P/2010 H2 (Vales)

Lore & Background

The comet underwent a massive outburst when it was discovered by Jan Vales on 16 April 2010. No prediscovery observations earlier than 15 April 2010 were found. Later analysis of data from the Catalina Sky Survey indicated that the outburst may have been ongoing for 15 hours at the time, resulting in its brightness increasing by a thousand-fold. Observations conducted on the day after discovery noted that its coma had undergone a significant increase in size, from 24–26 arcseconds to 34–38 arcseconds across.

Although calculated to have a relatively short orbital period, it was not recovered during its next apparition in 2017. On 17 March 2023, Toni Scarmato reported the observation of an object close to the predicted position of P/2010 H2, indicating a possible recovery of the comet. Further analysis in 2024 did not match the position of the initial reports, concluding that Scarmato's find is likely a different object. Further search attempts in 2015 and 2025 from the 4.3-meter Lowell Discovery Telescope failed to recover the comet, indicating a possible absolute nuclear magnitude fainter than 20.6, and a nucleus smaller than 0.5 km in diameter assuming a geometric albedo of 0.04. However it is still likely that it may have become inactive after the 2010 outburst instead of simply disintegrating.

Reader's Guide

P/2010 H2 (Vales) is notable as the only comet discovered by Slovenian astronomer Jan Vales as of 2025, and for its dramatic outburst that enabled its discovery. The comet has not been observed since its 2010 discovery, and multiple recovery attempts have failed, including searches in 2015, 2017, and 2025 using the 4.3-meter Lowell Discovery Telescope. A possible recovery reported by Toni Scarmato in 2023 was later discounted. The comet is expected to normally only brighten to magnitude 20 when near perihelion, making it extremely faint. Its small nucleus, possibly less than 0.5 km in diameter, and its failure to reappear suggest it may have become inactive after the outburst rather than disintegrating. The comet is part of the Unistellar citizen science tracking project, and its next opposition will occur on 27 June 2026. Its status as a quasi-Hilda comet, with frequent Jupiter encounters, adds to its interest for dynamical studies.

Did You Know?

• The comet's brightness increased by a thousand-fold during its discovery outburst in April 2010.
• It has not been observed since its discovery in April 2010.

Provisional Designation and the Path to a Permanent Number

P/2010 H2 (Vales) carries a provisional designation that places it firmly in the category of periodic comets, as indicated by the "P" prefix in its official label. Under the International Astronomical Union's nomenclature framework, this letter signals that the object follows a repeating orbit rather than a one-time passage through the inner solar system. The "2010 H2" portion encodes the year and approximate half-month of discovery along with a sequential identifier, while "Vales" credits the discoverer. Unlike comets that have already earned a permanent number—typically awarded after a confirmed second perihelion passage—P/2010 H2 remains in the unnumbered cohort. Should it ever be lost to observation or presumed destroyed, its designation would shift to a "D" classification. The IAU system also reserves other prefixes: "C" for non-periodic comets, "X" for objects with unreliable orbits, "I" for interstellar visitors, and "A" for misidentified minor planets or hyperbolic objects lacking cometary activity. This layered naming architecture ensures that every comet, whether tracked or lost, retains a unique and informative identity within the broader catalog.

Orbital Prediction and the Accumulation of Uncertainty

As a periodic comet, P/2010 H2 (Vales) belongs to a class of objects whose orbital periods fall below the two-hundred-year threshold or which have been confirmed across multiple perihelion passages. This repeatability is what makes them, in principle, far more predictable than their long-period counterparts. Yet the reality of tracking such orbits is far from straightforward. Gravitational perturbations from the major planets introduce small errors into the known trajectory, and those errors compound over successive revolutions. Beyond pure gravity, the comet's own activity—release of gas and other material that builds up its coma and tail—produces non-gravitational effects that nudge the orbit in ways difficult to model precisely. For a numbered periodic comet whose orbit has been well established, the next perihelion can be forecast with high accuracy. For an unnumbered object like P/2010 H2, the margin of uncertainty is larger, and the comet may not be found at the predicted sky position, particularly if its orbit has been subtly altered by planetary encounters or its own outgassing.

The Name Vales and the Rules of Comet Naming

In the vast majority of cases, comets take their name from the person or team who first observed and reported them, and P/2010 H2 (Vales) follows that convention, honoring the discoverer Vales. This practice stands in contrast to a small number of notable exceptions, such as 2P/Encke and 27P/Crommelin, where the comet is named not for the finder but for the individual who worked out its orbit. The naming system also has to contend with the reality that multiple comets can share the same discoverer's name. The Shoemaker–Levy family, for instance, includes nine periodic comets, and the NEAT survey has produced twenty-four. The IAU resolves the ambiguity through the number prefix or the full designation string, so that 181P and 192P are both "Comet Shoemaker–Levy" yet remain distinct. In informal literature, an additional numbering sequence is sometimes applied that skips non-periodic members of the same family, interleaving them between the periodic ones. For P/2010 H2, the name Vales serves as its permanent human identifier regardless of whether it eventually earns a number or is lost to the dark.

Observational Challenges in the Unnumbered Cohort

P/2010 H2 (Vales) sits among a population of periodic comets that have not yet secured a permanent number, a group that includes objects like P/2005 T5 (Broughton). Many of these unnumbered periodic comets share the characteristics of Jupiter-family members: orbital periods under roughly twenty years, relatively low inclinations, and paths that loosely coincide with Jupiter's own orbit. Such comets are notoriously difficult to track. Gravitational interactions with Jupiter frequently perturb their trajectories, sending them drifting away from the position astronomers expect to find them, and they are subsequently lost. Their surfaces tend to have very low albedos, making them faint even when relatively close to Earth. Because their orbits keep them nearer to the Sun than the distant Oort Cloud comets, they undergo more rapid volatile depletion over successive passages, growing progressively dimmer. These combined factors—perturbation, low reflectivity, and volatile exhaustion—mean that a comet like P/2010 H2 may be observed only sporadically, and its long-term survival as a visible object is never guaranteed.