Will C/2025 R3 Be the "Great Comet" of 2026?

Abstract

The apparition of a long-period comet represents one of the most dynamic events in planetary astronomy, offering a window into the primordial conditions of the solar nebula while simultaneously presenting a complex challenge in photometric prediction. Comet C/2025 R3 (PanSTARRS), a retrograde object discovered in late 2025, has emerged as a candidate for high-visibility status during its perihelion passage in April 2026. This paper provides an exhaustive examination of the comet’s orbital mechanics, physical parameters, and the optical phenomena that may govern its visibility. Central to this analysis is the potential for forward scattering enhancement—a geometric optical effect that could amplify the comet's brightness by several magnitudes, potentially elevating it to the status of a "Great Comet." Conversely, the analysis considers the significant risks of nuclear disintegration common to small Oort cloud objects, evaluating the comet's survival probability against the Bortle Limit and historical disintegration events. Through a synthesis of astrometric data, photometric models, and comparative cometary science, this report aims to provide a definitive forecast for the 2026 apparition.

I. Introduction: The Cometary Landscape of the Mid-2020s

The study of comets—icy remnants from the formation of the solar system—has undergone a renaissance in the mid-2020s, driven by advanced survey capabilities and a fortuitous influx of objects from the Oort Cloud. Comets are not merely celestial spectacles; they are carriers of volatile materials, water, and prebiotic organic compounds, preserving the chemical fingerprints of the protoplanetary disk that formed the Sun and planets 4.6 billion years ago.¹

The year 2025 proved to be a watershed moment for cometary astronomy, characterized by a series of significant discoveries that kept observers and theoreticians engaged. The inner solar system played host to a diverse array of visitors, including Comet C/2025 A6 (Lemmon) and Comet C/2025 R2 (SWAN), both of which reached the threshold of naked-eye visibility and provided critical data on coma morphology and gas production rates.³ Furthermore, the scientific community was captivated by the arrival of 3I/ATLAS, only the third interstellar object ever detected passing through our solar system, following 'Oumuamua and 2I/Borisov.³ This context is vital for understanding the excitement surrounding C/2025 R3 (PanSTARRS); it arrives at a time when the astronomical community is primed for high-cadence observation and possesses a refined understanding of cometary behavior derived from these immediate predecessors.

In September 2025, the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) at the Haleakalā Observatory in Hawaii added another object to this growing catalog: C/2025 R3 (PanSTARRS).³ While initially a faint, distant point of light, orbital solutions quickly revealed a trajectory that would take the comet deep into the inner solar system, passing between the orbits of Mercury and Venus. This specific orbital geometry, combined with the timing of its passage relative to Earth, has positioned C/2025 R3 as the primary candidate for the title of "Great Comet of 2026".¹

However, the designation of "Great Comet" is fraught with uncertainty. It is a label that implies not just scientific interest, but a visual spectacle accessible to the general public—a criterion dependent on the capricious nature of cometary outgassing and the structural integrity of the nucleus. As this report will detail, C/2025 R3 sits on a knife-edge between two divergent outcomes: a spectacular display enhanced by the physics of light scattering, or a rapid fading due to nuclear disintegration.

II. Discovery and Astrometric Characterization

The discovery of a new long-period comet is rarely a serendipitous event in the modern era; rather, it is the result of systematic, automated sky surveys designed to map the population of Near-Earth Objects (NEOs).

The Pan-STARRS Survey Mechanism

The detection of C/2025 R3 serves as a testament to the efficacy of the Pan-STARRS system. Located on the summit of Haleakalā on the island of Maui, the system utilizes a 1.8-meter telescope equipped with a 1.4-gigapixel camera—one of the largest digital cameras ever built. This system repeatedly surveys the sky, looking for transient objects that move against the background of fixed stars.³

On September 8, 2025, the survey identified a new object at a heliocentric distance of approximately 2.3 Astronomical Units (AU), placing it roughly halfway between the orbits of Mars and Jupiter.³ At the time of discovery, the object shone at a faint magnitude of 19.8, a brightness level nearly 400,000 times fainter than the faintest star visible to the human eye.⁶ Such a detection is routine for Pan-STARRS, but the subsequent astrometric follow-up revealed the object's cometary nature.

