StarHash: unique, memorable, and deterministic names for astronomical objects

Abstract

The naming of astronomical objects has represented among the most significant challenges in the record-keeping of the field since the very beginning. Long and unwieldy coordinate names, uninformative and ambiguous internal names, and the sheer volume of aliases accumulated for some of the most studied objects conspire to complicate our study of the celestial sphere. This paper proposes StarHash, a reproducible, open-source astronomical naming scheme based on the terrestrial concept of geohashing, but re-implemented from the ground up for the rigorous demands of astronomy. Every 3.2 arcsec patch of sky now has three words associated with it, enabling the precise localisation of astronomical sources, and an easily communicable and memorable identifier. A carefully selected wordlist reduces ambiguity due to plurals and homophones, whilst the use of format-preserving encryption minimises residual spatial correlation in StarHash-derived identifiers. Pre-computed names for several existing catalogues are provided, alongside a Python reference implementation for validation and integration into databases, transient brokers, and other similar projects. Although not intended to be the final word in the naming of astronomical objects, StarHash humbly provides a memorable alternative to the status quo, and is intended to spark a discussion about this most foundational of issues in astronomy.

Figures (5)

• Figure 1: Box plot of Hamming distance of $\approx$50M unique coordinate pairs uniformly distributed across the sky and their on-sky distance. The box spans the 1 and 3 quantiles, with the whiskers showing 1.5$\times$ the inter-quartile range. The dashed orange line corresponds to the expectation of on-sky distance for the uniform sky distribution.
• Figure 2: Box plot of Hamming distance of $\approx$50M coordinate pairs drawn from a Normal distribution of standard deviation 0.5 degrees. The boxes retain the same meaning as Figure \ref{['fig:allsky_hamming']}, but in this case any results sharing the same HEALPix index have been removed, as an artefact of the sampling process.
• Figure 3: HST image of SN 1987A, with the StarHash grid and names overplotted. The Author declines to comment on the academic suitability of some of the names. For visualisation purposes, the words have been stacked to provide a more compact representation over their hyphen-delimited form.
• Figure 4: All-sky Aitoff projection showing the StarHash names for a selection of notable astrophysical transients alongside their conventional IAU-allocated names. The dashed line indicates the Galactic plane. These names may be decoded back to their respective celestial coordinates in a fully deterministic way following the methods in Section \ref{['sec:methods']}.
• Figure 5: Box plot of Levenshtein edit distances of $\approx$50M unique coordinate pairs uniformly distributed across the sky (left) and drawn from a Normal distribution of 0.5 degree standard deviation (right) centred on the Andromeda Galaxy, with respect to their on-sky separations. The deviations seen at small and large edit distance are driven entirely by small number statistics and should not be interpreted as significant deviations from the rest of the distribution.