Thursday, 15 March 2018

NGC4244: A silver needle

Galaxy season's upon us again... that time of the year where the Earth turns away from the galactic plane in the northern hemisphere and more easily shows us the marvels that lay way beyond our Milky Way. Not that far away from us, at merely 14 million light-years' distance, lies a group of galaxies in the small but wonderful constellation of Canes Venatici, the dogs that hunt the great bear. Last year I already talked about the highly irregular "Train Wreck Galaxy", this year I'm taking you to its spectacular neighbour, NGC4244 or better known as the "Silver Needle Galaxy". 

There's no need to explain this nickname because the minute you point your telescope to it, you'll understand where it came from. It's one of those galaxies we see edge-on and for this reason we see it as a long streak with a brighter and wider area at its core. Yet, from the peculiar clumping of stars along its disk scientists conclude that it must have very loose spiral arms.

Sunday, 11 March 2018

IC2177 + RCW2/Gum1: The Seagull

On the border between the constellations of Canis Major and Monoceros flies a giant seagull, which astronomers identify as IC2177. Of course we're not talking about a bird but about an enormous hydrogen cloud in which active star formation takes place. This cloud spreads over such a great distance (3° across, the diameter of 6 full Moons!) and its surface brightness is so low that it can be quite challenging to observe visually. Even with my binoscope under a fairly decent sky, the body and wings of the Seagull Nebula merely appeared slightly brighter than the background. The seagull's "head" on the other hand, was more easy to make out around the bright star HD53367 (the "eye"), including some structures and a dark lane that ran from the nebula's centre towards its eastern rim and in which many people see the seagull's beak. 

The star HD53367 is quite interesting in its own right as it shows an unusual pattern in its spectrum. Scientists classify stars with this sort of pattern as "Be stars", more famous examples of which are Gamma Cassiopeiae and especially Achernar on the southern hemisphere. The reason why these stars emit these strange lines in their spectrum is because they spin so rapidly that they not only become very oblate, but that they also expel so much gaseous matter under the centrifugal force that it forms a disk around the star itself. This disk scatters the light from the star in such a way that its spectrum's altered. 

Lying almost 4,000 light-years away from us, the Seagull Nebula is producing literally hundreds of new stars, many of which illuminated the field of view of my telescope like a Christmas tree.



Thursday, 1 March 2018

NGC2022: Unnamed and underestimated

It amazes me time and time again that some of the most exotic and least-known objects still carry a popular nickname. Take IC418, for example, the Spirograph Nebula. Not that our Spirograph doesn't deserve a nick, much on the contrary since it's such a beautiful object. But then what about NGC2022, the brightest planetary nebula in Orion? It's a very popular nebula but still no-one seems to have found a nice name for it. 

I guess that the reason for this is that it's so small, although far from as small as IC418. In small to medium-sized telescopes NGC2022 appears almost stellar and you need a bit of aperture and especially very high magnifications in order to bring out some detail. At 507x, however, the bright ring of its inner shell stood out brightly against the thin haze of its outer envelope. Inside of the ring I saw strings of matter connecting it to the 16th magnitude central star, surrounded by abundant detail. I even thought to have caught a glimpse of a tiny star that looks as if it lies on the western part of the ring.

Distance estimates are always difficult with nebular objects and our best guess is that this nebula lies about 8,000 light-years away, so more than double the distance to the Spirograph. Yet, NGC2022 dwarfs it in size, indicating that it is far more evolved with its bright inner shell having almost caught up with its outer, which stretches over a light-year across. The extremely hot (surface temperature 108,000°C!) white dwarf whence the nebula originated has probably reached the point of maximum heating, after which it will cool down and extinguish slowly. 