Initial Observations and Designation

Following the initial alert, a global network of observatories contributed follow-up observations to refine the orbit. By late December 2025, the comet had brightened to approximately magnitude 16-17, confirming that activity—the sublimation of ices—had begun.⁷ The comet was officially designated C/2025 R3 (PanSTARRS) by the Minor Planet Center. The nomenclature breaks down as follows:

• C/: Indicates a non-periodic comet, or one with an orbital period greater than 200 years.

• 2025: The year of discovery.

• R: The half-month of discovery (the first half of September).

• 3: The third comet discovered in that half-month period.³

Distance and Approach Context

At the time of its discovery, C/2025 R3 was approximately 215 million miles from Earth. Its detection at this distance suggests a nucleus that is either relatively large or undergoing early, volatile-driven activity (such as the sublimation of Carbon Monoxide or Carbon Dioxide) well beyond the frost line.³ The "frost line" is the distance from the Sun where it is cold enough for volatile compounds like water, ammonia, and methane to condense into solid ice grains. Observing a comet crossing this threshold provides a timeline of activity that aids in predicting its performance at perihelion.

III. Orbital Dynamics and Trajectory Analysis

The destiny of any comet is written in its orbital elements. These mathematical parameters define the shape, orientation, and timing of the comet's path through the solar system. For C/2025 R3, the orbit is characterized by high inclination and a perihelion distance that subjects it to intense solar radiation.

Eccentricity and Origin

The eccentricity (e) of an orbit defines its shape. A perfect circle has an eccentricity of 0, while a parabola has an eccentricity of 1. Orbits with eccentricities greater than 1 are hyperbolic.

C/2025 R3 possesses an eccentricity of approximately 1.0003.⁶ This value slightly exceeds 1.0, technically making the orbit hyperbolic. However, in the context of long-period comets, this does not necessarily imply an interstellar origin (like 1I/'Oumuamua). Instead, it typically indicates a "dynamically new" comet arriving from the Oort Cloud—the spherical shell of icy bodies surrounding the solar system at distances of up to 100,000 AU. As these comets fall toward the Sun, planetary perturbations or non-gravitational forces (the "rocket effect" of outgassing) can impart a slight velocity boost, pushing the eccentricity just above 1.0.⁹ This distinction is crucial; dynamically new comets are often covered in highly volatile, "fresh" ices that can lead to deceptive brightening trends early in the apparition.

Inclination and Retrograde Motion

The inclination (i) of the orbit is approximately 124.7 degrees relative to the ecliptic plane (the plane of Earth's orbit).⁶ An inclination greater than 90 degrees signifies a retrograde orbit. This means C/2025 R3 orbits the Sun in the opposite direction to the planets.

• Implication for Velocity: Retrograde comets have high relative velocities with respect to Earth. When they pass us, they appear to move rapidly across the sky.

• Implication for Encounters: The high inclination means the comet spends much of its time well above or below the plane of the solar system, only diving through the ecliptic near perihelion. This minimizes the chance of gravitational disruption by Jupiter but complicates the viewing geometry for observers on Earth.

Perihelion Passage

The most critical moment in the comet's journey is perihelion—its closest approach to the Sun.

• Date: April 20, 2026 (approximate, solutions vary slightly by decimal days).³

• Distance (q): 0.498 to 0.499 AU.⁶

At roughly 0.5 AU, the comet will pass between the orbits of Mercury (0.39 AU) and Venus (0.72 AU).³ At this distance, the solar irradiance is approximately four times greater than what is experienced at Earth. This intense thermal environment drives the maximum rate of sublimation, converting water ice directly into gas and releasing the entrained dust that forms the coma and tail.

The Earth Encounter

Following perihelion, the comet's trajectory brings it toward Earth.

