Puneet Varma (Editor)

66652 Borasisi

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Discovery date  8 September 1999
Observation arc  4790 days (13.11 yr)
Discovered  8 September 1999
Argument of perihelion  194.98°
Discovery site  Mauna Kea Observatories
MPC designation  (66652) 1999 RZ253
Aphelion  47.291 AU (7.0746 Tm)
Inclination  0.56319°
Orbits  Sun
66652 Borasisi 1bpblogspotcomh4IWdAHPpFcTlUkQ9btL1IAAAAAAA
Discovered by  A. Trujillo, J. Luu and D. Jewitt
Minor planet category  trans-Neptunian object cubewano SCATNEAR
Discoverers  Jane Luu, Chad Trujillo, David C. Jewitt
Similar  Chad Trujillo discoveries, Other celestial objects

66652 Borasisi /ˌbɒrəˈssi/ is a binary classical Kuiper belt object. It was discovered in 1999 by Chad Trujillo, Jane X. Luu and David C. Jewitt and identified as a binary in 2003 by K. Noll and colleagues using the Hubble Telescope.



In 2003 it was discovered that 66652 Borasisi is a binary with the components of comparable size (about 100–130 km) orbiting the barycentre on a moderately elliptical orbit. The total system mass is about 3.4 × 1018 kg.

The companion (66652) Borasisi I, named Pabu /ˈpɑːb/ orbits its primary in 46.2888 ± 0.0018 days on an orbit with semi-major axis of 4528 ± 12 km and eccentricity 0.4700 ± 0.0018. The orbit is inclined with respect to the observer by about 54° meaning that is about 35° from the pole-on position.

Physical properties

The surface of both components of the Borasisi–Pabu system is very red.


Borasisi is named after a fictional creation deity taken from the novel Cat's Cradle by Kurt Vonnegut. In the book, Borasisi is the Sun and Pabu is the name of the Moon:

Borasisi, the sun, held Pabu, the moon, in his arms and hoped that Pabu would bear him a fiery child. But poor Pabu gave birth to children that were cold, that did not burn... Then poor Pabu herself was cast away, and she went to live with her favorite child, which was Earth.


Around 2005, Borasisi was considered as a target for the proposed New Horizons 2 after a Triton/Neptune flyby.


66652 Borasisi Wikipedia

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