The Bino-Dobson

As I already explained, one of the main problems that we, visual astronomy observers, have to confront is the desire to see more. Moving to a dark sky always helps a lot but even then our hunger for more can't be satisfied fully. Why can't I perceive that dustlane in that distant galaxy while my friend with his bigger telescope can? Why doesn't that nebula reveal those delicate filaments which I've seen on a photo? 

So in the end, many of us take the great leap forward and sell our telescopes in order to buy a bigger one. Which will keep us happy for a while until we're once more disappointed because also that bigger scope turns out to have its limits. At this point the astronomy community becomes divided. There's one half that resigns because of financial or practical reasons. Even if they can afford an even bigger telescope, where can they store it? Or how would it still be possible to transport such a monster to their preferred observation site? Or what would be the sense of buying something so big that it takes an hour to set up?

Then there is the other half. Those that never give in, regardless of the cost or practicality. They'd give an arm and a leg just to see that extra nebula filament with their own eyes. Yes, I have to confess... I'm part of this group, the group with unstoppable "aperture fever" (referring to the aperture of the telescope, or in other words the size of its lens or mirror). I used to own a respectable home-built 18" (46cm) Dobsonian telescope, which has given me many satisfactions for almost 10 years. But unfortunately it wasn't enough. Moreover, I experienced ever greater difficulties observing with one eye only. It's terribly tiresome and doesn't give you nearly as many satisfactions as observing with both eyes, such as with binoculars. The feeling of immersion, really "being there", floating through space without limits or boundaries that binocular observation offers can never be obtained with a single eyepiece, even the fancy ones with their 100° field of view. I've experimented for many years with all kinds of binoviewers, which split the light beam of a telescope in two so you can look with both eyes. I've used the cheap ones, the expensive Denk II and I've even been the proud owner of a gigantic 2" Siebert. In the end, none of them, not even the 2" model, satisfied me because they always resulted in a compromise with too many disadvantages such as light loss (even with the 2"!) and an undesired magnification increase. 

Hence the great leap forward: a binoscope. This is in fact two 18" Dobsonian reflectors glued together as it were, which you can use with both eyes like true binoculars, albeit that they are a little bit bigger. This time no more compromises and the true performance of a 25" to even 32" (faint objects) telescope! The only drawback is its size and above all its complexity to use. Let me make this clear: this is NO telescope for newbies or for people who don't like to collimate or fiddle with their telescope. This must be the most complex telescope design on the amateur market and I can assure you that aligning all of the mirrors is not child's play. But it has its compensations, such as an image so bright, rich, infinite, contrasty and even 3D-like that no other telescope could possibly compete. Perhaps I've finally found the telescope that will cure my severe case of aperture fever? Well, if this one won't, I don't think any telescope would. 

To conclude I'd like to express my sincere thanks to Mr. Otte, the builder of this amazing instrument, for his incredible craftsmanship, his personal and dedicated service and last but not least his friendship. It's a real pity that my scope was the last one that he's built and that he's giving up his telescope manufacturing company because it's only because of men like him that we amateur astronomers can truly enjoy the sight of the heavens.

 

 

Don't forget the sun!

Most people believe that you can only do astronomy at night and preferably in a remote place where the stars still form a sparkling blanket in the sky. Hence the rather awkward reputation that many astronomy enthusiasts enjoy. But that couldn't be further from the truth! 

Studying and analising the stars is extremely difficult because they're so mind-bogglingly distant. To give you an idea of what I'm talking about, imagine that the Earth's the size of a peanut. In that case the nearest star would be... 20.000 miles away! So if we want to study the physics and dynamics of a star, why would we go through all that trouble of studying such remote objects when we've got a very nice example threehundred thousand times closer to us? As you all know, the Sun is a star. Not a particularly bright one and certainly not a very big one I might add, but yet a very stable, middle-aged example. So if we understand our Sun, we can also understand other stars, even those that reside in the most distant galaxies. Therefore the observation of our Sun is a very important part of modern-day astronomy and also many amateurs have special equipment to observe our star in a safe way. Please, do not observe the sun with the unprotected eye! The story about Galileo losing his sight after having observed the sun is nothing but a hoax and in reality he became blind of cataracts. But if I were you I wouldn't try to find out what the sun looks like through an unfiltered telescope which can concentrate sunlight a thousandfold! However, there are plenty of methods and instruments out there which allow you to observe the sun in all safety. Unfortunately I haven't got them. But today I'd like to share the work of a friend who has.

