Saturday 24 December 2016

Towards the edge of our galaxy

Our galaxy, which we call the Milky Way, is some 100.000 lightyears across. In kilometres, that would be more or less! Our solar system lies in one of its less fashionable parts, in the heart of a spiral arm that's not even worthy the name. Astronomers refer to it as the "Orion Spur", because our part of the Milky Way's most visible in the constellation of Orion and because, as I said, it's not a full-grown spiral arm but a sort of spur in between the Saggitarius and Perseus arms. On the image below you can see an artist's concept of our galaxy and I've highlighted the position of our solar system with a red dot.

With my sketch, I want to take you towards the edge of our galaxy, towards the yellow dot on the map. Because there, 15.000 lightyears away, lies a beautiful open cluster, called NGC1193. It's a fairly difficult object because of its distance, but also because a lot of its light is being blocked by the dust of the large Perseus spiral arm. And yet, there it is... a middle-aged cluster which is slowly falling apart and stars that are beginning to leave the nest in which they were born. 

And with this, I'd like to wish all of you a Merry Christmas and a very Happy New Year. After a year of activity, my blog has grown considerably and that's all thanks to you, my dear, loyal readers. I hope you enjoyed my posts and I can assure you that I'll do my best to do even better next year. All my best wishes to all of you!!!


Thursday 22 December 2016

Stars in another galaxy

Have you ever wondered what the universe would be like in another galaxy? Well, the answer's quite simple: very similar to our own. Of course, every star's different and there are probably planets out there so weird that not even the wildest science-fiction writer could've invented them. But basically the universe's quite the same everywhere. Stars are what they are... big stars, small stars, hot ones and cold ones. Most will die quietly as planetary nebulae, others are so massive that they'll explode as supernovae. But all of them are born in huge hydrogen clouds. I've already shown you many examples of these star-forming regions, such as the famous Swan Nebula and I've even made a video about flying into the Orion Nebula

But let's go back to my previous sketch, the one about the Triangulum Galaxy (M33). On the bottom sketch I've added labels to highlight some of the star forming regions in that other galaxy which are already visible to ordinary amateur telescopes. Each of these bright knots in the galaxy's spiral arms is a nebula complex, similar to the Orion, Swan and other star-forming nebulae. Inside those knots, baby stars are born. 

By far the biggest of these nebulae in the Triangulum Galaxy is the one on the far left, which astronomers refer to as NGC604. Can you believe that this nebula's so big that it's 1.500 lightyears in diameter? That's the distance from the Orion Nebula to Earth! This makes it probably the biggest nebula complex in our entire local group of galaxies! Encouraged by the spectacle I observed at low magnification, I pushed the binoscope to 507x and pointed it at NGC604. What I saw nearly made me tumble on the ground (and I was standing 6 steps up on a ladder). Not only did I see some incredible detail in that nebula (the slant "H" or "M" really stood out), I was able to see individual stars in it! They were impossible to pinpoint exactly - they were so tiny and they seemed to be "dancing" across the nebula - so on my sketch I just put some random dots to give you the idea. But I did see them!

I had always assumed that it was impossible to see individual stars in other galaxies with an amateur telescope because they're simply too far away. The Triangulum Galaxy lies at a distance of 2,8 million lightyears! But I was wrong. It is possible with a sufficiently big telescope and good sky conditions. 

These dots are bright and hot baby stars, much like the trapezium stars in the Orion Nebula. One day planets will form from the debris around them (if that hasn't already happened) and they'll start their journey through their galaxy like our little Sun's flying around our Milky Way's centre. So you see... the universe's pretty much the same everywhere.

Tuesday 20 December 2016

M33 revisited

Almost a year ago I wrote about M33, the famous Triangulum Galaxy. The sketch I presented at the time was observed through my 100mm astronomical binoculars, which is in fact one of the best instruments to use on this object. The galaxy spans an area of almost 4 full moons in our sky, meaning that its light's dispersed over a large area. Therefore it appears very faint and doesn't support high magnifications well. An ordinary pair of binoculars, on the other hand, has a relatively low magnification compared to the combined aperture of its lenses and will show the galaxy as a small but reasonably bright smudge. Remember what I told you about magnification! Suppose the total amount of light a telescope can capture of an object is one of these mini jars of jam you get in a hotel. When you spread the jam on one slice of bread (small surface - low magnification), you will taste the jam quite well. But when you spread it on a whole loaf (large surface -  high magnification), its taste will hardly be noticeable. 

A telescope often struggles with these large and extremely faint objects and with good reason too. The main job of a telescope is not to magnify, as many people think, but to capture as much light as possible, concentrate it and let it all fit into your eye. The bigger the lens or mirror of a telescope, the more light it can capture and the better you'll see the object. But... every telescope also has a minimum magnification which is directly related to the size of its lens or mirror. If you go lower, not all of the light that the telescope captures will enter your eye anymore because its "exit pupil" will be too large. The "exit pupil" is the little image disk that comes out of the telescope and which you can observe. If this disk's larger that the pupil of your eye, some of its light will be lost and this would be the same as looking through a smaller telescope. If we suppose that the pupil of a young person can open up to 7mm in the total dark, a telescope with an 18" mirror has a minimum magnification of 65x. Below that, the "exit pupil" will be larger than 7mm and hence be larger than the pupil of your eye. An 8" telescope, on the other hand, can go as low as 28x, or 2,3 times less than the 18" telescope. At 28x the object will appear 2,3x smaller but also 2,3x brighter than at 65x. Of course, an 18" telescope gathers 5 times more light than an 8" telescope so it still holds the advantage over its smaller brother. 

Now let's talk about a binoscope. In theory, its combined optical tubes gather as much light as a telescope of 1,41 times its diameter. An 8" binoscope therefore has the same performance as an 11,3" monocular telescope. But... with the 8" binoscope you can go as low as 28x, whereas the 11,3" telescope has a minimum magnification of 41x! This is one of the biggest advantages of the binoscope: the same light gathering power and optical resolution as a much bigger monocular telescope, but with a much lower minimum magnification. 

If you want to know what this means for our large and faint galaxy, here's my sketch of M33 through my 18" binoscope:

Not only did I see the spiral arms in a way that I've never seen before, many bright star forming regions in the galaxy really stood out. Here's the sketch with labels:

In my next blog post I'll take you a bit closer...

Thursday 15 December 2016

Bethlehem's star

Some time ago someone asked me what the actual star was that appeared at Jesus' birth. It's a question that has occupied the minds of many scholars and religious leaders over the last millennia because when you go back to the period of Jesus' birth, let's say from 10 to 1 BC, you come to the conclusion that nothing interesting at all happened from an astronomical viewpoint.

Some say that it was a comet, but for as far as we know there were no bright comets in that period. Perhaps there was a one-off bright comet - certainly not all of them have regular orbits - but its appearance hasn't been recorded by anyone. 

Some argue that it was a supernova explosion, but this is impossible because these explosions always leave a visible trace in the sky

During the last 50 years, there have been ever more claims that the star wasn't a real star at all but in fact an unusual position of one or the other planet in one or the other zodiac sign. These claims are again very unlikely because they're always based on greek astrology - which is unfortunately still being used today - whereas the magi or 3 kings came from Persia. Just for your information, babylonian and persian astrology was completely different from its greek counterpart and was based on a system of 17 or 18 zodiac signs. This means that all of these planet-zodiac theories are based on the wrong information.

