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04.06.2009 14:08
#43
Cosmic sites: Remote space and personal perception meet at the monitor
Dr. Jayanne English of the University of Winnipeg's Department of Physics and Astronomy has submitted a new animation showing the cold hydrogen gas, which is invisible to human eyes, in our Milky Way Galaxy. Dr. English makes images from complex data sets aquired via telescopic observations of outer space, determining the colour and form of them as she sits in front of her computer screen.
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This five-frame animation, created by Dr. Jayanne English (University of Manitoba) with support from A.R. Taylor (University of Calgary), is of neutral hydrogen gas in our Milky Way Galaxy as mapped by the Dominion Radio Astrophysical Observatory in Penticton Canada. Jayanne's essay on the animation follows.

Link to animation


Cosmic sites: Remote space and personal perception meet at the monitor


To picture the universe when it was young, imagine a stormy sea of particles, smaller than atoms, colliding with each other. This plasma, on the whole, radiates more light than it swallows or absorbs. But it is the waves in this cosmic sea that have the most profound impact on the future of the universe. These waves provide the conditions necessary for the growth of galaxies. And galaxies, as the habitats of stars and their orbiting planets, constrain the development of living organisms like ourselves.  Recently the European Space Agency's Planck satellite was launched to study the fundamental origins of structure in our universe - that is, those waves in the cosmic plasma. Previous observations detected these waves as miniscule fluctuations in temperature in the light escaping from the primordial sea of particles known as the Cosmic Microwave Background Radiation (CMBR). This pervasive radiation keeps the empty space of the universe at 2.725 degrees above absolute zero. The fluctuations differ in amplitude from this temperature by a mere 1/10000 of a degree.

These primordial cosmic waves cannot be touched, tasted or heard. Rather we experience them, like almost all astronomical phenomena, by the electromagnetic radiation that they emit. We apprehend their characteristics and behaviour by analyzing their light. This makes vision our primary sense in astronomical studies. Radio, microwave, infrared, and X-ray telescopes extend our vision beyond the range of visual light, giving us access to these other parts of the electromagnetic spectrum. Captured in bits and bytes by electronic detectors and converted into data, the challenge is to render these photons so that we human beings can grasp the essence of the physical phenomena that we are investigating. The computer monitor facilitates this, embodying our exploration by engaging our faculty of sight. That is, we do not learn about the universe by merely thinking about it. Rather we employ our body, our eye-brain vision system in particular, in order to perceive physical facts, develop classifications, delineate concepts, and contrast metaphors.

More specifically, the astrophysicists' renderings and investigations of the minutae, called anisotropies, in the CMBR are manifest in text, equations and images, all displayed, manipulated and viewed on the computer monitor. Thus the monitor acts as an interface between 2 vast realms, one external and one internal. The external realm consists of the space-time dimensions of outer space and contains all the matter, energy, and physical phenomena within the universe. The other realm is the domain of the mind and the human capacity for reason, understanding and imagination. This interface is used to its full capacity when the monitor, like a telescope, extends the human vision system, displaying images created from the collected data. These images can be very naive, often reducing to contour plots, and rarely are they poetic. This is because for most of the electromagnetic spectrum, including the microwave region, defining what your eyes see as "believable" or "truth" would be meaningless. Instead images constructed from data, such as that acquired by Planck, are representations of measurable physical truths, such as variations in temperature and the dimensions of structures.

Extracting the measurements of the original temperature structure in the CMBR, those initial waves in the cosmic plasma, is, however, a severe challenge. The data collected by the satellite are very complex, entwining together time, distance, and motion. Since light travels at a measured finite speed, its progress is not instantaneous. The more distant an object, the longer it takes the light it emits to travel to our telescopes. Since Planck simultaneously observes structure from the nearby universe and light from the distant universe, its data contains temperature fluctuations from both the recent era of our existence and from our primordial past. Thus the raw images of the CMBR are, like the computer monitor, an interface for 2 other vast realms. In order to investigate the cosmic waves this interface between the current universe and the past universe needs to be scrutinized and assessed. Specifically the signals in the data from the radiation emitted by structures in our proximity need to be determined and removed before we can analyze patterns that strictly exist in the CMBR all with a view to understand the conditions which were in place shortly after the birth of space and time.

