The Many Infrared 'Personalities' of the Sculptor Galaxy
October 13, 2010
The Sculptor galaxy is shown in different infrared hues, in this new
mosaic from NASA's Wide-field Infrared Survey Explorer, or WISE. The
main picture is a composite of infrared light captured with all four of
the space telescope's infrared detectors.
The red image at bottom right shows the galaxy's active side.
Infant stars are heating up their dusty cocoons, particularly in the
galaxy's core, making the Sculptor galaxy burst with infrared light.
This light -- color-coded red in this view -- was captured using WISE's
longest-wavelength, 22-micron detector. The dusty burst of stars is so
intense in the core that it generates diffraction spikes. Diffraction
spikes are telescope artifacts normally seen only around very bright
stars.
The green image at center right reveals the galaxy's emerging young
stars, concentrated in the core and spiral arms. Ultraviolet light from
these hot stars is being absorbed by tiny dust or soot particles left
over from their formation, making the particles glow with infrared
light that has been color-coded green in this view. WISE can see this
light with a detector designed to capture wavelengths of 12 microns.
The blue image at top right was taken with the two
shortest-wavelength detectors on WISE (3.4 and 4.6 microns). It shows
stars of all ages, which can be found not just in the core and spiral
arms, but throughout the galaxy.
The Sculptor galaxy, or NGC 253, was discovered in 1783 by Caroline
Herschel, a sister and collaborator of the discoverer of infrared
light, Sir William Herschel. It was named after the constellation in
which it is found, and is part of a cluster of galaxies known as the
Sculptor group. The Sculptor galaxy can be seen by observers in the
southern hemisphere with a pair of good binoculars.
NGC 253 is an active galaxy, which means that a significant
fraction of its energy output does not come from normal populations of
stars within the galaxy. The extraordinarily high amount of star
formation occurring in the nucleus of this galaxy has led astronomers
to classify it as a "starburst" galaxy. At a distance of approximately
10.5 million light-years away, NGC 253 is the closest starburst galaxy
to our Milky Way galaxy. However, the starburst alone cannot explain
all the activity observed in the nucleus. One strong possibility is
that a giant black hole lurks at the heart of it all, similar to the
one that lies at the center of the Milky Way.
In late September of this year, after surveying the sky about
one-and-a-half times, WISE exhausted its supply of the frozen coolant
needed to chill its longest-wavelength detectors -- the 12- and
22-micron channels. The satellite is continuing to survey the sky with
its two remaining detectors, focusing primarily on asteroids and
comets. Read more about this survey, called the NEOWISE Post-Cryogenic
mission, at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-320 .
