Sky & Telescope - April 2025 - 13

ASTEROID TRACKS: NASA / JPL-CALTECH / UCLA; CRAFT: NASA
Farewell to
NEOWISE
From Earth's nearest neighbors to the edge of the observable universe, the
WISE/NEOWISE mission gave us an inimitable view of the infrared sky.
E
ven small spacecraft missions can take nearly a
career's worth of time to complete. Such was the case
with the Wide-field Infrared Survey Explorer (WISE).
First envisioned in 1994 and launched in 2009, WISE
mapped the whole infrared sky in six months, seeing
everything from nearby cool stars to the most luminous
galaxies in the universe. Following its fantastic success at
finding and characterizing hard-to-spot Earth-approaching
asteroids, this SUV-size spacecraft was given second,
third, fourth, and many more chances at life, eventually
conducting an extended survey that lasted until July 2024.
By the time natural orbital decay forced an end to the
mission, the core scientists had been working on it for
30 years. I am a relative newcomer to the project, having
started in late 2003 as a freshly minted PhD.
The WISE mission's original objective was to map the
entire sky in infrared wavelengths of light, which humans
perceive as heat. The four infrared channels that WISE
employed ranged from 3.4 to 22 microns, or wavelengths
roughly 5 to 30 times longer than the reddest light our
eyes can see.
Infrared light offers enormous advantages to astronomers.
Infrared cameras can peer through dust clouds that
are opaque at visible wavelengths. Distant galaxies whose
light has been stretched by their mind-boggling velocities
via the redshift effect become detectable at longer infrared
wavelengths. Finally, the faint sparks of heat emitted by
cool objects too dim to be seen at visible wavelengths can
appear as brilliant sources in infrared light.
Earth's atmosphere does a remarkably good job of
blocking a great deal of infrared radiation, though - or
holding it in like a thermal blanket, giving rise to the
heat-trapping greenhouse effect. This warmth makes it
difficult to see the faint heat emitted by distant objects
in space: Heat from the atmosphere and the telescope
itself creates an impenetrable glow that blocks out all but
the brightest infrared sources in the sky. One of my colTHE
SPACECRAFT Seen here in the lab before launch, the WISE
space vehicle's white cryostat encloses the instrument and also contains
the solid-hydrogen tanks, imaging optics, and detector arrays. The silver
dome-shaped cover was ejected shortly after launch.
sk yand tele scope .o r g * APRIL 2025 13

http://skyandtelescope.org

Sky & Telescope - April 2025

Table of Contents for the Digital Edition of Sky & Telescope - April 2025

Contents
Sky & Telescope - April 2025 - Cover1
Sky & Telescope - April 2025 - Cover2
Sky & Telescope - April 2025 - 1
Sky & Telescope - April 2025 - Contents
Sky & Telescope - April 2025 - 3
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Sky & Telescope - April 2025 - Cover3
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