Cometary Science Archive
Cometary Science Archive

Comet 361P/2017 S4 = 361P/2006 UR111 (Spacewatch)


E. Lilly, R. J. Wainscoat, and R. Weryk (Institute for Astronomy, University of Hawaii) reported the discovery of another apparent comet on four w-band CCD exposures taken with the 1.8-m Pan-STARRS1 telescope at Haleakala on 2017 Sept. 24.4 UT, together with earlier Pan-STARRS1 observations found subsequently back to Sept. 11. In each image, the object appeared slightly extended compared to nearby stars, and in a stacked image, there is possible evidence for a broad, low-surface-brightness tail extending towards position angle approximately 250 degrees.

Already on Sept. 24, Weryk suggested that the comet may be identical to an apparently asteroidal object of mag 19.7-20.3 discovered on 2006 Oct. 19 on Spacewatch images taken by J. V. Scotti with the Steward Observatory 0.9-m telescope at Kitt Peak; there had been other Spacewatch observations also that same month, back to Oct. 11, and the object was then given the minor-planet designation 2006 UR111 (cf. MPS 184334). Gareth Williams (Minor Planet Center) confirmed the linkage, and it was announced with both designations and then quickly numbered 361P.

The discovery details were announced on CBET 4433.

Orbit and Ephemeris

An ICQ ephemeris is available here.

Orbital elements and an ephemeris from the Minor Planet Center are available here.

Orbit diagram

An orbit diagram, when available, is posted here.


Images, when available, are posted here.

Light curve

A light curve of the photometry, when available, is posted here.


Published/tabulated photometric observations, when available, are posted here.

Recent photometric observations of this comet from the ICQ archive are available here.


Astrometric observations of this comet from the Minor Planet Center archive are available here.