But there's an even bigger mystery that none of the above possibilities can explain, i.e. how it was possible that the 3 kings who came from the east and who followed a star in the east could still end up in Bethlehem, in the west?!

The answer has only been discovered recently, in the 1980's if I'm not mistaking, and it's actually very simple. In order to explain it in a way that everybody can understand, I've created this small video. 

Enjoy and... Merry Christmas!!!


Friday 9 December 2016

A little butterfly

You may recall my blog post on the famous Ring Nebula (M57), in which I explained that this nebula's not a ring at all but a cylinder that we coincidentally see face-on. Today I'd like to present a very similar planetary nebula, but one that we see edge-on: M76 or the "Little Dumbbell", due to its resemblance to the much bigger and brighter Dumbbell nebula (M27). Personally I prefer to call it the little butterfly for obvious reasons.

On my sketch you can clearly see the bright central cylinder or the body of our butterfly The axis of the cylinder coincides with the rotational axis of our dying central star (which I couldn't identify during my observation). As I've explained before, the star's rotation causes an accumulation of matter along its equator, making it more difficult for the hot gas to escape from there. That's why many planetary nebulae have an elongated inner structure, or in extreme cases such as this become cylinders. 

The butterfly's wings on the other hand were formed much earlier, probably when our star was still a red giant that was running out of fuel and became unstable. It began to expand, cooled down, contracted under its own gravity, heated up and expanded again, blowing out large quantities of gas in the process. A good example of a star in this phase, ableit ten times more massive, is Betelgeuse. Eventually the star collapsed, expelling what remained of its atmosphere into space (the central cylinder). 

It's one of Messier's faintest objects but still surprisingly easy to observe, also in small telescopes (which may not reveal the "wings"). To my personal taste it's also one of the most beautiful planetary nebulae and every autumn night when I'm out under the stars I pay it a visit. It lies some 2.500 lightyears away from us and is headed towards us at 19km/s.

Monday 5 December 2016

The flying ghost galaxy

Those who've been following my blog have already been testimonies to many dramatic events that happen in the Universe around us. I've shown you the birth and the death of stars, supernova explosions and galaxies that have been ripped apart by unimaginably strong tidal forces. Today, I'd like to share a sketch of another incredible event: two galaxies that are crashing into each other!

NGC520, or popularly named the "flying ghost galaxy", is an object that's within reach of small telescopes under a dark sky. Right from first glance you'll notice that something's not quite right with it. It doesn't look like an ordinary galaxy at all, with a clear nucleus and spiral structure around it. A larger aperture telescope reveals the true nature of the cataclysm that started some 300 million years ago and that's now reached its most spectacular stage. Two nearby galaxies were attracted so much to one another by their mutual gravitational forces that they collided. However, you shouldn't think of this as the collision of two cars in a big fire ball. Given the enormous distances between the individual stars in a galaxy, it's highly unlikely that, when two galaxies meet, their stars will crash into each other. They'll simply fill the void and in the end the two galaxies will merge into a new and much bigger one. That being said, the tidal forces that these crashing galaxies generate, will seriously stir up the new entity and in turn this will lead to a burst of new star formation. 

Think of a galaxy as a cup of coffee with milk. Older galaxies that don't interact with others stop moving and become plain... the coffee being brown and uninteresting. Star formation comes to a halt. In younger galaxies - imagine these as coffee to which you've just added the milk - the gas clouds swirl and contract in the gravitational vortices, leading to the formation of many new stars. In the particular case of our flying ghost galaxy, the collision has added fresh milk and the gravitational pull is giving the whole a really good stir. Expect to see an explosion of new star births there!

The collision of galaxies is certainly not a unique event. Actually, in about 3,75 billion years the nearby Andromeda Galaxy is going to crash into ours! Our Sun will almost have reached the end of its life by then and honestly I don't think there will still be humans around to witness it, but as I explained, it won't be the end. It will be a new beginning.

Friday 2 December 2016

Street lights are destroying our lives

I've already written a lot about street lights and the adverse effect they have on our lives. I've even published a video to demonstrate that they actually reduce road safety instead of increasing it and that they make life a lot easier for burglars. Recent studies have also demonstrated a direct link between street lights and cancer! In spite of all this, tax payers around the world are still willing to cough up billions of €/$ to keep them burning.

But so far I haven't mentioned the biggest damage they cause to our planet yet, and with good reason too because most people couldn't be bothered less. I'm referring to the devastating effect street lights have on the greatest spectacle of our planet, the greatest work of art that any man has ever beheld: the night's sky. 

Most people have never really looked up. They're so busy with their own little lives, making as much money as possible, gathering a million likes on Facebook and commenting on the painfully stupid but yet incredibly important cows in the reality shows, that they seem to forget that their lives actually mean nothing at all. What is Earth anyway? A planet so insignificantly small that it would already completely disappear in the Sun's glow to an observer on Uranus. And our Sun's such an amazingly insignificant little star that it would not be visible to the naked eye anymore from a distance of merely 50 lightyears. That's hardly the doorstep to our backyard! 

Only those fortunate enough to have visited one of the ever rarer really dark places on Earth, a remote desert for example, realise what we've been missing over the last 60 years. Take a plane to Arizona, Namibia, the Sahara or Central Australia and you'll know what I'm talking about. It would be a useful lesson in humbleness that all of us should take. Just look at that incredible blanket of millions of stars and our Milky Way that shines down upon you like a bright string of clouds from horizon to horizon and you'll know that I was right.   

To show you the damage street lights have caused to our night's sky, I'm proud to present the work of Martijn, a Dutch astronomy friend and a highly talented artist. He made this series of 4 sketches of the Andromeda galaxy, the closest galaxy to our own, from 4 different locations. The first from his home town and a full Moon, the second from his home town without Moon, the third from a nearby somewhat darker location and the last from a place that we astronomers call "decent" (but far from perfect). What a difference, isn't it? Isn't it about time we switch those useless light off?



Wednesday 30 November 2016

Flying over the Moon...

I hate sketching the Moon. The reason for it is that it's too darn complicated. When you point any telescope at the Moon, be it a supermarket model or the biggest and most expensive gun on the market, be it at low or high magnification, you get so overwhelmed by the millions of details that it's easy to lose courage. Most Moon sketchers therefore stick to one or two craters at the time, even though there's so much more to see in the telescope's view. But unfortunately I can't do that. I always try to represent as accurately as possible what it was that I saw through my telescope and therefore it's such a pity to sketch only a detail and leave out all the rest. 

But a couple of weeks ago I got all of my determination and patience together and spent 3 hours behind the telescope to produce this sketch. Plus the bigger part of the following weeks to work it all out on the PC until I felt reasonably satisfied. There are still a couple of errors on it and some things still don't seem exactly right to me, but one day you just have to let go and publish. So here it is. I hope that you enjoy it.

