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Comet ISON

Comet ISON (C/2012 S1) was a sungrazing Oort Cloud comet that approached the Sun closely in late 2013 before disintegrating due to intense solar heating, marking it as one of the most observed comets in history.^[1]^[2] Discovered on September 21, 2012, by Russian astronomers Vitali Nevski and Artyom Novichonok using a 0.4-meter telescope at the International Scientific Optical Network (ISON) observatory in Kislovodsk, Russia, the comet was initially spotted at a heliocentric distance of approximately 6.3 AU (about 585 million miles).^[1]^[3] This marked its first and only passage through the inner Solar System, as it originated from the distant Oort Cloud, a spherical shell of icy bodies surrounding the system at distances up to 100,000 AU.^[1] Its hyperbolic orbit indicated a non-periodic trajectory with an orbital period exceeding hundreds of thousands of years, perturbed by distant gravitational influences into a solar inbound path.^[1] As it drew nearer, Comet ISON brightened dramatically, developing a prominent coma and tail visible to the naked eye by late 2013, prompting widespread public interest and earning it the nickname "Comet of the Century."^[1] The comet became the subject of an unprecedented international observing campaign, involving over a dozen NASA and ESA spacecraft—including the Solar and Heliospheric Observatory (SOHO), Solar Terrestrial Relations Observatory (STEREO), Mars Reconnaissance Orbiter, and MESSENGER—as well as ground-based telescopes and the International Space Station crew.^[1]^[4] Observations revealed the comet's nucleus was small, estimated at 1-2 km in diameter, and it began shedding mass and dust well before perihelion, with activity ceasing hours prior to its solar encounter.^[1]^[5] On November 28, 2013, Comet ISON reached perihelion at a distance of 0.012 AU (approximately 1.8 million km from the Sun's center, or 1.2 million km above its surface), passing within 2.7 solar radii in a highly eccentric orbit inclined at 62.4 degrees to the ecliptic.^[2]^[6] During this phase, the comet's nucleus likely fragmented about 8.5 hours before closest approach, releasing around 11,500 tonnes of dust and halting gas and plasma production, as detected by SOHO's instruments.^[7] Post-perihelion images from SOHO and STEREO initially showed a brightening remnant stream, suggesting partial survival, but the nucleus had fully disintegrated, leaving only fading debris that dimmed rapidly and became undetectable by mid-December 2013.^[4] This event provided valuable data on cometary disruption under extreme thermal stress, contributing to understandings of Oort Cloud dynamics and sungrazer behavior.^[7]^[6]

Discovery and Designation

Discovery

Comet ISON, formally designated C/2012 S1, was discovered on September 21, 2012, by astronomers Vitali Nevski from Vitebsk, Belarus, and Artyom Novichonok from Kondopoga, Russia, as part of the International Scientific Optical Network (ISON) project.^[9] The detection occurred using a 0.4-meter f/3 Santel reflector telescope equipped with a CCD camera at the ISON-Kislovodsk observatory near Kislovodsk, Russia.^[10] At the time, the comet appeared as a faint, diffuse object with an 8-arcsecond coma and an apparent magnitude of 18.8, requiring specialized equipment for observation.^[11]^[12] The discoverers reported the object to the Minor Planet Center (MPC), the International Astronomical Union's clearinghouse for astrometric observations of minor planets and comets, on the same day.^[13] Pre-discovery images from as early as December 28, 2011, taken by the Mt. Lemmon Survey, were soon identified, extending the observational arc and confirming its cometary nature.^[13] The MPC issued the provisional designation C/2012 S1 (ISON) on September 24, 2012, via Minor Planet Electronic Circular (MPEC) 2012-S63, where "C/" denotes a long-period comet, "2012 S1" reflects the discovery year and half-month (second half of September, first such object), and "ISON" credits the discovering network.^[13] Follow-up astrometry from observatories worldwide, including Pan-STARRS in Hawaii and additional ISON stations, rapidly accumulated data to refine the trajectory.^[13] Gareth V. Williams, associate director of the MPC, computed the initial parabolic orbit based on these observations, indicating an inbound path from the Oort Cloud with perihelion at approximately 0.012 AU from the Sun on November 28, 2013.^[13] Early analyses by comet dynamics expert Zdenek Sekanina further examined the object's brightness behavior and orbital peculiarities, highlighting its potential as a dynamically new comet.^[14]

