Cometary Hypothesis Research Articles

ВОПРОСЫ И ПЕРСПЕКТИВЫ ПРЕПОДАВАНИЯ ТЕМЫ «СОЛНЕЧНАЯ СИСТЕМА» ПО УЧЕБНИКАМ АСТРОНОМИИ

The article deals with the issues of teaching the topic "Solar system" of the discipline "Astronomy". The old textbook "Astronomy" by E.P. Levina and new - B.A. Vorontsova–Velyaminova, E.K. Strout and V.M. Charugin - in which the material about the planetary system is borrowed from publications of the last century. At present, what is stated in the textbook by B.A. Vorontsova-Velyaminov and E.K. Strout, the historically established idea of the formation and structure of the solar system (from planets alone) contradicts new discoveries and the observed harmonious structure of the solar system. The erroneousness of assigning the status of "minor planet" to asteroids of the main belt and many objects of the Kuiper belt is substantiated. this leads students to the misconception that there are many planets in the solar system. To the textbook "Astronomy" V.M. Charugin, the author of this article prepared a textbook "The Solar System of the 21st Century", which provides a model of the structure of the entire Solar System and the cometary hypothesis of its origin. The textbook contains a table "Periodic system of celestial bodies of the entire solar system" for astronomy classrooms, similar in significance to the table "Periodic system of chemical elements of D.I. Mendeleev.

The Geminid meteor shower radiant: a mathematical model

ABSTRACT The origin of the Geminid meteoroid stream and its parent body the asteroid (3200) Phaethon is still under discussion. The observed bimodal activity profile of the Geminid shower agrees with a cometary scheme of the stream formation. We show that the radiant areas for meteors of different magnitudes may also be used to provide arguments supporting or undermining the cometary hypothesis. We used semi-analytic and numerical models of the stream. The resulting model radiants for meteors of various magnitudes (masses) have peculiar patterns that might be detected in a real shower.

Heritage of the Kepler mission: Special object KIC 8462852 and criticism of the cometary hypothesis

Paradoxical properties of the KIC 8462852 object discovered in the course the Kepler mission are considered. It has been shown that the assumptions about the nature of the object as a swarm of cometary bodies, fragments resulting from catastrophic collisions of asteroids, or the KIC 8462852b exoplanet meet serious problems and even contradict the Kepler laws, if the eclipsing object is considered as a physical body orbiting a central star. According the energy and other requirements, the hypothetical orbit of KIC 8462852b does not meet the Dyson sphere conception either. In the paper, we used the materials of the study by Boyajian et al. (2015) and the subsequent publications on this theme.

The 1908 Tunguska cosmic body (TCB) explosion: Role of hydrogen thermonuclear explosion in support of cometary hypothesis

If the 1908 Tunguska cosmic body (TCB) explosion involved a comet, compressional heating of the comet was expected to create hydrogen and deuterium plasma. The velocity distribution of protons and deuterons in this plasma is not expected to be the Maxwell-Boltzmann distribution. It is shown that the use of a generalized momentum distribution leads to substantial increases of deuteron fusion rates and that a thermonuclear explosion may compete with a thermo-chemical explosion. Therefore, it may be possible that a thermo-chemical explosion induced a hydrogen thermonuclear explosion and both the thermo-chemical and thermonuclear explosions occurred in the 1908 Tunguska event. Experimental tests of this hypothesis are proposed.

Are the sungrazing comets the inner source of pickup ions and energetic neutral atoms?

We present arguments that at least part of the inner source of pickup ions in the solar wind might be the material released by sungrazing comets. Based on a statistical analysis of sungrazing comets detected over almost eight years of LASCO operation (1996 -- September 09 2004) an overwhelming majority of the observed sungrazers belong to the Kreutz group of comets, follows tightly clumped orbits and break up at $\sim 40 - 4$ solar radii in a well defined region of space. The material released from these comets could be (after ionization) an important portion of the inner source of pickup ions (PUIs), as the local mass flux of the inner source and cometary PUIs seem comparable. We indicate time intervals during the year when the cometary PUIs could be observed from a spacecraft on the Earth's orbit (from the end of July until the end of the year) and show three time intervals when they should be observable by Ulysses (from its launch time until the end of 1990, from the end of November 1994 until mid-May 1995 and from February 2001 until the end of July, 2001). We argue that the PUIs from the inner source should include both singly and doubly charged ions and that this cometary hypothesis alleviates some difficulties (in particular, the issue of hydrogen deficit) in the interpretation of the inner source as solar wind neutralized on dust grains close to the Sun.

Near-Earth object velocity distributions and consequences for the Chicxulub impactor

AbstractAn Opik-based geometric algorithm is used to compute impact probabilities and velocity distributions for various near-Earth object (NEO) populations. The resulting crater size distributions for the Earth and Moon are calculated by combining these distributions with assumed NEO size distributions and a selection of crater scaling laws. This crater probability distribution indicates that the largest craters on both the Earth and the Moon are dominated by comets. However, from a calculation of the fractional probabilities of iridium deposition, and the velocity distributions at impact of each NEO population, the only realistic possibilities for the Chicxulub impactor are a short-period comet (possibly inactive) or a near-Earth asteroid. For these classes of object, sufficiently large impacts have mean intervals of 100 and 300 Myr respectively, slightly favouring the cometary hypothesis.