The subject of my sketch is the area near the famous Ptolemaeus crater (bottom). With a diameter of 153km it's a very big one. The lava-flooded floor's surrounded by walls up to 2.900m high and is scattered with tiny impact craters, two of which were easily visible. To the south (up on my drawing) lies the slightly younger Alphonsus crater. It still features this typical central peak and its debris-covered surface is cut by a network of rilles. Further north (top of the sketch) lies Arzachel, relatively young and intact. Its prominent central peak rises 1.500m above the crater floor and its sharp wall are up to 3.600m high! These craters form the eastern border of Mare Nubium, the southern sea of clouds, which at the time of sketching was still awaiting dawn. On the right lies the ancient Albategnius crater with its eroded and heavily bombarded cliffs, which surprisingly still rise up to 4.000m above the crater's floor. 


Monday 21 November 2016

It happened on the 4th of July 1054

No, not Independence Day! The Vikings had only just arrived in Newfoundland, let alone Columbus or Mayflower settlers. On this particular day chinese astronomers recorded the appearance of an unusually bright star in the sky. It was five times brighter than Venus and remained clearly visible even during daylight for 23 days. It then continued to remain visible to the naked eye at night for another two years. The carefully compiled chinese records are confirmed by later Japanese and Arab documents and it was also portrayed by the Pueblos and Mayas and accounts of it are still being told in Aboriginal legends. 

Strangely enough, no trace of this mysterious new star can be found in contemporary European literature, apart from some unreliable sources dated many centuries later. However, we have to consider that Europe was going through a period of disaster. Edward the Confessor's reign over England was weakened by internal struggles and local barons incessantly conspired to seize more power. Holy Roman emperor Henry III was constantly on the war path against the Hungarians, Flemings and Poles, neglecting his German homeland that lay in ruin. The Normans conducted violent raids against Byzantium. Only months earlier Pope Leo IX had excommunicated the Patriarch of Constantinople, bringing about the great schism between the Catholic and Orthodox churces, and had died soon afterwards, leaving also Rome in turmoil. 

The most likely reason why it wasn't mentioned is that many people in Europe must've believed that the star announced the end of the world. In the early Middle Ages it was generally thought that the universe had been created to last for 6.000 years (1.000 for every day of creation), 5.000 of which had already passed by the time Jesus was born. So anyone living in Europe around the year 1.000 would not have felt very much at ease and the sudden appearance of that new star must've struck many people with terrible fear.

But two years later the star had gone, seemingly without leaving a trace, and business in Europe and the rest of the world was still as usual. It was not until 1921 that scientists lay the connection between a strange nebula, discovered in 1731, and the events described in the chinese chronicles. This nebula, M1 or popularly nicknamed the Crab Nebula, happens to be the home of the strongest X-ray source that we observe in our sky: the Crab Nebula's pulsating radio star, or pulsar. It is what remains of a star so violently compressed by a supernova explosion that it's become a tiny but heavy ball of neutrons that rotates at a very high speed. Pulsars have an extremely powerful magnetic field and emit radiation in a beam not necessarily aligned with their rotation axis. This means that we observe regular radiation "pulses" that come from those stars according to their rotation speed. To put it simple, they're oversized lighthouses. In the case of our Crab Pulsar, the lighthouse shines in our direction 30,2 times per second. Now that's fast, isn't it? The nebula which hides the pulsar to visual observers is all the rest of our exploded giant star and over time scientists have been able to measure a significant increase in size. Not surprising since the supernova blast expelled the star's atmosphere at an incredible 20.000km per second (!) and even today it keeps expanding at 1.400km/s. Given time, the still fairly young and compact Crab Nebula will be ripped apart and dissipate into space, just like the Veil Nebula which is a remnant of a supernova that happened some 5.000 years earlier and of which only delicate filaments of gas can still be observed. Considering its respectable distance of more than 6.000 lightyears, the Crab Nebula is still one of the brightest planetary nebulae in the sky. Imagine what an explosion it must have been!

Wednesday 16 November 2016

Has anyone ever seen a black hole?

The answer is yes. Actually, there are black holes out there that anyone can see and you don't even need a gigantic telescope for it. Surprising, isn't it? Aren't black holes supposed to swallow all matter that comes too close and aren't they supposed to be so massive that even light can't escape from them? Yes, of course, but the interesting bit happens just before the matter disappears in the apparently bottomless, black void. 

Imagine this incredible black hole, a sort of cosmic whirlpool that attracts anything unfortunate enough to come too close. Entire stars are being ripped apart by its unequalled gravitational pull and form dense clouds of matter around the hole before being absorbed. Pressure increases up to a point that the highly compressed gas begins to emit vast quantities of radiation in all frequencies of the electromagnetic spectrum, also in visible light; radiation that only just manages to escape from the boundaries of the black hole. So if we want to find a black hole, you don't have to look for a black spot in space but for an unusually bright spot! A spot so bright that, even though perhaps only a thousand lightyears across, it emits so much light and other radiation as an entire galaxy! 

Now have a look at my sketch. The object in question is M77, a very large barred-spiral galaxy, nearly twice the diameter of our Milky Way. You can clearly see its spiral structure and the bar-like structure at its centre's more than obvious. I was also thrilled to be able to make out the extremely faint halo that surrounds it and which also consists of many billions of stars. But the most interesting part is its core. Look how small and bright it is! It alsmost looked stellar through my telescope! This is what scientists call an Active Galactic Nucleus;  an extremely compact core because of the accretion of vast quantities of matter by the supermassive black hole at its centre, which possibly contains a mass of 15 million suns. These "AGNs" are the most luminous objects in the entire universe and this particular one's probably the closest to Earth, being at a distance of merely 47 million lightyears. These days scientists believe that every galaxy has a black hole in its core which acts like the gravitational engine that makes it swirl, grow, create stars and hence create life. But this one must definitely be one of the biggest in our backyard. Get your telescope out and have a look at it too!


Friday 11 November 2016

Taking a spaceship deep into the Orion Nebula

I've already posted about the bewildering Orion Nebula (M42) here and here. So far we've remained at a respectable distance. Now buckle up because I'm going to take you on a wild roller coaster ride deep into the heart of the nebula. 

It's a beautiful night with a highly transparent mountain sky. My 18" binoscope's set. Magnification's 507x. Put your eyes against the widefield lenses. You feel as if you're falling into them... ever deeper... breakneck speed... you're dazzled... all around you are bluish clouds of hot gas... filaments that are reaching out at you... an amazing sensation of depth overwhelms you... stars lie embedded everywhere in the nebula and shine like street lights through the mist... so many bright little spots... so many newborn suns, nurtured by the giant cloud until they're old enough to be expelled and start their journey through space... every single one of them will probably form planets, dreams of the future in this currently violent and deadly corner of our universe... the radiation from all of these young and hot stars is scorching... hydrogen and oxygen reach high states of excitation and glow in the absolute dark... they glow so much that at a distance of 1.300 lightyears this cloud can still be seen quite easily with the naked eye... lanes of dark dust are drifting by, absorbing light as in an autumn sunset...

And there are you, a tiny little person, an insignificant insect in the middle of this nebula that's 24 lightyears across. You could send a text message from one end to the other and you'd only get a reply 48 years later! Still, some people believe that they're the most important part of this universe. Astronomy would be the best cure for them.

Wednesday 9 November 2016

One peanut for the price of two

When William Herschel discovered this planetary nebula back in 1785, he saw two separate lobes and believed them to be two separate objects that were so close that they seemed to run into one another. That's why a century or so later this nebula received two different ID numbers: NGC2371 and NGC2372. But today of course we know that it's just one single planetary that's arrived at the point where it starts breaking up. 

