inside milky way beginners' notes from scratch
Austria, 2012 - ....
Geographic coordinates: Latitude 48.2666, Longitude 16.3166
Whether it is time, speed, distance or mass - cosmic dimensions are vast and far beyond anything humankind may ever fully conceive. Everything up in the sky is so huge and far that we are unable to even vaguely imagine the universe in its entire magnitude. Thinking of the cosmic dimensions and distances within our solar system, our galaxy or even the entire universe, our imagination is stretched to its limits and we are much more overwhelmed with wonder rather than being able to understand what we see in the night sky. To bring to mind that Earth and billions of other celestial objects are kept on their orbits by mass and gravity even at such enormous, inconceivable dimensions between them is just amazing and makes us just more curios about the question: "why is that?". Simply put, the fact that we can't comprehend the vast expanse, the immense periods of time and forces of gravity that determine the run of cosmic events fuels our fascination about the orbs in the night sky and the mysteries of the universe, how it came to existence and where it ends, if it ends at all.
Beyond the incomprehensible
How big is the universe is one of the most obvious questions of mankind since centuries, but hard to imagine, let alone to conceptualise. Due to the continuous expansion of the universe, the diameter of the observable universe is currently estimated at 93 billion light-years (in continental Europe 93 Milliarden or 93.000.000.000 ly). A light-year is a linear measure, i.e. the distance light travels in a vacuum in one Julian year, which is equal to 9.460.730.472.580,8 km or approximately 5,88 trillion miles, and that is far, really very far. In terms of light-speed the Moon is 1,3 seconds away from us, Earth is just 8 minutes away from the Sun, but Neptun is already 4 hours (!) away from the Sun. Even though we are aware that light travels at a very high speed of approximately 300,000 km per second, such huge numbers don't tell us much. We know that the measure of a light-year is used in astronomy for practical reasons and that any numbers in connection with light-years represent huge distances, but we are simply unable to conceptualise such an immense scale. It may help to at least vaguely conceive cosmic dimensions if we put distances into perspective by applying measures we can relate to better, rather than talking about lightyears or astronomical units.
Remember, for example, that NASA's space probes Voyager 1 and 2 were launched in September 1977 and August 1977, respectively, on a mission to explore our solar system. In August 2012, 35 years later, Voyager 1 has left our solar system and crossed into interstellar space. Even though Voyager 2 was launched before Voyager 1, due to its different mission it has entered interstellar space only in December 2018, while Voyager 1 was already 6.000.000.000 kilometer away in interstellar space.
35 years of exploration of our solar system at a speed of approximately 17 km/s or 61.000 km/h (!), during which Voyager 1 and 2 have travelled a distance in the size of a grain of sand compared to the distances to our interstellar neighbourhood, let alone the vastness of the Milky Way. Nevertheless, even our "tiny" solar system is huge, really huge, in fact too huge for us to fully comprehend its scale.
In order to conserve power of Voyager 1 for its long journey into interstellar space, scientists decided to switch off its cameras forever. However, on the advice of Carl Sagan in 1980, NASA decided finally in 1989 yet to turn the camera around for one final picture. The result is the famous "Pale Blue Dot" image, a look back at our home planet Earth, made on 14 February 1990 from a distance of around 6,055 million kilometers or 3,762 million miles respectively. The transmission of 60 frames, initially stored in an onboard tape recorder of Voyager 1, by radio signal travelling at the speed of light took nearly 5 1/2 hours.
It's not just amazing, it's simply mind-boggling. Just think about, this is planet Earth, that's here, that's us where we all live on our one and only vulnerable home . . . , and think about how we treat it during the relatively short period of time of our presence on Earth, given the inevitable cosmic events that will not spare our Sun and planet Earth. The photograph was interpreted in Carl Sagan's 1994 book, "Pale Blue Dot", as an impressive representation of humanity's minuscule and ephemeral place amidst the cosmos.