Naming

Upon its detection, Comet ISON received the provisional designation C/2012 S1 from the International Astronomical Union (IAU), where "C/" indicates a non-periodic comet, "2012" denotes the year of discovery, "S" signifies the second half of September, and "1" marks it as the first such comet reported in that period.^[15]^[1]^[16] This provisional label was later supplemented by the official name Comet ISON, an acronym for the International Scientific Optical Network (ISON), the collaborative astronomical survey program responsible for its discovery; under IAU guidelines, comets identified through such organized efforts are often named after the detecting program or institution rather than individual discoverers.^[1]^[17]^[18] As a dynamically new comet originating from the Oort cloud on a hyperbolic orbit (eccentricity > 1), it adhered to IAU protocols that prioritize provisional designations and program-based names for non-periodic objects, forgoing traditional proper names typically reserved for short-period or historically significant comets.^[18]^[15]^[19] In scientific literature and popular references, it is frequently denoted simply as "Comet ISON" or "the sungrazer" due to its trajectory bringing it within 1.2 million kilometers of the Sun's surface at perihelion, classifying it among sungrazing comets that approach extremely close to the solar photosphere.^[1]^[20]^[21]

Orbital Characteristics

Trajectory and Parameters

Comet ISON (C/2012 S1) originated in the Oort cloud, the spherical shell of icy bodies surrounding the Solar System at distances up to 100,000 AU. Its inbound trajectory was nearly parabolic, with an eccentricity of approximately 1.00002, rendering the orbit slightly hyperbolic and indicative of a dynamically new comet on its first (and only) passage through the inner Solar System without significant prior gravitational perturbations. This high eccentricity implies minimal binding to the Sun, consistent with Oort cloud comets perturbed into the inner system by distant stellar encounters or galactic tides.^[22]^[1] The comet's orbit was inclined at 62.4° to the ecliptic plane, a steep angle that positioned it to approach from the southern celestial hemisphere. It reached perihelion on November 28, 2013, at a distance of 0.012 AU (approximately 1.8 million km) from the Sun's center, passing within 1.2 million km of the solar surface. At this point, the comet's speed peaked at approximately 378 km/s (1.36 million km/h), driven by the steep gravitational potential well near the Sun. Prior to perihelion, ISON entered the inner Solar System from the outer regions, crossing Jupiter's orbital radius (5.2 AU) around December 2012 at a heliocentric distance of about 5 AU, with its closest approach to Jupiter being approximately 5.5 AU from the planet and no significant path alteration. The inbound velocity at 1 AU was approximately 42 km/s, consistent with its Oort cloud origin.^[22]^[4]^[23]^[24] The specific orbital energy, a key parameter determining the comet's fate, is calculated as

\xi = \frac{v^2}{2} - \frac{GM}{r},

where v is the velocity, r is the heliocentric distance, G is the gravitational constant, and M is the Sun's mass. For ISON at perihelion, \xi > 0 due to the combination of high speed and close approach, confirming the unbound hyperbolic trajectory and predicting ejection from the Solar System on an outbound path inclined similarly to the inbound leg. If the nucleus had survived intact, non-gravitational forces from outgassing might have slightly deflected the trajectory, but observations post-perihelion revealed disintegration, with surviving dust and fragments following a dispersed but fundamentally hyperbolic path away from the Sun.^[22]^[1]

Physical Properties

The nucleus of Comet C/2012 S1 (ISON) was estimated to have a diameter of approximately 1–2 km prior to perihelion, based on Hubble Space Telescope observations that derived an effective radius of 0.68 ± 0.02 km assuming a low geometric albedo of 0.04 and a linear phase function.^[25] The shape was irregular, consistent with typical cometary nuclei, though direct imaging resolution was insufficient to resolve detailed features.^[25] This low albedo value of ~0.04 reflects the dark, dust-covered surface common among Oort Cloud comets.^[25] The composition included a mixture of water ice, carbon monoxide, carbon dioxide, and dust grains containing organics and silicates such as crystalline olivine and pyroxene.^[26]^[27] Active volatiles like CO and CO2 drove early outgassing, with water ice becoming more prominent closer to perihelion, leading to significant mass loss through sublimation and dust ejection.^[26]^[28] The rotation period was inferred to be approximately 14.4 ± 1.2 hours from photometric variability in the inner coma, likely driven by asymmetric jet activity from active regions on the nucleus.^[29] The overall mass was estimated at around 5 × 10^{11} kg, derived from models of nucleus radius, assumed density of 1000 kg/m³, and observed dust and gas production rates.^[28] Due to its close sungrazing approach at 2.7 solar radii, the nucleus exhibited structural weakness, undergoing cataclysmic fragmentation around 17 solar radii from the Sun, where dynamic sublimation pressure and tidal forces exceeded its tensile strength of ~0.2–4 Pa.^[28] This vulnerability was exacerbated by the comet's trajectory, resulting in partial vaporization and dispersal of fragments.