The thin shells of hot gas, remnants of the dying star's atmosphere, have been blown so far away - 1,3 lightyears to be precise - that they are splitting in two half spheres before disintegrating further. The central star has reached its maximum temperature of 118.000°C and will soon start to fade. Difficult to see through the telescope were the two "ansae", plumes of gas that  blew out of the star's polar regions where the atmosphere's less thick and that now form ethereal "clouds" at the astonishing distance of 3 lightyears from the central star (above and below on my sketch). Remember that the nearest star to Earth lies at a distance of 4,25 lightyears so you get a good idea of how far these ansae have wandered off from their origin. It's interesting to compare them to the ansae of the much younger and more active Saturn Nebula, which are clearly still plumes that are escaping from the polar chimneys. It's a bit like the smoke from a steam train that blows out in a puff and when the pressure's released leaves a dark cloud in the sky that quickly evaporates. In the case of our "Peanut Nebula", the clouds are almost gone. 

I absolutely had to share this object with you because it's an often neglected gem in the winter constellation of Gemini. With the nearby and famous Eskimo Nebula which attracts most of the spotlights, the little and somewhat obscure Peanut hardly receives any attention. Shame on us astronomers!  


Wednesday 26 October 2016

Some incredible lunar sketches

There are a lot of sketching colleagues to whom I bear the utmost respect. Today I'd like to present two of them who're creating lunar sketches so real that you get the impression that you're flying over the Moon's surface in an Apollo lander. 

On the sketch below, my American friend Randolph chose to draw the western part of Mare Nubium, the "Sea of Clouds". On top lies Bullialdus, with its diameter of 61km a medium-sized impact crater which stands out even more because it lies in an isolated and featureless area. Its wall rise more than 2.500m above the plains that surround it whereas its crater floor sinks almost 1.500m below them, apart from the central mountains which reach 1.000m above the floor. On the sketch you can clearly see the well-preserved terraces of the inner ramparts. Below the sketch's centre lies a much older crater, called Kies. It's a bit smaller - 44km across - and its floor's completely covered with solid lava, leaving only remnants of the original rim that stick out above the lunar surface. Near the bottom you can see the Mercator promontory which form the southern edge of the "sea". Interesting to note are the bright "scars" between the two main craters and east of Kies. Those are rays of the famous Tycho crater, which lies some 400km more to the south. This particular crater's very young, well... only 108 million years old... and the dust and debris that blew up when a crashing asteroid created it, spread some 1.500km across the lunar surface. These rays are still quite evident as you can also see here.

A second sketch that I'd like to present was made by Giovanni, a dear Italian friend of mine. He chose to represent crater Marius at dawn. The best times to observe the Moon are when it's crescent or waning because the rising or setting sun casts long shadows behind the mountains and crater walls, as you can see here. Also Marius is quite isolated, at the heart of the vast Oceanus Procellarum ("Ocean of Storms") and, just like Kies, its floor (41km in diameter) is completely flooded by basaltic lava. The hills in its vicinity, however, are even older and have a volcanic origin, rather than being debris of an asteroid impact. Recently a Japanese probe discovered a large cave skylight in one of these hills that goes 90m deep. This could be a favourable spot for future lunar colonisation. 

You can see much more of Giovanni's incredible work on his blog here!

Monday 24 October 2016

How to make astronomical sketches - Part 06

Hello all!

Here's the sixth episode of my video tutorial about astronomical sketching: creating a realistic nebula. I hope that you enjoy it!

Tuesday 18 October 2016

We all have to start somewhere

When rummaging in some old boxes I came across a plastic folder containing my very first astronomical sketches. Back in 1983 I was still a kid but incredibly passionate about the stars, as is obvious from the sketch and the many details I added about the observation. Do you want to know how I made it? You're going to laugh... :-) First, I drew a black disk with india ink for the field of view of my little 60mm refractor with 20mm Kellner eyepiece. By the way, can you believe that I was incredibly proud of that eyepiece at the time? For those of you who don't know anything about telescope eyepieces... suffice to say it equals staring through a small keyhole and these days such an eyepiece would only be used as a doorstop. The object was M13, a globular cluster somewhat bigger than M15, which in my first telescope looked exactly like how I've drawn it: a dull, greyish blob. But... now we come to the real masterpiece: the three stars I chose to portray as well. I painted those with the only bright white substance I could lay my hands on... corrector fluid! Let's say that at times emerging artists have to improvise. :-) 

Browsing through the dozen or so sketches I made this way, brought back fond memories of innocent days and unstoppable dedication to the discovery of astronomy. We should never lose this passion because, although seemingly childish and therefore too often neglected, it will push us to new heights. It's the spirit that drove an extraordinary genius like Bach to write the St. Matthew Passion or Leonardo da Vinci to paint the Mona Lisa. It will also drive you to achieve new goals which you'll be so proud of afterwards, just like I'm proud of my latest sketches, yet convinced that I can do even better next time. I'm not a genius at all. Heck, I'm just an ordinary guy making ordinary sketches that you too can make just as well, as I'm demonstrating with my video series. But nonetheless the satisfaction's equally strong as if you'd created the greatest of all masterpieces.


Friday 14 October 2016

Beauty lies in the details

Of course, during a public star party everybody wants to see big and spectacular things such as the Moon, the planets, sizzling globular clusters or large and complex nebulae like the one in Orion. If I then show a small but fascinating planetary nebula, such as the Blue Flash, people start to become a bit bored and say: "Nice, but can't you show us something interesting"? This is of course perfectly understandable because most people who've never looked through a telescope don't really know what to look for and, more importantly, how to look. Therefore they fail to see all the tiny detail that you can see on the sketch of the Blue Flash; the lovely, frail filaments of gas which contain the spirit of a star that's just died. If I then turn my telescope to an incredibly distant galaxy such as the one here, NGC6906, they'll simply leave in disappointment and try their luck at someone else's telescope. 

But next time, don't run off so quickly. Take your time. Absorb what's in the field of view. Relax. Let it talk to you. You'd be amazed how much there actually is to see here apart from the "incredibly faint blob" which you see at first glance. First, look at this galaxy's nucleus. It isn't simply round, but has this bar-like structure running through it (click here for explanation). Then look at the spiral arms. There are at least four of them which are clearly visible, two above and two below the nucleus. They're deliciously thin and razor-sharp, don't you agree? Now I'll add some figures. This galaxy's twice as large as our Milky Way and contains 1 trillion stars. Yes!! It's travelling away from us at the incredible speed of 4.800km... per second! That's almost the distance between London and New York... in one second! And finally, it lies 214 million lightyears away from us. 

Of course, loyal readers of this blog have become used to astonishingly vast numbers so there's nothing unusual here, and this is indeed so. There's nothing out of the ordinary about this particular galaxy. Yet, it has its own personality and in spite of the almost imcomprehensible distance it does its best to show us how beautiful it actually is. Therefore, look a bit closer next time you get the chance. I'm sure that you'll be amazed!

Tuesday 11 October 2016

NGC6888: Suppose that a gigantic star nears the end of its life...

