Comet Vulcan's Unobserved August 17, 1999 Flyby

Scientific Paper
Title	Comet Vulcan's Unobserved August 17, 1999 Flyby
Read in full	Link to paper
Author(s)	Glen W Deen
Keywords	orbits, star, comet, earthquake, Vulcan
Published	2010
Journal	Proceedings of the NPA
Volume	7
No. of pages	10
Pages	106-115

Read the full paper here

Abstract

This paper presents a case for a comet's low-altitude flyby of Earth on August 17, 1999 with a perigee over Nairobi, Kenya that nobody observed. This flyby maneuver is inferred from two daylight observations near the Moon on August 11, 1999 (during a solar eclipse) and August 14, 1999 (my own observation of a lunar transit 10 minutes before sunset), and one nighttime observation in the glare of a bright star on April 6, 2000 by an astronomer attempting to observe an asteroid occultation of that star. This paper offers a possible, if improbable, explanation as to how this comet could have managed to avoid being seen at night under such circumstances over that time span. This paper suggests five strategies for a comet to escape observation by comet hunters. This comet has apparently used each strategy at one time or another to escape detection. The geocentric 2-body orbits in this paper are preliminary because they ignore the gravity of the Moon, the Sun, and the other planets. Consequently I do not use any observations before August 17, 1999 in determining the orbital elements. Instead, I assume that this comet flyby event triggered the 7.6 magnitude Izmit, Turkey earthquake that occurred on August 17, 1999. My plan is to cure this deficiency (2-body orbit) in a subsequent paper that will use the Jet Propulsion Laboratory's Horizon Ephemeris System to perform a rigorous numerical integration of the equations of motion. The initial heliocentric state vector for that integration will be computed from the state vector at the perigee of one of the preliminary orbits specified in this paper.

Overview

Glen Deen's paper is a first-person observational report wrapped around an orbit-fitting exercise. Its claim is that a small comet — which he identifies with the object nineteenth-century observers took for the intra-Mercurial planet Vulcan — made a hyperbolic pass within a few hundred kilometres of the Earth's surface on 17 August 1999, was never seen at night, and triggered the magnitude 7.6 Izmit earthquake in Turkey a few minutes later by tidally flexing the crust along its ground track.

The paper departs from the mainstream account on several fronts at once. It revives Vulcan, discarded after Einstein's 1915 account of the anomalous precession of Mercury's perihelion, but reinterprets it not as a planet inside Mercury's orbit but as a near-Earth comet whose apparent solar transits were opaque nucleus silhouettes seen at roughly lunar distance. It proposes tidal triggering of a major earthquake by a small passing body. And it invokes a terrestrial "ether wind" flowing radially outward from the Earth to explain why the comet's tail would point away from the Earth rather than away from the Sun, hiding the tail behind the coma so that the object could masquerade as a planetary nebula. Deen is unusually candid about the status of all this: he calls the case "circumstantial", says his own model "does not prove" the hypothesis, and describes an earlier prediction scheme of his own as "a bogus math model".

The argument

The observational chain

Four observations are offered.

1. 26 March 1859 — Edmond Modeste Lescarbault's reported solar transit at Orgères-en-Beauce, taken at the time for the planet Vulcan proposed by Le Verrier. Deen reads it as the comet's nucleus silhouetted at about one lunar distance. He answers Emmanuel Liais's contemporary refutation (Liais watched the Sun from Brazil and saw nothing) by arguing that at such close range parallax would have carried the transit path off the solar disk for southern-hemisphere observers. Earlier unexplained transits by Stark (1819), Decuppis (1839), and Lowe and Sidebotham (1849) are mentioned in the same connection.
2. 11 August 1999 — a small comet-like object in the field of the total solar eclipse webcast from Amasya, Turkey. Deen argues it was near the Moon rather than near the Sun, on the grounds that its tail was only about 1 arcminute long at 1 arcminute from the solar limb, whereas a genuine SOHO sungrazer photographed in March 2010 showed a 55-arcminute tail at 38 arcminutes from the disk.
3. 14 August 1999 — Deen's own observation, in an 8-inch Celestron at 100×, of a small comet transiting the crescent Moon in daylight from Plano, Texas, about ten minutes before sunset. He describes a semicircular coma about one arcminute across with a short fan-shaped tail, the whole thing brighter than the lunar surface, crossing in about two minutes. He reported it to Brian Marsden at the Central Bureau for Astronomical Telegrams and it was never confirmed. He calls it "the defining event of my life". Because the paper's orbit model is Moonless, this observation is deliberately excluded from the fit.
4. 6 April 2000 — Spanish astronomer Ricard Casas, attempting an asteroid occultation of the 8th-magnitude double star HIP 66600 in Virgo, logged an unexplained nebulosity around the star. Deen suggests this was the comet's coma, and that the outbound asymptote of the hyperbolic geocentric orbit lay precisely at that star.

Five evasion strategies

The paper's structural problem is that a comet this close should have been seen by many people. Deen offers five ways it could have escaped: be dormant while in the night sky; while active, stay near the Sun's line of sight, in Earth's shadow, or below the horizon; hide behind the Moon between the eclipse and the lunar transit, "flying in formation with the Moon from Earth's viewpoint"; rely on cloud during the flyby (August being the South Asian monsoon); and afterwards masquerade as a planetary nebula by keeping proper motion small until the coma dissipates. He notes that hyperbolic proper motion falls to 1°/day by 1.6 days after perigee and to 14.7 arcsec/day by 30 days.

