KFL@MIT-MC.ARPA ("Keith F. Lynch") (12/20/85)
I recall that the reason a ninth planet was looked for was because one was necessary to explain perurbations in the orbits of Uranus and Neptune. Pluto was found. But it appeared to be too small to expalin the perturbations unless it had an unbelievably high density or unless the disk we were seeing was not the whole planet but just a bright spot, a reflection of the Sun on the shiny sphere. A few years ago, a moon on Pluto was discovered. Study of its orbit has proven that Pluto is small, that we have seen the whole disk, which is not shiny, and that its density is low. Nobody seems to have mentioned that that puts us back in where we were before Pluto was discovered. What IS causing those perturbations? Is there a tenth planet? Could it have gone undiscovered for this long? Does anyone know what the explanation is? Is anyone looking for a tenth planet, or am I missing something? If the perturbations are still unexplained, where can I get data on where Uranus and Neptune have been? I would like to use such data to try figuring out the mass and location of the tenth planet myself. ...Keith
mcgeer@JI (Rick McGeer) (12/20/85)
As I recall, the existence of a 10th planet is pretty much taken for granted in the astronomical community. But it's unlikely we're going to find it, for two reasons: (1) It will be dim. Isn't it true that Pluto has a very high albedo? Assuming that the 10th planet is a gas giant, it will have a much lower albedo than Pluto and will also be further away from the Sun -- hence much dimmer than Pluto, and Pluto is something like 10th magnitude anyway. (2) It will have a very low angular velocity, so much that it will be extremely difficult to pick out from among the fixed stars. Assume Bode's Law holds (I know, most people think it's an interesting bit of numerology, nothing more. But it's the only assumption I have, and, anyway, you can make a quasi-case for it by talking about the distribution of particles in the gas cloud that became the solar system). Anyway, under that assumption, planet X is at 77.2 AU, way out in the boonies. By Kepler's Harmonic law, that makes its period 77.2^3/2, or: 678 years, which works out to an angular velocity of about 32 minutes of arc (about half a degree) per year. Pluto, by contrast, has about a degree and a half of arc per year, or about three times as much -- and it took years of Tombaugh's time on a flicker machine to spot Pluto. There's one other objection, too -- previous planet hunts took place in and about the ecliptic, in a pretty narrow band of sky. I've heard speculation that eccentricity increases with distance from the sun, so you'd have to search a wider sky band, too. -- Rick.
Lynn.es@XEROX.ARPA (12/24/85)
Soon after Tombaugh found Pluto, it was fairly evident to him that he had not found the perturbation cause. During the 30's and 40's he completed a photographic survey of a wide band about the ecliptic without finding anything. So either the wandering ways of Uranus and Neptune are 1) errors in measurement, 2) caused by another effect (dust disks, Oort cloud, whatever), 3) caused by a planet that was very far from the ecliptic when Tombaugh photographed, or 4) caused by a planet too dim to show up in Tombaugh's survey. Pluto runs about magnitude 13 to 14, and if I remember right, Tombaugh's survey should have found anything brighter than 16 or so. You can check the details by reading Tombaugh's recent book, titled something like "Out of the Darkness". I have heard of a few astronomers (Charles Kowal at Palomar is the only name I can remember right now) interested in the tenth planet, but no results. It seems the data are inconsistent, so they have to decide whose observations to consider too unreliable to use. Also, the effect is only a little larger than the expected errors of measurement. One idea is to look for the planet in the IRAS satellite IR sky survey. It is said to be far more sensitive to a planet-type object than Tombaugh's survey. All you have to do is weed out the several hundred thousand objects found by IRAS that are not planets! Even among moving objects in the IRAS data, thousands of asteroids clutter up the search. There are also some pessimists that claim we will eventually find the tenth planet in the 1% of the sky that IRAS missed photographing. /Don Lynn
Dave-Platt%LADC@CISL-SERVICE-MULTICS.ARPA (Dave Platt) (12/27/85)
Well, I'm working strictly from memory... but here's what I recall about some work done on the "tenth planet" problem in the past few years... About five years back (I think), someone did a fairly extensive analysis of the orbits of Uranus, Neptune, and Pluto, using the best-available estimates on the masses of these planets. The results indicated that there might be a tenth planet located roughly twice as far from the sun as Pluto is, on the average; its mass was estimated to be approx. 