Monday, 25 June 2018

Saturn revisited

I rarely sketch the Moon or planets. They're terribly demanding objects if you want to capture them properly and all in all I've never been a passionate planetary observer. Perhaps I'm still influenced by my childhood, when I passed many happy Saturday mornings (and nights) at the Urania observatory near Antwerp, Belgium. After a one-year introductory course we got to choose between the various working groups in order to participate in miscellaneous projects under the supervision of the group leaders. These groups were i.a. Solar System, Comets and Meteors, Weather, Photography and during my final year there was even a Maths Group! Can you believe it? 14-15 year old kids that go to the observatory on a free Saturday to study Math! Hardly surprising they only had two members.

Without a minute's hesitation I chose Deep Sky, the group that focused on everything beyond our solar system. It was by far the most popular group and it also had the funniest and most popular leaders. There used to be some sort of playful rivalry between the groups and especially Deep Sky became increasingly notorious for havoc and disaster. We disturbed a funeral whilst measuring the speed of sound (because the guys making the sound pulses simply didn't realise what was going on at the church at the other side of the car park), we broke down a three-dimensional model of dozens of stars of Ursa Major which had taken others months to assemble (it was an accident, I swear) and someone had mistaken the weather group's rain gauge for a urinal (it looked exactly the same anyway). Later, when leadership of the Deep Sky group passed on to me, this didn't improve at all and on many occasions we touched the very limit of what the others considered bearable. That being said, in spite of being noisy and a bit out of control, no-one can deny that eventually we were the most productive and passionate group of them all. In the era before Internet and mobile phones we had organised a telephone chain and minutes after I had given the alert we were all on our way to the observatory to do an all-nighter of serious deep-sky with the good old (and very awkward) 25cm Kutter telescope. We laughed and we cheered and we booed at the other groups, we went to the chip shop at 1 and to the baker's at 4 (for oven-fresh buns - you had to see the baker's face when we entered his workshop at this rather unusual hour) and we watched the sun go up from the telescope tower's balcony (and we watched the neighbours opening the curtains of their bedrooms in peejays... and closing them again right away). But in the end we all went home with a map full of new drawings and dreams of the many sparkling or faint objects we had observed. We became a bunch of eternal friends and we took the oath of Deep Sky forever. 

Unfortunately, it was not to be. Tension between the various groups escalated into a serious conflict and after 5 years of dedicated leadership I was given the sack. It's something that I still feel bad about, although I must admit that my autistic nature didn't provide me with the maturity to run the group properly. On the other hand I daresay that Deep Sky had become so popular, especially under my leadership, that I had to manage twenty kids whereas the other groups hardly had any members left. Perhaps because children need some time off during the weekends and prefer doing astronomy in a playful way, not in detention? Yet, even if all of this hadn't happened, I realise now that nothing can last forever and eventually even I, the perpetual, curious, autistic kid, had to grow up. 

The disdain for the Moon and planets's still a bit there though. :-)


And with labels...

 

Friday, 22 June 2018

M80 - Out of the shadow

M80 is a globular that's sadly neglected because of the vicinity of predominant M4, which seems so much bigger and brighter. Yet, it's about time that we change all that because M80's a true marvel to behold. 

Actually, M4 only seems much more impressive because hovering at only 7,200 light-years away it's one of the closest globular clusters to our Solar System. In reality, M80's nearly fifty percent bigger and brighter and it still is an impressive sight, even from its more than 32,000 light-years' distance. Containing several hundreds of thousands of stars in a sphere not even one hundred light-years across, it's one of the most densely populated clusters. Yet I had absolutely no problem resolving it completely and I noticed a myriad of lovely star chains and structures. It also appeared even more bluish than most of its kin. I can only speculate that, due to its density, star atmospheres get blown away even more easily through interaction with other stars, exposing the hot, white-blue interior of the otherwise very old stars. As you may recall, globular clusters are among the oldest entities in the universe, often older than the galaxy they accompany. Another explanation is that this particular cluster contains an exceptionally high number of so-called "blue stragglers", very young stars that have been captured by the cluster. 

So next time you point your telescopes at Scorpio, please don't forget this little jewel.


Monday, 18 June 2018

NGC6567: a planetary in full expansion

Young planetary nebulae are not always easy to find because of their tiny size they usually resemble an ordinary star at low telescope power. Yet, with the aid of a nebula filter - UHC or OIII, which blocks all light frequencies apart from those predominantly radiated by these nebulae - they easily stand out as a bright and somewhat fat star against the dark background. If you then increase magnification to as much as your telescope or sky conditions allow, you'll often be surprised. Due to their high surface brightness they let you use extreme high power and not seldom show some extraordinary detail.