• Date of Closest Approach: April 26–27, 2026.¹²

• Minimum Distance: Approximately 0.489 AU (roughly 44 to 47 million miles).⁹

While not an historically close approach (compared to Comet Hyakutake's 0.1 AU passage in 1996), a distance of 0.49 AU is sufficiently close to allow a modest comet to appear significantly brighter and larger in the sky. The timing is also fortuitous; the comet approaches Earth just one week after perihelion, meaning we observe it when it is hottest and most active.²

Ephemeris and Constellation Path

The comet's path across the celestial sphere is dictated by the combination of its orbital motion and Earth's revolution.

• Winter 2025/2026: The comet resides in the constellation Pegasus, moving slowly as it is still distant.⁷

• April 2026 (Perihelion): The comet dives toward the Sun, moving through Pisces. It will be located just below the "Great Square" of Pegasus.¹³

• Late April/May 2026: Following the Earth flyby, the comet moves rapidly into Cetus and Eridanus.¹⁵ This southward motion will shift the best visibility from the Northern Hemisphere to the Southern Hemisphere in early May.¹²

IV. Physical Properties of the Nucleus

While orbital elements describe where the comet is, the physical properties of the nucleus determine what we see. The nucleus is the solid core of the comet—a conglomerate of rock, dust, and water ice, often described as a "dirty snowball."

Absolute Magnitude (H)

The intrinsic brightness of a comet nucleus is quantified by its absolute magnitude (H). This is defined as the apparent magnitude the object would have if viewed from a distance of 1 AU from both the Sun and the Earth, at a phase angle of zero degrees.¹⁶

• Reported H Values: Estimates for C/2025 R3 range from H = 11.4 to H = 12.2.⁷

These values provide a critical constraint on the size of the nucleus. Using standard albedo assumptions (where cometary nuclei are extremely dark, reflecting only about 4% of incoming light, similar to charcoal), an H value of 12 corresponds to a diameter of approximately 1 to 2 kilometers.¹⁶

• Comparison: The Great Comet Hale-Bopp (1997) had an absolute magnitude of roughly -1.0, implying a nucleus diameter of 60 kilometers. Comet Hyakutake had an H of roughly 7 or 8.

• Analysis: C/2025 R3 is an intrinsically small object. It is not a giant like Hale-Bopp. Its potential for "greatness" relies not on its size, but on its activity per unit surface area and the optical geometry of its encounter.

Activity Profile (Slope Parameter n)

The rate at which a comet brightens as it approaches the Sun is governed by the slope parameter, n.

• Standard Model: A steadily sublimating body typically follows an inverse-square law for reflection (brightness increases by a factor of 4 if distance is halved) combined with an activity factor. The standard formula uses n=4, meaning brightness varies with the fourth power of the distance.

• C/2025 R3 Data: Current light curve fits suggest an n value between 4.0 and 4.6.⁷ This indicates a "healthy" comet that is responding predictably to solar heating, brightening slightly faster than the standard model.

Chemical Composition Implications

As a long-period comet, C/2025 R3 likely retains a pristine crust of super-volatile ices such as nitrogen (N2), carbon monoxide (CO), and carbon dioxide (CO2). These ices sublimate at very low temperatures, far from the Sun. This can lead to an early "turn-on" of activity.

• The "Oort Cloud Imposter" Risk: A known phenomenon with dynamically new comets is that they appear bright at large distances due to CO sublimation, but fail to brighten significantly when they reach the inner solar system because their water-ice reserves are insulated or the volatile crust is depleted. However, the consistent n=4 slope observed so far suggests C/2025 R3 may have a robust water-ice sublimation mechanism kicking in.¹⁸

V. Photometric Modeling and Light Curve Analysis

The "Light Curve" is the prediction of the comet's brightness over time. For C/2025 R3, there is a dramatic divergence in predictions, driven by the uncertainty of how the dust will interact with sunlight.

The Baseline Prediction (Conservative Model)

Using the standard magnitude formula for comets, here H is absolute magnitude, Δ is distance from Earth, and r is distance from Sun.