Observations and Visibility

Pre-Perihelion Phase

As Comet ISON (C/2012 S1) entered the inner Solar System in late 2013, it became increasingly accessible to ground-based observers. By early October, the comet had brightened to around magnitude 9.6 and was visible through 4-inch amateur telescopes during moonless periods, particularly in the predawn sky from the Northern Hemisphere.^[30] Its visibility improved dramatically in mid-November following a sudden outburst, reaching magnitude 5.4 by November 14 and becoming detectable to the naked eye under dark skies, low on the eastern horizon near dawn.^[31] Brightness continued to surge, peaking at approximately magnitude -1 by late November, just before perihelion on November 28.^[32] Outgassing intensified as the comet approached the Sun, driving the development of its coma and tails. Solar heating triggered the release of dust and volatiles, forming a symmetric, greenish-blue coma approximately 1.2 arcminutes across by October 9, consistent with emissions from cyanogen and diatomic carbon gases.^[33] A prominent dust tail emerged in October, extending several arcminutes and appearing reddish due to scattered sunlight on submicron-sized particles pushed anti-sunward by radiation pressure.^[33] Observations indicated a steady dust production rate of about 0.14 kg/s, with the tail's color becoming redder farther out, reaching over 10% redder than solar spectrum beyond 10,000 km.^[34] Telescopic monitoring captured key details of the comet's approach. On October 9, NASA's Hubble Space Telescope imaged ISON at 1.49 AU from the Sun, revealing an intact nucleus too small to resolve amid the expanding coma, with early estimates suggesting 3-4 km diameter, later revised to 1-2 km; no signs of fragmentation despite increasing solar proximity.^[33]^[35] By late November, the Solar and Heliospheric Observatory (SOHO) began tracking ISON with its LASCO C3 coronagraph starting November 27, as the comet entered the instrument's field of view at about 13 million miles (0.14 AU) from the Sun; it brightened to magnitude +0.5, showing a well-defined coma and tail before transitioning to the narrower C2 field.^[32] These observations confirmed ongoing activity without structural failure prior to perihelion.^[36] Predictions positioned ISON as a potential "great comet," with expectations of daytime visibility due to its hyperbolic orbit and close solar approach, potentially rivaling historic spectacles like Comet Hale-Bopp.^[37] Amateur and professional networks anticipated naked-eye views worldwide from mid-November onward, especially post-outburst, though survival through perihelion remained uncertain given the intense tidal and thermal stresses.^[38]

Perihelion Passage

Comet ISON reached perihelion on November 28, 2013, at 18:25 UT, passing at a heliocentric distance of approximately 0.0124 AU (about 1.8 million km from the Sun's center), where intense solar radiation and gravitational forces subjected the nucleus to extreme conditions.^[32] In the hours preceding this closest approach, observations from the Solar and Heliospheric Observatory (SOHO)'s Large Angle and Spectrometric Coronagraph (LASCO) C3 instrument revealed a gradual fading of the comet's brightness, starting around November 28.1 UT when the heliocentric distance was about 17 solar radii, with the light curve following a trend proportional to r_H^{+2.7} to r_H^{+6.3}, where r_H is the heliocentric distance in solar radii.^[39] The central condensation of the coma disappeared by approximately November 28.5 UT, indicating significant structural changes as the nucleus entered the LASCO C2 field of view around 13:00 UT.^[39] Signs of tidal disruption became evident as the nucleus elongated along its leading edge until perihelion, likely due to the combined effects of solar tidal gravity—exceeding the comet's Roche limit—and thermal stresses from surface temperatures approaching 5,000 °F (about 2,800 K), sufficient to vaporize refractory materials.^[40] The LASCO C2 and C3 coronagraphs captured this phase, showing saturation in the comet's head from November 27.13 UT to 28.53 UT in C2 images and similar effects in C3 until 28.46 UT, obscuring fine details behind the occulting disk during the final approach.^[39] Just prior to perihelion, a sudden brightening occurred around November 28.6 UT at about 5 solar radii, possibly from a final outburst releasing dust, followed by rapid dimming post-passage as the remnant faded proportional to r_H^{-2.0} to r_H^{-2.7}.^[39]^[7] Initial assessments from these observations indicated that the nucleus had fully disintegrated before or during perihelion, with no detectable central condensation or active nucleus emerging afterward, leaving only an extended dust tail visible in LASCO images as the debris cloud expanded.^[39]^[7] Spectral data from SOHO's SUMER instrument, collected starting at 18:02 UT, showed low signal levels with no evidence of gas or plasma emission, supporting the conclusion that outgassing ceased hours before perihelion due to the destruction of the nucleus.^[7] By November 29 UT, the remnant had faded dramatically, appearing as a faint, diffuse streak without a distinct head, confirming the comet's demise during its solar encounter.^[32]