10 Earth-masses, and its current position was far outside of the orbital plane of the known planets (I don't recall the figure for certain, but I'm pretty sure it was at least 40 degrees and may have been as much as 60 degrees). The researcher who announced the results of the calculations claimed to have narrowed the probable location of the "new" planet down to a fairly small portion of the sky (10 degrees square?). As I remember it, several observatories did an extensive blink-comparison scan of that portion of the sky, comparing some old file negatives with current photos... and didn't find anything. So... several possibilities come to mind. 1- There is something in that portion of the sky, but it's too dim to be seen with standard optical instruments... possibly a planet with an *extremely* low albedo (would have to be *very* low for a planet with a ten-earth mass to be invisible), a black hole (where are the gammas?), or something small/massive/dim at a greater distance than was calculated (an old neutron star, or a very cold burnt-out dwarf star?). 2- There's nothing in that portion of the sky... the orbits of the outer planets are indeed being perturbed, but there's not a single object doing the perturbing; instead, we're seeing the net effect of a large number of smaller objects, whose vector sum happens to point in the direction indicated by the orbital calculations. Perhaps there's a lot of old, cold matter (comet precursors?) floating around outside the orbit of Pluto; the Oort cloud (or something related to it) may come in a lot closer than we had thought, or be much denser than previous calculations had indicated. 3- Something else is going on. Possibly there's some exotic thingie floating around not far from our solar system... a cosmic "string", a dense clump of photinos or axons (sp?), or some other strange form of "dark matter". Cosmologists are still trying to figure out how much dark matter exists in our galaxy (and in the universe), and what forms that dark matter takes... neutrinos with a nonzero mass, supersymmetric particle partners, etc. etc. and so on. Possibly this dark matter occasionally forms into clumps, sufficiently coherent and massive to tweak the orbits of the outer gas giants in our solar system, but sufficiently isolated to be invisible (except by its gravitational interaction with our system). Maybe the "shadow world" is actually out there! Take your pick. The jury is still out, of course... we can't yet say that there is no tenth planet, only that we haven't unambiguously detected the presence of one. I rather like the third alternative; if it's true, it would once again bring home the realization that the universe is stranger than we have yet imagined.
msb@lsuc.UUCP (Mark Brader) (12/29/85)
Rick McGeer (mcgeer@JI) writes: > It will have a very low angular velocity, so much that it will be extremely > difficult to pick out from among the fixed stars. Assume Bode's Law holds > (...it's the only assumption I have...) ... its period [will be about] > 678 years, which works out to an angular velocity of about 32 minutes of arc > (about half a degree) per year. Pluto, by contrast, has about a degree and a > half of arc per year, or about three times as much -- and it took years of > Tombaugh's time on a flicker machine to spot Pluto. Like Don Lynn, whose article did a nice job of answering all the other points that have been raised, I reference the book "Out of the Darkness", written in 1978 by Clyde Tombaugh and (for the historical matter) Patrick Moore. The truth is that it took only a few months for Pluto to be detected on the Blink-Comparator. The computation of 32 minutes of arc per year is irrelevant. The trick is to use the motion of the Earth: instead of detecting the planet's orbital motion, you detect its parallax, which is much larger. For simplicity assume a direct circular orbit coplanar with ours, with 81 AU radius. Then at opposition, Sun, Earth, and planet will be in a straight line, and the Earth-planet distance will be 80 AU. Figure the Earth's orbital angular velocity around the sun as 1 degree per day. Then Earth will be moving with respect to the planet at 1/80 degree per day, or 3/4 minute of arc per day. Note, PER DAY. The planet's net apparent motion will be the difference of this and its much smaller orbital motion. What Tombaugh did, under the direction* of Slipher and Slipher of the Lowell Observatory, was to photograph the sections of the sky that were near to being directly opposite the sun, and to compare (with the Blink- Comparator) pictures taken, usually, 2 days apart. In the case of the actual discovery the pictures were taken 6 days apart because of weather or something, and the two blinking images of Pluto were far enough apart that he had to search (briefly) to find the second one after finding the first. So it should be clear that the slow motion is no obstacle to a Blink- Comparator search. Even if it was, the searcher could simply use plates with a long time interval between them. The dimness, of course, is another matter. Tombaugh said that he could have detected an object 2-3 magnitudes fainter than Pluto, but his eyesight was apparently exceptional. *Tombaugh had no university education at the time -- he was hired as an assistant because he was felt to have potential. Correctly! Mark Brader Usenet readers will see this in net.astro, the proper group by their standards, and net.space. The three earlier articles are in net.space alone, because they originated from the ARPA side, and there's no ARPA gateway to net.astro.