One of the nearby structures that is convolved (or in other words entwined) into the CMBR data, and which could significantly impact our interpretation of Planck's observations, is our own Milky Way Galaxy. The filaments and clouds of cool hydrogen gas in our relatively local environment will generate some microwave, as well as radio, radiation. While historic surveys indicated little gas exists in the halo above the disk of our spiral Galaxy, those observations were like brief glimpses compared to Planck's deep, probing stare. Faint gas could be detected if longer observing times were used. However how can the Milky Way gas be isolated from more distant objects containing gas? The solution is to observe the motion of the gas. Our Galaxy rotates, has fountain-like outflows, and accreting gas clouds. While their speeds are hundreds of kilometres per second, this is much less than the thousands of kilometres per second recessional velocity of other galaxies.


Fig. 1. Print-style layout, channel-by-channel, of a few velocity channels in a cube created from DRAO Planck Deep Field data acquired by Taylor et al.

Radio telescopes can capture motion. Consider your television monitor which for each frequency (channel) presents images from a different broadcasting station. Similarly, a radio telescope for each frequency (channel) receives a different image, though in this case all images are associated with a specified position on the sky and each channel is associated with a specific velocity. The resulting data is, instead of a single 2-D picture, a cube which is a stack of images for a range of velocities. This cube must be rendered on the computer monitor in order to detect continuous, related structures and to make measurements of their physical aspects. While a cube could be printed out channel by channel onto sheets of paper, as in Fig. 1, this does not generate the more significant comprehension of the phenomena that occurs during the manipulation of the data by software interfaces that can rotate, tip, slice, and vary the brightness of the cube when it is displayed on the computer. The right-hand-side of Fig. 2 shows a screen-shot of a data cube rotated and tipped using KARMA visualization software.



Fig. 2. Screen-shot of a portion  of the DRAO Planck Deep Field cube displayed in Karma Visualization software. The window on the left shows 3 faces of the cube, with one slice (channel) in the larger rectangle. The window on the right displays the data cube rotated and tipped.

The animation for this article also provides an illustration of a data cube. The cube was acquired, by A. Russ Taylor (University of Calgary) and his team, in order to determine how significantly the Planck observations will be effected by any faint gas in the Milky Way. They used the Dominion Radio Astrophysical Observatory's (DRAO) Synthesis Telescope to examine an apparently empty part of the Galactic halo, discovering faint, diffuse cold gas structures which could generate microwave radiation. Each frame in the animation that displays these "ribbons" of gas represents a different velocity within the few hundred kilometre per second range associated with our Galaxy.

For this animation, I have assigned the initially black and white data a set of colours - a few examples of the black and white channels are in Fig. 1. My colour selection is a metaphor for the Doppler shift; it is a fact that the colour (or peak wavelength) of light emitted by gas flowing towards a viewer will shift towards the blue end of the electromagnetic spectrum while light emission from receding gas shifts towards the red end. Of course the eye-brain vision system perceives these colours in the opposite sense: blue appears to recede into the background of an image and red appears to jump to the foreground. In the animation I retain the scientific colour legend (e.g. blue moves towards the viewer) but adapt the selected colour in an attempt to also visually support the legend. For example, in the most blue-shifted frame I’ve selected a light, warm blue (cyan) in order to use warmth and a light-dark contrast to give the sense that this gas approaches the viewer. I have split red into magenta and yellow, assigning dull yellow to the most red-shifted emission to indicate that the preceding magenta frame is more blue-shifted. If the ribbon of gas was flowing in one direction, the colour would smoothly transition across the front face of the cube in that direction as the animation advanced, creating a rainbow-like band that steps from pale cyan to blue through magenta to orange. Instead what we see here is that each colour is spread across the cube's face. As such we can apprehend that the gas is in turbulent motion rather than flowing. Finally there is a frame with "dots". These are energetic, young, active galaxies too distant to be resolved into their disk or elliptical shapes. They were captured by the DRAO Telescope at the same time as it observed the velocity data. Their inclusion turns this animation into a metaphor for the blending of distance and proximity at an interface. The metaphor is even more strongly emphasized in the 2-D image of the animation in Fig. 3 where the stacked images in the cube have been merged into a single 2-D image, entangling the distant active galaxies and the local gas, the past with the recent.