It'll explode as a supernova, right? Yes, it probably (but not necessarily) will. But let's talk about what happens just before the inevitable end. I've already written a lot about planetary nebulae, shells of gas ejected by ordinary stars that run out of hydrogen and become critically unstable. Eventually the remaining, extremely hot core, will cool down as a white dwarf and extinguish while the ever-expanding bubble of gas - the planetary nebula - will dissipate into space. Also our Sun will suffer the same fate. 

Supermassive stars, on the other hand, like to go with a bang. We're talking about stars which are ten to even forty times as massive as our Sun. By the time they run out of hydrogen and become red supergiants, they start fusing nitrogen or heavier elements in their core. They expand so much that they don't have a real surface anymore. Imagine an ocean full of gigantic tidal waves... gas blown up by the unstable core and then pulled back by gravity... One such example is Betelgeuse. This giant star's arrived at a point where it starts shedding its atmosphere into space and at a fast rate too. 

Now let's fast forward many thousands of years. Our giant star's blown vast quantities of gas into space. A planetary nebula on steroids, as it were. These stars, however, are so massive that they're able to regain some stability after having got rid of their outer atmosphere. They contract and become extremely hot with surface temperatures reaching 200.000°C (against 5.500°C for our Sun!). Stellar winds from the revived star that's now fuelled by the heavier elements in its core generate a tremendous shock wave. You've probably already seen footage of a nuclear explosion where the shockwave blows everything in its surroundings to smithereens. Well, this is worse. About a gazillion times worse. The stellar winds from a "Wolf-Rayet" star can reach velocities of 3.000km... per second! They quickly catch up with the previously expelled gas bubble and cause such havoc as you can see on my sketch (note the bright central star at the centre of the nebulosity). In the end, the "Wolf-Rayet" star will collapse and explode as a supernova.

Such "Wolf-Rayet" stars are quite rare because they can only come from the most massive of stars, which are also rare because they don't form very often and have exceptionally short lives. It's estimated that there are only some 500 "Wolf-Rayets" in our Milky Way, 206 in M33 and only 154 in M31. Although the Andromeda Galaxy's bigger than ours, it doesn't contain as many supermassive stars because it has a much lower metal content.

The object of my sketch is called the "Crescent Nebula", or NGC6888 in scientific terms. It's a fairly difficult object at the heart of the constellation of Cygnus and needs quite a bit of telescope to be admired fully. But my binoscope clearly showed me the many ripples caused by the violent radiation of the central star. It lies 5.000 lightyears away from us.

Thursday 6 October 2016

There are sooooooo many stars

A very wise person once said that the universe's so mind-bogglingly large that it would be a serious waste of space if it were just for us. The Sun's an insignificant little star among the 100 billion others in our galaxy alone (200 to 300 billion if you count in dwarf stars), and according to the best estimates astronomers can come up with there must be at least 100 billion galaxies in the universe. If you then consider that most stars have a planetary system, it would be most unlikely that we were on our own. After all, scientists are no longer asking themselves if there ever has been (or still is) life on Mars but when we're finally going to find undisputable proof of it and there are at least three or four other candidates for life in our solar system. So imagine how much other life there must be out there! Life, no matter how primitive, almost seems to be inherent to the formation of planets.

Take a look at this sketch... In the centre you see a galaxy (denominated NGC6928) comparable in size and shape to our own. Yes! That blob's just like our Milky Way and contains at least as many stars! It lies 200 million lightyears away from us and therefore we see it as it was 200 million years ago. The light that we now see from the galaxy started its journey towards Earth at the era of the Triassic-Jurassic mass extinction, the event that wiped out about 50% of all life on our planet, which in turn created the opportunity for the dinosaurs to become the dominant species. I'm telling you this so that you'd get the right sense of proportion.

On the top-left there's another galaxy (NGC6930), which is of the barred-spiral type (see here for explanation) and slightly smaller. But that's not all. If you look very carefully on the right of the main galaxy, you might see a faint little blob. Also that's a galaxy (NGC6927), but with a diameter of "only" 36.000 lightyears a fairly small one. Are we over and done with? No! Look on the top-right, between the two stars near the border. If you've got good eyes, you might see yet another little galaxy (NGC6827A) there. With a diameter of 17.000 lightyears it's rather a dwarf galaxy, but still it contains many billions of stars. Now go back to NGC6930, the brighter galaxy on the top-left. If you take a good look at its lower extremity, you may again see a kind of blob. Also this is a galaxy, a bit more distant, which lies behind NGC6930 and which scientists refer to as UGC11590.

That's all that I managed to see with my telescope and my eyes. Photographs of this area, on the other hand, will show you yet another, much more distant galaxy that lies exactly between the two main ones. The whole group of galaxies is travelling away from us at a speed of 4.100km... per second!

So how many stars are there in this view? There must be at least 1 trillion!!!! Just in this tiny little corner of our universe which I zoomed into at a magnification of 285x!

No, we're definitely not alone. The problem, however, is that communication with any extraterrestrial in one of those galaxies would be a bit slow because it would take 200 million years for our message to arrive.


Tuesday 4 October 2016

The jewel inside the glitterball

Last week I talked about M15, the sparkling glitterball in the constellation of Pegasus. Well, today I'd like to take a deeper look into this beautiful globular cluster because it hides a tiny little secret. You need quite a bit of telescope, clear skies and a sufficiently high magnification in order to spot it between those thousands of bewildering stars but using a nebula filter you can't miss it. 

Most nebulae emit a large part of their light in a couple of very specific wavelengths of the visual spectrum, predomiantly ionised oxygen and hydrogen. Stars on the other hand emit light in all wavelengths. If you use a filter that blocks all the light, except for these very specific frequencies, the stars become significantly dimmer and the nebula leaps to the foreground. Such was the case when I magnified the M15 cluster to 507x and screwed the nebula filters on my eyepieces. The stars turned bluish and less bright, whereas a tiny patch near the top-left of the cluster's nucleus seemed to light up. This patch is a planetary nebula right in the cluster's core. It's one out of only four planetary nebulae that have been found inside globular clusters thusfar and was named after its discoverer: Pease 1.

So you see... the life of a star is the same all across the universe: they're born, life their life and when their fuel runs out they die, leaving a beautiful and bright cloud of gas for us to admire.

How to make astronomical sketches - Part 05

Here's the fifth episode of my video series about astronomical sketching: stars on the pc.


Thursday 29 September 2016

Sparkling glitterball

No, this blog post isn't about a wild seventies' disco night. It's about globular clusters.

On public star parties, there's usually a little professor around: a cute little boy or girl that already knows everything about the planets and stars and who'd been moaning all day until his (or her) parents finally gave in and took him on a 50-mile drive to an incredibly remote spot in the mountains in total darkness in order to meet us astronomy goons. Obviously he can't wait to cast an eye into my telescope and so for starters I point it at a globular cluster. Then, before I guide him up the ladder, I assign him with a very important scientific mission: "Please, this is incredibily important! You have to count exactly all the stars that you see!"