mink@cfa.UUCP (Doug Mink) (12/30/85)
*** REPLACE THIS LINE WITH YOUR LINE-EATER ***
As someone with a professional interest in the positions of the outer
planets (I predict occultations), I have followed recent searches for a
tenth planet with great interest. In fact, positions of Uranus obtained
from observations of occultations of stars by its rings (star-planet to
about a milliarcsecond) have helped narrow down the search region for
the supposed Planet X. Unhappily, the best solar system ephemeris I
have available, JPL's DE-125, produced for the Voyage Uranus encounter
(see there IS a net.space connection), still fails to match Neptune's
observed position. As I've been trying to predict occultations by
Neptune's satellite, Triton, so its size can be determined before
Voyager encounters Neptune in 1989, I need Neptune positions better than
any current solar system models can produce. If Planet X is found, I
hope it cleans up the orbits of the outer planets.
A sidelight on Pluto's discovery: A few years ago a friend of mine with
an intimate knowledge of the Harvard College Observatory photographic
plate stacks enlisted me in a quest for prediscovery Pluto positions.
He checked plates from 1870 to 1910 because no positions in that period
had been published despite numerous plates of the proper part of the
sky. It turns out that Pluto was fainter than the plates exposed for
the average patrol exposure duration could detect until 1920 or so, though
a couple of long exposure plates after 1910 showed it. Since Pluto is so
faint that it could only be detected photographically, it's no surprise
that Percival Lowell didn't find it and that discovery took until 1931.
-Doug Mink
{harvard|genrad|allegra|ihnp4}!wjh12!cfa!mink
Center for Astrophysics
60 Garden St.
Cambridge, MA 02138wildstar@nmtvax.UUCP (01/02/86)
Andrew Jonathan FineOrganization: New Mexico Tech, Socorro
Keywords:
Perhaps the "tenth planet" is not actually a planet, but perhaps a weak
stellar companion to Sol, already known as "Nemesis".franka@mmintl.UUCP (Frank Adams) (01/03/86)
I have for some time suspected that there are a fair number of sub-stellar objects in the galaxy, which are not associated with any star system. I have seen estimates that a mass of .07 times that of the sun is the minimum required to ignite fusion. Proxima Centauri seems to be near this lower limit. Although there may be a lower limit to the size of the objects produced by the processes which produce stars, it seems unlikely that this point coincides with the ignition point. How many such objects are there likely to be? For stars, there is a clear relationship between size and frequency: the smaller the size, the more stars there are at that scale. There is no reason to believe this does not hold down to near the lower limit for the process. Thus if objects appreciably smaller than .07 solar mass can be created in this way, one expects them to considerably outnumber the stars. There is reason to think that objects as small as .0001 solar mass are possible, since this is the approximate size of the outer giant planets (Uranus and Neptune), which seem to have been formed in a similar fashion (although as part of the formation of the sun, not as independent events). The question is, could such objects be responsible for the observed perturbations of the orbits of the outer planets? A quick calculation reveals that an object of .05 solar mass would have to be at a distance of about 300 AU to produce an effect comparable to a giant planet at Pluto's orbit. This is still only 1/2000 of a light year; it doesn't seem likely that there could be enough objects of this size that one would expect an object this close, but we could be dealing with an unusually close approach. The other possibility is that objects on the order of .0001 solar mass are freqent enough that one would expect the nearest to be no more than 100 AU or so away. I don't have access to a size/frequency comparison for stars, so I don't know how reasonable such a frequency is. This would still, I think, be low enough that one would not expect an observably close encounter of such an object with the sun in the time in which we have been making observations. The uniformity of the orbits of most of the planets puts an upper limit on the frequency of such encounters; however I suspect that the strangeness of Pluto's orbit can be explained as the result of such an encounter. (Perhaps also Uranus's rotational tilt? I don't know how likely it would be for a close encounter to change the rotational axis while leaving the orbit roughly circular.) Disclaimer: I have no professional training in Astronomy, and have not attempted to really rigorously work out the consequences of this hypothesis. Frank Adams ihpn4!philabs!pwa-b!mmintl!franka Multimate International 52 Oakland Ave North E. Hartford, CT 06108
