Forward - Spacewatch 1991 VG

From: Neil Trevor Clifford <>
Date: Tue, 14 Mar 1995 15:11:13 -0500

Hello folks,

I thought I'd post this article not because of the 'little green men'
theory, but the possibilty that this might be some object resulting from
an earlier (Earth originated!) mission. I wonder whether anyone has any
suggestions as to possible candidates beyond those discussed.

|> From "the Skeptic" (ISSN 0726-9897) Vol 15, No. 1, pp. 8-9.
|> Published by: Australian Skeptics Inc.
|> PO Box A2324
|> Sydney South NSW 2000
|> Australia
|> ====================================================
|> Of Asteroids and Aliens
|> By Dr Duncan Steel
|> This article is a pre-emptive strike. In a scientific journal called
|> _The Observatory_ will appear shortly a paper in which I make the
|> suggestion that an object observed in the Earth's vicinity
|> (astronomically-speaking) in late 1991 was perhaps an alien probe.
|> However, I do not _believe_ that it was such an (hypothetical)
|> object. To me, as a practising scientist, that makes good sense: if
|> you come to a certain conclusion then you should make that conclusion
|> clear, regardless of your personal beliefs (for which read 'biases').
|> When I looked into the data pertaining to this object, I found that a
|> case could be made for it being of unknown provenance (ie alien), so it
|> is good practice to say so. But I anticipate that various UFOlogists,
|> journalists and other yahoos will say that 'astronomer believes object
|> was an alien spacecraft,' when I don't; but it is a plausible
|> explanation. I just want to put on record somewhere that I _don't_
|> believe it to have been an alien object, and where better to do that
|> than in _the Skeptic_?
|> The facts are these. In early November 1991 a peculiar object was
|> spotted by Jim Scott, using the so-called Spacewatch telescope at Kitt
|> Peak in Arizona. That telescope is the first fitted with a CCD video
|> camera to be used for routine searching for asteroids and comets near
|> the Earth, and the team there have made many pioneering discoveries.
|> The object in question is called 1991 VG, which is an asteroidal
|> designation: 1991 tells you the year, 'V' means that it was found in
|> the first half-month of November (that being the 21st half month of
|> the year, V being the 22nd letter in the alphabet, and we don't use
|> 'I' since it could be confused with a '1'), and 'G' means that it was
|> the seventh object classified in that half-month. So that's the
|> terminology.
|> Most asteroids found are in the main belt between Mars and Jupiter,
|> but the name of the game for Spacewatch folk, and my own group at
|> the Anglo-Australian Observatory, is looking for asteroids on
|> eccentric Earth-crossing orbits (which could, at some time, hit our
|> planet). 1991 VG was on an Earth-crossing orbit, and was found very
|> nearby, astronomically speaking, about seven times as far away as the
|> Moon. The observations obtained by Scott soon showed that its orbit
|> was very similar to that of the Earth, having an orbital plane less
|> than half a degree inclined to our own, and a near-circular path. Its
|> brightness suggested that it was only 8 to 20 meters in size,
|> depending upon how much sunlight one assumes that it reflects. The
|> suggestion was therefore made that this was not an asteroid at all,
|> but actually a rocket booster which by chance had returned whence it
|> came. That idea was boosted by observations from the European
|> Southern Observatory in Chile, which showed that it appears to flash.
|> Such flashing is often seen in the case of artificial satellites going
|> overhead, with occasional glints occurring as they spin and some flat
|> metallic face catches the Sun.
|> So it appeared that 1991 VG was not an asteroid after all, but some
|> artificial object. Another thing counting against it being a natural
|> asteroid was its orbit: such a very Earth-like orbit would lead to
|> close approaches to the Earth every 50 years or so, with the
|> terrestrial gravity then causing the orbit to be changed (as was
|> actually observed). If it were a natural body, it would need to have
|> arrived in such an orbit within the past millennium or so, which is
|> unlikely. For example, one possible origin would be as ejecta from a
|> massive impact on the Moon, but those occur infrequently, and in any
|> case the flashing observed could not be explained in that way.
|> Another way of phrasing what I'm doing is this. Three possible
|> origins for 1991 VG come to mind, and for each we can estimate a
|> probability. One is that it is/was an asteroid; call that probability
|> A. The second is that it was a man-made body returning to our
|> vicinity, call that probability B. The third is that it was of alien
|> origin, call that probability C. Those three probabilities sum to
|> unity: A+B+C=1. In the presence of perfect information, one derives a
|> value of one for one of them, and zero for the other two. But we
|> don't have perfect information (as is the case in most scientific
|> investigations), so we have to assess A, B. and C as best we can. So
|> far I have found that A is small (it seems unlikely that it was an
