, Sirius B, a smaller-than-Earth ember of a dead star, (or white dwarf) pictured right, has a surface temperature of around 19 000 degrees Centigrade hotter than the star at the centre of our Solar System and about 400 000 times Earth’s gravity.
Credit: NASA, ESA/G. Bacon (STScl)

But now to look for another shape among the stars. If the intriguing asterism at the centre of the constellation of Orion happens to bear an uncanny resemblance to some mysterious ‘warning sign’ along the heavenly highway, then perhaps the hazard it would alert space travellers to is located nearby. Just as a certain patch of ocean on Earth has strange rumour and infamy surrounding its name, perhaps the three-pointed sector of space distinguishable to the left of Orion is none other than the ‘Bermuda Triangle of the Macrocosm’! To bring this celestial wonder to life overhead simply point your finger at Orion’s orangish shoulder star Betelgeuse, swing your hand left towards the next brightest star in the vicinity, a star which goes by the name Procyon, from there cut a slanting line down to the Dog Star, and finally sweep back up to the start to complete your triangle. Once drawn however you will have just formed a shape most stargazers instead refer to as the ‘The Winter Triangle’.

The Winter Triangle asterism : If you enjoyed joining up that grand isosceles in the sky known as the Summer Triangle during July and August, you will have no less fun at drawing an equilateral triangle between these three more brilliant stars at this time of year.
(Image credit: Nick Parke/Stellarium)

So what about that new star we added to help form our triangle? Well the star pattern to the left of the Hunter and level with his head in which Procyon is located is the constellation of the Little Dog, Canis Minor. For those of us with an interest in all-things-cosmic but who wilt somewhat at the prospect of pending eye-straining sky hunts for star patterns whose stick figure interpretations still seem to leave much to be desired once ‘fully connected’, should find much solace in this constellation! With minimum effort you will have ‘bagged’ the constellation and earned another observational badge by the time you have connected the constellation’s first star to the second, as this celestial animal’s stellar form contains only two. (Perhaps therefore to use the word “pattern” in this context is straining its meaning somewhat since this simplest of constellations is no more than a mere ‘line’ in space!) Canis Minor’s second star, Gomeisa, is the slightly dimmer one diagonally above and to the right of Procyon with a magnitude of 2.9.

Swinging round on our heels now 180 degrees to explore the northern part of the sky, the ‘constellation collectors’ among us may likely let out an exclamation of satisfaction as simultaneously we now complete another key pair of star patterns from the celestial sphere’s full pack. While Ursa Major probably owns the broadcasting rights for the title “most recognised star pattern of the northern celestial hemisphere”, the Great Bear’s sidekick, the Little Bear is testament to the fact that in terms of a constellation’s total territory in space, size isn’t everything. In comparison to constellations with far more expansive celestial domains, Ursa Minor seems insignificant, yet the star pattern of the Little Bear in reality punches well above its weight with the legendary title of ‘Pole Star’ also attributed to its name.

The Circumpolar constellations: With Ursa Minor, The Little Bear finally completing this fabulous suit of constellations, can you identify them? (You may need to refer to your past Astronotes to help!)
(image credit: Nick Parke/Stellarium)

This celebrated star, Polaris, perhaps better known to many as the North Star lies more or less directly above our planet’s north pole and axis of rotation, but far out in space. As such it makes a wonderful marker for one and all to navigate by, whether they be stargazers today or sailors of old. This however is not where its charm ends though, for with Earth’s rotation once every twenty-four hours giving terrestrial-bound humans the impression that the ‘sky’ is turning once every day, the Pole Star’s prime position in the heavens enables it to stand serenely centre-stage while the entire stellar circus moves around it. With it being a star of a more average magnitude, a little pointer in the heavens can be helpful while you are out observing to ensure that it is indeed the North Star you have located.

Stellar Sat-Nav: Whether you find yourself doing so for astronomical purposes or simply because you are lost, undoubtedly the handiest method for seeking north in the heavens is to start at the Great Bear and then move to the Little Bear. More precisely, extend your pointer line out from the two end stars in the Plough asterism and roughly five ‘saucepan depths’ away you will stumble upon the North Star. (Image credit: Nick Parke/Stellarium)

 

As Earth’s axis of rotation is currently performing a slight slow motion “wobble” (just like some giant spinning top), we know that an upward-pointing arrow at the north pole would in fact  have pointed at different ‘Pole Stars’ in the past while the axial line moved along this circular path of deviation. Bearing in mind though that Earth’s rotational axis takes around 26 000 years to find the same point along this circular “wobble path”, the North Star should retain its current title of ‘Pole Star’ for some considerable time yet. One point we have already settled is that the true source of the star’s fame is its privileged and unique position above our planet in space, its recognition does not come from any special attributes the star has in and of itself. That said there still exist two classic ‘North Star myths’ which we can dispel in passing. We know that it is not the brightest star in the celestial sphere as that title belongs to another with which we are familiar, moreover as a 2nd magnitude star it would not even come close. Secondly in terms of its proximity to Earth it lies a fairly comfortable 341 light years away, so with many other stars in the Milky Way lying closer to our Solar System than this, the closest of all being only 4.4 light years away, there’s actually little upon which to base the notion of Polaris as our closest stellar neighbour.

Last but not least, with the night sky rarely failing to give observers something fresh to put their eyes to month from month, February’s night sky brings something else out from behind its velvet curtain.

While the planetary king of the gods has been reigning over the winter night sky without rival for the last few months, a challenger is on the warpath. Mars, the planetary god of war is slowly but surely attempting to invade Jupiter’s nocturnal kingdom, and by next month will unequivocally be vying for attention higher in the sky. For the moment though, with buildings and trees to hide the red trouble-maker from view, we, like Jupiter may scarcely catch a glimpse of our terrestrial neighbour for some time yet. None-the-less if you have found the mention of its name to be like a rash that just will not go away, some opportunities may indeed be open to you this month to find relief and feast your eyes on that distinctively orange VIP of the heavens. By the end of the month, Mars will rise as high as 27 degrees into the sky. Having said that, if getting up to observe the Red Planet at four in the morning in the south doesn’t appeal to you, you may prefer to score that one off the list and consider option two: viewing Mars at midnight from 22 February onwards when its ascension will at least be 10 degrees up from the horizon ESE, and after a close pass of the Moon’s disc with that of Mars, the Red Planet will not be competing with the glare of our natural satellite.

The Red Planet: Having paid its lengthy homage to the daytime sky, the planet Mars makes a grand return to the nocturnal celestial hemisphere.
(image credit: Nick Parke/Stellarium)

So if you find yourself wanting to take up the observational challenge, as always an elevated viewpoint such as a hill or mountainside above any obstructions should increase your view of the celestial hemisphere, extending its ‘dome’ back down toward the skyline. Don’t forget though to pack a scarf, optical aid, phone (and preferably a friend) in your skywatching bag before going off planet-hunting!

(Article by Nick Parke, Education Support Officer)