Fig. 3. The colorized channels in the 3-D animation merged together into a single 2-D image. This shows ribbons of turbulent gas in our Milky Way super-imposed on distant, young active galaxies. (The colourized cube was produced using the Gnu Image Manipulation Program.) 

The image and animation are unfamiliar and abstract to the viewer, who may clutch at Rorschach-like visions of spooks in order to attach meaning to this material.  However what is more important is the meaning of this dataset to explorations of our host Galaxy and our assessment of the CMBR. Since these images do not have structures than can instantly be categorized like, say, remnants of exploding stars, the loops of solar flares, or the swirling clouds on Jupiter, we must apply some effort to digest their contribution to the stable, scientific facts constituting the framework of our understanding of the universe.  And at this point in human history it is the computer and its monitor that facilitate the transformation of these colourful ink-splotches into physical objects that can be classified.

Unlike the printed page, the image on the monitor is maleable. Different grayscales can be applied, colour contrasts implemented, and perspectives redrawn, all in real time. The printed page can be held and viewed, but the image on the computer offers an opportunity to use our bodies more fully, engaging our hand on the mouse as well as our eye-brain vision system when we manipulate the data using various software packages that display these data. George Lakoff and Mark Johnson (Philosophy in the Flesh: The Embodied Mind and Its Challenge to Western Thought, 1999) in their description of the philosophy of "embodied realism" point out that much thought is completely inaccessible to direct conscious introspection and that reason is necessarily tied to our bodies since it develops out of our perceptions and manipulations of our environment. If our understanding of reality is largely created by our cognitive unconscious then exploiting the peculiarities of our human eye-brain vision system, that is, extending its capacities beyond the telescope via display software, becomes beneficial. Perceiving data on the monitor allows us to interface with, and engage, our vast inner space, the part of our mind from which concepts, metaphors and categories percolate toward consciousness.

Lakoff and Johnson also point out that scientific categories formed by the human mind can accurately match divisions of things in the world, resulting in stable scientific knowledge. From my perspective, the technologies that extend our embodied perceptions not only extend the range of categories available to fit phenomena in the real world, but facilitate significant changes in our perceptions, conceptions, and classifications. This engagement allows us to aim for unexplored territory and experience the counter-intuitive. For example, before photographic film existed it was not known that hot stars were blue-ish while cool stars were red; intuition suggested that stars should all be white.  Photography has been replaced by the computer monitor which provides the interface between the vast external realm of astronomical data and our minds by being the site of our physiological experience during the process of exploring the cosmos. In the example of the radio telescope dataset above, this interface has allowed us to discover unexpected gas and categorize it as "relatively local" and turbulent in motion. Astronomers can now use these characteristics to remove the impact of local structures from the signal of the distant cosmic waves in the CMBR observed by the Planck satellite. Continuing to employ the monitor they will use Planck's data to assess the uncertainties in acceleration of the universe's expansion, test whether the universe’s scale inflated drastically during an era near the beginning of time, and attempt to grasp the natures of dark matter and dark energy.


Dr. Jayanne English is an associate professor in the Department of Physics and Astronomy at the University of Winnipeg and is known for her astronomy public outreach images. You can read her writing about the visualising outer space from telescopic observations online at horizonzero.ca (issue 06 titled See) and on her website.

The animation was made by Jayanne English (University of Manitoba) with the support of A. R. Taylor (University of Calgary) and NSERC for the DRAO Planck Deep Field project.
 
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