Now have a look at my sketch and smile. There are about a hundred thousand of them :-)

Globular clusters are more or less spherical objects that contain many thousands of stars and which accompany our Milky Way, or other galaxies as well. These clusters are among the most spectacular objects in the sky, especially when observed through a medium to large telescope which allows you to distinguish all of the individual stars right into the cluster's core. This particular one, M15, is 175 lightyears across and lies more than 33.000 lightyears away from us. It's also one of the most compact globulars that we know as it has undergone a "core collapse". Scientists believe that there may be a black hole in it which caused this sudden contraction. Another surprising fact about globulars is that they're not young objects at all. Originally, scientists believed that they were made up of stars which had been ejected from our galaxy. But in reality they were formed at about the same time as our Milky Way, some 12 billion years ago, very similarly to the the formation of planets around newborn stars. However, star formation within the globular clusters began much sooner than within the galaxy itself and so they contain some of the oldest stars in the universe. Given that the universe itself is estimated to be some 13,8 billion years old, these globulars and their stars have been around for most of that time. In comparison, our Sun and solar system are "only" 4,5 billion years old. 

Globular clusters are also incredibly dense, as you can see on the sketch. Whereas the nearest star to our solar system lies 4,2 lightyears away, the stars in the globular's core are at least a thousand times closer to one another. If you'd like to know what it would be like to live in a globular cluster, imagine that the whole sky's filled with stars that are 10 to 20 times brighter than the full moon! Such an environment would be most unfavourable for planets because of the constant gravitational interaction with nearby stars and therefore it's highly unlikely that we'd find life there. But they remain unparallelled in beauty when observed from good old Earth.

How to make astronomical sketches - Part 04

Here's the fourth episode of my video series about astronomical sketches: preparing the sketch on the PC.


Tuesday 20 September 2016

Saturn's mirror image

Like I already explained in other posts, every planetary nebula has its own little character and that's what makes them so fascinating to observe. The Saturn Nebula, or NGC7009 in scientific language, got its nickname from its obvious resemblance to the ringend planet. But there's much more. It's a fairly young nebula, estimated to be no more than 6.000 years old, and it's in full expansion phase (phase III - see my explanation here). The inner shell's incredibly complex and shows structures in all three dimensions, which I was able to distinguish quite well. Stellar winds are extremely high, even up to the point that we see "handles" (ansae) appearing at the poles, where the gas manages to escape more easily. Gas and dust build up near the dying star's equator, making it more difficult for the gas to flow out from there. This is why many planetary nebulae have an elongated or even hourglass appearance and why the famous Ring Nebula's in reality cylindrical. The white dwarf at its centre, the dying remnant of what once a medium-sized star and now not larger than a planet, is currently emitting 20 times more light than our Sun.

Planetary nebulae are generally small but very bright objects, making them stunning to look at, even with small telescopes and under light-polluted skies. So what are you waiting for to discover this one? It's currently at its highest position in the sky and eagerly awaiting for your visit.

Sunday 18 September 2016

The ring is fake... and a little surprise...

The most famous of all planetary nebula is probably the object that Charles Messier catalogued as number 57 back in 1779, more commonly known as the Ring Nebula. A small telescope will already reveal the doughnut shape consisting of ionised gas that's being expelled by what once was a star slightly bigger than our Sun. Some 7.000 years ago this star ran out of fuel and began to die slowly, ejecting its atmosphere into space whereas the star's hot nucleus will cool down and extinguish over the next billions of years. It was actually the first time that I managed to see this particular central star with my own eyes. Being of the 15th magnitude, the star isn't that impossible to see through a telescope as such, but the still fairly bright nebulosity in the "hole" of the doughnut tends to hide it. The ring itself's currently reached a diameter of almost 1 lightyear and is expanding at a rate of 20 to 30 km/s, some 70.000 to 100.000 km/h! Comparing old photographs to recent ones, the difference in size's quite noticeable! The nebula's also headed straight towards us, but being at a distance of 2.000 lightyears it would need more than 21 million years to reach us, by which time it will have dissolved completely.

The most recent observations with the Hubble space telescope revealed an even bigger surprise. The Ring Nebula's not a doughnut at all, but it's a cylinder! Astronomers didn't notice it at first because we see the cylinder end-on, as you'd look through the hole of a roll of toilet paper. The Hubble's high resolution snapshots, however, clearly showed clouds of dust flowing out of the central star which are silhouetted against the outer portions of the ring. Such barrel or hourglass shapes are not uncommon at all among planetary nebulae. Thick layers of gas and dust around the waist of the star often slow down the expansion in that direction, leaving the gas free to flow out from the poles. 

But there's more to see in my sketch apart from this spectacular nebula and I intentionally didn't place it at the centre. On the right and slightly up you may see a small, fuzzy patch, even with a sort of irregular shape. This is a galaxy, a bit smaller than our Milky Way, which lies at the incredible distance of 230 million lightyears! It's of the barred spiral type, which means that the spiral arms do not originate from the core itself, but that there's a bar-like structure that goes through the core. The spiral arms originate from the outer edges of that bar. Obviously this is all but impossible to see on my sketch. This little galaxy's so remote that you can't even see its nucleus unless you've got a sizeable telescope and an almost perfect sky. So you can imagine how happy I was that I could still make out some structure in it.   


Friday 16 September 2016

How to make astronomical sketches - Part 3

Here's the third episode of my video series about astronomical sketching, in which I explain how to sketch the object itself. I hope you that enjoy it!

Tuesday 13 September 2016

The floating swan

Some astronomical objects are of such rare beauty that I, with my limited writing skills, can't find the right words to describe them. Therefore it's probably best that I let my sketch do the talking for me. M17, aka the Swan Nebula (or also Omega Nebula, although I still don't know why), is one of the brightest star forming regions in our sky and under very good conditions already visible to the naked eye as a brighter knot in the Milky Way. Its structure's also quite similar to that of the famous Orion Nebula, with the difference that we see the Swan edge-on rather than face-on. Buried inside this nebula lies a very young cluster of newborn stars, believed to be only 1 million years old, containing some 800 members. The radiation from these extremely hot baby stars causes the gas cloud, some 15 lightyears in diameter, to glow. The cloud of interstellar matter of which the Swan is but a part, however, is at least 40 lightyears in diameter and has a total mass of 30.000 Suns! Another 1.000 stars are being formed in these outer regions, which in turn are beginning to emit light as well. So we expect that this nebula will still significantly gain in visible size and brightness over the next millennia. Currently, the main nebula does look a bit like a swan, doesn't it? It appears to be floating on a lake of ethereal nebulosity, with its bright "eye" gazing at us. This particular star's often used as a reference by scientists to measure radiation, the distribution of hot gas and the expansion velocity of the nebula. The distance of this nebula complex's estimated to be between 5.000 and 6.000 lightyears.

I can still remember very well the first time that I've looked at this object! It was the end of August 1986 and my family and I were on holiday in the south of France. Obviously I'd brought my telescope with me, which was my loyal 68mm Vixen refractor. One evening I had finally convinced my parents to go for a drive away from the beach and somewhat up in the mountains, so that my brother and I could have a look at the incredibly dark sky that you could still find there. It may have been a coincidence, but one of the first things that I noticed, was this strange little knot in the Milky Way, just above Sagittarius. I immediately pointed my scope at it and there it was. I didn't really see a swan in it back then, more a sort of bright, elongated patch with a kind of a hook at one end. I also couldn't see any of the surrounding nebulosity of course, with my limited instrument and 20mm Kellner eyepiece. But the sketch I made that evening may perhaps still be lying around somewhere at the observatory of Urania, near Antwerp, Belgium. It was the most beautiful sketch I had ever made during my youth and I'll never forget it. It's definitly one of my favourite objects and nearly every summer night when I'm out under the stars I simply must pay it a visit. I hope that you will do so too.