Take this little bugger, for example. NGC6567 lies some 4,000 light-years away from us in the direction of the marvelous Sagittarius Stellar Cloud. It gets lost somewhat in the extremely rich star field of the centre of our galaxy, but with the aforementioned method you'll still be able to find it without too many difficulties. At 507x it becomes obvious that this is a planetary nebula and not a star. What's more, its bright inner ring, an enormous bubble of ionised gas that the dying star's expelled some 4,000 years ago, just leapt out at me. This bright bubble's currently expanding at 13km/s, which is not exceptionally high. Yet without any doubt this nebula will become much more spectacular in the course of the following millennia, when it will expand further.

Sunday, 10 June 2018

The Eskimo... again...

In one of my first posts I talked about NGC2392, otherwise known as the Eskimo Nebula for obvious reasons. It does look like a head wrapped in a parka hood, doesn't it? 

This winter, during a very clear (but teeth-chattering cold) night I finally pointed the binoscope at it and pushed power to 507x. There are these moments when an 18" binoscope not just performs on par with high-quality photographs but even outperforms them. This was one of these moments. 

Astronomical sketching is a very subjective form of art and often artistic creativity tends to take the upper hand on true scientific observation. It's a delicate balance because we sketchers want to show the viewer every detail we (think we) have spotted. Observation through a telescope, however, usually resides at the very edge of what a human eye can possibly capture; staring at a faint object for minutes if not hours, direct vision, averted vision, trying to avoid any external interference. Sometimes it gets so bad that the whole image starts dancing in front of our eyes, especially with one-eyed viewing, and we get overwhelmed by fatigue. Therefore it's generally so hard to tell whether certain details were really observed or merely intuitively suggested. 

Then there's the question of how you want to represent these faintest of details. If you draw them clearly, the image easily gets "overdone" and albeit artistically pleasing and massively impressive, you can't really state that that's exactly how you've seen the object at the eyepiece. Any viewer who'd look through a telescope after being wowed by such a drawing would be seriously disappointed. 

Personally, I prefer to draw everything as realistically as possible, even if I have to make some details all but invisible. This may perhaps result in less impressive sketches and I've already read a lot of criticism on my work on-line, like someone claiming that he can see a lot more with his 9,25" SCT. Well, if that's the case, I'm very happy for him. My aim is to give the viewer (hopefully) the same challenge as I had behind the eyepieces. "Can you see it or not?" I don't care if my sketches don't look as fancy as some others. 

Astronomical sketching is not a competition.  

Yet, in the particular case of the Eskimo, I didn't have to hide any details at all because this is exactly how it appeared at first glance.


Friday, 25 May 2018

NGC3242: Jupiter's Ghost

Low on the horizon, for northern observers, during the early spring months... in an otherwise seemingly empty part of the sky you may stumble upon this big and bright planetary nebula. It's popular name "Jupiter's Ghost" refers to its similar apparent size and shape compared to the biggest planet of our solar system. In reality this nebula is some two light-years across and is still in full expansion. It merely appears the size of Jupiter because it is 1,400 light-years away.

The bright inner halo, the central star's dying breath, was blown into space some 1,500 years ago and is now rapidly catching up with the large outer shell which gradually built up during the final phase of the star's life. It's central star of 11th magnitude was not that easy to see, although it's radiating at over 150,000°C and lighting up the gas bubble around it. The gas is heated up to the extent that it begins to ionise and emit a bluish-green light of its own. Actually, we're catching this nebula right at its brightest phase. Within the next couple of thousand years it will expand further, fade and eventually dissolve into space.


Thursday, 17 May 2018

NGC5005: Black holes lead to star formation?

Yes, I know, it's a bit of a strange title for this post. Let's have a close look at NGC5005, a galaxy that's not in our immediate vicinity (estimates vary greatly from 45 to 113 million light-years, with an average of 65). It's a fairly bright galaxy in Canes Venatici, the hunting dogs, which can be seen quite easily with a modest telescope. 

Through the binos at 285x, it revealed a wonderful amount of detail, such as the darker arc on the left. But what we're really interested in, is its nucleus. Spectroscopic analysis revealed that the heart of this galaxy contains a lot of non or weakly ionised atoms, such as O, O+, N+, and S+. Scientists classify galaxies with such a cloud of weak ions in their core LINERs, which stands for "Low-Ionisation Nuclear Emission". This is nothing unusual and as it appears up to a third of all galaxies could fall under this category. The question however, is what causes this enormous cloud, which may swirl inward up to 750km/s! Scientists are still heavily debating on that, but significant x-ray emissions in the case of NGC5005 seem to confirm a super-massive black hole in its centre. Another observation that we make, is that this ion cloud produces some serious star formation. Usually not a lot of stars are formed in the nucleus of a galaxy, which therefore contains an older star population, and most starburst activity is generally concentrated in billowing spiral arms. 