Post-Perihelion Phase

Following its perihelion passage on November 28, 2013, Comet ISON exhibited no signs of an intact nucleus, with observations confirming complete disintegration into a diffuse dust cloud that dispersed rapidly over subsequent days.^[41] The Comet ISON Observing Campaign (CIOC) reported on December 2, 2013, that the comet had fully disrupted, leaving only a fan-shaped debris stream visible in solar observatory imagery from SOHO and STEREO, which faded as the particles spread out.^[42] The remnants' visibility declined sharply post-perihelion, becoming undetectable to the naked eye by early December 2013 due to the rapid dissipation of the dust and gas envelope.^[42] Ground-based follow-up efforts by over 30 observatories worldwide, coordinated through the CIOC, captured images of the fading tail in late November and early December, but no new fragments or central condensation were identified amid the elongating debris trail.^[41] Amateur and professional astronomers using wide-field telescopes documented faint, diffuse glows until late December, with the last unconfirmed ground-based detection attempted on December 29, 2013, using a 180 mm telephoto lens in Hawaii, revealing only possible residual haze.^[43] Efforts to detect the remnants continued into January 2014, but no verifiable observations were made, as the dust cloud had dispersed beyond telescopic limits by mid-January when Earth crossed ISON's orbital plane.^[43] The surviving particles followed the comet's original hyperbolic trajectory, ejecting them out of the Solar System at speeds exceeding the Sun's escape velocity, with no anticipated return for billions of years.^[44]

Scientific Results

Compositional Analysis

Comet ISON's volatile inventory, as revealed by infrared spectroscopy, included water (H₂O) as the dominant species, alongside carbon monoxide (CO), ethane (C₂H₆), methane (CH₄), methanol (CH₃OH), ammonia (NH₃), formaldehyde (H₂CO), hydrogen cyanide (HCN), and acetylene (C₂H₂).^[45] Abundance ratios relative to H₂O for CO, C₂H₆, and CH₄ remained constant with heliocentric distance (Rₕ) and were below the mean values observed in other Oort cloud comets, indicating relative depletions in these species.^[46] In contrast, CH₃OH was depleted at Rₕ > 0.5 AU but approached average levels closer to the Sun, while NH₃, H₂CO, HCN, and C₂H₂ showed enrichments at Rₕ < 0.5 AU compared to typical cometary values.^[45] The dust component consisted of carbon-rich grains dominated by micron-sized particles, with inclusions of silicates and organic refractories.^[47] Thermal modeling of mid-infrared observations constrained the grain size distribution to favor small particles (peak ~1–10 μm) and high porosity, consistent with a composition where carbonaceous materials outnumbered silicates.^[47] These organics likely included complex refractory matter, contributing to the overall carbon enrichment observed in the coma. Spectral analysis identified key emission features from photodissociation products in the coma, including CN and C₂ radicals in the optical range, and OH from water dissociation. Infrared and submillimeter observations detected CO₂ through its vibrational bands and confirmed HCN via rotational lines, with the latter showing a production rate of (3.0 ± 0.1) × 10²⁶ molecules s⁻¹ at Rₕ ≈ 1 AU.^[48] The HCN/H¹³CN isotopic ratio of 88 ± 18 aligned with the protosolar value, indicating minimal fractionation.^[48] Outgassing rates for water, derived from [O I] 6300 Å and OH emission, followed a power-law dependence: Q(H₂O) = (1.89 ± 0.11) × 10²⁸ Rₕ⁻³.¹⁰ ± 0.¹ molecules s⁻¹ over Rₕ = 1.8–0.44 AU inbound.^[49] Pre-perihelion models indicated peak water loss rates approaching 10⁵ kg s⁻¹ near Rₕ ≈ 0.5 AU, driven by an active nucleus fraction of 50–100% and a major outburst at Rₕ ~0.6 AU.^[49] The active area decreased from ~10 km² at Rₕ > 1.2 AU to ~5 km² at Rₕ = 0.9–1.2 AU before surging, suggesting heterogeneous surface activity.^[49] Compared to other Oort cloud comets, ISON exhibited depletions in hypervolatiles like CO (<<10% relative to H₂O) but enrichments in less volatile organics such as HCN and H₂CO near perihelion, consistent with formation in the outer protoplanetary disk where such species could condense efficiently.^[45] This profile aligns with dynamical models placing Oort cloud progenitors beyond 30 AU, where hypervolatile ices dominate but processing alters abundances.^[50] Production rates for gas species were estimated from photometry using scaled Haser models, where Q ≈ (I / A) × (Δ² / g(α)) × f(Rₕ), with I as observed brightness, A the albedo or fluorescence efficiency, Δ the geocentric distance, g(α) the phase function, and f(Rₕ) incorporating heliocentric scaling; this approach yielded consistent Q values across optical and IR data for CN and OH.

