Comet C/2026 B2 (Sun-Gao): A New Long-Period Comet Discovered by Chinese Amateur Astronomers

In January 2026, while most of the world was ringing in the new year, a team of amateur astronomers in western China spotted something faint and fuzzy drifting through the constellation Vulpecula. Within days, the Minor Planet Center confirmed it: C/2026 B2 (Sun-Gao) was a previously unknown comet — a visitor from the outer reaches of the solar system making its first recorded approach to the Sun in over 230 years.

Named after its discoverers at China's Xingming Observatory, C/2026 B2 is a long-period comet on a highly elliptical orbit that brought it within 1.28 AU of the Sun in early January 2026. While it won't rival the great naked-eye comets, it's a fascinating object for amateur astronomers and a testament to the vital role that citizen scientists continue to play in comet discovery.

Discovery: Amateur Astronomers Strike Again

C/2026 B2 was discovered by Guoyou Sun and Xing Gao using the Xingming Observatory-KATS (Kilodegree Automatic Transient Survey) facility at Nanshan, in Xinjiang, China. The observatory sits at an altitude of 2,068 meters in the arid mountains of western China — far from city lights and blessed with some of the clearest skies in East Asia.

The discovery images were captured in mid-January 2026, with the first report submitted by S. Jia on January 21, 2026. Initial observations showed a faint coma but no visible tail, typical of a comet first caught at moderate distance from the Sun.

Within days, 66 observations from observatories worldwide — including the Lowell Discovery Telescope and numerous international facilities across Europe, Asia, and North America — confirmed the cometary nature of the object. The Minor Planet Center published the discovery in MPEC 2026-B203 on January 29, followed by a corrected orbit in MPEC 2026-B205.

The Discoverers

Xing Gao is one of China's most prolific amateur astronomers. He built Xingming Observatory in 2006 and has been responsible for discovering multiple comets, including C/2008 C1 (Chen-Gao) and P/2009 L2 (Yang-Gao). Guoyou Sun, based in Wenzhou, Zhejiang, previously co-discovered C/2015 F5 (SWAN-Xingming) with Gao.

Together, they represent the best of amateur astronomy — dedicated sky watchers using modest but well-calibrated equipment to make discoveries that advance our understanding of the solar system. As of 2024, Xingming Observatory's tally includes 3 comets, 15 asteroids, 90 supernovae, 63 novae, and 111 dwarf novae — a remarkable record for a facility built and operated by enthusiasts.

Orbital Characteristics: A 233-Year Journey

The corrected orbital elements for C/2026 B2 reveal an object on a vast, looping trajectory through the solar system:

Parameter	Value
Perihelion date	January 9.78, 2026 (TT)
Perihelion distance	1.2776 AU
Eccentricity	0.9663
Inclination	59.70°
Orbital period	~233 years
Classification	Long-period, nearly isotropic
Nearest to Earth	January 30, 2026 (~2.03 AU)

With a perihelion distance of 1.28 AU — just outside Earth's orbit — C/2026 B2 doesn't get particularly close to the Sun. This limits its peak brightness: the comet lacks the intense solar heating that drives the spectacular outgassing and tail formation seen in sungrazers.

The eccentricity of 0.9663 means the orbit is highly elongated but just barely bound to the Sun — it's an ellipse, not a hyperbola, so C/2026 B2 will return. But with an orbital period of approximately 233 years, the next perihelion passage won't occur until roughly 2259.

The high inclination of 59.7° tilts the orbit well out of the plane of the planets, classifying it as a nearly isotropic comet. This orbital geometry suggests it originated in the Oort Cloud — the vast spherical shell of icy bodies surrounding the solar system at distances of 2,000 to 200,000 AU.

Observing C/2026 B2

C/2026 B2 is not a naked-eye comet, but it's accessible to well-equipped amateur astronomers.

