Press Release

First Spectacular Images from SAO’s IRAC Camera on Spitzer Space Telescope

By SpaceRef Editor
December 18, 2003
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Washington, DC- NASA today released the first spectacular images from the
Infrared Array Camera (IRAC) instrument on board the Spitzer Space
Telescope. The pictures, taken at infrared wavelengths of light, revealed
remarkable details in objects ranging from nearby star formation regions to
distant spiral galaxies. The images are but a taste of what will come from
IRAC, which was developed for NASA by a team led by the Smithsonian
Astrophysical Observatory (SAO), with Giovanni Fazio as the Principal

“We are absolutely thrilled by the performance of IRAC, which has met or
exceeded all expectations,” says Fazio. “Every time we take a picture, we
see something spectacular!”

The three IRAC objects featured in today’s press conference at NASA
Headquarters are emission nebula IC 1396, spiral galaxy Messier 81 (M81),
and Herbig-Haro 46 (HH 46).

“Together, these three images show how IRAC will serve as a ‘time machine,’
giving us new information about the past, present, and future of our cosmos.
Combined with its ability to peer into the distant past of the universe by
studying highly redshifted galaxies, IRAC truly is lifting the cosmic veil
and revealing hidden wonders,” says Fazio.

IC 1396

The first, and arguably the most dramatic, IRAC image shows a section of the
bright emission nebula IC 1396, which is located about 2500 light-years from
the Earth in the constellation Cepheus. An emission nebula is a cloud of
hydrogen gas ionized by the strong radiation from hot, young stars and
glowing like a neon sign. IC 1396 in visible light is known as the “Elephant
Trunk” nebula. On viewing the IRAC photo, scientists suggested that the
“Flying Dragon” or “Flaming Ghost” nebula might be more appropriate.

The region of IC 1396 imaged by IRAC is a globule of gas and dust about 12
light-years in size. In visible light, it appears as a dark silhouette
against the background of glowing nebular gas. Yet IRAC revealed it to be
shining brightly at infrared wavelengths.

This globule is a remnant of a much larger molecular cloud complex in
Cepheus that already has formed populous star clusters. This leftover blob
of gas and dust is being sculpted by the intense radiation from nearby
massive, hot, young stars.

“Radiation and hot winds are carving away the nebula like rust sandblasted
from an old car. Eventually, it will vanish completely. We’re lucky to have
caught it in the act, to get a chance to see these stunning ethereal wisps
before they disappear,” says Fazio.

Messier 81

The second IRAC photo shows the spiral galaxy M81, located about 12 million
light-years away in the constellation Ursa Major. In many ways, M81 is a
near-twin to our own Milky Way galaxy.

“By studying M81, we can get an outsider’s view of our home. This is what
aliens would see if they looked back at the Milky Way,” says Fazio.

In visible light, M81 displays an unremarkable disk and central bulge of
stars. Dust lanes wind throughout the disk, hiding details of the galaxy’s
structure and composition. IRAC sweeps away that obscuration to clearly
separate M81’s stars (dominant in the near-infrared) from its hot dust (most
visible at mid-infrared wavelengths). In doing so, IRAC uncovered areas
where star formation is taking place, visible in the image as
infrared-bright clumpy knots within the well-defined spiral arms. The huge
amounts of dust revealed by IRAC, and the associated hydrogen gas, will
provide raw materials for future star formation.

The photo of M81 is a four-color composite of infrared light at wavelengths
of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (yellow), and 8.0
microns (red).

Herbig-Haro 46

The third IRAC image shows HH 46, a glowing curved line of gas marking a
shock wave that is blasting through the interstellar medium. HH 46 and its
partner, HH 47, show where twin jets of material spew out in opposite
directions from a previously hidden source, plowing through anything in
their way.

The sharp infrared eyes of IRAC exposed the source of these jets – a young
protostar embedded in an obscuring cloud of matter.

“This youngster is still forming, and like any youngster, it’s acting up a
bit,” says Fazio.

Most young stars produce powerful jets during their birth, in a process yet
to be fully understood by scientists. Those jets may help the star to
collect infalling material by removing excess angular momentum. Without
them, like an ice skater who pulls in his arms while spinning in place, the
star soon would whirl so fast that centrifugal forces would stop its growth.

While powerful jets are believed to assist forming stars, the jet of HH 46
is particularly strong, speeding outward across more than 9 light-years of
space. (For comparison, the closest star to the Sun is only 4 light-years

The Infrared Array Camera is one of three science instruments on board the
Spitzer Space Telescope. IRAC was developed by SAO and built at the
NASA/Goddard Space Flight Center. The Spitzer Space Telescope mission is
managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif., a
division of the California Institute of Technology.

The Spitzer Space Telescope, launched August 25 from Cape Canaveral, Fla.,
uses state-of-the-art infrared detectors to pierce the dusty darkness
enshrouding such celestial objects as galaxies, stars, and planet-forming
discs around stars. It is the fourth of NASA’s Great Observatories, which
include the Hubble Space Telescope, Chandra X-ray Observatory and Compton
Gamma Ray Observatory.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics is a joint collaboration between the Smithsonian Astrophysical
Observatory and the Harvard College Observatory. CfA scientists, organized
into six research divisions, study the origin, evolution and ultimate fate
of the universe.

SpaceRef staff editor.