Dynamical Implications

Comet ISON, designated C/2012 S1, originated from the Oort cloud, a distant reservoir of icy bodies surrounding the solar system at distances of tens of thousands of astronomical units. Backward integration of its orbit, accounting for planetary, stellar, and galactic perturbations, reveals that it was a dynamically new comet with an original semi-major axis exceeding 10,000 AU, indicating minimal prior influence from the inner solar system. The primary mechanisms injecting such comets into observable orbits are the galactic tide, arising from the Milky Way's gravitational potential, and occasional close encounters with passing stars, which gradually alter the angular momentum of Oort cloud objects over millions of years. These perturbations transform loosely bound, nearly radial orbits into hyperbolic or long-period paths that bring comets inward, as confirmed by detailed orbital cloning simulations.^[51] Simulations of ISON's passage at perihelion, approximately 0.012 AU from the Sun, highlighted the vulnerability of small comet nuclei to tidal forces. Numerical models predicted a tidal breakup threshold dependent on the nucleus's density, size, and rotation; for a typical cometary density of around 0.5 g/cm³ and a nucleus radius of about 1 km, survival was deemed likely unless prograde rotation or low density exacerbated stresses. However, ISON's actual disintegration near perihelion underscored the fragility of such bodies, with post-event analyses showing that nuclei smaller than 2 km often exceed the Roche limit, leading to fragmentation. The tidal radius r_t can be approximated by the formula

r_t = \left( \frac{M_\text{comet}}{M_\text{sun}} \right)^{1/3} d,

where M_\text{comet} is the comet's mass, M_\text{sun} is the Sun's mass, and d is the perihelion distance; for ISON's parameters, this yielded a critical radius below which tidal disruption was inevitable. These models, informed by historical sungrazing comet data, emphasized that rubble-pile structures common in Oort cloud comets amplify disruption risks at solar distances under 0.01 AU.^[52] Following its disruption, the released dust grains from ISON exhibited diverse trajectories influenced heavily by solar radiation pressure, which accelerated smaller particles into hyperbolic orbits while larger ones followed more bound paths. Observations post-perihelion revealed an elongated dust tail spanning over 10^5 km, with grain dynamics governed by the parameter \beta, the ratio of radiation pressure to gravitational force, typically ranging from 0.1 to 1 for micron-sized particles in ISON's coma. This scattering produced a fan-like structure in the tail, diverging from the surviving fragment's path and contributing to the comet's fading visibility. Such behavior illustrates how disruption events redistribute material, with radiation pressure effectively sorting grains by size and altering their future orbital evolution.^[28]^[53] The fate of Comet ISON provided key insights into the overall fragility of Oort cloud comets, refining dynamical models for their survival rates and interactions with the inner solar system. Its breakup validated predictions that a significant fraction of incoming long-period comets—potentially up to 50% for small nuclei—disintegrate due to thermal and tidal stresses, informing estimates of the Oort cloud's depletion over time. These findings also extend to interstellar objects, such as 'Oumuamua and Borisov, by highlighting structural weaknesses in pristine, distant icy bodies, thus improving simulations of their stability during solar encounters and the broader dynamics of extrasolar planetesimal populations.^[53]^[51]