Another way to form an idea of the dimensions of just our solar system and our interstellar neighbourhood is, for example, to imagine that a journey from our planet to the sun on a commercial airliner, assuming the average distance of 149.597.870 kilometer, would take about 19 years. In comparison, such a journey to the most distant planet Neptun would take around 600 years(!) or by car 5.400 years! And yet, our solar system appears ridiculously small compared for example to our interstellar neighbourhood, not to mention the vastness of the Milky Way or even the universe as we know it today. The closest star to our sun, Proxima Centauri, is "just" about 4,22 light years away from us. It would take 47 million years to drive there by car, or 5,22 million years by plane if you are in a hurry. Sending Voyager 1 to Proxima Centauri at a speed of 61.000 km/h would take mind-boggling 73.000 years for that distance of "only" 4,22 light-years or around 39,900,000,000,000 km.
For the most part we are all living our lives in our own little bubble, focussed on ourselves and people close to us, so why even ask or attempt to answer such fundamental questions, why even think about something so abstract like the magnitude of cosmic space or the principles of the universe.
However, when we leave our everyday worries behind and ask ourselves how the universe came about and if there is a greater plan for it, our thoughts can easily ascend into spiritual realms. Knowing more about the universe, our way of looking at things on earth may be put into the right perspective and our rivalries, big ones as small ones, appear ridiculous. Amidst such huge dimensions of space, mankind appears negligible and Earth like a mere particle, a tiny blue dot that will disappear one day within the blink of a cosmic second in the vast cosmic ocean. Relative to the universe as man believes to know it, Earth appears insignificant, and yet so precious as a lonely living planet. To get a better understanding of the universe is also about self discovery, it tells us more about ourselves. Let's be aware about: we are not separate from the universe, we are a product of it and the universe is literally in us. As Professor David Kipping says in one of his public lectures "Why we might be alone", that we are perhaps the diamonds of the Universe, and, by quoting Carl Sagan, that we are the way by which the Universe learns about itself.
Floating intellectually in these celestial spheres and wondering what the fate of earth will be in distant times, we may begin to understand that the greatest threat to life on earth is the human race itself. Simply put, humanity as a whole doesn't appreciate our incredible gift of existence, all while taking for granted how magnificent it is to be here.
Stellarum Fixarum Sphaera immobilis
and how we came to know what we know today (a chronology since the 15th century)
Imagine, that our Sun is just the size of a single grain of sand. But our sun is just one of an unimaginable huge number of stars, it is surrounded by over 200 billion of them in our own Milky Way galaxy. In fact our sun is just a speck of dust in a vast beach of stars, but the Milky Way galaxy is in itself just one of billions of galaxies scattered throughout the universe.
Think about that for a moment. Isn’t it remarkable, that the human race has managed to deduce so much about what the (observable) universe looks like. Let’s put this achievement into context: from our advantage point, living on a tiny speck called Earth, orbiting around this single grain of sand, we’ve managed to deduce the size and shape of the observable universe. This seems as one of the humans greatest accomplishments. It is an astonishing story of how we gazed upwards from our isolated and unremarkable planet Earth and began to deduce the shape size and origin of everything that there is, it is the story of how we came to understand reality at the largest scale - the story of everything we can observe in the universe.
Sitting under the night sky, above the atmosphere and beyond the moon and beyond that the planets and stars, but then wondering what’s the totality of everything there is - it’s a question we all asked at one point or another. I remember as a kid looking up at the stars and wondering, whether space indeed went on forever as I was told, or whether the universe had an end and what would then be beyond that end where "nothing" begins and how to imagine that "nothing". Today we’re just beginning to understand just how complex this question really is.
Nicolaus Copernicus
Nicolaus Copernicus (19 February 1473 – 24 May 1543) was a Renaissance polymath who is best known for his formulation of a model of the universe that placed the Sun rather than Earth at its center. The publication of Copernicus's model in his book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), just before his death in 1543, was a major event in the history of science, triggering the Copernican Revolution and making a pioneering contribution to the Scientific Revolution.