Fitting the orbit

Six Keplerian elements need three (RA, Dec) observations. Deen has two usable ones, giving four constraints; he adds the earthquake onset time and assumes a perigee distance, leaving four unknowns solved with Microsoft Excel Solver. Two solutions are tabulated, with perigee distances of 1.01 and 1.10 Earth radii — altitudes of about 64 km and 637 km. Both are retrograde and hyperbolic (e > 1). Perigee falls 11 min 15 s and 6 min 18 s before the earthquake respectively. The ground track for the 1.1 solution passes within 213 km of Honolulu, 242 km of Taipei, 482 km of Calcutta, 544 km of Bombay, 175 km of Nairobi and 102 km of Rio de Janeiro.

The trigger-wave model

The epicentre near Izmit lies some 4,800 km from the Nairobi perigee footprint, so Deen abandons any requirement that the two coincide and instead models a seismic P-wave launched from the moving footprint. Amplitude decays as A = A₀ exp(−ωt/2Q), taken from Fowler's The Solid Earth with lithospheric Q = 200. Since the comet's mass is unknown he defines the launch amplitude only in relative terms, A₀ = (0.25/h)², with h the altitude in Earth radii. Because the footprint sweeps along the ground track, its radial velocity relative to the epicentre Doppler-shifts the wave, ω = ω₀ v_wave/(v_wave − v_source), with an unshifted frequency f₀ = 42.667 cycles per minute scaled off the Beijing seismogram trace. Average P-wave speeds are interpolated from the USGS travel times to five cities near the ground track (Tokyo, Beijing, Kathmandu, Nairobi, Lima).

The result is the paper's one quantitative discriminator. Peak received amplitude occurs 11.2 minutes before the quake for the 1.01 orbit and 6.0 minutes before for the 1.1 orbit; the propagation-timing constraint is satisfied 2.25 minutes after the amplitude peak in the first case and 1.27 minutes before it in the second. Since the trigger must precede the peak, Deen concludes that the 1.1 Earth-radii perigee is the better solution.

Assessment

The paper's real virtue is its honesty about its own evidential weight. Deen states plainly that the orbit "was optimized to force the star to become its radiant", so the close agreement in his Figure 9 "is unremarkable"; he flags the 2-body model as provisional and names the n-body integration he intends to do; and he sets out in advance what would refute part of his tail argument (the direction of the Shoemaker–Levy 9 fragments' tails at Jupiter). The internal arithmetic that can be checked is right: the stated perigee-to-quake intervals of 11:15 and 6:18 follow correctly from his tabulated perigee epochs and the 00:01:39 UT onset, and the Doppler and attenuation formulae are used as written in his source.

The difficulties are severe, and most of them are quantitative. First, the trigger amplitude law is the wrong physics for the job. Tidal forcing — a differential effect — scales as M/r³ with r measured from the Earth's centre, not as 1/h² with h the altitude above the surface. Deen's expression diverges as the comet skims the ground, and it is a gravitational-attraction law rather than a tidal one; between his two candidate orbits it differs from the correct scaling by a large factor, so the amplitude curves that select the 1.1 orbit over the 1.01 orbit are not trustworthy.

Second, and more damaging, is what happens when a mass is put in. The paper avoids naming one, but the requirement is inescapable: to raise a tide at the Earth's surface merely equal to the Moon's, a body at 1.1 Earth radii would need a mass of about 4.4 × 10¹⁷ kg — for cometary densities of 500–1000 kg/m³, a nucleus roughly 95 to 120 km across, larger than any comet nucleus known. Lunar tides raise crustal stresses of order a kilopascal and are not observed to trigger magnitude-7.6 ruptures, so an actual trigger would require a good deal more than that. An object of that size at 637 km altitude would subtend nearly ten degrees of sky and outshine everything but the Sun and Moon — no set of evasion strategies covers that. Conversely, a comet small enough to have been overlooked exerts a tide far too weak to matter.

Third, the two candidate orbits are separately impossible in ways the paper does not address. At 1.1 Earth radii a rubble-pile body of density 1000 kg/m³ is deep inside the Earth's Roche limit, which lies near 4.3 Earth radii for that density; it would be tidally disrupted — precisely the fate of Shoemaker–Levy 9, the comparison the paper itself raises. And the 1.01 solution puts the object at 64 km altitude, well inside the atmosphere and below the 80–120 km band where meteors ablate; at the perigee speed such an orbit demands (escape speed there is already 10.7 km/s, and a hyperbolic orbit exceeds it) the result is a bolide of extraordinary brightness sweeping a ground track across Honolulu, Taipei, Calcutta, Bombay, Nairobi and Rio. Nothing of the kind was recorded on 17 August 1999. The angular rate is also punishing for the concealment argument: at perigee the object moves across the sky at roughly 5 degrees per minute, so "small proper motion" applies only well after the encounter.

Fourth, the fit is underdetermined in a way that makes the agreement it reports uninformative. Four adjustable elements are solved against four constraints from two positions, with the perigee distance assumed. A hyperbolic orbit constrained to pass through two given sky positions can generally be made to do so; the outbound radiant coinciding with HIP 66600 is an input, not a result. The one genuinely independent test — the trigger-wave timing — depends on the amplitude law criticised above and on a P-wave frequency read off a printed seismogram.

Finally, the ether-wind explanation of tail orientation is asserted with no supporting calculation and no independent evidence, and it is required to do heavy lifting: without it the tail points anti-sunward and the planetary-nebula disguise fails. The nineteenth-century identification is likewise offered as a possibility rather than demonstrated; Deen himself concedes that linking the 1819, 1839, 1849 and 1859 transits into a single ephemeris would need repeated close flybys of Venus and Mercury so finely tuned that the comet would have to "behave as if it were a spacecraft". Readers should treat the paper as a well-documented anomaly report and an explicit research programme rather than as a demonstration.

See also

• Glen W Deen
• Perihelion Precession of Mercury
• Aether
• Doppler Effect
• Category:Astronomy
• Category:Catastrophism