To me, the nebula looked very much like a grape so I'd like to baptise it officially "Grape Nebula". Perhaps you have a better proposal for a nickname? I'm all ears... :-)

Friday, 23 February 2018

NGC1964: More black holes

Galaxies are entities far beyond the power of our little human brains to grasp. Yes, we think that we understand what they are because we see their nucleus and the spiral arms that whirl around it. But do we really realise what it is we're seeing? Do we, for instance, really understand that the billions of stars that make up the Milky Way that spans across the sky only comprises but a small part of our own galaxy? Do we really have any idea what hundreds of billions of stars actually mean? How much is a hundred billion anyway? And given that there are at least a hundred billion galaxies in the visible universe, each containing hundreds of billions of stars, it would be sheer arrogance to state that the Earth lies at the centre of the Universe and that we, tiny humans, are its divine culmination. 

Now point your telescope again to Orion's feet, to the unknown constellation of Lepus, the hare. In my previous post I've shown you an unexpectedly beautiful planetary nebula in that constellation. Now I'd like to show you a distant galaxy there. NGC1964 lies about 65 million light-years away from us. That's not exceptionally distant since our universe has a radius of over 13 billion light-years, but still, the light of this galaxy started its voyage to Earth around the time that the asteroid, which caused the extinction of the dinosaurs, hit us. So that's a considerable distance. The thing that struck me at first glance, was that this galaxy has a very bright, almost stellar-like core. It immediately reminded me of M77, a galaxy which has a particularly big black hole in its nucleus. The strange thing about black holes is that they're not really black as seen from Earth, but as a matter of fact they're very bright. That's because matter clumps together around it, pulled in by its enormous gravitational force, and becomes extremely dense and hot. So when you see a galaxy with a core like this, rest assured that it contains a super-massive black hole!

Tuesday, 20 February 2018

IC418: The Spirograph

There's so much unknown beauty up there that it never ceases to amaze me. In the dark constellation of Lepus, the hare, at the feet of mighty Orion, you'll find this little bugger. It's obviously a planetary nebula, and one that listens to the denominator IC418, but more commonly known as the Spirograph Nebula. It's nick refers to its complex, almost mathematical structure. 

Experts among you will already have guessed that this nebula's still quite young, hardly 2,600 years old, and in full expansion. Though very small in spite of its relatively close distance of 3,600 light-years, you'll quickly notice some extraordinary details if conditions allow you to push telescope power. Its bright outer shell, gas that was expelled when the star was still in its red giant phase, shines brightly under the heat of the brilliant white dwarf in its heart. The inner shell, on the other hand, appeared much brighter still and seemed to sparkle in the atmospheric turbulences of our Earth. This inner shell is the dying star's atmosphere that was blown away into space after nuclear fusion had become critically unstable. Soon the inner shell will expand so quickly that it'll catch up with the much slower outer envelope, possibly even break through it in order to form ansae, like the ones of the Saturn Nebula

So keep your eye on this one because it still has a lot in store for us in the near future... er... in the next couple of thousand years. 

Thursday, 15 February 2018

Berkeley 21: The edge of our galaxy

Loyal readers of my blog know that I'm obsessed with faint fuzzies... objects so difficult to see that you sometimes wonder whether what you see is real or whether you've entered the realm of science fiction. But perhaps the objects that fascinate me more than anything else are extremely remote (and therefore faint) open clusters. Last year already I took you to Berkeley 19, a cluster that lies even beyond the outermost spiral arm of our galaxy. Today, I'd like to take you just a little bit closer, to a distance of merely 16,000 light-years, right in the heart of this outermost spiral arm. There lies this old star cluster, denominated Berkeley 21, the light of which is nearly completely extinguished by the interstellar dust of the broad Perseus spiral arm which lies between the outer arm and our own. In other words, prepare for something very difficult to see. 

At 104x, I only got a hunch of a fuzzy patch... the suspicion that I had nailed it. It was not until I pushed telescope power to 285x that the cluster revealed itself and at 507x most of its stars could be resolved, albeit with great difficulty. For your information, the brighter stars you see on my sketch all lie a lot closer to us!

Star clusters in that extremely remote part of our galaxy are usually very old because the gravitational influence of the galaxy is a lot less and interstellar matter's not stirred up as much. So don't expect a lot of spectacular star formation there. And if eventually a star cluster does form, it stands a much better chance of remaining compact. Berkeley 21 therefore could be many billions of years old, perhaps even be as old as our galaxy itself.