Copernican heliocentrism is the astronomical model developed by the Renaissance astronomer Nicolaus Copernicus and published in 1543. This model positioned the Sun near the center of the Universe, motionless, with Earth and the other planets orbiting around it in circular paths, modified by epicycles, and at uniform speeds. The Copernican model challenged the geocentric model of Ptolemy that had prevailed for centuries, which had placed Earth at the center of the Universe.
Quite apart from the fact that the Copernican model of heliocentrism was absolutely revolutionary - so much so that Copernicus had fears publishing his work during his lifetime - there appeared to be a very simple answer regarding the universe until 500 years ago. It was the prevailing belief, that the Earth and the planets were enclosed in a vast thin spheric shell of rotating stars that were fixed in position. But in the 16th century, something happened, which would shatter this view of the universe. It would set the human race on a journey to uncover the true structure, size and shape of everything.
SN 1572 - the phenomenon
In 1572, a type 1A supernova in the constellation of Cassiopeia - an event of unimaginable scale of an exploding star - would have become visible on planet Earth. It was known as the “phenomenon” and to anyone who saw it, it must’ve been an extremely shocking and mysterious appearance in the sky, more brightly than Venus and even visible during the day. It comes as no surprise that religious explanations were put forward for this bizarre and unsettling event; one interpretation of the new star, voiced by certain intellectuals, held that it was the very star the Wisemen had seen in Bethlehem 1,570 years earlier - suggesting that this new star might proclaim an event of such immense significance as the incarnation of God on earth.
Thomas Digges - the first to expound the Copernican system in English
The phenomenon, fascinated and mystified many people across Europe, and in England it fired the imagination of Thomas Digges. But just when Digges began to study this mysterious, believed "new star", it started to grow dimmer. His mentor and fellow astronomer named John Dee reasoned with him that this phenomenon could be a moving star, something previously thought to have been impossible.
In Dee's theory it had perhaps grown brighter as it approached the Earth and faded as it had gone away. Although this theory was wrong, it got Digges thinking about the true nature of the stars that surround the Earth, it began to seem very unlikely that they were all arranged in a thin spheric shell. Maybe this apparent shell was just an illusion. It would take Thomas Digges another four years before he published his strange idea and when he did, it was in the form of a simple diagram, added to a translation of the works of Nicolaus Copernicus, the man who first argued that it was not the Earth, but the Sun, that stood at the center of the universe. However, while Copernicus' diagram was still with the notion of a fixed shell of immoveable stars, Digges’ model was absolutely revolutionary.
Like Copernicus he has the sun at the center with the Earth in orbit around it along with the other planets, but he has taken the stars out of their outer shell and scattered them out into endless space. This diagram was describing a radical new picture of the cosmos, one where the stars in the sky now existed fixed in an infinite space, and that is a moment Europeans started to think of the world as unbounded, as an infinite world without end, where stars we were suspended within an infinite static universe.
Heinrich Olbers
But this picture of everything produced a strange paradox. If this infinite universe contained an infinite number of stars, then why was it dark at night in the traditional view of the universe. It was very soon that a static, infinite universe was ridiculous and that is because in such a universe, where there would be an infinite number of stars and every line of sight from us intercept with one of these stars, the Universe could not be dark. It should be glowing as bright as our sun we know.
Although Thomas Digges first raised this question, it became known as the Olbers' paradox, also known as the dark night paradox, that says the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. As simple as the question sounds, it would take until the 20th century to find a satisfactory answer why the sky is not as bright as the day. Solving Olbers' paradox would require many great scientists who weren’t afraid to think differently, radically differently. It is about understanding the shape, size and origin of everything there is. Without this understanding, the puzzle would be impossible to solve. Perhaps one of the reasons was that until the end of the 1700s everything that lies outside the solar system was pretty much uninteresting for astronomers. Astronomy was the science about our solar system, of the Earth and the planets, satellites and comets. The stars were kind of glorified, but rather uninteresting. At the end of the 18th century, however, all that would change.