Saturday 3 September 2016

A slightly blue snowball

At first sight, all planetary nebulae look more or less the same. They look like fuzzy little disks and nothing much else. But appearances may deceive as I shall explain in this post. I can't stress enough how important it is to observe properly. When you get the chance to look through a telescope, please, relax and take your time. Don't feel pressured; other people will wait. Let your eye (or eyes in the case of a binoscope) adjust to the image. It can take minutes before the really interesting details appear and it's exactly the detail that makes every planetary nebula unique.

Let's talk about NGC7662, for example, or in human language: the Blue Snowball. It's one of the brightest and most easily visible planetaries on the northern hemisphere and you can already spot it with a small telescope. The Snowball has the typical three-layer structure of a fairly young nebula, in scientific terms a phase II. In the first phase, the dying star ejects its atmosphere but the remaining central star's still too cool to ionise the gas bubble and hence make it glow. Phase II is the so-called compression phase. Gravity compresses the star so much that its temperature rises to 100 million °C! The gas bubble's heated up to 10.000°C and even 25.000°C nearer to its centre. Extreme stellar winds blow up the bubble, creating a cavity in the nebula's centre and different layers of gas around it. Imagine that you're ploughing snow with a shovel, pushing it in front of you. You'll notice that the snow will also form different "waves", the largest of which against the shovel, a smaller one in front of the first and an even smaller one in front of the second. This is exactly what we're seeing here: A very bright and thick internal bubble, a less dense outer bubble and a very faint halo around it. In the third phase, the central star reaches its maximum temperature and the density contrast between the inner and outer shells is the highest. Eventually we reach phase IV. The central star begins to cool down and the nebula's violent expansion process slows down. The inner shell catches up with the outer and the clear structures that you can observe in a phase II or III nebula fade. Eventually the nebula will dissolve into space and the central star will extinguish.

But there's more. The winds generated by the incredibly hot central star are certainly not uniform and at times sudden bursts may appear. This is exactly what we observe in the Blue Snowball, where the inner shell is ruptured at opposite sides by such a burst of high-energy particles. 

Finally, these nebulae feed the universe with heavier and complex elements which were formed in the star before it died. The Blue Snowball, for example, contains a large amount of iron in its outer shell. Perhaps one day these elements will form the planets around a newborn star?

Tuesday 30 August 2016

The tadpole galaxy

Often you could accuse astronomers of being overly fanciful when they invent nicknames for the things they've discovered or the constellations they've assigned. You might even believe that the astronomy society's a less successful branch of alcoholics anonymous. :-) But at times you don't need a lot of fantasy to understand why a certain object was given a certain name. Such is the case with the distant galaxy that's the protagonist of this sketch.

I've taken my new binoscope for a five nights' holiday in the Dolomites, at an elevation of 2000 metres and under a sky of a rare darkness. The goal: hunt the faintest fuzzies! The "tadpole galaxy"(or scientifically UGC10214 or Arp188) is quite faint indeed, being of magnitude 14,4, but it's one of the most spectacular of them all. Most galaxies are round or elliptical but this one has an unusual straight tail that's 280.000 lightyears long. Scientists believe that a smaller and more compact galaxy's come too close and that their mutual gravitational forces slung it around the "tadpole". Gas, dust and millions of stars were torn out of the larger one and formed the striking tail. Over time, the "tadpole" will lose its tail, which will probably contract into dwarf galaxies that accompany their mother. The intruder's not visible on the sketch because it now lies somewhere behind the "tadpole", but it can be seen on high-resolution photos of the Hubble space telescope. My binoscope's quite powerful but certainly not that powerful. Bear in mind that this particular galaxy lies at a distance of a whopping 460 million lightyears and therefore it must be the most distant object that I've observed thusfar. 

For those with a keen eye... there's a second galaxy on my sketch, smaller and even fainter. Its scientific denominator's PGC57108, it's of magnitude 15,5 and lies at approximately the same distance. I dare you to find it! :-) 

Thursday 11 August 2016

The eagle's glowing eye

There are so many planetary nebulae out there that sketching all of them would be close to impossible. As you know, they're dying stars that've just shed their atmosphere into space. When I use the term "just", we're talking about only several thousands of years ago, which is a nanosecond compared to the age of the universe. Their incredibly hot core heats up the resulting gas cloud up to the point that it starts to emit light on its own. Slowly this cloud of gas will expand and dissolve into space whereas the core, the remaining white dwarf star, will cool down and eventually extinguish. 

Planetary nebulae are called this way because they truly look a bit like a planet, with their generally round shape. But if you zoom into them, they'll reveal a surprising amount of detail. Gas filaments, structures and different layers give every single planetary nebula a character of its own and make every new one that you observe also a new experience. Yesterday I showed you the "Blue Flash" nebula. Not that far from it you can find this little fellow: the "Glowing Eye" in the tail of the constellation of Aquila, the eagle. With its magnitude of 11,9 it's within reach of most telescopes but due to its tiny size it can be quite tricky to find. For my sketch I used a magnification of 507x, which brought out quite some detail. I could easily see the brighter rim and some filaments of the inner sphere, which does look a bit like an iris. Its central star was also a lot more prominent than the one of NGC6905. 

The distance of this little gem is estimated at 6.500 lightyears...   

Wednesday 10 August 2016

The Blue Flash

NGC6905 is a wonderful planetary nebula in the small but remarkable constellation of Delphinus. Loyal readers of my blog will already have guessed that this nebula is what's left of a dying normal-sized star. The star's nucleus still survives and has turned into an extremely hot white dwarf star with a surface temperature around 150.000°C. In comparison, the temperature on our Sun's surface is only 5.500°C. A white dwarf's a very peculiar kind of star because its size is comparable to that of the Earth whereas its mass is not much different to our Sun's. Needless to say that it's extremely dense and "heavy". Unlike a normal star, no nuclear fusion takes place in it anymore; it's light and energy emission being solely the result of the remaining heat of what was once an active nuclear fusion reactor. With time, this star will therefore slowly cool down and fade until all that's left is a ball of mainly carbon. This cooling process takes a lot of time, many billions of years, and therefore there aren't such carbon balls or "black dwarves" around yet because the universe simply isn't old enough. 

This particular white dwarf was clearly visible in my binoscope. But perhaps more interesting for visual astronomers, the star's atmosphere was expelled into space and now forms a rapidly expanding bubble of gas filaments around the white dwarf. Also these filaments were more than evident in the binoscope at a magnification of 285x. Actually, I was amazed at the amount of detail that I was able to make out. This planetary also has two extremely faint "wings" just above and below the main nebula on this sketch. These were difficult to see and I've tried to represent just that. Some people therefore call it a mini-Dumbbell nebula because it does look a bit like a smaller and fainter version of the famous nebula in Vulpecula. 

The "Blue Flash" however lies a lot further away from us: 7.500 lightyears compared to 1.300 for the Dumbbell. But I hope that my sketch will encourage you to visit this fainter and more distant planetary as well because it really deserves it.   

