~e; infra-red|green|blue = infraRGB imaging
human being <email@example.com>
Tue, 28 May 2002 15:53:29 -0500
[the near infrared imaging of the universe, via what may be
digital cameras (not film) cooled to near absolute zero to
get such photographs. it would be interesting to see what
differences such an imaging technique would show, on earth.]
From: Ron Baalke <baalke@ZAGAMI.JPL.NASA.GOV>
Subject: The Infrared Sky Goes Digital
The Infrared Sky Goes Digital
Jet Propulsion Laboratory
March 28, 2002
Would it be possible to see the entire sky without ever stepping outside?
Well, if you have access to a computer, the answer would be ?yes,? thanks to
the Two Micron All-Sky Survey (2MASS), the most detailed digital map of the
heavens ever made.
"These telescopes have given us the first detailed global view of our Milky
Way Galaxy and the galaxies that lie beyond," said Dr. Michael Skrutskie of
the University of Virginia, the survey's principal investigator. "The
resulting databases and source catalogues are a treasure trove which will be
mined for discovery by scientists and the public alike for decades to come."
A Huge Undertaking
This tremendous task was accomplished by dividing the sky into nearly 60
thousand strips, each covering roughly the area of a toothpick held at arm's
length. Two dedicated telescopes, one in Arizona, the other in Cerro Tololo,
Chile, patiently scanned these strips of sky every night, weather
permitting, for nearly four years.
While observations concluded in February 2001, the massive data reduction
efforts have continued at the Infrared Processing and Analysis Center on the
The 2MASS software automated what would have taken astronomers decades to do
using conventional techniques. The system processed over 100 million
individual frames, stitching them together into larger images while
simultaneously identifying and measuring the properties of all the stars and
galaxies seen within them.
An Infrared Perspective
The 'Two Micron' part of the sky survey refers to the part of the spectrum
viewed by the survey's digital eyes. Near-infrared light has a wavelength
about four times longer than visible light, well beyond the limits of human
vision. The survey telescopes employed sophisticated electronic cameras
cooled to temperatures not far above absolute zero to see into this part of
The cameras simultaneously captured the sky in three different colors of
infrared light. By remapping these colors into the visible colors of red,
green, and blue, astronomers have produced full color images of the sky that
look similar to ordinary visible light images, but show different features.
Even well-known objects like the Orion Nebula take on striking new
Near-infrared light offers several advantages to astronomers. It more easily
penetrates clouds of dust like those found across the Milky Way, revealing
stars and galaxies that are completely hidden in visible light. It is also
more sensitive to the largest population of stars in the Galaxy, the ones
that are smaller and cooler than the Sun. The Two Micron All-Sky Survey
observations open up the universe for studies of previously unknown stars
and lay bare the internal structures of distant galaxies.
The Galaxy Inside-Out
One stunning product of the survey is an 'inside-out' view of our own Milky
Way Galaxy. Constructed from the database of half a billion stars
automatically identified by the processing software, it gives an
unparalleled census of the Milky Way's geography and population.
Evident in striking detail is the flat disk, punctuated by thin lanes of
dense dust clouds. Towards the center we find the galactic bulge surrounding
the inner nucleus of the Milky Way, long thought to harbor a supermassive
The view also extends beyond just the local Milky Way stars. Just beneath
and right of the galactic center we can see the star clouds associated with
our nearest neighbors: the Large and Small Magellanic clouds. A very sharp
eye can even pick out a faint 'finger' of stars in the lower left side of
the galactic bulge; this is the first direct image ever made of a small
dwarf galaxy recently discovered to be in the process of merging with the
Getting the Pictures
The Two Micron All-Sky Survey has opened up new views of the universe,
literally allowing people to see the whole sky in a different light. And
anyone with access to a web browser can enjoy the visual feast.
The catalogues and images are distributed freely to the astronomical
community and the general public via the Internet. Nearly half of the sky is
currently available, and processing is ongoing for the final data release,
expected in late summer 2002.
When the final sets of catalogues and images come online, they will consist
of about 2 terabytes (that's 2,000 gigabytes, or 2 million megabytes!) of
The final release will include catalogues of about half a billion stars and
2 million galaxies. Over one million research-quality images of the whole
sky will be available in each of the three infrared colors observed by
2MASS. Such huge data sets represent part of astronomy's future, as
scientists learn interesting new things by analyzing terabyte-sized sets of
Fortunately the astronomy enthusiast has more direct access to this
fantastic sky imagery. A new '2MASS Showcase' gallery contains a selection
of the very finest full color images from the survey, some at resolutions
suitable for printing full posters!
In addition, the existing Image Gallery and Picture of the Week archives
contain hundreds of images of interesting objects throughout the Galaxy and
beyond. Even the most demanding visitors should be able to find the infrared
views of their favorite objects now that the sky is online for everyone to
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