Inputting the current parameters (H=11.4, n=4.6, Perihelion q=0.5), the baseline prediction for late April 2026 is:

• Maximum Brightness: Magnitude +6 to +8.²

• Visual Impact: At magnitude 8, the comet is well below the threshold of naked-eye visibility (approx magnitude 6). It would be visible only in binoculars or small telescopes as a faint, diffuse patch of light. In this scenario, C/2025 R3 would be a scientific curiosity but not a public spectacle.

The Optimistic Prediction (Dynamic Model)

However, several sources cite a potential peak brightness of magnitude +2.5 or even +3.0.⁴

• Visual Impact: Magnitude 3 is comparable to the stars of the constellation Cassiopeia or the belt stars of Orion. A comet of this brightness would be easily visible to the naked eye from a dark site and could potentially show a visible tail.

The bridge between the conservative Magnitude 8 and the optimistic Magnitude 2 is a phenomenon known as Forward Scattering.

VI. The Physics of Forward Scattering

The potential for C/2025 R3 to become a "Great Comet" rests almost entirely on optical physics, specifically the scattering properties of micron-sized dust particles.

Mie Scattering Explained

Light scattering by particles comparable in size to the wavelength of the light (such as cometary dust grains) is described by Mie theory. Unlike a diffuse reflector (like the Moon) which is brightest when the Sun is behind the observer (opposition), cometary dust is strongly forward scattering.

• Analogy: Consider driving a car toward a setting sun with a dirty windshield. The dust on the glass glows brilliantly because it scatters the sunlight forward into your eyes.

• Mechanism: When sunlight hits a dust grain, it is diffracted. For particles of the size found in cometary comas (1 to 10 micrometers), this diffraction lobe is concentrated in the forward direction.

The Phase Angle Criticality

The intensity of this scattering is dependent on the phase angle (the angle between the Sun, the Comet, and the Observer).

• Backscattering (Low Phase Angle): Sun is behind the observer. Standard brightness.

• Forward Scattering (High Phase Angle): Comet is between the Sun and Observer. Enhanced brightness.

According to orbital ephemerides, C/2025 R3 will reach extremely high phase angles during its Earth encounter in late April 2026.

• Predicted Phase Angle: The angle is expected to peak between 135° and 167° around April 26.⁹

• The Marcus Model: Researcher Joseph Marcus has developed models quantifying this enhancement. At phase angles exceeding 140°, the brightness of a dust-rich coma can be amplified by factors of 10 to 100 (2.5 to 5 magnitudes).²¹

Conditions for Enhancement

For this enhancement to occur, the comet must be dusty.

• Gas vs. Dust: Comets release both gas (which glows by fluorescence) and dust (which reflects/scatters sunlight). Forward scattering only affects the dust. If C/2025 R3 is a gas-rich but dust-poor comet, the enhancement will be negligible.

• The Unknown: We currently do not know the dust-to-gas ratio of C/2025 R3. However, recent observations from December 2025 noted a "green coma," which typically indicates diatomic carbon (gas) emission.²³ If the dust production lags, the optimistic magnitude 2 forecast may not materialize. Conversely, if the heat of perihelion liberates vast quantities of dust, the comet could flare brilliantly, as Comet McNaught did in 2007.²²

VII. Comparative Cometary Analysis and Disintegration Risks

To contextualize C/2025 R3, we must compare it to historical precedents and assess the risks inherent to its size.

The "Great Comet" Criteria

The term "Great Comet" is subjective, but astronomer John Bortle established three loose criteria ²⁴:

1. Large/Active Nucleus: Essential for sustained brightness.

2. Close Approach to Sun: To drive activity.

3. Close Approach to Earth: To maximize apparent size.

Scorecard for C/2025 R3:

• Nucleus: Weak/Small (H=11-12). (Fail)

• Sun Approach: Good (0.5 AU). (Pass)

• Earth Approach: Good (0.49 AU). (Pass)

Comparison with historical comets helps visualize the potential:

• Comet McNaught (2007): Had extreme forward scattering and perihelion proximity, but a much larger nucleus.

• Comet Hyakutake (1996): Passed much closer to Earth (0.1 AU). R3 is 5x further away.