William Herschel
It was that time, when in a small and unremarkable house in Bath, England, the German-British astronomer William Herschel, his sister Caroline and a brother would develop and build a new generation of telescopes using highly polished metallic mirrors that would capture much more starlight than glass lenses and allow them to see further out into space than any human had ever done before. With his powerful telescopes, Herschel and his sister Caroline would scar the heavens night after night and cataloging stars. With it, he also discovered a new planet in our solar system, that is Uranus.
Given the state of scientific knowledge at the time, it was possible for Herschel to observe everything there was to see. However, a nagging problem soon arose. Herschel and his colleagues discovered cloud-like objects in the night sky known as nebulae. Perhaps the Milky Way was not all there was; perhaps some of these nebulae were actually gigantic galaxies of stars located far beyond the Milky Way. Unfortunately, there was no way to answer this question reliably. The problem was that, despite Herschel's technological achievements, there was no means at the time to accurately measure astronomical distances.
Bringing the planets closer
A safe way to completely excite one’s interest in the universe is to buy a telescope and get out there, where the sky is dark enough to gaze at celestial objects.
Should you, however, search for answers to questions like “what is out there?” or “where do we come from and where do we go?” you may also buy a good book, brew yourself a cup of hot tea and curl up in your comfy chair. Why? Viewing the night sky through a good telescope with such fundamental questions in mind is a safe method to face just more questions and get fewer answers plus a runny nose once in a while. Go out for stargazing if you possess strong self control that you can stop and go home when it’s about time. Otherwise, if you like to get lost in space wondering about things you can’t conceptualise, bring enough warm clothing, hot drinks and a couple of good friends who enjoy doing the same thing.
The chronology of our mistakes and modest accomplishments until the first good viewings, starting from scratch on the learning curve, is considerable. For beginners there is a lot of good literature available, with useful, essential information, profound facts and details about astronomy. Those who consider buying a telescope to enjoy clear views of the deep sky should begin with a good book and perhaps with a decent binocular instead of buying right away an expensive telescope.
We've skipped that part of viewing with a binocular. In July 2012 we've figured out a shop in Vienna selling Meade telescopes. Not being aware about the enormous variety of telescopes available for different purposes at different quality, performance and the wide range of prices, we thought we could go there and pick up a telescope straight from the shop. We were wrong. While listening to an experienced salesmen who explained to us in detail the pros and cons of Refractor telescopes, Newtons and Dobsons, we, the greenhorns, were constantly at risk to get ahead of ourselves. Not knowing everything ahead of us we finally ordered a universal 8 inch Schmidt-Cassegrain telescope, a computer controlled Meade LX90 ACF with GPS support and some important accessories. In retrospect we bought a quite good telescope, which should outlast many years of use. It’s kind of a “tell me what you want to see and I will deliver - telescope”, which, once it is understood and correctly aligned, is able to center 30.000 celestial objects stored in its database, provided the location and viewing conditions are good.
Schmidt-Cassegrain Telescope
Meade LX90 ACF-8
Advanced-Coma-Free
Clear aperture: 8" / 203mm
Focal length: 2000 mm, Focal ratio: f/10
Resolving power: 0.570 arcseconds
Optical Tube: (OTA D x L) 231mm x 425mm
Mounting: Cast-Aluminum fork mount
Viewfinder: 8 x 50mm with crosshair
Control: AutoStar GOTO, Automatic tracking system
GPS positioning, Database with 30.000 Objects
Weight: 15,0kg + 9,0kg
For transport of the LX90 we've purchased a universal carrying case from JMI (USA), suitable for Meade LX90 and LX200 telescopes. It’s an important accessory to protect the telescope during transport and for storage if not in use. An external 12V / 22Ah power pack or 8 x 1,5V C-type internal batteries provide the power supply to the telescope. Since the delivery of the telescope was delayed for a few weeks, we had plenty of time to read literature about basics one should know before using a telescope, and to look out for some additional, useful eyepieces.