Public and Media Impact

Media Coverage

Comet ISON garnered extensive media attention throughout 2013, often billed as the "Comet of the Century" due to predictions of its exceptional brightness upon reaching perihelion.^[54] This hype was fueled by early observations suggesting it could become visible to the naked eye worldwide, prompting widespread coverage in outlets like BBC News, which highlighted its potential as a rare celestial spectacle originating from the Oort Cloud.^[55] NASA amplified the excitement through its Comet ISON Observing Campaign (CIOC), a coordinated international effort that engaged professional and amateur astronomers via websites, social media, and educational resources to maximize data collection and public involvement.^[56] In the lead-up to perihelion, key events included NASA's press conference on November 26, 2013, where scientists discussed survival odds and observation strategies, drawing live media interest from sources like Chemical & Engineering News.^[57] The European Space Agency (ESA) and NASA jointly provided live streams from the Solar and Heliospheric Observatory (SOHO), capturing real-time images that went viral across platforms, including dramatic pre-perihelion shots shared by CNN.^[58] Hubble Space Telescope images, such as the April 2013 portrait revealing ISON's icy nucleus and dust tail, were featured prominently in media like BBC's "Big Picture" series, emphasizing its pristine, primordial composition.^[59]^[60] The comet's disintegration during perihelion passage on November 28 shifted narratives from optimism to disappointment, with immediate coverage in major outlets. BBC reported on the initial "death" of ISON based on SOHO imagery showing a faint remnant, while CNN detailed the event's unfolding via solar fleet observations, noting the loss of the anticipated post-perihelion display.^[61]^[62] Scientific American's post-event analysis contrasted the pre-flyby hype with scientific insights gained from the breakup, underscoring how the event, though a public letdown, enriched understanding of sungrazing comets.^[63] Nature similarly framed it as the "Death of a Comet," highlighting the transition from media-fueled expectations to rigorous post-analysis of its dynamical fate.

Public Visibility and Legacy

Comet ISON became visible to the naked eye for observers in the Northern Hemisphere during early to mid-November 2013, appearing as a faint, fuzzy object with a short tail in the predawn sky to the east.^[64] By November 15, following an outburst, it reached a magnitude of around 5.5, allowing unaided viewing under dark skies from suitably dark locations, though its low altitude limited observations in many locations.^[65] As the comet neared perihelion on November 28, 2013, increasing solar proximity obscured it in the Sun's glare, preventing naked-eye sightings during its closest approach.^[1] The anticipation surrounding ISON spurred significant public engagement, with the NASA-led Comet ISON Observing Campaign (CIOC) coordinating amateur contributions via dedicated websites and social media platforms to collect global observations.^[66] Tools like the free Comet Watch app enabled real-time tracking by directing users' devices toward the comet's position, enhancing accessibility for enthusiasts.^[67] NASA's outreach included educational resources on comet science, fostering public understanding of solar system origins through school programs and online materials tied to the campaign.^[68] ISON's legacy lies in reigniting public and scientific interest in sungrazing comets, as its passage yielded the largest dataset on a single comet to date, informing models of Oort Cloud dynamics and pristine icy body evolution.^[1] The event's data continues to support studies of long-period comets, though no major observational updates have occurred since 2014 following its disintegration. Its hyped yet tragic trajectory provided lessons for tempering predictions of future "great comets," exemplified by C/2019 Y4 (ATLAS), which similarly fragmented near perihelion in 2020 amid comparable media excitement.^[69] Culturally, ISON's demise as the self-proclaimed "comet of the century" inspired documentaries such as PBS's Comet Encounter, which chronicled the global anticipation and scientific pursuit, while online discussions highlighted themes of cosmic unpredictability.^[70] The narrative of a "doomed comet" resonated in popular media, underscoring the interplay between astronomical hype and real-world outcomes.^[71]

