55 citations · 170 across the 32 of their papers we have counts for
32 papers
Fragmentation and History of Comet Pair C/1844 Y1 and C/2019 Y4
Zdenek Sekanina
I call attention to extraordinary features displayed by the genetically related long-period comet pair of C/1844 Y1 (Great Comet) and C/2019 Y4 (ATLAS). The issue addressed most ex…
On the Existence of a Super-Kreutz System of Sungrazing Comets
Zdenek Sekanina
In the context of a recently proposed contact-binary model of the Kreutz system, all its members are products of the process of cascading fragmentation of the two lobes of the pare…
On Elusive Observations and a Sly Companion of Comet Wirtanen (C/1956 F1)
Zdenek Sekanina
Noting that the extensive astrometric observations of the double comet Wirtanen (C/1956 F1) made by E. Roemer have never been published, I replicate the contents of a fortuitously…
Populations of the Kreutz Sungrazer System in a SOHO Database
Zdenek Sekanina
Discovery of nine populations in a set of 193 select SOHO Kreutz sungrazers (Sekanina 2021) is confirmed for the first time via a histogram of the true longitudes of the ascending…
Kreutz Sungrazers: Summary of Recent Modeling and Orbits of the SOHO Objects
Zdenek Sekanina
I summarize and streamline the results of recent modeling of the orbital evolution and cascading fragmentation of the Kreutz sungrazers. The model starts with Aristotle's comet --…
The Great Comet of 1106, a Chinese Comet of 1138, and Daylight Comets in late 363 As Key Objects in Computer Simulated History of Kreutz Sungrazer System
Zdenek Sekanina, Rainer Kracht
We present the results of our orbital computations in support of the recently proposed contact-binary model for the Kreutz sungrazer system (Sekanina 2021, 2022). We demonstrate th…
Unprecedented Daylight Display of Kreutz Sungrazers in AD 363?
Zdenek Sekanina
In the context of the recently proposed contact-binary model (Sekanina 2021), I investigate the circumstances of the first perihelion passage of the Kreutz sungrazers in orbits wit…
Estimating Dimensions of the Nucleus of Great September Comet of 1882 from Motions of Its Fragments
Zdenek Sekanina
Data on perihelion fragmentation of the Great September Comet of 1882 (C/1882 R1), a prominent member of the Kreutz sungrazer system, are employed to estimate the size of the nucle…
The End of an Era in Cometary Astronomy: The Deceleration of Comet Encke
Zdenek Sekanina
It is noted that effective very recently, the orbital motion of Encke's comet has become affected by a very slight nongravitational deceleration. Soon after J. F. Encke established…
On the Detection and Distribution of Nongravitational Accelerations in the Motions of Long-Period Comets
Zdenek Sekanina
Even though the orbital motions of most long-period comets are found to comply with the gravitational law, a rapidly increasing minority of these objects is found to display detect…
Enigmatic Nebulous Companions to the Great September Comet of 1882 As SOHO-Like Kreutz Sungrazers Caught in Terminal Outburst
Zdenek Sekanina
I investigate the nature of the transient nebulous companions to the sungrazing comet C/1882 R1, known as the Great September Comet. The features were located several degrees to th…
New Model for the Kreutz Sungrazer System: Contact-Binary Parent and Upgraded Classification of Discrete Fragment Populations
Zdenek Sekanina
The structure of the Kreutz system of sungrazing comets is shown to be much more complex than formerly believed. Marsden's (1989) division into three subgroups (I, II, IIa) is now…
Sublimation of Water Ice from a Population of Large, Long-Lasting Grains Near the Nucleus of 2I/Borisov?
Zdenek Sekanina
Potential effects of sublimation of water ice from very slowly moving millimeter-sized and larger grains, a product of activity at ~10 AU or farther from the Sun driven presumably…
Note on the HST Image of Comet 2I/Borisov Taken on 2019 October 12
Zdenek Sekanina
The image of comet 2I/Borisov taken by the Hubble Space Telescope on October 12 shows a fan-like feature in the inner coma, which extends over a few arcseconds from the nuclear con…
Are 2I/Borisov and Oort Cloud Comets Alike?
Zdenek Sekanina
The interstellar comet 2I/Borisov bears a strong resemblance to Oort Cloud comets, judging from its appearance in images taken over the first six weeks of observation. To test the…
Comments on a Recent Review Paper on Near-Sun Comets
Zdenek Sekanina
It is noted that some results of the author's research papers cited in the comprehensive review paper "The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets" by G. H. J…
Outgassing As Trigger of 1I/`Oumuamua's Nongravitational Acceleration: Could This Hypothesis Work at All?
Zdenek Sekanina
The question of what triggered the nongravitational acceleration of 1I/`Oumuamua continues to attract researchers' attention. The absence of any signs of activity notwithstanding,…
1I/`Oumuamua and the Problem of Survival of Oort Cloud Comets Near the Sun
Zdenek Sekanina
A 2000-2017 set of long-period comets with high-quality orbits of perihelion distance <1 AU is used to show that the objects that perish shortly before perihelion are nearly exclus…
1I/`Oumuamua As Debris of Dwarf Interstellar Comet That Disintegrated Before Perihelion
Zdenek Sekanina
Intrinsically faint comets in nearly-parabolic orbits with perihelion distances much smaller than 1 AU exhibit strong propensity for suddenly disintegrating at a time not long befo…
Preperihelion Outbursts and Disintegration of Comet C/2017 S3 (Pan-STARRS)
Zdenek Sekanina, Rainer Kracht
A sequence of events, dominated by two outbursts and ending with the preperihelion disintegration of comet C/2017 S3, is examined. The onset times of the outbursts are determined w…
Major Outburst and Splitting of Long-Period Comet C/2015 ER61 (Pan-STARRS)
Zdenek Sekanina
In early April 2017, five weeks before passing through perihelion, the dust-poor comet C/2015 ER61 was observed to undergo a major outburst, during which its intrinsic brightness i…
Orbital Evolution, Activity, and Mass Loss of Comet C/1995 O1 (Hale-Bopp): II. Nucleus and Companions as Compact Clusters of Massive Fragments
Zdenek Sekanina
The prime objective is to settle a contradiction between a high nongravitational acceleration affecting the orbital motion of comet C/1995 O1 and its enormous nucleus by modeling i…
Orbital Evolution, Activity, and Mass Loss of Comet C/1995 O1 (Hale-Bopp). I. Close Encounter with Jupiter in Third Millennium BCE and Effects of Outgassing on the Comet's Motion and Physical Properties
Zdenek Sekanina, Rainer Kracht
This comprehensive study of comet C/1995 O1 focuses first on investigating its orbital motion over a period of 17.6 yr (1993-2010). The comet is suggested to have approached Jupite…
Study of a Potential Relationship Between Two Long-Period Comets and Rapid Inward Drifting of Aphelion Due to Orbital-Cascade Resonance
Zdenek Sekanina, Rainer Kracht
We study a potential genetic relationship of comets C/1846 O1 and C/1973 D1, whose apparent orbital similarity was tested by Kresak (1982) only statistically, using the Southworth-…