Wednesday 3 August 2016

A veil in summer sky

I've already talked about supernovae before, cataclisms that mark the death of a giant star. Nuclear fusion becomes unstable... the star collapses under its own gravity which in turn causes the violent expulsion of the entire star's atmosphere in a matter of seconds. The acute energy release may be as high as 1044 Joules or the entire energy output of the Sun during its whole 10-billion year life! The expelled matter may reach velocities up to 30.000km/s or one tenth of the speed of light! 

But as dramatic and spectacular as they appear, the remains of the star fade quickly and after a couple of months all that's left is an incredibly dense core that consist of neutrons. Although perhaps only 10km in diameter,the neutron star's density is 1015 higher than that of normal matter and hence it's incredibly heavy. In some cases it may be heavy enough to continue to collapse under its own gravity until it has become a point. At which stage it becomes a black hole: an object with such a high mass that you'd need to travel faster than light in order to escape from it. That's why we can't observe anything within them because nothing, not even light, travels fast enough to escape. 

But supernovae are not just the end. The blast is so strong that heavier elements such as metals are formed and expelled into the universe. So in a sense a supernova feeds the universe with a lot of complex elements which one day may be needed for the creation of planets and... life. And not all's destroyed instantly. Almost 6.000 years ago a vehement supernova lit up 1.400 lightyears from us in the constellation of Cygnus. As far as I'm aware no observation reports from that day exist so we can only speculate how our ancient ancestors stared at the sky in awe when an insignificant star suddenly became brighter than the full Moon. Now, thousands of years later, the remains of that explosion are still visible in a small to medium telescope: the Veil nebula. What I've sketched here is just a part of the eastern region. The total Veil nebula complex is 110 lightyears in diameter, or in our sky this equals 6 full moons, and continues to expand at a breathtaking rate. Gas filaments that mainly consist of oxygen are heated up and ionised by the blastwave of the supernova explosion and start to emit light themselves. Exactly these frail filaments are what makes this nebula so jaw-droppingly lovely to look at and in a big instrument such as my binoscope the spectacle surpasses even the wildest imagination. I just had to share this with you and I sincerely hope that you enjoy it.

How to make astronomical sketches - Part 2

Earlier than planned, I'm releasing the second part of my video series about astronomical sketching techniques. In this episode I'm focusing on the sketching of the background stars, something which is often overlooked but which highly contributes to the overall result. 

Sketching stars is not just putting dots on paper. In order to make the drawing as accurate as possible you need to master an easy technique which I demonstrate in the video. 

I sincerely hope that you enjoy it!

Wednesday 27 July 2016

How to make astronomical sketches

Astronomical sketching is becoming ever more popular, and with good reason too. Not only is it great fun and does it give additional value to the extraordinary hobby that astronomy is, it's also the best way to learn how to observe. Astronomical objects are usually faint or have details that can only be discerned through a good adaptation to darkness, patience and experience. When you're sketching such an object, you're forced to concentrate on the image but yet relaxed enough to let the details leap out at you. My astronomy teacher 35 years ago therefore told me that in order to learn how to observe one should start sketching. And so I did and I'm still extremely happy for the advice that he gave me as a kid. 

In order to give everyone a hand at sketching, I'm creating a series of videos in which I'll reveal all of my little secrets. Of course, They'll only contain my personal techniques whereas there are just as many techniques as there are sketchers. But nevertheless I hope that my videos will be useful to everyone and I sincerely hope that you'll enjoy them.

Here's the first about preparation. I'm afraid that the second will only follow in September due to... holidays. :-) But I'll keep you informed through my blog whenever a new video's released.

Happy viewing!

Friday 22 July 2016

Saturn, the extraordinary planet

Ever since Galileo pointed his little telescope to Saturn, the 6th planet of our Solar System has always been observed with marvel and wonder due to its extensive ring system. Saturn's not the only planet with rings. The first probes that were sent to the outer Solar Sytem in the seventies, discovered that also Jupiter, Uranus and Neptune have a number of rings, albeit not nearly as big and spectacular as Saturn's of course. The ring system looks very impressive and is indeed 282.000km across. However, at most places it's only 30ft thick (!) apart from a few areas where the thickness increases to a few kilometres. If Saturn were a ball with a diameter of 1m, the rings would actually be 10.000 times thinner than a razor blade! Their origin is still uncertain and the most prominent theories suggest that they are the remains of a former moon that got too close to the giant planet and was ripped apart by tidal forces, or that it's just debris left over from the time that the planet was formed. They consist of water ice particles, with some traces of rocky elements, ranging from 1cm to 10m in size. Next year the rings are at their most visible because they'll be completely slanted towards us, and so they already show well on the sketch that I've made. But since Saturn's tilted, just like Earth, the angle at which we see the rings changes over a 28-year period (the time it takes Saturn to orbit the Sun). In 2009 we saw the rings edge-on and as such they were difficult to see, a phenomenon which will happen again in 2025. The ring system is extremely complex with different densities and even gaps. The most famous "gap" is the Cassini Division, which you can see clearly on the sketch and is easily visible already with a small telescope. It's not really a gap but just a region of lesser density, some 4.800km wide. The Encke Division, nearer to the edge, was hardly visible during this observation due to the extremely poor conditions. It's a 325km gap caused by a tiny moon, Pan, that orbits within it! 

Saturn itself is the second-largest planet of our Solar System, with a diameter roughly nine times that of Earth. Though it's mainly composed of gas, for the largest part hydrogen and helium, and hence its density's a lot less, resulting in a mass about 95 times that of our planet. Ammonia crystals in its upper atmosphere are responsible for the pale yellow hue. Wind speeds can reach 1.800km/h, which is much faster than the speed of sound and even faster than the hurricanes on Jupiter, but not as fast as the winds on Neptune. 

No less than 62 moons have been identified, excluding the hundreds of moonlets that hide within the rings. Titan, the largest of which, can also easily be spotted with a small telescope or binoculars and is seen here on the far right. It is the second largest moon in our Solar System, after Jupiter's Ganymede and it's even much bigger than Mercury (sorry, Astrologists), though not as massive. What's more interesting, Titan's the only moon known to have a dense atmosphere and it's the only place apart from Earth where stable bodies of surface liquid have been found, albeit liquid methane and ethane instead of water. But Titan's methane cycle is very similar to the water cycle on Earth and also its general aspect is thought to be the same, with oceans, dunes, rivers and mountains. Unfortunately, its thick and cloudy nitrogen atmosphere (denser than Earth's!) prevents the surface from being examined visually so we had to use infrared and radar to discover it. Given the presence of many complex molecules and the conditions similar to those on primordial Earth, many scientists have highlighted Titan as a candidate for extraterrestrial life. Although there are many obstacles such as the extremely cold surface temperature of -179°C and the absence of CO2. In 2004 a simple probe was sent down to its surface which transmitted a lot of interesting readings back to Earth. Scientists hope to send a more powerful probe to Titan within the next decade.

In total I could see 5 moons, less than I could expect with my new 18" binoscope, but as I already mentioned, the conditions were terrible. I was actually doing a test run of the telescope and still had to complete a lot of work on the correct alignment of the two telescope tubes. Therefore I chose to observe from an illuminated car park with an asphalt surface after a very hot day. Probably the worst place one could choose for astronomical observing because asphalt absorbs a lot of heat and re-emits it during the night, causing a lot of horrible heat turbulences. But now the telescope's finally ready for use and I can't wait to take it up in the mountains. Be ready for more sketches soon!