Iain is a British astronomer with decades of experience and just like me he's a keen sketcher. In fact, I often see him as a source of inspiration so I regard it an honour when he allowed me to post his work here. Recently Iain published a 60-frame animation of 6 different sketches showing a spectacular solar prominence. A prominence is an ejection of gas from the sun's atmosphere, often loop-shaped and reaching hundreds of thousands of miles into space. Indeed, the Earth would look tiny in respect! The process that generates them still isn't completely understood but usually they form within a day's time and they may persist for weeks or even months. The animation shows the changes of the prominence in the period of one day:

I'd also like to invite you to visit Iain's stunning blog on which you can also find some amazing solar photographs and photo animations he made, apart from his beautiful deep-sky work:

http://fouragesofsand.blogspot.it/

Enjoy!

And now I'll be gone for a couple of weeks because... I'm getting married next Friday. :-) But don't worry... I'll be back!

The wealthy charioteer

Auriga is a very rich constellation because the Milky Way runs through it and therefore it houses many star clusters and nebulas. Although it's interesting to note that it lies exactly on the opposite side of the centre of our galaxy! Its Latin name means "charioteer" as it is often identified with the legendary Athenian hero Erichtonios, who was credited with the invention of the four-horse chariot. 

When you take your binoculars and point it at Auriga, you'll easily notice why even ordinary field binos make a perfect instrument for observing the night's sky. Here's a combination of three views through my 100mm binoculars, showing you three of the most famous star clusters: M37 (on the left), M36 (centre) and M38 (on the right). I already posted a zoomed-in sketch of M37 here which was made with my old 18" telescope, so now you can make a comparison between a telescope and binoculars. As you can see, both instruments are perfectly complementary because they're doing a different job: the binos offer a wide field of view and allow you to travel across the heavens, whereas the telescope zooms in on a particular object and shows you the smallest details. 

As you'll remember, M37 is already a fairly old star cluster, with an estimated age between 400 and 550 million years, and yet it is extraordinarily rich with over 500 identified members. Usually star clusters break up as they grow older, torn apart as they are by the tidal forces of our galaxy, and the stars each go their own way. But M37 on the other hand has remained extremely compact, probably because it's such a large and compact cluster and the gravitational pull of the group is strong enough to counter the pull from our galaxy.

M36 is much younger than its neighbour, estimated 25 million years, and it contains a lot less stars as well - about 60. But due to its young age the stars are still much hotter and therefore this smaller cluster, even though it lies at roughly the same distance (4.100 lightyears), looks slightly brighter to us. If it were closer, it would actually very much resemble the famous Pleiades. 

And then there's M38. As far as age is concerned, it lies exactly between the other two: 220 million years. It contains twice the number of stars of M36 but here our galaxy's gravitational influence is evident and it's structure has become very irregular. Most observers describe it as an oblique cross, rather than it having a standard circular shape. With time it will dissipate ever more until the cluster will be gone completely.

But this isn't all! If you look carefully, the three have yet another companion, albeit a much smaller one, denominated NGC1907. It lies just a tad to the bottom-left of M38... can you spot it? This little cluster contains only 30 members because most of its stars have already gone their own way. It's about the same age as M37 so here you see what usually happens to older star clusters. Scientists have also measured some interaction with nearby M38, although they were born in different regions of our galaxy and obviously have a different age as well. So probably we'll have to conclude that the pair are just having a coincidental fly-by. 

Mirach's Ghost

Mirach is the brightest star in the constellation of Andromeda. It has a deep red colour indicating that it's cooled down significantly as it expanded to a size roughly 100 times our Sun towards the end of its life. Its colour is so stable that it has served as one of the references for stellar classification. Apart from this, you wouldn't expect anything particular about it. It's just an old giant star without any characteristics that would make it worthwhile dedicating a sketch to it. Well, at first sight anyway.

But hoho... Wait a minute! What's that faint patch on the right of the field of view? Yes, that's right! It's a galaxy! It's not all that easy to see because bright Mirach is slightly blinding you and that's why they nicknamed it "Mirach's Ghost". Now you see it, now you don't. But when you let your eyes adjust to the field of view it will certainly leap out at you, even through not very large telescopes. 