Monday, 12 February 2018

NGC2129: Others taking the credit

How many times have I already argued that appearances can be so deceiving when observing the night's sky? Sirius shines so brightly that you'd easily think it must be the biggest star out there, but then you realise it only lies 8 light-years away from us. Deneb, the brightest star in Cygnus, looks a lot fainter than Sirius from our perspective, but radiates no less than 200,000 (!) solar luminosities at us from its 1,400 light-year distance. 

Now look at this lovely open cluster, NGC2129, which you'll find on the border between Gemini and Taurus. It's an easy target even for binoculars and that's mainly due to the two bright stars at its centre. Now what if I told you that in reality these two stars aren't even remotely close to the cluster and that they only appear to be part of it from our perspective? Indeed, the brightest of the two (HD250290) is an ordinary, 3 solar mass yellow giant, which lies 1,800 light-years away. Its fainter "sister" that lies slightly below (HD250289) is a similar yellow giant but it lies at a distance of 2,700 light-years. And the rest of the cluster? Well, you'd have to travel three times as far, 7,200 light-years to be precise. So those two bright stars have nothing to do with it whatsoever, nor are they related to each other. They just happen to float in front of this lovely, remote cluster which contains about three dozen stars and which is slowly breaking up under the gravitational force of our galaxy. 


Friday, 2 February 2018

STF867: The joys of double star observing

How can you ever get bored looking at the stars? There are literally billions of them and every single one has its own personal character and story. None, however, show their particular nature as well as binary stars. It's still not clear how many stars are actually double or multiple star systems, but estimates range from 50% for smaller, Sun-like stars to even 80% for massive, hot giants. 

Many of these double stars are a real pleasure to observe, as I've already shown you many times before. Sometimes the challenge is that they're so close together that they're on the limit of what a human observer can distinguish with his amateur telescope. Procyon springs to mind. Others are easier to separate and show the most amazing, contrasting colours, like Ras Algheti. The choice's nearly infinite and I often ask the computer of my telescope to amaze me at random. And then you come across star systems that have hardly been observed by anyone, but who'll mesmerise you with their beauty.

Has anyone of you ever heard of Struve 867? It's just one entry to the enormous list of the famous 19th century German Astronomer. And yet, when my telescope turned to this little star in Orion, I was so charmed that I immediately took my sketchbook. 

The main star is a 7th magnitude white giant that shines 286 solar luminosities at us from the respectable distance of 1,300 light-years. It's companion, only 2.2 arc-seconds apart, appeared orange to me. At magnitude 8.88 it's considerably dimmer and slowly revolves around the main star from a distance of 876 times the distance between the Sun and the Earth (AU or Astronomical Unit). To give you a better idea, that's 25 times the distance from here to Pluto. They only appear almost glued to each other because they're so far away from us. 



Sunday, 28 January 2018

K 2-1: Never be discouraged

I've written this already a couple of times before, but never be discouraged by a strange object denominator. There's so much more to discover beyond the classic Messiers and NGCs and often you'll be amazed by what you find. Take this strange planetary nebula, for example. Its name is Kohoutek 2-1, after its Czech discoverer, and it lies about halfway between Elnath (B├Ęta Tauri) and Iota Aurigae. Although it's obviously not the brightest of planetaries, it immediately leapt out at me when it moved into the field of view of my binoscope. Even more so, I had no difficulties at all noticing that this particular planetary is way out of the ordinary. As you know, planetary nebulae are usually round or elliptical, hence the nick "planetary" nebulae because they look a bit like a planet. This one's a whole different league with its strange lobes and wonderful structures.

I've found very little information about this little nebula, but I suspect that its central star's binary. I did have the impression to have seen a tiny companion which I've also represented in the sketch. This would certainly explain a lot because the gravitational pull and radiation of a companion star would severely disrupt the nebula's shape.