So may we conclude that a black hole can be so powerful as to cloak itself with a cloud of ionised gas in which thousands of new stars are born? 




Thursday, 3 May 2018

Frosty Leo... again

I've already written about this highly unusual planetary nebula in construction two years ago and will repeat most of this post here, to give you some background information on IRAS 09371 + 1212, or in other words "Frosty Leo". 

When I made my first observation, I was unfortunately limited to 200x, which is far from sufficient if you want to see some detail in this tiny puff of mostly water crystals. So here's my recent observation with the binoscope and... yes... at 507x details were abundant!


Nature is ruthless. It gives life and make stars sparkle so brightly in our sky that uncountable poets have dedicated their most beautiful work to them. But unfortunately, all beauty must fade and everything that has a beginning also has an end. Even so the seemingly perpetual stars which eventually have to die too. I've repeatedly written about dying stars, either the ones that go fairly quietly through the formation of a planetary nebula, or the ones that grant us the unforgettable spectacle of a supernova explosion. Today, I'd like to show you a star that's literally exhaling its dying breath. We're talking about a so-called protoplanetary nebula, nicknamed "Frosty Leo", and this nickname isn't far-fetched at all as I shall explain. 

When a small to medium-sized star reaches the end of its life cycle, it runs out of fuel to sustain nuclear fusion and becomes highly unstable. Its interior collapses and the shock wave that this causes literally blows the star's atmosphere into space, where it will form large gaseous shells or "bubbles" around the remains of the star. The contraction of the dying star's core will in turn generate so much heat that it will reignite fusion of helium into heavier elements, such as carbon, oxygen and even iron. The star's radiation continues to blow up the "bubble", which eventually dissipates into space, and heat it up to a point where the gas ions start to emit light as well. This is what we call a "planetary nebula". 

In the case of Frosty Leo, however, we're not quite there yet. We're actually witnessing the collapse of the star and the initial expulsion of its atmosphere. Its last breath, as a matter of speaking. At this low magnification it's almost impossible to see, but the star's atmosphere is blown away in two opposite lobes which keep expanding at a rate of a whopping 25km/s. Remember that in order to escape from Earth's gravity a rocket needs an initial velocity of 11,2km/s or 33 times the speed of sound, so imagine how fast the nebula around Frosty Leo is forming!

As I said, the nickname wasn't chosen by chance or after a very successful party because its discoverers had to celebrate their findings. No, the nickname derives from the fact that the nebula consists for a large part of... water-ice grains! Plus of course that it resides in Leo. For the time being it's perhaps the only such nebula that we know of, so this makes it doubly interesting. Another weird fact is that it lies 10,000 light-years away from us and an unusual 3,000 light-years above the galactic plane. Therefore it must have been a very lonely star, condemned to die in complete isolation.

In the next millennia Frosty Leo will keep expanding and eventually the nebula, which currently only reflects the light from the star, will light up, adding another Crystal Ball or Eskimo to our skies. But let's not be impatient. This object is already a great spectacle and much more so from a scientific standpoint. 
 
 

Monday, 30 April 2018

M94: a galaxy that's difficult to explain

In the area of the M51 group of galaxies, but considerably closer to us, at 16 million light-years, lies this little treasure. M94 is definitely one of the most spectacular galaxies in the Messier catalogue, as we see it face-on and also given it's fairly high surface brightness. In larger telescopes it becomes obvious that this isn't just a normal spiral galaxy but that it consists of a bright inner ring (with complex spiral structure), some 50,000 light-years across, and a faint outer halo that extends at least 30,000 light-years beyond that. 

For the time being, scientists are having difficulties finding a plausible explanation for this odd, double-ring shape because both the accretion of a smaller galaxy or interaction with a neighbour don't seem to add up in this case.  What's more, there appears to be very little dark matter present in it. This is very controversial because current models fail to explain how a galaxy could form without a sufficient amount of dark matter.

There's more. At first it was believed that the bright, swirling inner structure was by far the most active region in this galaxy and we do observe some serious star-forming there indeed. Recent IR and UV studies, however, revealed that the outer halo is not an ordinary ring of stars, but a complex structure of spiral arms which is surprisingly active. In fact, there's twice as much star formation going on in this outlying region and also this raises some eyebrows. A possible explanation could be that star formation in the outer halo is simply more efficient.

