[meteorite-list] Tunguska Event Part 2 of 2

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 09:48:14 2004
Message-ID: <3BDD4031.947F65FA_at_lehrer1.rz.uni-karlsruhe.de>

Sky and Telescope, December 1978, pp. 497-498:

The Tunguska Event and Encke's Comet


The B e t a T a u r i d meteor shower, which peaks at just the right
time of year, has a radiant only 10° from the Tunguska object's radiant,
well within the uncertainty of the latter. This Beta Taurid shower is
produced by the meteor stream associated with Comet Encke.
As Dr. Kresak remarks: "The orbit of Comet Encke can be brought into
intersection with the Earth's orbit at the point of the Tunguska event
by a mere rotation of the nodal line from longitude 334° to longitude
278°. In respect [to] the low inclination and differential secular
perturbations, this change appears plausible ... The distance from the
point of the Tunguska encounter to the orbit of Comet Encke, 0.18
astronomical unit, is not excessive, since the nighttime Taurids are
annually observed up to distances twice as large. Remembering that the
radiant position of the Tunguska object is uncertain to at least 10°,
the agreement is essentially perfect. "
According to a 1975 analysis by the Soviet astronomer V.A. Bronshten,
the initial mass of the object was 10^8 to 10^9 kilograms, and it
exploded at a height of five to seven km. Assuming tentatively a density
equal to that of ice, Kresak calculates the initial diameter as 100
meters for this body, which was completely destroyed in 10 seconds
before reaching the ground.
There are several reasons why this object was probably not an active
comet nucleus, but the extinct remnant of one. Statistics of observed
comets seem to indicate that there are no active objects with nuclear
diameters as small as 100 meters. Furthermore, as the diagram of the
intersecting paths of the earth and Tunguska object shows, for several
weeks before the encounter on June 30, 1908, the object was favorably
placed in the evening sky more than 20° from the sun. If an active
comet, it might well have been discovered, but as an extinct one it
would have gone undetected.
"The identification of the Tunguska object as an extinct cometary
fragment appears to be the only plausible explanation of the event; and
a common origin with Comet Encke appears very probable," is Dr. Kresak's
conclusion. He notes that a possible connection with this comet had
previously been suggested in 1969 by I.T. Zotkin.

Orbital elements for Comet Encke:

Perihelion distance q = 0.330 890 AU
Eccentricity e = 0.850 220
Period p = 3.28 years
Argument of perihelion w = 186.2443°
Longitude of ascending node = 334.0416°
Inclination i = 11.9391°


Best wishes,

Bernd
Received on Mon 29 Oct 2001 06:40:33 AM PST