henry@utzoo.UUCP (Henry Spencer) (01/03/86)
> Perhaps the "tenth planet" is not actually a planet, but perhaps a weak > stellar companion to Sol, already known as "Nemesis". Alas, Nemesis has met its fate :-). (Quick digression: the theory alluded to here is the notion that periodic extinctions are caused by near approaches of a companion star, which is in a *very* long-period orbit [30MY or so], stirring up the Oort cloud and causing a rain of comets into the inner Solar System.) The problem with making the Sun a binary star is that Nemesis has to be a godawful long way out to have such a long orbital period, and it appears that such an orbit simply is not very stable over geological time scales. It is not consistent with extinctions at clockwork-regular intervals, at the very least. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
werner@aecom.UUCP (01/04/86)
> Andrew Jonathan FineOrganization: New Mexico Tech, Socorro > Keywords: > > Perhaps the "tenth planet" is not actually a planet, but perhaps a weak > stellar companion to Sol, already known as "Nemesis". Named (or so claimed by the author of the paper) such because if such a companion is not found, the publication will prove to be HIS nemesis. -- Craig Werner !philabs!aecom!werner "Illness strips away superficiality to reveal reality in etched detail."
friesen@psivax.UUCP (Stanley Friesen) (01/06/86)
In article <971@mmintl.UUCP> franka@mmintl.UUCP (Frank Adams) writes: > >I have for some time suspected that there are a fair number of sub-stellar >objects in the galaxy, which are not associated with any star system. >.... Although there may be a lower limit to the size of the objects >produced by the processes which produce stars, it seems unlikely that this >point coincides with the ignition point. > >How many such objects are there likely to be? For stars, there is a clear >relationship between size and frequency: the smaller the size, the more >stars there are at that scale. There is no reason to believe this does not >hold down to near the lower limit for the process. Thus if objects >appreciably smaller than .07 solar mass can be created in this way, one >expects them to considerably outnumber the stars. There is reason to think >that objects as small as .0001 solar mass are possible, since this is the >approximate size of the outer giant planets (Uranus and Neptune), which >seem to have been formed in a similar fashion (although as part of the >formation of the sun, not as independent events). > As far as I know the mode of formation of the outer planets is *very* close to that for stars. In fact a number of simulations suggest that a very small change in initial conditions would have left a small (type M or K) star where the Jovian planets are now. Given the large number of binary(and larger) star systems, this seems quite reasonable. Thus I see no reason at all why Uranus sized object could not form independently also. Actually, I would expect the distribution of sizes to peak at some point and taper off, thus the smallest objects would likely be quite rare. But this would still leave quite a few Jupiter/Saturn sized objects running around. -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ttidca!psivax!friesen@rand-unix.arpa
friesen@psivax.UUCP (Stanley Friesen) (01/06/86)
In article <6258@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: > >Alas, Nemesis has met its fate :-). > >(Quick digression: the theory alluded to here is the notion that periodic >extinctions are caused by near approaches of a companion star, which is in a >*very* long-period orbit [30MY or so], stirring up the Oort cloud and causing >a rain of comets into the inner Solar System.) > >The problem with making the Sun a binary star is that Nemesis has to be a >godawful long way out to have such a long orbital period, and it appears >that such an orbit simply is not very stable over geological time scales. Another nail in the coffin. A recent re-analysis of the original study(a statistical analysis of extinction rates) has strongly suggested that the periodicity (actually 26MY) is wholely an *artifact* of the statistical methodology used, in particular the sampling method. The later study used a Monte-Carlo simulation of uniform random extinctions and found that the method used by the original study *still* showed a 26MY periodicity! -- Sarima (Stanley Friesen) UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen ARPA: ttidca!psivax!friesen@rand-unix.arpa