• Comet Donati (1858): A classic dusty comet. R3 has similar geometry but likely a smaller nucleus.²⁵

The Disintegration Hazard

The greatest threat to the C/2025 R3 apparition is the physical destruction of the nucleus. Small comets are fragile. The thermal shock of perihelion (rapid heating) and the tidal forces of the Sun can fracture the nucleus or cause it to completely sublimate away.

The Bortle Limit:

John Bortle derived an empirical limit for comet surviva. For a perihelion distance (q) of 0.5 AU, the survival limit is roughly absolute magnitude H = 5.2.

• C/2025 R3 Status: With an H of 11–12, C/2025 R3 is significantly fainter than the Bortle Limit.²⁶ This suggests a high probability of disintegration.

Historical Precedents for Disintegration:

• C/2019 Y4 (ATLAS): Looked promising but fragmented before perihelion.

• C/2021 A1 (Leonard): Survived perihelion but showed signs of crustal failure and fading.²⁶

• C/2024 G3 (ATLAS): Disintegrated near perihelion in January 2025.²⁷

• Statistical Analysis: Studies indicate that roughly 25% of long-period comets with small perihelion distances fail to survive.²⁹ Disintegrating nuclei often display "non-gravitational acceleration" (unusual movements due to gas jets) and low gas production rates.

Implication: There is a distinct possibility that C/2025 R3 will brighten on approach, then suddenly fade into a "headless" cloud of debris just as it reaches its best viewing geometry in April 2026. This "phantom comet" scenario would be scientifically interesting but visually disappointing.

VIII. Observational Phenomenology and Viewing Geometry

Assuming the nucleus survives, the observational window for C/2025 R3 is brief and geometrically complex. The apparition can be divided into three distinct phases.

Phase I: The Approach (January – March 2026)

• Status: Telescopic Object.

• Brightness: Magnitude 16 brightening to 10.

• Location: Constellation Pegasus.⁷

• Description: The comet will be a faint fuzz visible only in large amateur telescopes (8-inch aperture or larger). Astrophotographers will begin tracking the development of the coma and the first hints of a tail.

Phase II: The Perihelion Passage (Mid-April 2026)

• Status: Critical Transition / Potential Disintegration.

• Date: April 15–22, 2026.

• Brightness: Rapid brightening from Mag 8 to potentially Mag 3 (if scattering engages).

• Geometry: The comet is very close to the Sun (elongation < 25 degrees).

• Viewing:

• Northern Hemisphere: Visible very low in the east before sunrise or west after sunset.

• Key Event: The New Moon on April 17, 2026, provides dark skies right before the comet reaches its closest point to the Sun.² This is the "high stakes" window where observers will know if the comet has survived.

Phase III: The Earth Flyby (Late April – May 2026)

• Status: Maximum Visibility (The "Great" Window).

• Date: April 26–May 5, 2026.

• Brightness: Peak forward scattering. Potentially Mag 2–4.

• Location: Moving rapidly from Pisces into Cetus and Eridanus.¹⁵

• Viewing:

• Northern Hemisphere: The comet dips lower in the sky, becoming difficult.

• Southern Hemisphere: The comet moves rapidly southward, becoming a potentially spectacular evening object for observers in Australia, South America, and Southern Africa.¹²

• Phenomenology: If the comet is dusty, the tail may appear "broad" and diffuse due to the scattering angle, potentially resembling a fan of light rather than a thin streak.

Date	Event	Est. Mag (Base)	Est. Mag (Scatter)	Status
Jan 13, 2026	In Pegasus	16.4	16.4	Telescopic Only 9
Apr 17, 2026	New Moon	7.0	5.0	Binocular? 2
Apr 20, 2026	Perihelion (0.49 AU)	6.1	3.5	Difficult (Solar Glare) 9
Apr 27, 2026	Earth Flyby (0.49 AU)	6.0	2.5	Peak Visibility (S. Hemisphere) 13

IX. Scientific Implications and Future Surveys

Beyond the visual spectacle, C/2025 R3 offers significant scientific value.