NGC404, its scientific name, is a dwarf galaxy at the reasonably close distance of 10 million lightyears. Yet, it is classified as a so-called "field galaxy" because it doesn't seem to have any gravitational interaction with other galaxies, even though it's quite near to our local group. The poor little thing just lies there, completely isolated and very inactive. Like other early-type galaxies such as M105, there's very little star formation going on and it appears to be slowly dying. Scientists believe that at some point it had a spiral structure and hence was very active but that a dramatic merger with a companion, some 1 billion years ago, reduced it to its almost vegetative state. Very few details can be discerned and especially through amateur telescopes you shouldn't expect to see more than a blurry little patch. Analysis revealed however that it has a pair of haloes of neutral hydrogen and that it houses a massive black hole too. 

So all in all, the combination of two seemingly uninteresting objects, Mirach and NGC404, still make a wonderful observation. Especially since both the star and the galaxy have a lot in common: both have reached the end of their life and both display very little activity. Astronomy isn't always about spectacles, cataclysms and dazzling star fields. Sometimes, something very simple can prove to be a beautiful tableau.

Frosty Leo

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.

I know, it's very difficult to see on this sketch and it's all my fault. I had made some modifications to my telescope which had the nasty consequence that I couldn't increase magnification beyond 206x anymore. Unfortunately, to have a good look at this little buddy you should use a lot more. But nevertheless you can still more or less see what I'm talking about: that rather bright, fuzzy little patch near the drawing's centre. This is 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 lifecycle, it runs out of fuel to sustain nuclear fusion and becomes highly unstable. Its interior collapses and the shockwave 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.

Betelgeuse's Ring

Betelgeuse, Orion's right shoulder, is a most fascinating star. Not only is it the 8th brightest star in the sky but also its strong, red colour has inspired all cultures around the world since the dawn of civilisation. As I've explained before, a red colour means that a star's actually quite cold. The temperature on its surface is barely 3.000°C, which is 2.500°C cooler than our Sun. But... Betelgeuse's also one of the largest stars that we know. It's so large that if it were at the position of our Sun, its surface would extend beyond Jupiter's orbit. Or to give you a better idea of its size... imagine that the Earth is a grain of sand with a diameter of 1mm. In comparison, our Sun would be the size of a grapefruit. And Betelgeuse would be... Wembley Stadium! That's how big it is! Then again, although Betelgeuse could contain 1,6 billion suns, its mass is estimated to be only 20 solar masses, making it an extremely low-density star. What's more, Betelgeuse is rapidly losing a lot of its mass. Observations with our most powerful telescopes revealed that it's ejecting enormous plumes of gas. Its surface is also terribly unstable and scientists believe that the star's contracted more than 15% over the last 20 years. Also its brightness shows big variations; the biggest of any bright star in our sky. In 1927 it only appeared to be the 20th brightest star but sometimes it outshone Rigel and Procyon to become the 6th brightest. 

The reason for all of these spectacular figures is that Betelgeuse's arrived at the end of its very short life. Also this is hard to believe if you consider that our Sun's 4,6 billion years old and only halfway its lifecycle, but Betelgeuse's only 10 million years old! It was born long after the age of the dinosaurs, in the period that the big apes appeared and the flora and fauna on Earth started to take their present shape. The greater the mass of a star, the faster it consumes its energy source and eventually dies. We believe that Betelgeuse was born in the Orion Nebula complex as a star with a very large mass which burnt up very quickly. When its core ran out of hydrogen, it started to fuse helium into oxygen and carbon, greatly expanding the star's radius and causing the star to cool down. Claudius Ptolemy described Betelgeuse as ruddy in the 1st century AD, but interestingly, Chinese astronomers who observed the star 3 centuries earlier, said it was yellow. So we could conclude that the cooldown from a yellow to red supergiant star occured very recently. 

Another interesting fact is that Betelgeuse's shooting through our universe at a speed of 30km/s, more than 3 times the speed a rocket needs to escape Earth's gravity or 90 times the speed of sound! As such, it's creating a shockwave that distorts space around it. Gas and dust are blown away and ripple in its wake and this is exactly what I wanted to show you on my sketch. I know, it's very difficult to see. Believe me, I had a hard time seeing it through my binoculars but eventually I did notice a kind of weird, dark triangle surrounding the star. This triangle's known as Betelgeuse's Ring and they are clouds of dust blown away by the quickly approaching giant star. So indeed, these clouds are dark because they're closer to us than the star and so they partly block its light. 