In September 2012 the Meade LX90 has finally arrived in Vienna, well protected in a huge box. After we have fixed the telescope on the tripod we performed an initial setup and manual test. The motors whirred and the telescope was moving into the right directions. We were quite surprised by the size of such a Schmidt-Cassegrain telescope, even though the 8" LX90 is one of the more compact models. Some simple but important accessories were still missing in order to be successful in viewing celestial objects. A star map, a dimmable red LED flashlight and a small aluminium suitcase to store eyepieces is the minimum that is necessary for stargazing outdoors.
First observations
In autumn 2012 the nights were mostly clear. One day there was an extremely beautiful moonrise, so we went out into the cold of the night for the first time. Observing the moon through a ND-filter was really great. The LX90 was perfectly tracking the moon in the center of the eyepiece. We were amazed by a large, crisp and detailed image of the crescent with lots of texture because of the sunlight throwing nice shadows on the moon's surface. After fixing a borrowed 2-inch eyepiece the viewing comfort was noticeably enhanced compared to the standard 1,25 inch eyepiece. On that evening we decided to upgrade the telescope with a 2 inch diagonal and 2 inch eyepieces. It is important to use the original Meade Series 5000 2" mirror diagonal on the 8 inch LX90 not only for its premium quality, but also because this diagonal will fit within the fork mount when slewing the optical tube to a vertical position, while third-party diagonals may block and damage the drives of the telescope.
The autumn weather forecasts were promising for our first observation from a site outside Vienna, where we could aim for the full program, from a proper two-star alignment of the telescope to a guided observation tour. In the meantime we performed a reset of the telescope in order to eliminate some potentially wrong settings made during the initial setup a week before, have initialized the AutoStar controls once more and have set some useful options in the AutoStar menu. End of September 2012 we have placed the LX90 at a site outside the city in the Wienerwald north-west of Vienna. It was a clear night, but of course the view was impaired by the light pollution of the nearby city. Anyway, it was the first good opportunity to extensively practice on the LX90, from alignment of the telescope to visual viewing. We had to patiently wait well five minutes or more until the telescope has completed its GPS fix. This was way too long, which, however, seems to be a problem with that particular location as it turned out later. The sidereal tracking rate of the LX90 was working fine and kept all celestial bodies perfectly in the center. We had again a great sight of the moon and we could view Jupiter for the fist time, well enlarged and pretty clear. Very impressive indeed!
With a diameter of 142.800 km at a distance of 778 million km from our sun, Jupiter is the fifth planet and one of the brightest objects on the night sky. Jupiter is a planet made up of gases, mainly hydrogen, helium and methane, and there is even a little water.
Later in October we met with some friends to set up the telescope again in the Wienerwald. We could again perform a two-star alignment of the LX90, after which it has precisely centred the objects selected from the database and delivered great views later that night. Unfortunately we had to end our session before midnight because of too much fog and moist in the air. While the metallic surface of the telescope became quite wet, the dew shield did a good job and protected the front glass from fog. In such case it is important to let the telescope become dry over night and box it only the next day.
In April 2013 the constellation of Sun, Earth and Saturn was good to focus the telescope for the first time on Saturn, the sixth planet from the Sun and second largest planet in our solar system. It is a gas planet and the most distant visible to the naked eye. Saturn is best known for its planetary rings that make it a unique, worthwhile object for observation and at that time the rings of Saturn were nicely tilted. Saturn and its rings are best seen when the planet is at, or near, opposition, the configuration of a planet when it is at an elongation of 180°, and thus appears opposite the Sun in the sky. Saturn orbits the sun at a distance of 1,434 million kilometers, with an orbital period of 29,45 years.
After doing some dry runs during wintertime to improve our skills in operating the Meade LX90 ACF, we were meanwhile able to mount, position and align the telescope pretty fast. We were able to find Polaris almost blindly by knowing our 48,15 degrees latitude here in Vienna and the GPS fix of the LX90 worked as expected. Mostly Arcturus and Vega are chosen by the telescope's computer among the brightest stars in the northern hemisphere for an "easy" two-star positioning and alignment. Within fifteen minutes we were ready to start viewing. Saturn was quickly selected from the AutoStar database and - voila - it was in the center of the eyepiece. What a gorgeous sight and wonderful experience to observe Saturn through a telescope. Saturn's maximum distance to Earth is roughly 1,2 billion kilometers (or 7AU) and we could nicely see the planetary ring system that orbits around Saturn. By mounting a more powerful 17 mm 2" eyepiece we've raised magnification to about 117 and later by an additional 2x Barlow lens to 235, which made Saturn completely unfold its beauty in the vastness of space.
