An eerie
cloud that glowed briefly in the night sky Saturday was no UFO. It was created
by humans - more specifically a NASA rocket built to make clouds that shine at
night.
The rocket
launched as part of an experiment to artificially create so-called noctilucent -
or night-shining
- clouds, the highest clouds on Earth. They naturally appear around 50 miles (80
km) above Earth's high latitudes and are also known as polar mesospheric
clouds.
Saturday
night's rocket experiment lifted off at 7:46 p.m. EDT
(2346 GMT) from NASA's Wallops Flight Facility on Wallops Island, Va. It
created a brief
light show that was visible across the United States' East Coast and
sparked calls from curious skywatchers as far away as Boston, according to the
Associated Press.
"It
was very impressive ... albeit short-lived," said Joe Rao, an instructor and guest lecturer
at New York's Hayden Planetarium, who witnessed the event. Rao is also SPACE.com's
skywatching columnist.
The
experiment created a man-made noctilucent cloud using the fourth stage of a
NASA Black Brant XII suborbital sounding rocket that spewed exhaust particles
173 miles (278 km) above Earth. Ground-based radar and camera stations recorded
the resulting cloud's formation and illumination. The U.S. Naval Research Laboratory
and Department of Defense's Space Test Program oversaw the launch, which it
called the Charged Aerosol Release Experiment.
NASA has
observed naturally
occurring night-shining clouds using its AIM satellite. The Naval Research
Laboratory and Space Test Program also uses a satellite called STPSat-1 to
observe the phenomena and also used the spacecraft to observe Saturday night's
man-made cloud.
"We
weren't exactly sure what we were going to see, as this was the very first time
that a noctilucent cloud experiment was attempted," Rao said. "Would it be
something obvious to the eye, or something rather faint?"
The
result, he added, was spectacular.
Rao
described the cloud as "a brilliant object" that displayed
a wide, fan-shaped tail shortly after it was created. But the artificial
phenomenon was over in just a few minutes.
"The
"head" of the comet (which was the rocket's fourth stage) rapidly
faded out and the "tail" gradually faded over the next minute or so
into the background of the sky," Rao said.
Scientists
will use the measurements of the artificial cloud to better understand natural
noctilucent clouds, as well as help predict the effects of rocket engine
exhaust in the upper atmosphere.
Saturday
night's experiment was a cooperative effort by NASA, the United States Naval Research
Laboratory, the Defense Department's Space Test Program and several
universities. But the stunning cloud it created was seen by more than just the
project's scientists.
"I'm
sure many unsuspecting folks up and down the East Coast were surprised by this
very unusual sight," Rao said.
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