Nature and destruction of the Tunguska cosmical body

The problem of the nature of the Tunguska Cosmical Body (TCB) is closely related to the mechanism of its disintegration which ended with an explosive disburse. The only hypothesis capable of explaining such a process is the idea that TCB was a fragment of a comet. Three alternative hypotheses are considered here. They assume the TCB to be: (i) a fragment of a stony asteroid; (ii) a porous snowball; and (iii) a plasmoid. It is shown that the first of them is not plausible because the fragmentation and explosion of an asteroid should result in the scattering of numerous fragments over the ground. They, however, have not been found on the terrain for many years by many tens of explorers who have carried out a careful analysis of the soil and peat. Bodies like a porous snowball or a plasmoid cannot exist in the Solar system (they should be unstable). The history of the cometary hypothesis is followed in the article, starting from its original formulation in a book by the well-known astrophysicist H. Shapley (1930. Flights from Chaos. A Survey of Material Systems from Atoms to Galaxies. N.Y.: McGraw-Hill, p. 57–58. Russian translation: From Atoms to Milky Ways. Moscow: ONTI, 1934), who has priority over F. J. W. Whipple [the latter having put this hypothesis 4 years later ( Whipple, 1934. On phenomena related to the Great Siberian meteor. Quart. Journ. of the Roy. Meteorol. Soc. 60, 505–513)]. Simultaneously with the evolution of this hypothesis our ideas of the structure of cometary nuclei have also varied. Estimates of the main parameters of the TCB — its initial mass m, initial velocity v and energy of explosion E e — are examined. The following quantities are assured to be the most probable: m=2×10 6 t, v=31 km/s, E e=5×10 23 erg. The mentioned value of v corresponds to the Zotkin–Kresak hypothesis that the TCB was a fragment of the Encke comet. Sekanina’s criticism against this hypothesis is examined. During recent years, three analytical theories of the sequential disintegration of large bodies in the atmosphere have been put forward by Grigoryan (1979: Motion and disintegration of meteorites in the planetary atmospheres. Cosmic Res. 17(6), 875–893), Hills and Goda (1993: The fragmentation of small asteroids in the atmosphere. Astron. J. 105(3) 1114–1144) (their theory is physically equivalent to Grigoryan’s theory), and by Chyba et al. (1993: The Tunguska 1908 explosion: atmospheric disruption of a stony asteroid. Nature, 36 (1) 40–44.). The comparison of all the three theories is presented. It is shown that the theory of Chyba et al. overestimates the altitudes of disruption of the meteoroid compared to other theories. The results of the numerical simulations of the process in the free-Lagrangian and the Eulerian approximation (Svettsov V.V., Nemchinov I.V., Teterev A.V., 1995. Disintegration of large meteoroids in Earth’s atmosphere: theoretical models. Icarus 116, 131–153) are also analysed. The results of numerous studies examined either do not contradict the cometary hypothesis of the TCB nature or the discrepancies (e.g. in the case of Chyba et al., 1993) can simply be explained. An interpretation is presented for the anomalous sky glow observed after the TCB fall, west of the treefall epicenter, in Russia and in West Europe. It was first put forward by the author ( Bronshten, 1991: Nature of the anomalous illumination of the sky related to the Tunguska event. Solar System Res. 25(4), 490–504) and considers the secondary scattering of solar light by the dust of the head of the comet that entered the Earth’s atmosphere simultaneously with the TCB.

The nature of the Tunguska meteorite

Abstract— Arguments in favor of the cometary origin of the Tunguska meteorite are adduced along with reasons against the asteroidal hypothesis. A critical analysis is given for the hypotheses by Sekanina (1983) and Chyba et al. (1993). On the basis of the azimuth and inclination of the trajectory of the Tunguska body with plausible values of the geocentric velocity, the semimajor axis of the orbit and its inclination to the ecliptic plane are calculated for this body. It is noted that the theory of the disintegration of large bodies in the atmosphere put forward by Chyba et al. (1993) is crude. Applying more accurate theories (Grigoryan, 1979; Hills and Goda, 1993) as well as taking into account the realistic shape of the body yield for the cometary body lower disruption heights than obtained by Chyba et al. Numerical simulations carried out by Svettsov et al. agree well with the cometary hypothesis and the analytical calculations based on Grigoryan's theory. The asteroidal hypothesis is shown not to be tenable: the complete lack of stony fragments in the region of the catastrophe, cosmochemical data (in particular, the results of an isotope analysis), and some other information contradict this hypothesis. It is shown that stony fragments that would have originated in the explosive disruption of the Tunguska body would not be vaporized by the radiation of the vapor cloud nor as a result of their fall to the Earth's surface.

The cometary hypothesis of the K/T mass extinctions

The cometary hypothesis of the K/T mass extinctions