But as I said, Betelgeuse's fast life of rock 'n roll will soon come to an end. It's already terribly unstable. Cooldown's reached a critical point. Iron's building up in its core. And then... it will explode in a gigantic supernova explosion, probably within the next 100.000 years already. It will be brighter than a full Moon and last for several months! But don't worry, there's no need for panic. Betelgeuse's between 500 and 600 lightyears away and although some lunatics have predicted doom or even judgement day, the radiation from this explosion will be far less than the radiation we receive from our Sun, so we'll be quite safe.

   

More beauty in Leo

In one of my previous posts I talked about tree lovely galaxies that the lioness bares in her belly. But if we move slightly towards her chest (wow... soon I can start writing romance novels... :-) ) we find more beauties. On this sketch you can see the M96 group of galaxies. In reality this group is still much larger than what I could catch with the already enormous field of view of my binoculars and it contains at least 24 members, 4 of which are visible here. 

M96 is the brightest of them all and proudly rests at the centre of my sketch. It's a spiral galaxy with rather weak but still clearly visible spiral arms, about the same size as our own galaxy. Measurements revealed that its gravitational centre is not in the middle but a bit off due to gravitational interaction with the other members in the group. Interesting to note is that ultraviolet emissions from the core suggest that it contains a supermassive black hole!

M95 can be found on the right. It's a galaxy with a fairly strange shape because its spiral arms appear to form a ring around the centre, rather than to originate from it. In reality it's a "bar-type" galaxy, which means that it has a bar-shaped structure across its centre from which originate the spiral arms, but its bar is rather weak and hardly visible. It certainly wasn't visible through my binos although I could see a hint of the ring of spiral arms. The nucleus itself is surrounded by an enormous star-forming region some 2.000 lightyears across. 

Then we move to the little group on the top-left. The brightest member of this subgroup is denominated M105. It's an "elliptical" galaxy, meaning that it lacks the spiral arms and structure of spiral or lenticular galaxies. Once it was believed that these smooth and shapeless galaxies were young and that they'd evolve into spiral galaxies, but this turned out to be false. On the contrary, star formation is very low in them and most stars are much older than the stars found in spiral galaxies.  However, it contains an even bigger black hole that the one in M96: it has a mass of 2*10⁸ solar masses!

 

To the left of M105 we find its closest companion, denominated NGC3384. It's a lenticular or disk-shaped galaxy. These are somewhat intermediate between elliptical and spiral galaxies and together with the former they tend to be quite old with little star formation going on, although they do have a much clearer structure. Over 80% of the stars in this galaxy were found to be more than a billion years old. Invisible to amateur telescopes but still very interesting is that NGC3384 and M105 share a large ring of neutral hydrogen, 650.000 lightyears in size, in which star formation has been observed. 

Last but not least, I present you a challenge. There's a small, third galaxy near the M105 subgroup and I hope that you can find it. It was extremely difficult to see through my binos anyway so I wanted to let you suffer just as much as I did when I was trying to locate it. :-) It's referred to as NGC3389 and although it appears to be a member of this subgroup and hence as a member of the M96 galaxy cluster, it isn't part of it at all! It lies twice as far away from us and is therefore a remote background object that only coincidentally seems to reside close to M105 and NGC3384. It's also a completely different type of galaxy than the other two, with a clear spiral structure and a high emission of blue light which indicates a huge quantity of active hydrogen and a lot of very young stars. But unfortunately this little galaxy ended up in a remote and isolated part of our universe, without any close companion.  

The M96 cluster lies at a distance of 32 million lightyears and is in turn part of the Virgo supercluster of galaxies. This supercluster is truly gigantic as it not only contains the already vast and crowded Virgo cluster, but also the M101 group, the M82 group, the M65 group, the M51 group, the Draco group and... our own local group of galaxies. The supercluster's a whopping 110 million lightyears across and is defined as such because there is gravitational interaction between its various members, however distant. And here's the good news: there are millions of these superclusters in our universe. How about that for perspective?