The World Egg Universe
Images – Frequently Asked Questions
What are these images?
Why are the images shaped
liked eggs?
What is the white form stretching across all these images? What are the
other bright spots?
What is
the Planck satellite, and what was its mission?
How were the
images in this exhibition created?
What data was used?
What is the
resolution of the data, and of the images?
What are the
colors of the images? Are they real?
How has this
same data been visualized by others?
How do the
prints relate to the painting on display?
In Universe Baby Picture (the print and the painting), why has the
microwave foreground been included?
Are these prints
scientifically valid or useful?
What are these images?
These images are all depictions of the entire universe, seen
from the earth, looking out into the cosmos in all directions.
Why
are the images shaped liked eggs?
These oval images are based on the
Mollweide projection,
which is a way of mapping a spherical surface onto a flat surface, with
minimal distortion. If you imagine cutting the oval shape out, and bending
it around the long axis, you can see how it relates to the celestial sphere.
What is the white form stretching across all these images? What are the
other bright spots?
The central white form is the Milky Way galaxy. The images
are oriented to the galactic center, using
galactic coordinates. If you have ever looked up on a clear night and seen the milky way glowing
as a line across the sky, you will recognize how this image is oriented.
Bright spots correspond to other strong microwave sources, some relatively
nearby, others more distant. This
image identifies some of these, such as the Magellanic Clouds and the
Andromeda galaxy.
What is the
Planck satellite, and what was its mission?
The European Space Agency’s Planck satellite was designed to
do a complete microwave survey of the universe, at a higher resolution than
any previous mission. The major scientific question of interest was to
study the Cosmic Microwave Background radiation (CMB), the echo of the Big
Bang that is observed everywhere in the universe. The CMB, originally
thought to be completely uniform, has been observed to have slight
variations. Scientists hope to gain insight into the early universe by
studying these variations. An excellent description of of how the CMB
was observed and analyzed by the Planck scientists can be found at
http://sci.esa.int/planck/51551-simple-but-challenging-the-universe-according-to-planck/.
How were the images
in this exhibition created?
The Planck satellite performed a multi-year mission,
observing the universe in every direction, and taking measurements at nine
different channels, all in the microwave spectrum. Thousands of scientists
and technicians were involved in the planning and execution of the mission,
and the analysis of the data. This data was published, and I downloaded
it. I created the images in this series using astronomical software (Aladin/CDS)
to handle the data and create monochrome single-channel images, and imaging
software (Photoshop) to create layered, composite color images.
What data was used?
The Planck dataset (e.g. available at
http://irsa.ipac.caltech.edu/data/Planck/release_1/all-sky-maps/index.html)
contains many versions of the mission data. The raw observation data was
cleaned and processed in a variety of complex ways. I ended up using the
cleaned “sky-map” version of each of nine channels from the HFI or LFI
detectors: 30,44,70,100,143,217,353,545, and 857 GHz. For the image
Universe Now and Then I also used an additional three channels: the
Cosmic Background Radiation, which was calculated in three different ways,
and distributed as SMICA, NILC, and SEVM.
What is the
resolution of the data, and of the images?
The data for most channels was collected in a 1024x1024
equal-area grid (HEALPix
coordinates). This means that each channel has one megapixel of
grayscale information. Thus the data for each of the images in the
show contains 9 or 12 megapixels . When this information is mapped with a
Galactic Mollweide projection, individual pixels appear as diamond shapes,
which can be very faintly discerned in the images here. The color images
were built from layers of projected and upsampled data, to reach the 34
megapixel color resolution of the prints. The layers were combined in
Photoshop using a wide range of blending and adjustment options to bring out
the maximum amount of visual detail possible and to remove projection
artifacts. The final Photoshop file contained over 80 layers, and required
over 2 gigabytes of storage.
What are the
colors of the images? Are they real?
The satellite “sees” in the microwave spectrum, at far
lower frequencies than visible light. To visualize the data, it is
necessary to assign colors to the different frequencies. This technique is
sometimes referred to as “false-color”, although that designation makes more
sense when “natural” colors are replaced by others; in this case most of the
radiation depicted is simply not present in the visible spectrum. Therefore
the choice of color for a visualization is (or can be) a free one. In each
of the three images, I used that freedom for different purposes.
For
Microwave Universe,
I chose a somewhat natural palette, suggesting a “white-hot” glowing center,
cooling to a dark periphery.
For
Universe Baby Picture –
Planck # 1, I playfully altered the spectrum to suggest the canonical
colors of infancy – the pink and blue of hospital swaddling blankets.
For
Universe Now and Then,
I superimposed the microwave foreground onto a background of the CMB
radiation, using a much more restrained version of the baby-picture palette.
How has this same
data been visualized by others?
The European Space Agency produced a visualization of
the Planck All-Sky data (e.g. here:
http://spaceinimages.esa.int/Images/2010/07/The_microwave_sky_as_seen_by_Planck).
Their color and compositing choices were different than mine. You can
also see their visualizations of the individual channels:
http://sci.esa.int/science-e-media/img/6b/Planck_composite_all-sky_Frequency_BLACK_v5.jpg.
How do the
prints relate to the painting on display?
As an artist who has used scientific imagery for many years,
I have always been interested in the way that color has been used in
visualizing data. I made a series of paintings called Macrocosm, all
based on astronomical images. When NASA’s WMAP satellite (Planck’s
predecessor) mapped the CMB starting in 2001, people began to refer to the
resultant images as “baby pictures of the universe”. I was inspired to
create a painting using the “baby” colors of pink and blue. I used an oval
canvas as a support, for its further suggestion of birth.
One of the features of the
painting is that it has a wealth of chaotic, invented detail that was not
derived from the WMAP data, but that is intrinsic to the physical process of
making a painting. The relative low-resolution of the WMAP survey compared
to Planck was ideal for this (mis)use of the data. When the Planck data was
released at a much higher resolution, I was inspired to make my first
all-digital works, creating a more-or-less straight interpretation of the
data.
In Universe Baby Picture (the print and the painting), why has
the microwave foreground been included?
I take it as artistic license. Strictly speaking, it is the CMB, visualized on its own,
that has most often been referred to as the “Baby Picture of the Universe”.
However, when I examined the NASA images showing the process of analytical
subtraction that was required to see the CMB, I found the intermediate
images more visually compelling. I decided to leave the Milky Way and rest
of the foreground in the original painting (and again in the print).
The print Universe Now and Then is an attempt to follow my original
artistic impulse (to use a pink-and-blue-color gradient to represent the CMB)
but still make an image that had a more direct scientific meaning. In
this image the microwave foreground and background are visualized at the
same time, but also clearly distinguishable.
Are these prints
scientifically valid or useful?
All three prints are visualizations of the original
data, and although I have deviated from the standard conventions of
astronomical visualization, I believe they are valid images. Much of my
work as an artist dealing with scientific imagery has been in exploring and
making visible just such conventions of representation.
Clearly the Universe Baby
Picture print uses a palette that prioritizes aesthetic pleasure over
differentiation of fine structure. However, Microwave Universe and
Universe Now and Then are attempts at a natural rendering that I hope
will reveal nuances in the data that were not visible before. I created
Universe Now and Then in response to feedback from some of the Planck
scientists, who suggested that it would be interesting to see the Microwave
foreground rendered on top of and in contrast to the CMB.