jlm@uvacs.UUCP (Jerrold L. Marco) (01/07/86)
> extinctions are caused by near approaches of a companion star, which is in a > *very* long-period orbit [30MY or so], stirring up the Oort cloud and causing > a rain of comets into the inner Solar System.) > Question: Wouldn't a massive rain of comets leave evidence on all the inner planets? My recollection is that on the moon, which has been reasonably well charted, evidence of recent bombardment is scarce. Can someone with more knowledge than I comment on the corellation between the times of mass extinctions on earth and the estimated times of comet strikes on the moon (or on other inner planets, to the extent that such information is available)? *** REPLACE THIS LINE WITH YOUR MESSAGE ***
jtk@mordor.UUCP (Jordan Kare) (01/08/86)
>> >> Perhaps the "tenth planet" is not actually a planet, but perhaps a weak >> stellar companion to Sol, already known as "Nemesis". > > Named (or so claimed by the author of the paper) such because if such >a companion is not found, the publication will prove to be HIS nemesis. > Nemesis can't be the "tenth planet" affecting Neptune's orbit, as it would be too far away (and would move both Neptune and the rest of the solar system including the sun by the same amount). There is a theory that Planet X (either "ex" or "ten" depending on how much you like Roman numerals :-) exists, and has a peculiar orbit that precesses in such a way as to disturb the cometary cloud and cause comet showers (and extinctions) every thirty or so million years. This is an alternative to the Nemesis theory, but it doesn't work, on various (rather complicated) celestial mechanics grounds, leaving Nemesis as the leading hypothesis. Also, "Nemesis" was not the first choice for the name of the companion star. Since (if it exists) it was responsible for killing off the dinosaurs, first choice was to name it after the most famous mythological dragon killer and call it "George". -- A Muller Group Nemesis Hunter
jtk@mordor.UUCP (Jordan Kare) (01/08/86)
Sorry I didn't catch this before my preceeding posting >> Perhaps the "tenth planet" is not actually a planet, but perhaps a weak >> stellar companion to Sol, already known as "Nemesis". > >Alas, Nemesis has met its fate :-). > >(Quick digression: the theory alluded to here is the notion that periodic >extinctions are caused by near approaches of a companion star, which is in a >*very* long-period orbit [30MY or so], stirring up the Oort cloud and causing >a rain of comets into the inner Solar System.) > >The problem with making the Sun a binary star is that Nemesis has to be a >godawful long way out to have such a long orbital period, and it appears >that such an orbit simply is not very stable over geological time scales. >It is not consistent with extinctions at clockwork-regular intervals, at >the very least. >-- > Henry Spencer @ U of Toronto Zoology > {allegra,ihnp4,linus,decvax}!utzoo!henry This is not correct. Extensive simulations (Notably by Piet Hut of the Princeton Institute for Advanced Studies) have shown that the mean lifetime of Nemesis's orbit is roughly a billion years. The orbit is disturbed by passing stars, dust clouds, etc. but can easily remain stable enough to explain the few data we have, which only cover the last 250 million years (a mere moment... :-)) If Nemesis was formed with the solar system, then it probably started in a closer orbit and has been perturbed out to its present distance; in another couple of billion years it might be gone (so we need to find it quick :-)). The evidence for periodic extinctions and periodic cratering, which the Nemesis theory was created to explain, is subject to dispute. (The evidence for catastrophic impacts associated with extinctions is very strong; only the periodicity is speculative). But IF periodic extinctions do occur, the Nemesis theory DOES explain them, and is still the ONLY theory which does so successfully. Despite what you may read in the New York Times editorial pages, Nemesis lives on.... Jordin Kare Formerly of UC Berkeley/LBL Astrophysics Home of Nemesis and much, much more....