Probing the Oort Cloud

Every long-period comet is a data point from the edge of the solar system. C/2025 R3 represents a specific class of "small" Oort cloud objects. Understanding the size distribution of these objects helps constrain models of the solar system's formation. If small comets are abundant, it implies a different collisional history in the early nebula than if they are rare.

Volatile Inventory

Spectroscopic analysis of the comet's coma during perihelion will reveal the ratio of water (H2O) to other volatiles like carbon monoxide (CO), methane (CH4), and ammonia (NH3).

• D/H Ratio: A critical measurement is the Deuterium-to-Hydrogen ratio in the comet's water. Determining if cometary water matches Earth's ocean water is central to understanding the origin of Earth's habitability. C/2025 R3 adds another sample to this vital inventory.¹³

The Era of LSST

The discovery of C/2025 R3 by Pan-STARRS is a precursor to the era of the Vera C. Rubin Observatory (Legacy Survey of Space and Time, or LSST). Set to begin full operations in the mid-2020s, LSST will detect thousands of such comets at much greater distances.³¹ C/2025 R3 serves as a calibration object for these future surveys, helping astronomers understand how faint, distant detections evolve into active inner-solar-system comets.

X. Conclusion

Comet C/2025 R3 (PanSTARRS) stands as a fascinating case study in cometary unpredictability. It possesses the orbital geometry requisite for a spectacular display: a perihelion passage inside the orbit of Venus followed by a close approach to Earth, perfectly timed to exploit the physics of forward scattering. Under the most optimistic models, it could flare to magnitude 2, becoming a naked-eye object with a fan-like tail in the twilight of April 2026—a true "Great Comet" for the Southern Hemisphere.

However, the physical reality of the object commands caution. With an absolute magnitude of ~12, the nucleus is small, likely under 2 kilometers in diameter. It sits well below the Bortle Limit for survival, carrying a high risk of disintegration as it faces the solar furnace.

For the astronomical community and the public alike, C/2025 R3 represents a cosmic lottery ticket. It may crumble into dust, leaving only a ghostly cloud of debris, or it may survive to light up the spring skies, amplified by the very dust it sheds. Regardless of the visual outcome, its passage provides a vital opportunity to study the fragile icy bodies that populate the distant reaches of our solar system. Observers are advised to monitor the comet closely in March and early April 2026; the behavior of the nucleus in those weeks will determine whether we are greeting a "Great Comet" or bidding farewell to a disintegrated one.

Works cited

1. Comets: News, features and articles | Live Science, accessed January 13, 2026, https://www.livescience.com/space/astronomy/comets

2. Will Comet C 2025 R3 PanSTARRS Become The Sky's Next Big Spectacle of 2026, accessed January 13, 2026, https://usaherald.com/will-comet-c-2025-r3-panstarrs-become-the-skys-next-big-spectacle-of-2026/

3. A New Celestial Visitor Just Entered Our Solar System — and It Could Be the 'Great Comet of 2026', accessed January 13, 2026, https://www.greenmatters.com/pn/a-new-celestial-visitor-just-entered-our-solar-system-and-it-could-be-the-great-comet-of-2026

4. Will Comet C/2025 R3 (PanSTARRS) be the 'great comet' of 2026? - Space, accessed January 13, 2026, https://www.space.com/astronomy/comets/will-comet-c-2025-r3-panstarrs-be-the-great-comet-of-2026

5. This Comet Might Be from Interstellar Space. Here's How We Could Find Out., accessed January 13, 2026, https://www.space.com/possible-interstellar-comet-identified.html

6. C/2025 R3 ( PanSTARRS ) - Seiichi Yoshida, accessed January 13, 2026, http://www.aerith.net/comet/catalog/2025R3/2025R3.html

7. C/2025 R3 (PANSTARRS) - In-The-Sky.org, accessed January 13, 2026, https://in-the-sky.org/data/object.php?id=287739

8. Weekly Information about Bright Comets (2026 Jan. 3: North), accessed January 13, 2026, http://www.aerith.net/comet/weekly/current.html