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Comet ISON: Faded Glory (27-30 November, 2013) - SOHO Hotshots
Nov 30, 2013 · At first the comet was thought to have disintegrated during its fiery encounter, with just a remnant of its tail continuing along ISON's ...Missing: facts | Show results with:facts
[30]
Incoming Comet ISON Appears Intact to NASA's Hubble
In this NASA Hubble Space Telescope image taken on October 9, the comet's solid nucleus is unresolved because it is so small. If the nucleus broke apart ...
[31]
CHARACTERIZING THE DUST COMA OF COMET C/2012 S1 (ISON) AT 4.15 AU FROM THE SUN - IOPscience
### Summary of Dust Coma and Tail Findings for Comet ISON Pre-Perihelion
[32]
A Timeline Of Comet ISON's Dangerous Journey - NASA
Jul 15, 2013 · Comet ISON was first discovered by Russian astronomers, Vitali Nevski and Artyom Novichonok, using the International Scientific Optical Network ...Missing: period | Show results with:period
[33]
Comet of the century ISON finally visible to naked eye | New Scientist
Nov 15, 2013 · It is now visible to the naked eye. ISON is expected to keep brightening over the next few weeks – and could become a once-in-a-century comet ...<|control11|><|separator|>
[34]
Dazzling Comet of 2013 May Be Among Brightest Ever Seen - Space
as bright as a first or last quarter moon — and some astronomers announced (as also has been ...
[35]
Preliminary Analysis of SOHO/STEREO Observations of Sungrazing ...
Jan 27, 2014 · Abstract:We present photometric and morphological analysis of the behavior of sungrazing comet C/2012 S1 ISON in SOHO and STEREO images ...
[36]
Study examines comet ISON's chances of surviving its close brush ...
Oct 9, 2013 · Unless ISON is very unusual, it should be dense enough to resist tidal disruption. ... ISON to remain a viable comet well after perihelion.Missing: SOHO LASCO<|control11|><|separator|>
[37]
[PDF] Initial Results From the Comet ISON Observing Campaign (CIOC ...
Abstract: In this paper we present an overview of the observing results and cometary behavior found for. C/2012 S1 (ISON) during its 2012 – 2013 apparition.
[38]
What happened to comet ISON? - Phys.org
Dec 5, 2013 · The much-anticipated flyby of the sun by Comet ISON on Thanksgiving Day 2013 is over, and instead of becoming a Great Comet… "Comet ISON ...
[39]
https://arxiv.org/abs/1401.7028
[40]
Death Of A Comet - NASA Scientific Visualization Studio
Dec 26, 2013 · Comet ISON shone brightly as it approached the sun on Nov. 28, 2013. A portion of the comet survived the trip around the sun ...Missing: VLT | Show results with:VLT
[41]
[PDF] THE EVOLUTION IN COMPOSITION OF ICES IN COMET D/2012 S1 ...
Mar 16, 2016 · We report results from long-slit high-resolution (λ/Δλ ≈. 25,000) spectra of Comet ISON on 10 pre-perihelion UT dates between 2013 October 22 ...
[42]
the Evolution in Composition of Ices in Comet D 2012 S1 (ISON ...
Mar 16, 2016 · Abundance ratios for CO, C2H6, and CH4 with respect to H2O remained constant with Rh and below their corresponding mean values measured ...
[43]
Comet C2012 S1 (ISON)s Carbon-rich and Micron-size-dominated ...
Jul 1, 2014 · [3] Our thermal models yield constraints the dust composition as well as grain size distribution parameters: slope, peak grain size, porosity.Missing: scientific | Show results with:scientific
[44]
[PDF] the hcn/h13cn ratio in c/2012 s1 (ison)
Using combined autocorrelation spectra from 28 active antennas, we recovered extended HCN coma emission from comet C/2012 S1 (ISON), resulting in a fourteen- ...
[45]
Evolution of H2O Production in Comet C/2012 S1 (ISON) as Inferred ...
Feb 22, 2018 · We present H2O production rates for comet C/2012 S1 (ISON) derived from observations of [O I] and OH emission during its inbound leg, ...Missing: analysis papers
[46]
Comparing Comet Compositions with Protosolar Nebula Models
We seek insights into where and when these objects formed by comparing the range of abundances observed for nine molecules and their average values across a ...
[47]
The catalogue of cometary orbits and their dynamical evolution
We present the CODE catalogue, the new cometary catalogue containing data for almost 300 long-period comets that were discovered before 2018.
[48]
[1309.2288] Will Comet ISON (C/2012 S1) Survive Perihelion? - arXiv
