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AlexBlackwell
There is an interesting paper by Hsiang-Kuang Chang et al. (as well as an accompanying News and Views piece by Asantha Cooray) in the August 10, 2006, issue of Nature about a potential "first ever observation of small (less than 100 metre diameter) trans-neptunian objects (TNOs)" in our solar system based on observations of another star, Scorpius X-1 (Sco X1), by the Rossi X-ray Timing Explorer satellite.

See the Editor's Summary for a brief synopsis and links.
Rob Pinnegar
Cute (and interesting).

Next on the agenda, I guess, will be looking at other X-ray sources at various ecliptic latitudes. If this idea is Kosher, those micro-occultations ought to decrease in frequency away from the ecliptic.
AlexBlackwell
QUOTE (Rob Pinnegar @ Aug 9 2006, 03:28 PM) *
Cute (and interesting).

Next on the agenda, I guess, will be looking at other X-ray sources at various ecliptic latitudes. If this idea is Kosher, those micro-occultations ought to decrease in frequency away from the ecliptic.

For those who may not have access to Nature, you may wish to check out the Supplementary Information for the Chang et al. paper. I believe Nature makes all Supplementary Information freely available, and sometimes it's pretty insightful.

As for future observations of this type, Chang et al. merely conclude with:

QUOTE
More RXTE observations of Sco X-1 are needed to improve the statistics of our current results. Future X-ray observations of Sco X-1 and other sources with new instruments of higher sensitivity could build on this discovery to shed further light on the formation of our Solar System.


However, an excerpt (references omitted) from Asantha Cooray's accompanying News and Views piece is, pardon the play on words, a little more illuminating:

QUOTE
But despite the high X-ray luminosity of the Scorpius X-1 source, it was not bright enough to allow a study of these expected small changes. A dedicated space-based monitoring mission, optimized for precision stellar occultation measurements at millisecond time intervals, could search for diffraction patterns to establish the exact extent of the debris field. Whipple, a mission currently under consideration by NASA, would be able to monitor occultations due to small bodies as far away as the hypothesized Oort cloud at the extreme edge of the Solar System.
ljk4-1
One quadrillion "members" of the outer Sol system?

http://arxiv.org/abs/astro-ph/0608239

The detection method was that sensitive it could detect so many of what
I presume are dust particles? Or are most of them much bigger than that?

I am almost amazed the Pioneers and Voyagers didn't have a collision already.

I hope New Horizons has its deflector shields up.
David
QUOTE (ljk4-1 @ Aug 14 2006, 05:44 PM) *
One quadrillion "members" of the outer Sol system?


Perhaps these are the missing Oort Cloud objects?
hendric
QUOTE (ljk4-1 @ Aug 14 2006, 12:44 PM) *
One quadrillion "members" of the outer Sol system?

I am almost amazed the Pioneers and Voyagers didn't have a collision already.


Ah yes, the lure of large numbers...One quadrillion is only 1E15. If we projected all of them on a sphere at 100 AU, there would be 32 billion per square AU, or about 1 per every 270,000 square miles. Considering that Voyager's antenna covers only 2.2E-5 square miles, chances are they're pretty safe. smile.gif
nprev
Well stated, Hendric....sometimes it's hard to grasp just how BIG space really is, in all three dimensions.

Still, I confess that I'm a bit nervous about the fact that NH will transit through Neptune's L5 (I think; might be L4) point...more worried about the effects of potential dust ablation given NH's velocity WRT the Sun than a direct collision with a Neptunian Trojan. unsure.gif
edstrick
Space is Big.
Space is Dark.
It's hard to find...
....a place to park!
(Burma Shave)

I am going to withhold judgement on what they're seeing till somebody with entirely different instrumentation observes a bright x-ray point source (Sco X1 is the brightest) and sees the same population of "occultations"

There was this whole theory of invisibly black water containing disintigrating mini-comets hitting the Earth (Univ. Iowa prof. named something Frank?) based on dark spots in UV airglow images of the Earth's upper atmosphere. It ended up very nasty, with true believers latching onto bad science, and I don't think the dust is settled yet from that fray. But I was never convinced that the dark spots were instrumental artifacts and not real quenching of airglow in Earth's atmosphere.

I'm afraid the same sort of thing could be happening here, though the "weirdness factor" of the result is much lower.
ljk4-1
QUOTE (hendric @ Aug 15 2006, 01:33 AM) *
Ah yes, the lure of large numbers...One quadrillion is only 1E15. If we projected all of them on a sphere at 100 AU, there would be 32 billion per square AU, or about 1 per every 270,000 square miles. Considering that Voyager's antenna covers only 2.2E-5 square miles, chances are they're pretty safe. smile.gif


I was being primarily facetious. I am mainly interested in seeing that we get more
than just one source to analyze that region of space to confirm or deny the RXTE
findings.

Maybe David Brin was right after all.

cool.gif
ljk4-1
Michael Ashley is part of a team observing the effects of small objects in the Kuiper Belt region of the solar system. These objects are between 300m and 1km in size and can't be seen with a telescope, or even a space telescope. These observations may affect ideas about how the solar system originally evolved in the very early stages.

http://www.abc.net.au/rn/scienceshow/stori...06/1712664.htm#


To quote:

Robyn Williams: Lots of lots of rocks floating around there.

Michael Ashley: Yes.

Robyn Williams: How many? Thousands?

Michael Ashley: No, many more than that. It's very hard to say. There have been a thousand or so discoveries of large ones over several hundred kilometres in size but we think there could be 10 to the 11th power or more rocks going down to very small sizes.

Robyn Williams: That's a huge number.

Michael Ashley: It's an incredible number.

and...

Robyn Williams: Yes, and we just got a new official tenth planet the other day, didn't we?

Michael Ashley: Xena UB313, yes, it's marginally bigger than Pluto. In fact, Pluto is actually just a member of the Kuiper Belt. It's one of the largest ones but it is a Kuiper Belt object.
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