dsmith@HPLABSC (David Smith) (01/09/86)
> As I recall, Voyager (I or II) detected the tenth planet. It lies > between Saturn and Uranus, and is rather small. It has been named > Charon, (Roman god that paddles the boat across the River Styx, I > think). This planet probably doesn't account for all of the > perturbations of Uranus and Neptune, either. Charon is Pluto's moon, and was discovered by earth-based telescope. But, the four probes in the outer solar system (or beyond, if being farther out than Neptune constitutes being beyond) are of value in finding planet X, because their positions are more precisely known than those of the planets. Gravitational perturbations in their paths are more detectable. Also, they might get closer than Neptune to planet X. David Smith hplabs!dsmith dsmith%hp-labs@csnet-relay
ethan@utastro.UUCP (Ethan Vishniac) (01/10/86)
> > As I recall, Voyager (I or II) detected the tenth planet. It lies > > between Saturn and Uranus, and is rather small. It has been named > > Charon, (Roman god that paddles the boat across the River Styx, I > > think). This planet probably doesn't account for all of the > > perturbations of Uranus and Neptune, either. > > Charon is Pluto's moon, and was discovered by earth-based telescope. > On the other hand, Chiron is the name of a small chunk of rock and ice orbiting between Saturn and Uranus. Its mass is much too small to produce detectable perturbations in the motions of any of the major planets. Chiron, like the asteroids, is considered a minor planet. -- "These are not the opinions Ethan Vishniac of the administration of {charm,ut-sally,ut-ngp,noao}!utastro!ethan the University of Texas, ethan@astro.UTEXAS.EDU but they are the opinions Department of Astronomy of your favorite deity, who University of Texas is in daily communication with me on this (and every other) topic.
henry@utzoo.UUCP (Henry Spencer) (01/10/86)
> > As I recall, Voyager (I or II) detected the tenth planet. It lies > > between Saturn and Uranus, and is rather small. It has been named > > Charon, (Roman god that paddles the boat across the River Styx, I > > think)... > > Charon is Pluto's moon, and was discovered by earth-based telescope. He's thinking of Chiron, I think. Charon is Pluto's moon. Chiron is a, well, an object, orbiting roughly between Saturn and Uranus. It's too small to qualify as a planet, really. Nobody is entirely sure just what it is, last I heard, although there is strong speculation that it may be a sort of super-comet that got deflected into its present orbit. I seem to recall that Chiron too was discovered from Earth. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
Lynn.es@XEROX.ARPA (01/10/86)
Slocum's recollection of Chiron being touted as a tenth planet is correct, but his details have drifted a bit from how it happened. First, the name was Chiron, not Charon the satellite of Pluto. Chiron was only briefly touted as a tenth planet, but soon became generally regarded as an asteroid. This judgment is based on its small size. We just had to learn to ignore our previous notion that asteroids should not be located beyond Saturn. In any case, its small size means it has pretty negligible gravitational effects on the outer planets, so is not the cause of the unexplained perturbations that lead us to believe there is a Planet X. Chiron was discovered from earth-based photographs taken at Palomar by Charles Kowal. I don't think it has ever been photographed by a spacecraft. /Don Lynn
ran@ho95e.UUCP (RANeinast) (01/13/86)
> > > As I recall, Voyager (I or II) detected the tenth planet. It lies > > between Saturn and Uranus, and is rather small. It has been named > > Charon, (Roman god that paddles the boat across the River Styx, I > > think). This planet probably doesn't account for all of the > > perturbations of Uranus and Neptune, either. > > Charon is Pluto's moon, and was discovered by earth-based telescope. > I believe this person is referring to Chiron. This was an asteroidal body found around 1978(?), and indeed has a non-typical orbit (for an asteroid--I think the original poster is correct about the orbit). Note that despite the orbit, it still has an asteroid-type name, that is, Trojan War people. Chiron was the wise centaur who tutored Achilles, Hercules, and Asclepius [Am. Her. Dict]. I'm pretty sure Voyager had nothing to do with the discovery. It is coincidental that Charon and Chiron were discovered and named at about the same time. -- ". . . and shun the frumious Bandersnatch." Robert Neinast (ihnp4!ho95c!ran) AT&T-Bell Labs
wls@astrovax.UUCP (William L. Sebok) (01/19/86)
In article <6279@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: >I seem to recall that Chiron too was discovered from Earth. It was discovered by Charles Kowal of Caltech using the Palomar 48" Schmidt. I was there at the time. I forget the year but it was sometime in the late seventies. -- Bill Sebok Princeton University, Astrophysics {allegra,akgua,cbosgd,decvax,ihnp4,noao,philabs,princeton,vax135}!astrovax!wls