To make the picture even more interesting, the nebula's surrounded by a lovely, loose cluster of tiny stars, denominated "Skiff 3". Again, no other information to be found anywhere. The nebula would be 3,600 light-years distant, but the for the cluster I can only guess that it lies way beyond.

Friday, 26 January 2018

NGC1555: Hind's Variable Nebula

T Tauri is a very young star that's only just emerged from the cocoon of dust and gas in which it was born. Fusion's just ignited in its core but is still unstable. Soon, this star will blow away the dust that's still surrounding it and grow into adulthood as a stable main-sequence star, fusing hydrogen into helium. 

For the moment we're not quite there yet as you can see. The star has a distinct yellow-orangy colour and varies in brightness as fusion still needs to stabilise. The surrounding dust glows in its light, obviously with the same variations as the star. I had the impression that also the nebula appeared slightly yellowish, but that's obviously an optical illusion due to the proximity of such a strongly coloured star. Still I couldn't resist adding a bit of yellow to the nebula too, for artistic reasons and because it renders the illusion at the eyepiece. 

It also seems that this nebula was significantly brighter when it was discovered in the late 19th century. The famous German astronomer Friedrich Struve reportedly found another, similar nebula very close to NGC1555 and this discovery was confirmed by others. Strangely enough, this nebula, which had been catalogued as NGC1554, couldn't be found anymore a decade after its discovery, nor has it been found ever since. Scientists now speculate that it was a transient portion of the same reflection nebula complex. 

T Tauri and its surrounding nebula lie approximately 500 light-years away.


Wednesday, 24 January 2018


Procyon, bright and yellowish, is the brightest star in the winter constellation of Canis Minor, the small dog, and the eighth brightest star in our sky. Not that it's a big and impressive star as such, but its relative brightness merely originates in its proximity. At a distance of only 11.4 light-years, Procyon is the 14th closest star to our Solar System. Let's say it lies right under our doorstep, in astronomical terms. For the rest it's nothing out of the ordinary, with a mass s.5 times that of our Sun and a diameter twice as big. It also boasts a solar-like corona which it heats up to 1.6 million °C. Procyon's much younger than our Sun though, but after 1.7 billion years it has already depleted its entire hydrogen supply and fusion has started to expand outside of its nucleus. It's preparing to evolve into a much bigger, helium-fusing red giant, which will happen in the next 10 to 100 million years.

Nothing out of the ordinary, you'd say. Yet, this inconspicuous, bright star hides a little secret. It had already been suspected in the early 19th century due to irregularities in the star's proper motion, but it was not confirmed visually until 1896. Procyon is indeed double, the main star orbited by a tiny companion that's extremely difficult to observe. Procyon B lies 4.3 arc-seconds from Procyon A, which should be doable also in small telescopes, but the problem is that A shines 15,000 times more brightly than B and therefore the little one disappears into A's glare. Even with my binoscope I had a really hard time separating the two and I had to wait for that moment of perfect seeing to detect the companion, as I've tried to reflect in my sketch.  

B revolves around A in a highly eccentric orbit which takes it as close as 9 AU (Astronomical Unit - the distance between the Earth and the Sun) and as far as 21 AU over a 40-year period. It's a white dwarf only 30% larger than the Earth but contains 60% of the Sun's mass. Its average density is therefore a whopping two tonnes per cubic inch! Scientists believe that B was once bigger and hotter than A and therefore it evolved a lot faster. When it got older, it evaporated much of its mass onto A, which gradually became the dominant star in the system. We find that A is indeed quite rich in heavier elements, byproducts of advanced nuclear fusion in B. 

No evidence for planets has been found to date and even if there were, they would probably not be suitable to sustain life due to the distortion and radiation of this extreme double star system. However, a large ring of dust has been detected. 

PS: The image doesn't show well in Blogger, but B lies slightly to the bottom-right of A...

Monday, 15 January 2018

Jonckheere 320: Off the beaten path again

Most amateur astronomers prefer to stick to the well-known Messier and NGC catalogues when preparing their observation night as the more exotic ones like Minkowski, Kohoutek, Berkeley and the likes have the reputation of being too difficult for basic, amateur instruments. Nothing, however, could be further from the truth. Yes, there are some pretty invisible objects in those catalogues which even in my big binoscope refuse to reveal themselves. On the other hand, some of these more exotic objects turn out to be surprisingly easy.

