Developed in the mid-19th century, astrophotography has spawned many scientific subdisciplines useful to the work of astronomers, who strive to convey what our cosmos is like. But, for most of us, the thrill of astrophotography lies simply in its beauty and power to reveal what our eyes cannot see. Now Finnish astrophotographer J-P Metsavainio has developed an experimental technique that takes ordinary astrophotography a step further, as shown by the 3D animations of nebulae in this post. He told EarthSky:
Due to huge distances, real parallax can’t be imaged in most of the astronomical objects.
I have developed an experimental technique to convert my astropics to artificial volumetric models …
The models are based on some known scientific facts and an artistic impression. They give an approximation to the real structure of the nebula, an educated guess … a feel to the object and an idea, what it must really be like.
I collect distance and other information before I do my 3-D conversion. Usually there are known stars, coursing the ionization, so I can place them at right relative distance. If I know a distance to the nebula, I can fine-tune distances of the stars so, that right amount of stars are front and behind of the object.
I use a “rule of thumb” method for stars: brighter is closer, but if a real distance is known, I’m using that. Many 3-D shapes can be figured out just by looking carefully the structures in nebula, such as dark nebulae must be at front of the emission nebulae in order to show up etc.
The general structure of many star forming regions is very same, there is a group of young stars, as an open cluster inside of the nebula. The stellar wind from the stars is then blowing the gas away around the cluster and forming a kind of cavitation – or a hole — around it. The pillar-like formations in the nebula must point to a source of stellar wind, for the same reason.
How accurate the final model is, depends how much I have known and guessed right. The motivation to make those 3-D-studies is just to show, that objects in the images are not like paintings on the canvas but really three dimensional objects floating in the three dimensional space.
I have done the animations from astronomical images shot by me. The interesting thing about this technique is, that only elements from the original 2D-image are used.
Only the volumetric information gets added. The main principle is to first separate high and low signal to noise components from the image, high signal objects are mainly stars. After the first step I have separate images from the nebula and stars.
The method used is very accurate, as you can see.
How 3D-images are done. After the first step, the nebula layer of the image get splitted to an elemets by it’s structure. Then a 3d-mesh is made by the brightness of the nebula. This can be done since the gas in the nebula emits a light of it own and the thickness of the nebula can be estimated by the amount of light.
Then I split the star image to a separate layers by the star brightness and the color index. If there are stars with a known distance, like ones coursing the emission of the nebulosity, I separate them to a different layers, all the steps are done “semi automatic”.
At the final step all the image information, nebula and stars, are projected to complex 3D-suffaces and some tweaking can be done three dimensionally.
Rest of the work is traditional animation work.
Bottom line: J-P Metsavainio in Finland has developed a technique for converting astrophotographs to artificial volumetric models resulting in animated GIFs. They help convey the idea of what these objects in space must really be like.