In the following years our skills in preparing the LX90 for observations became constantly better and quicker, making it easier for us spontaneously decide to go out for viewing. Meanwhile we have also collimated the telescope for the first time, as we've learned that it is crucial for best performance of Schmidt-Cassegrain (and Newtonian) telescopes. Our collimation was successful and noticeably improved the viewing quality. Collimation is the precise alignment of the scope's secondary mirror with the primary mirror. As tricky as the procedure can be, it is important to do it once in a while since only a small misalignment due to vibrations during transport of the telescope may decrease the viewing quality.
Searching for deep-sky objects seems hopeless when the telescope is set in the outskirts of a city like Vienna. One night, however, we accidentally stumbled over Messier 03 and - wow - we could indeed view a well defined star cluster in a distance of 33.000 light-years away from Earth. It's simply amazing!
Messier 03 is the third object recorded in the Messier catalogue. It's a cluster that consist of approximately half a million stars, of which 274 are identified as variable stars, and it can be seen during springtime halfway between the stars Arcturus and α (Cor Caroli) in the constellation of Canes Venatici. Meanwhile we know that most amateur astronomers consider Messier 03 one of the finest northern globular clusters. Another achievement of us greenhorns.
It should be mentioned that observing the night sky can be very nice even without a telescope. A decent binocular mounted on a solid tripod can be surprisingly good for viewing objects of our solar system, or, if you just want to be overwhelmed by the mind-blowing number of "nearby" stars at the night sky, point it at any direction. The photograph below shows the night sky at Palmschoß in South Tyrol (Alto Adige) in Italy, where we stayed at the Rosalpina hotel located 1.800 meters above sea level. To watch the sky in such a remote place with almost no light pollution was a rare opportunity to view the sky and our Milky Way half night long. It was the best view of the night sky we had so far in Europe, however, not as impressive as the stars and the very bright Orion Arm of Milky Way above Lake Tharthar in the 1980's. Lake Tharthar is a remote place in the deserts of Iraq north of Fallujah, where in a large region no artificial light existed.
Night sky at Palmschoss (Italy, Brixen 2013), Leica M, Summilux-M 35mm f/1.4 ASPH.
By the way, all stars that we can see are within Milky Way and of course we can only take pictures of the Milky Way from inside the galaxy, which means there are no images of the Milky Way as a whole. Any picture showing the entire Milky Way is a simulation. Best estimates tell us that the Milky Way is made up of approximately 100 billion (100.000.000.000) to several hundred billion of stars. These stars form the shape of a disk whose diameter is about 100,000 light years. Our solar system is located 27.000 light-years from the center of the Milky Way, on the inner part of the Orion Arm. Just as the Earth orbits around the Sun, the Sun and our solar system goes around the center of the rotating Milky Way at an orbital speed of approximately 220 km/second or 792.000 km/hour. That's pretty fast, isn't it, but yet this is just 0,073% of the speed of light. It takes around 250 million years for our Sun and the solar system to go all the way around the center of the Milky Way.
From Palmschoß our home galaxy was clearly visible. Since the telescope stayed in Vienna we took a series of photographs with a digital camera fitted with a 1:1.4/35mm lens and mounted on a tripod. During this 16 second exposure an asteroid apparently has crossed the image section and left its traces on the sensor. What a nice coincidence, and what a beautiful night to wonder about the Milky Way, the universe and why things are as they are . . .
To find out more basic facts and figures about astronomy, our Milky Way and the universe you may visit NASA's website Imagine the Universe! and other websites linked above.
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