+ Play
Audio
|
+ Download Audio | +
Email to a friend | +
Join mailing list
Sept.
2, 2008: There's more than one way to watch a meteor
shower.
One,
the old-fashioned way: Find a dark place with starry skies
and count the meteors streaking overhead. Two, the new way:
Find a dark place with starry skies and then completely
ignore the meteors. Instead, watch the Moon.
That's where the explosions are.
On
August 9th, a pair of amateur astronomers on opposite sides
of the United States did it the new way. With the Perseid
meteor shower just underway, they fixed their cameras on the
Moon and watched meteoroids slam into the lunar surface. Silent
explosions equivalent to ~100 lbs of TNT produced flashes
of light visible a quarter of a million miles away on Earth.
It was a good night for "lunar Perseids."
"I
love watching meteor showers this way," says George Varros,
who recorded this impact from his home in Mt. Airy, Maryland:
The flash, which lit up a nighttime patch of Mare Nubium (the
Sea of Clouds), was a bit dimmer than 7th magnitude--"an
easy target for my 8-inch telescope and low-light digital
video camera."
Hours
later, another Perseid struck, on the western shore of Oceanus
Procellarum (the Ocean of Storms). This time it was Robert
Spellman of Azusa, California, who caught the flash. "It's
exciting to witness these explosions in real time," he
says. "I used a 10-inch telescope and an off-the-shelf
Supercircuits video camera."
Rob
Suggs of NASA's Meteoroid Environment Office has reviewed
the data. "They look real to me," he says. "The
flashes appear in multiple video frames and the light curves
are similar to other lunar meteors we've recorded in the past."
Suggs
would know. Along with colleague Bill Cooke, he leads a team
at the Marshall Space Flight Center that has recorded more
than 100 lunar explosions since 2005. "We monitor lunar
meteors in support of NASA's return to the Moon," Suggs
says. "The Moon has no atmosphere to protect the surface,
so meteoroids crash right into the ground. Our program aims
to measure how often that happens and answer the question,
what are the risks to astronauts?"
Above:
A map of 100 lunar meteors observed by astronomers at the
Marshall Space Flight Center since 2005. Every impact on the
map was bright enough to see with an amateur telescope. [more]
NASA's
official lunar meteor observatories are located in Alabama
and Georgia. Both were off-line on August 9th, so the NASA
team didn't see how many Perseids were hitting the Moon that
night.
"This
shows how amateur astronomers can contribute to our research,"
points out Suggs. "We can't observe the Moon 24-7 from
our corner of the USA. Clouds, sunlight, the phase of the
Moon—all these factors limit our opportunities. A global network
of amateur astronomers monitoring the Moon could, however,
approach full coverage."
By
day, George Varros is a software engineer at NASA headquarters.
After work, he takes off his NASA badge, goes home and fires
up his self-described "barely adequate" telescope.
"Until a few years ago, I really didn't like the Moon because
it interfered with my observations of comets and meteors. Then,
in 1999 during the Leonid meteor storm, (fellow amateur astronomer)
David Dunham photographed six lunar impact events from my backyard
in Maryland," Varros recalls. "I was hooked."
Dunham's
observations inspired not only Varros, but also NASA. "Our
own observing program can be traced back to those early amateur
observations of lunar Leonids," says Suggs.
A
major advance in lunar meteor detection came in 2006 in the
form of LunarScan, a computer program written by amateur astronomer
Pete Gural that searches digital video of the Moon for split-second
flashes. Using LunarScan, Varros has bagged at least a dozen
lunar meteors. Three of them were observed simultaneously
by the NASA team in Alabama, confirming the fidelity of Varros'
techniques. (LunarScan may be freely downloaded from Varros'
web site; NASA uses the program,
too!)
Right:
Spellman's lunar Perseid, recorded from his home near Los
Angeles at 0406 UT on Aug. 9, 2008. [more]
Like
Varros, Robert Spellman's interest in lunar meteors began
with the Leonids of 1999. "I read about the success of
amateurs recording impact flashes," he recalls. "I've
been in love with the Moon since my first observation when
I was five years old, and I wanted to conduct an observing
program with scientific value. Lunar meteors were a natural."
Spellman's
day job is at the Natural History Museum of Los Angeles and
the La Brea tar pits where he works as an educator. He also
conducts public astronomy programs three nights a week at
the Griffith Observatory. The rest of his evenings he devotes
to the Moon.
Spellman
uses no special software to catch his impacts. "I look
for the flashes in real time," he says. "Although
it may sound tedious to stare at a blank screen for hours
on end, the prospect of seeing an explosion keeps me alert.
In future, I do plan to use LunarScan to increase my success
rate."
Suggs
hopes other amateurs will take up this hobby, not only to
improve NASA's lunar impact statistics, but also to support
the agency's LCROSS mission: In 2009, the Lunar CRater Observation
and Sensing Satellite (LCROSS) will intentionally dive into
the Moon, producing a flash akin to a natural lunar meteor.
Unlike natural meteoroids, which hit the Moon in random locations,
LCROSS will carefully target a polar crater containing suspected
deposits of frozen water. If all goes as planned, the impact
will launch debris high above the lunar surface where astronomers
can search the ejecta for signs of H2O. The impact
flash (if not hidden by crater walls) and the debris plume
may be visible to backyard telescopes on Earth: details.
Ready
for meteor watching--the new way? NASA offers a FAQ
and telescope
tips to help you get started. Good hunting!
SEND
THIS STORY TO A FRIEND
Author: Dr.
Tony Phillips | Credit: Science@NASA
more
information: |
NASA
Meteoroid Environment Office -- home of the lunar
impact monitoring program
The
Buddy System: "We ordinarily require confirmation
of an impact flash by at least 2 telescopes. This is
essential for faint, fast (1 video frame) flashes to
avoid confusing cosmic rays and satellite glints,"
explains Rob Suggs. "When a single telescope captures
a multi-frame flash with that classic light curve decay,
we can be fairly certain it was an impact. This was
the case for the independently observed Perseids of
Spellman and Varros. But it's still better to have more
than one telescope pointed at the Moon. We encourage
amateurs to get a buddy a few miles away to observe
at the same time; multiple telescopes allows confirmation
of the fainter and much more plentiful impacts."
2008
Perseids: The 2008
Perseid meteor shower began in early August and
peaked on August 13th. Lunar meteors were not visible
during the peak because on peak-night the Moon was nearly
full and offered no dark terrain to observe. August
9th, off-peak, was a better date for lunar Perseids
because the Moon was only 60% full and 40% dark, much
better seeing lunar meteors.
George
Varros' lunar impact
home page
Robert
Spellman's lunar
impact home page
NASA's
Future: US
Space Exploration Policy |
|