Sep 9, 2013 · We present new numerical simulations and interpret them in context with the historical track record of comet disruptions and of sungrazing comet ...
[49]
Catastrophic Disruption of Comet ISON
Nov 9, 2016 · Orbital computations suggest that the SCUBA-2 emission peak ... Sekanina, Zdenek (Jet Propulsion Lab., California Inst. of Tech ...
[50]
Comet ISON: Will the 'Comet of the Century' live up to the hype?
Jul 19, 2013 · This comet has been dubbed the "Comet of the Century," but some astronomers think it won't survive its trip past the sun. About these ads. When ...
[51]
Ison: The comet of the century - BBC News
Nov 23, 2013 · Ison has come from the Oort cloud, a belt of comets on the very edge of the Solar System, where it has been for the last 4.6 billion years.Missing: CNN American Hubble SOHO images
[52]
Astronomers gear up for 'Comet of the Century' - NBC News
Mar 18, 2013 · NASA has brought together a small team of experts to organize an observing campaign for Comet ISON, which could potentially shine as brightly as ...
[53]
All Eyes On Comet ISON - C&EN - American Chemical Society
Nov 27, 2013 · ... press conference on Nov. 26. PRISTINE BEAUTY. Comet ISON ... “This is perhaps the most observed comet ever,” noted Jim Green, director of NASA's ...
[54]
A comet's tale - ESA
28/11/2013 22217 views. ESA / Newsroom / Highlights. Comet ISON's close encounter with the Sun, as seen by the ESA/NASA SOHO satellite. Did the comet survive?
[55]
Big Picture: Hubble snaps image of comet Ison - BBC
Apr 24, 2013 · On 10 April, the Hubble Space Telescope caught sight of comet Ison, which is set to get much nearer in the coming months.
[56]
Hubble snaps icy comet ISON
a possibility as the ...
[57]
Hope still for 'dead' Comet Ison - BBC News
Nov 29, 2013 · All that could be seen was a dull smudge in space telescope images - its nucleus and tail assumed destroyed. But recent pictures have indicated ...Missing: CNN American Hubble
[58]
Comet ISON sweeps near sun, shows signs of life - CNN
Nov 29, 2013 · Comet ISON appears as a white smear heading up and away from the sun on Thursday, November 28. Scientists initially thought the comet had been disintegrated by ...
[59]
Death of a Comet: What We Learned from the Passing of ISON
Dec 13, 2013 · Scientists were less than thankful this year on Thanksgiving Day (November 28) when they watched the famous Comet c/2012 S1, aka ISON, ...Missing: disintegration BBC CNN SOHO images
[60]
Comet ISON Enters the Final Countdown | The Planetary Society
With only 10 days until perihelion, comet ISON will soon disappear into the Sun's glare. During this time, we will monitor it with an armada of solar satellites ...Missing: confirmation | Show results with:confirmation
[61]
Comet ISON heads for a close encounter with the sun - CBS News
Nov 25, 2013 · Should it survive, ISON (pronounced EYE'-sahn) would be visible with the naked eye through December, at least from the Northern Hemisphere.
[62]
[PDF] Pro-Am Collaboration for Support of NASA Comet ISON Observing ...
The NASA. Comet ISON Observing Campaign (CIOC) has lever- aged professional-amateur collaborations via web and social media as part of its mission to facilitate ...
[63]
How to see Comet ISON: New app points the way - CBS News
Nov 18, 2013 · Called Comet Watch, the free app is available for the iPhone or iPad. Updated by the minute, the app promises to point users in the direction of ...Missing: public engagement websites educational
[64]
The NASA Comet ISON Observing Campaign - Space Daily
Feb 27, 2013 · The goals of this NASA campaign, and thus of the CIOC Team, are to assist both ground and space-based NASA observatories, and private ...
[65]
Comet Y4 ATLAS Breaks Up...Enter Comet F8 SWAN
Apr 15, 2020 · Comet Y4 ATLAS broke its over-performing trend early last week, disintegrating into several fragments as observers watched on.<|control11|><|separator|>
[66]
Comet Encounter | Full Episode - PBS LearningMedia
Jun 8, 2016 · Through this documentary, explore the history of comet encounters over the ... A new celestial object is hurtling into our corner of space: the comet Ison.Missing: doomed memes
[67]
Comet ISON Latest: Nasa Video Captures Last Moments Of Doomed ...
Dec 3, 2013 · Comet ISON Latest: Nasa Video Captures Last Moments Of Doomed 'Comet Of The Century'. WATCH: The Final Moments Of Comet ISON. Huffington Post UK.