Take Jonckheere 320 (J320), for example. It's a small planetary nebula in Orion, almost halfway between Bellatrix and Aldebaran. Actually, it's so small that it was originally mistaken for a double star and it takes as much magnification as circumstances allow you to bring out the details. But searching with an OIII filter will surely make it stand out against the background and I didn't have any difficulties at all finding it. When you then push telescope power to the max, you'll notice that this little gem has a lot of interesting detail on offer. 

Its bright central area boasts a lot of filaments and structures, as is typical for a young planetary nebula in full expansion. I even managed to get a glimpse of its "ansae", puffs of hot gas that are ejected from the central star's poles at the incredible speed of 43km/s. The central area itself rotates at 13km/s which is surprisingly fast. Usually stars tend to rotate slower as they grow older, but in this case the dying star's still driving the surrounding nebula into a fast spin. 

Unfortunately, the central star itself was invisible to me, but this has probably everything to do with its great distance. Measurements differ greatly, as is usually the case with nebulous objects, but 15.000 light-years seems to be the more popular value. This obviously also explains why it appears so small to us. And yet... being so far away and still shining so (reasonably) brightly in our sky... this planetary must really be something extraordinary.

Wednesday, 10 January 2018

The Horsehead

Few objects stimulate the imagination as much as the famous Horsehead Nebula (B33 in technical terms). Its suggestive shape has amazed people ever since its discovery in 1888 and it's become one of the most photographed objects in the sky. Unfortunately, to us, humble visual observers, this extraordinary patch of dust is a daunting target. Yes, I've read all of the reports that say that it was "easy to see in a C8" and I've even seen sketches, observed through a 6" without filters (!), that show it in all of its glory (and almost in 3D-Technicolor too). But are they trustworthy? No, unfortunately not. 

Sometimes, we visual astronomers behave like fishermen who claim to have caught a five-foot sardine. It's not just about showing off, but we also want to convince ourselves that we've really seen a very difficult object, even though it was on the border of visible, or sometimes beyond. Who can blame us? Often we spend many hours trying to find it, peering through that tiny little hole of our telescope's eyepiece until our other eyelid's sore of keeping it shut, our whole body's shivering because of the biting cold, our limbs numb, our noses dripping, our foreheads frosted, our brains begging us to go back indoors and preferably to sleep. Yet, we persevere because we want to find that particular object. It's like a trophy we desperately want to hang on the wall. 

In the case of our beloved Horsehead, which is so incredibly faint that it was hardly visible through my 18" binoscope, things tend to get a little out of hand. A H-Beta filter helps a lot to bring it out and makes this nebula accessible to smaller scopes under dark skies, but don't expect miracles. Given that a pair of these filters'd cost me €400 and that they're only useful on a handful of objects, I preferred to try and find it without. And with success, although it remained extremely faint as I've tried to reflect in my sketch. The background nebulosity, scarcely illuminated by the embedded newborn stars was hardly apparent as a somewhat lighter half of the field of view, compared to the darker left half. Something that struck me much more was the almost total absence of little background stars in that left half. Obviously, the light of background stars is completely blocked by the enormous cloud of dark dust that cuts through the field of view and of which the Horsehead is just a bulge sticking out. Fortunately for us, this peculiar bulge drifts in front of the delicate bright nebula behind it (IC434) and therefore becomes "easily" visible. Well, let's say that I've seen it. This whole area, some 1,500 light-years distant, is but a part of the gigantic Orion Molecular Cloud, a vast region in space where a lot of star formation takes place. Also the Orion Nebula is just a part of this complex. 

Much more evident in the same field of view, is a reflection nebula called NGC2023 (bottom-left on my sketch). Being over 4 light-years across, it's actually one of the largest reflection nebulae in our sky, brightly illuminated by the young and extremely hot giant star that lies within it.