|> asteroid).
|> Next I attack B. 1991 VG had an orbit slightly bigger than that of
|> the Earth, meaning that it _could_ (not _would_) come close to the
|> Earth once every 16.75 years. That means that an approach early in
|> 1975 was possible, and early-to-mid-1958 (although an approach in 1975
|> could have altered the orbit by enough to make an approach perhaps in
|> 1959 feasible). An inspection of the records of mankind's launches
|> into space showed that there were no candidates from 1975. In October
|> 1974 the Russian Luna 23 was sent to the Moon, and hit it, so count
|> that one out. I thought that the upper stage from the American launch
|> of the German satellite Helios 1 in December 1974 was a possibility,
|> but then I learnt that it was put back into geocentric (rather than
|> heliocentric) orbit. From the earlier period there were no candidates
|> until late in 1958 (and of course the space age began only the year
|> before), but none of these could be made to fit the observations
|> unless some force acted upon them which was not known to have occurred
|> (like fuel left on board venting due to a leak, or perhaps solar
|> radiation pressure giving a push).
|> The consensus though, was that 1991 VG could not be linked with
|> surety with any launches in the late 1950s or the mid-1970s. Another
|> possibility was one of the Apollo upper stages used in the Moon
|> landings, which could be suggested to have hung around in orbit near
|> the Earth and Moon for a few years, and then escaped (unobserved) in
|> 1975. Again, this would be hypothesising an event which is not known
|> to have occurred.
|> Even if one were to accept the possibility that 1991 VG was a
|> man-made rocket returning to our vicinity, one then might estimate the
|> probability that it would be spotted. Only the Spacewatch telescope
|> is capable of discovering such small, faint, moving objects (which is
|> why our knowledge of small asteroids has been revolutionised since
|> Spacewatch began operations in 1989). Using the amount of sky which
|> is covered by its scans, and the number of nights each year in which
|> observations are made, and so on, I estimated that there was about a
|> one-in-2,000 chance that any arbitrary object with the brightness of
|> 1991 VG would be spotted, given that it came somewhere within the
|> geocentric distance occupied by 1991 VG when it was found (about 3.3
|> million kilometres). Passage within that distance, assuming that 1991
|> VG was not under control, occurs about once every 50 years. Thus if
|> 1991 VG were a solitary, uncontrolled rocket body, one would expect
|> Spacewatch to spot it about once every 100,000 years. On that basis
|> one has to conclude that B (the probability of it being a man-made
|> object) is very small.
|> Since we know that A+B+C=1, and we have derived small values for A
|> and B, that implies that C must be substantial. It is on that basis
|> that I suggested, very tentatively, that it is a candidate as an alien
|> spacecraft. In fact my bias says that it was a man-made body, but a
|> scientific analysis indicates that this would require a fluke to
|> have occurred. That is, _a priori_ its discovery was unlikely; but _a
|> posteriori_ things are as they are, not as we might believe them to
|> be.
|> There is also another piece of evidence that supports the 'alien
|> probe' interpretation. Although 1991 VG was first spotted when it was
|> 3.3 million kilometres from the Earth, it actually passed just 485,000
|> kilometres from our planet. If it were an uncontrolled object
|> (either an asteroid or a fluke returning man-made rocket body) then
|> passage within that 3.3 million kilometres would occur at a random
|> distance. Only about one in 40 would come within 485,000 kilometres.
|> That argues for it indeed having been under control: an alien probe
|> coming to take a look at us, but keeping a distance away at which they
|> thought they were safe from detection (well beyond the grasp of
|> military radars). One might object that the same sort of statistics
|> would apply for an alien craft as outlined above for man-made craft
|> (one discovery per 100,000 years), but that would be in error: if this
|> were an alien craft under control then it could buzz repeatedly past
|> the Earth, but under free flight (as observed) whilst within the grasp
|> of our telescopes.
|> OK, one last time, I don't believe that 1991 VG was an alien object,
|> but the simple analysis above does lead to the conclusion that it is a
|> decent candidate for consideration. Most of us have heard about the
|> Search for Extra-Terrestrial Intelligence (SETI), which seems to be
|> the only science with nothing to study (just pulling their tails). A
|> sub-division of that is SETA, or Search for Extra-Terrestrial
|> Artifacts. All I'm suggesting is that the SETA people might at least
|> have something to argue about. And some Skeptics might like to put in
|> their two cents worth too.
|> ==========================

Neil Clifford                Mail for PGP key           *MIME spoken here*
Received on Tue Mar 14 1995 - 15:52:03 UTC

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