 

Sunday, 22 April 2018

M63: a spring sunflower

Sunflowers are usually a thing of summer, but there's a very peculiar one that blooms in spring already. Point your telescope, or even your binoculars, under the big dipper's handle and you'll easily find this spectacular galaxy. Number 63 on Messier's list looks very much like a sunflower indeed, with it's bright, yellow core and flocculent spiral arms. Unlike "grand design" spiral galaxies, the spiral arms of M63 appear patchy, like a heap of cotton balls. It was also one of the first galaxies in which a spiral structure was recognised, by Lord Rosse, halfway the 19th century. 

The Sunflower Galaxy lies approximately 37 million light-years away from us and is a part of the M51 galaxy cluster, along with a few smaller ones. 

Physically, the Sunflower is a very active galaxy and every knot is an area of intense star formation. More interestingly, photographs revealed a wide halo around it which materialised most likely after an encounter with a dwarf galaxy, somewhere within the last 5 billion years. From the specific properties of the stars in this halo, scientists believe that this dwarf galaxy might have originated in our own local galaxy group.

Now as for the cherry on the cake: look slightly to the left of our Sunflower and you may spot a tiny smudge. No, it's not an extended part of M63, nor is it an accompanying dwarf galaxy. It's proper motion, a breathtaking 23,500km/sec away from us or almost 8% of light speed, is far too great for it to be anywhere near M63, or within the boundaries of our area of the known Universe. It's a giant galaxy, denominated PGC4018103, three times the diameter of our Milky Way, that lies 1.2 BILLION light-years away from us. As such, it's probably the most distant object I've observed so far. Just imagine... The few photons of this galaxy that I managed to capture with my eyes, left their origin when the first multicellular life-forms emerged in the Precambrian seas.


Tuesday, 17 April 2018

EGB6: Interesting faintness

Yes, I simply love the challenge of spotting extremely faint objects and especially large, frail planetary nebula in the last stage of their existence. As you know, when a star dies, it suddenly expels its outer layers which are subsequently blown away by the violent radiation of the remaining stellar core, the so-called "white dwarf". After many millennia, however, these shells of hot gas grow so large and thin that they start to dissolve in the void of space. This is exactly what we witness here, in this extremely large planetary that was discovered in 1984 by Ellis, Grayson and Bond. Visually this is one of the toughest objects to see and it was not without difficulty that I managed to discern its broken annular shape, with its western rim slightly brighter. Nevertheless it was just a tad easier than PuWe1, which was really on the limit of visibility.

How difficult they may be for us, humble visual amateurs, these extremely old and diffuse planetaries offer a great opportunity for scientific study, more specifically in the way they dissolve into space and how their central star extinguishes. In the case of EGB6, another very interesting discovery was made. Strange infrared emission knots in the spectrum of its central star, pointed to the existence of an obscure companion star, probably a faint red dwarf. Recent observations with the Hubble space telescope, revealed that some of the expelled matter of the central star was captured into an accretion disk around this companion!


Sunday, 8 April 2018

M3: autism power!

I hate sketching globulars. Really, I hate it. The reason for that is obvious... there are simply too many stars to sketch and after hours staring at them through the eyepieces you're overwhelmed with dizziness and a hammering fatigue. You're craving to go to bed and cursing yourself because you stubbornly set out on a job that you knew was going to be impossible from the start. But there you are... half a page filled with stars and still another half to go. Should you give up and let all of those hours of work be in vain? Or should you continue unabatedly, even though you can't think straight anymore and every muscle in your body's throbbing and aching?

In the end it took me almost two nights to sketch all of this, and then almost an entire month behind the pc in order to turn it into a somewhat realistic digital image. So please, don't expect me to do this kind of insane sketch often. 

But perhaps this sketch was appropriate in this time of the year, when we're celebrating autism week, because in a sense this sketch shows what an autistic person is capable of... which extraordinary talents and rock-hard determination may lay hidden under that often absent gaze. 

AUTISM POWER! :-)

About M3, it's one of the brightest globular clusters in the sky, just under the limit of naked-eye visibility. At a distance of 33,900 light-years, it lies beyond the centre of our Milky Way. Only 180 light-years across, it contains some 500,000 stars! Globular clusters are among the oldest entities in our universe, often being older than the galaxy they accompany. Therefore the stars in those clusters are also among the oldest and reddest (coolest). Strangely enough, these globulars appear mostly bright and blue through a telescope. The reason for that is that these stars are packed together so much in such a small volume that their outer layers are often stripped away through tidal interactions, exposing their hot (blue-white) interior. The blue colour I added to many of the stars in my sketch was not observed as such but was added as a random effect to create more depth (a globular truly looks three-dimensional through a binoscope) and to reflect the cluster's brilliance and overall bluish appearance.


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. 

Enjoy!


 

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

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.