1998 SM165: A large Kuiper belt object with an irregular shape

W. Romanishin, S. C. Tegler, T. W. Rettig, G. Consolmagno, B. Botthof

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The recent discovery of an ancient reservoir of icy bodies at and beyond the orbit of Neptune - the Kuiper belt - has opened a new frontier in astronomy. Measurements of the physical and chemical nature of Kuiper belt objects (KBOs) can constrain our ideas of the processes of planet formation and evolution. Our 1.8-m Vatican Advanced Technology Telescope and charge-coupled device camera observations of the KBO 1998 SM165 indicate its brightness periodically varies by 0.56 magnitudes over a 4-h interval. If we assume a uniform albedo of 0.04, which is typical of values found in the literature for a handful of KBOs, and an "equator-on" aspect, we find 1998 SM165 has axes of length 600 × 360 km. If our assumptions are correct, such dimensions put 1998 SM165 among the largest elongated objects known in our solar system. Perhaps long ago, two nearly spherical KBOs of comparable size coalesced to form a compound object, or perhaps 1998 SM165 is the residual core of a catastrophic fragmentation of a larger precursor.

Original languageEnglish (US)
Pages (from-to)11863-11866
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number21
StatePublished - Oct 9 2001

ASJC Scopus subject areas

  • General


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