Current Brightness

As of late February 2026, the comet has been observed at approximately magnitude 12.8 with a coma diameter of about 0.6 arcminutes. This puts it within reach of:

• 10–12" telescopes with CCD/CMOS imaging (relatively straightforward)
• 8" telescopes under dark skies with careful visual observation
• Smaller scopes with long-exposure astrophotography

Where to Look

The comet is currently moving through the constellation Delphinus (the Dolphin), heading northward. Key coordinates for late February to March 2026:

• Right ascension: ~21h–22h
• Declination: +23° to +27° (well-placed for Northern Hemisphere observers)
• Elongation: ~37° from the Sun (observable in the early evening western sky)

Brightness Forecast

Date	Expected Magnitude	Constellation
February 28, 2026	~13.4	Delphinus
March 10, 2026	~13.7	Delphinus
March 31, 2026	~14.2	Equuleus
April 30, 2026	~15.0	Pegasus

The comet is fading as it recedes from both the Sun and Earth after its January perihelion. The best observing window is now through mid-March 2026, before it dims below the reach of most amateur equipment.

Important caveat: Comet brightness predictions are notoriously unreliable. Outbursts — like those regularly seen in 29P/Schwassmann-Wachmann — can cause sudden, dramatic brightening. Monitor the Comet Observation Database (COBS) for the latest observed magnitudes.

The Initial Orbit Confusion

C/2026 B2's discovery came with an unusual wrinkle: the first published orbit was wrong. The initial MPEC 2026-B203 listed a perihelion distance of 2.61 AU and an eccentricity of 1.78 — a hyperbolic trajectory that would have classified the object as potentially interstellar, similar to 'Oumuamua or 3I/ATLAS.

This sparked brief excitement in the astronomical community. Could this be another interstellar visitor? The answer came quickly: a corrected orbit published in MPEC 2026-B205 just days later showed the true perihelion distance was 1.28 AU with an eccentricity of 0.97 — firmly bound to the Sun.

The error illustrates a recurring challenge in comet orbit determination: early observations spanning only a few days provide insufficient arc to precisely constrain orbital parameters. The difference between an eccentricity of 0.97 (a very elongated ellipse) and 1.78 (a dramatic hyperbola) can hinge on a handful of astrometric measurements. This is why the Minor Planet Center waits for extended observation arcs before confirming whether objects are truly interstellar.

2026: A Busy Year for Comets

C/2026 B2 arrives during what's shaping up to be an exceptional year for comet watching:

• C/2026 A1 (MAPS): A Kreutz sungrazer discovered in early January 2026, headed for an extremely close solar perihelion on April 4–5, 2026. If it survives the encounter, it could become visible to the naked eye — but many sungrazers disintegrate.

• C/2025 R3 (PanSTARRS): Discovered in September 2025, this comet is being watched as a potential "great comet" candidate for 2026, though predictions remain uncertain.

• 3I/ATLAS: The third confirmed interstellar object, discovered in July 2025, continues to be studied by telescopes worldwide as it recedes from the inner solar system.

• 29P/Schwassmann-Wachmann: The solar system's most active cryovolcanic comet reaches opposition on March 11, 2026, and has already produced multiple outbursts in early 2026.

For observers equipped with telescopes and imaging equipment, 2026 offers an embarrassment of riches. The challenge isn't finding comets to observe — it's choosing which ones to prioritize.

Why Amateur Discoveries Still Matter

In an era of automated sky surveys like ATLAS, ZTF, and the upcoming Vera Rubin Observatory, it might seem like amateur comet discoveries should be a thing of the past. But C/2026 B2 proves otherwise.

Professional surveys are optimized for specific science goals — asteroid detection, supernova searches, or wide-field mapping. They can have blind spots: regions of sky too close to the Sun or Moon, cadences that miss fast-moving objects, or software pipelines that filter out diffuse sources like comets in favor of point-like asteroids.

Amateur astronomers like Sun and Gao fill these gaps. Operating independently, using their own equipment, and often reviewing images by eye rather than through automated algorithms, they catch objects that slip through the professional nets. The Xingming Observatory's remarkable discovery record — achieved with equipment costing a fraction of professional surveys — demonstrates that dedicated amateurs with dark skies and persistence remain essential partners in astronomical discovery.

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Explore more comets and interstellar visitors: track 3I/ATLAS in real time, learn about the ice volcano comet 29P, or discover what comet tails tell us about the solar wind.