9. C/2025 R3 (PANSTARRS) | astro.vanbuitenen.nl, accessed January 13, 2026, https://astro.vanbuitenen.nl/comet/2025R3

10. C/2024 G3 (ATLAS) - Wikipedia, accessed January 13, 2026, https://en.wikipedia.org/wiki/C/2024_G3_(ATLAS)

11. Lightcurve of C/2025 R3 (PANSTARRS) - COBS - Comet OBServation database, accessed January 13, 2026, https://cobs.si/comet/2663/

12. When and how to watch the 'great comet of 2026', accessed January 13, 2026, https://www.newsbytesapp.com/news/science/comet-c-2025-r3-may-be-visible-from-earth-this-april/story

13. Great Comet candidate C/2025 R3 races toward April 2026 sky event - Türkiye Today, accessed January 13, 2026, https://www.turkiyetoday.com/lifestyle/great-comet-candidate-c2025-r3-races-toward-april-2026-sky-event-3212836

14. 'Great Comet of 2026' spotted by astronomers, accessed January 13, 2026, https://dunyanews.tv/en/Technology/929468

15. Comet C/2025 R3 (PanSTARRS): We May Already Know When The Best Comet Of 2026 Is Coming, accessed January 13, 2026, https://www.iflscience.com/comet-c2025-r3-panstarrs-we-may-already-know-when-the-best-comet-of-2026-is-coming-82207

16. Conversion of Absolute Magnitude to Diameter for Minor Planets, accessed January 13, 2026, https://www.physics.sfasu.edu/astro/asteroids/sizemagnitude.html

17. Asteroid Size Estimator - Nasa CNEOS, accessed January 13, 2026, https://cneos.jpl.nasa.gov/tools/ast_size_est.html

18. Why Predicting Comet Brightness Is So Tough - Space, accessed January 13, 2026, https://www.space.com/20347-comet-brightness-predictions-difficult.html

19. Comet C/2025 R3 PanSTARRS: How to See It in April 2026 - Star Walk, accessed January 13, 2026, https://starwalk.space/en/news/comet-c2025-r3-panstarrs

20. Is a Once-In-A-Decade ‘Great Comet’ About To Appear In 2026?, accessed January 13, 2026, https://orbitaltoday.com/2026/01/04/is-a-once-in-a-decade-great-comet-about-to-appear-in-2026/

21. Forward-Scattering Enhancement of Comet Brightness. III. Prospects for C/2010 (Elenin) as Viewed from the, accessed January 13, 2026, http://www.icq.eps.harvard.edu/C2010X1_ICQ_MSS-R2.pdf

22. international comet quarterly, accessed January 13, 2026, http://www.icq.eps.harvard.edu/marcus_icq29_119.pdf

23. comets-ml@groups.io | Messages, accessed January 13, 2026, https://groups.io/g/comets-ml/messages?subsort=1&limit=1&index=31574

24. Great comet - Wikipedia, accessed January 13, 2026, https://en.wikipedia.org/wiki/Great_comet

25. Forward-Scattering Brightness Enhancement of Halley's Comet in 2061, accessed January 13, 2026, https://www.hou.usra.edu/meetings/acm2023/pdf/2348.pdf

26. Comet Leonard has broken into pieces as it rounds the sun: report - Space, accessed January 13, 2026, https://www.space.com/comet-leonard-broke-up-pieces

27. Is super-bright Comet ATLAS G3 disintegrating? - EarthSky, accessed January 13, 2026, https://earthsky.org/tonight/brightest-comet-of-2025-atlas-g3-southern-hemisphere/

28. On the disintegration of the 3I/ATLAS object, accessed January 13, 2026, https://xras.ru/en/project_diary.html?post_id=3175

29. [PDF] Destruction of Long-period Comets | Semantic Scholar, accessed January 13, 2026, https://www.semanticscholar.org/paper/9eeb84c78fa7fff0bae6ed7cf845e91eb70c59c6

30. New Year, New Comets: Two Targets in January 2026, accessed January 13, 2026, https://starwalk.space/en/news/upcoming-comets

31. 8 astronomy discoveries that wowed us in 2025 - Space, accessed January 13, 2026, https://www.space.com/astronomy/the-top-astronomical-discoveries-of-2025