From: LARRY KLAES (email@example.com)
Date: Wed Feb 13 2002 - 19:28:34 PST
----- Original Message -----
From: Larry Kellogg
Sent: Wednesday, February 13, 2002 4:39 PM
Cc: Larry Kellogg
Subject: Our Solar System as seen by Alien Astronomers
Good midweek day to you all.
Ric Campo, who used to work with us on the Pioneer missions and Lunar
Prospector mission and now with Lockheed/Martin on Gravity B, passed
me this link on the space.com site.
What caught his eye was that "Pioneer gets credit for something".
Just for the record, Pioneer 10 will have been heading out into space
for 30 years as of March 2, 2002. - LRK -
By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
12 February 2002
If alien astronomers from a nearby star system pointed their version
of the Hubble Space Telescope
at Earth, astronomer Markus Landgraf believes they would not see our
planet but they would find
hints of our presence.
With their infrared camera, the smart aliens would detect a vast
donut-shaped ring of dust with a
classic hole in the middle, all surrounding a yellow star. A little
math, Landgraf says, and they
could deduce the presence of a large planet, like Jupiter, that had
cleared out the hole. They would
also spot Neptune's signature scrawled in the dust.
If this culture's astronomical knowledge were as advanced as ours,
they would then wonder if a planet like
their own, a habitable world, also orbited the yellow star.
Landgraf, an earthbound astronomer working in Darmstadt, Germany, as
a mission analyst for the European Space
Agency, studies data collected by a pair of space probes that left
Earth three decades
ago. His research, along with that of some colleagues, is making a
mirror out of our solar system, one that reflects on other stars and
the planets they might harbor.
Faster than a bullet
Our solar system's donut is made up of dust grains of many sizes. In
order to see signs of planets in the dust, the alien astronomers
would need to tune their instruments to spot the smallest dust.
Landgraf studies this, too, bits that are just one-hundredth of a
millimeter, or dozens of times tinier than a typical grain of sand.
It is everywhere in our solar system, zipping around ten times faster
than a rifle bullet.
Near Earth's orbit around the Sun, there is about one spec of this
small dust in each cubic kilometer of space, Landgraf says. If there
were no planets circling the Sun, the dust inside Jupiter's orbit
would be at least twice as dense, he said.
The densest portion of the dust donut is beyond Saturn's orbit, at
about fifteen times the Sun-Earth distance.
Here, larger dust grains rule.
The Pioneer 10 and 11 spacecraft found this far-out, high
concentration of dust in the 1970s and early '80s. Previously,
astronomers had expected dust to thin out with distance from the Sun,
because they knew that solar radiation created drag on the dust
particles, causing them to spiral inward to the Sun.
Ever since the Pioneer findings, astronomers have wondered where all
the dust comes from. Since theory held that such dust would
eventually be shipped to the Sun, there must be some mighty dust
factories out in the suburbs of the solar system, replenishing the
supply. Landgraf and his colleagues have estimated that 50 tons of
dust are produced every second.
As with many things in the universe, violent collisions are behind it all.
Using the old Pioneer data, Landgraf and his colleagues demonstrated
through computer modeling that comet-like objects beyond the orbit
of Neptune are the sources of the dust.
"They tend to collide with each other," Landgraf explains. "Much like
a brick you let fall from your roof that hits the ground in your
driveway, they explode into millions of pieces."
The solution might seem obvious. But the distant comets, often called
Kuiper Belt Objects, were not
known until the early 1990s. Only in the past five years or so has
anyone tried to link them to the dust, Landgraf said.
The research revealed another dust-generation method at work, too.
Alien dust -- typically even smaller particles -- wafts through the
galaxy, and our solar system continually plows through it, Landgraf
said. Like sandpaper, this interstellar dust rubs on comets and
makes more dust.
See the web site for the rest of the story - I got you to Pioneer 10
and 11 and that is what caught my eye also but there is more, so
check out the whole story.
A few more snips about Pioneer 10 for those new to the list - LRK -
Launched on 2 March 1972, Pioneer 10 was the first spacecraft to
travel through the Asteroid belt, and the first spacecraft to make
direct observations and obtain close-up images of Jupiter. Famed as
the most remote object ever made by man, Pioneer 10 is now over 7.3
billion miles away (Until 17 February 1998, the heliocentric radial
distance of Pioneer 10 had been greater than that of any other
manmade object. But late on that date Voyager 1's heliocentric radial
distance, in the approximate apex direction, equaled that of Pioneer
10 at 69.419 AU. Thereafter, Voyager 1's distance will exceed that of
Pioneer 10 at the approximate rate of 1.016 AU per year). The
spacecraft made valuable scientific investigations in the outer
regions of our solar system until the end of its mission on 31 March
1997. The Pioneer 10 weak signal continues to be tracked by the DSN
as part of a new advanced concept study of chaos theory. Pioneer 10
is headed towards the constellation of Taurus (The Bull). It will
take Pioneer over 2 million years to pass by one of the stars in the
Pioneer 10 distance from Sun : 79.66 AU Speed relative to the Sun:
12.24 km/sec (27,380 mph) Distance from Earth: 11.84 billion
kilometers (7.36 billion miles) Round-trip Light Time: 21 hours 56
Pioneer 10 had another successful track on 7/9/01 - exactly one year
after the last pointing maneuver. The original results back on 7/9/00
- weak signal - seemed to indicate that the maneuver may have
failed. The signal strengths from the latest tracks, however,
indicate that last year's weak signal was probably due to the onboard
one-way oscillator. Therefore, we conclude that the maneuver did
work, and another pointing maneuver will not be necessary until first
Larry Lasher, Pioneer Project Manager
And for bragging rights - the image of the Pioneer data is from the
Pioneer 10 Telemetry system re-written to run on a Mac Quadra 950 by
yours truly back in 1995. The red switches indicates that there were
some items out of limit. Cold, is Cold, is Cold when you have shut
most everything off except Dr. Van Allen's Geiger Tube Telescope.
The application software that was used to write the program was
National Instrument's LabVIEW version 3.0, which is now in version
My how time does fly when you are having fun.
If you any suggestions or comments please feel free to write to my Ames e-mail
WHAT THE MIND CAN CONCEIVE, AND BELIEVE, IT WILL ACHIEVE - LRK
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-- Larry R. Kellogg firstname.lastname@example.org http://lunar.arc.nasa.gov
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