Comet Borrelly /bɒˈrɛli/ or Borrelly's Comet (official designation: 19P/Borrelly) is a periodic comet, which was visited by the spacecraft Deep Space 1 in 2001. The comet last came to perihelion (closest approach to the Sun) on May 28, 2015 and will next come to perihelion on February 1, 2022.[2][1]

Comet Borrelly Nucleus.jpg
Discovered byAlphonse Borrelly
Discovery dateDecember 28, 1904
1905 II; 1911 VIII; 1918 IV;
1925 VIII; 1932 IV; 1953 IV;
1960 V; 1967 VIII; 1974 VII;
1981 IV; 1987 XXXIII; 1994 XXX
Orbital characteristics
Epoch September 8, 2001 (JD 2452160.5)
Aphelion5.83 AU
Perihelion1.35 AU
(February 1, 2022)[1][2]
3.59 AU
6.8 a
February 1, 2022[1][2]
Earth MOID0.37 AU (55 million km)
Physical characteristics
Dimensions8×4×4 km[3]
Mean radius
2.4 km[4]
Mass2×1013 kg[5]
Mean density
0.3 g/cm³[6]
AlbedoAlbedo: 0.03[7]

Deep Space 1 returned images of the comet's nucleus from 3400 kilometers away. At 45 meters per pixel, it was the highest resolution view ever seen of a comet.[8]


The comet was discovered by Alphonse Borrelly during a routine search for comets at Marseilles, France on December 28, 1904.

Deep Space 1 flybyEdit

Animation of Deep Space 1's trajectory from 24 October 1998 to 31 December 2003
   Deep Space 1 ·   9969 Braille ·   Earth ·   19P/Borrelly

On September 21, 2001 the spacecraft Deep Space 1, which was launched to test new equipment in space, performed a flyby of Borrelly. It was steered toward the comet during the extended mission of the craft, and presented an unexpected bonus for the mission scientists. Despite the failure of a system that helped determine its orientation, Deep Space 1 managed to send back to Earth what were, at the time, the best images and other science data from a comet.

The orbits of three periodic comets, 1P/Halley, 19P/Borrelly and 153P/Ikeya-Zhang, set against the orbits of the outer planets.


  1. ^ a b c MPC
  2. ^ a b c Seiichi Yoshida (2014-08-10). "19P/Borrelly". Seiichi Yoshida's Comet Catalog. Retrieved 2014-10-29.
  3. ^ Weaver, H. A.; Stern, S.A.; Parker, J. Wm. (2003). "Hubble Space Telescope STIS Observations of Comet 19P/BORRELLY during the Deep Space 1 Encounter". The Astronomical Journal. The American Astronomical Society. 126 (1): 444–451. Bibcode:2003AJ....126..444W. doi:10.1086/375752. Retrieved 2008-12-16.
  4. ^ "19P/Borrelly: Facts & Figures". Archived from the original on 2014-08-09. Retrieved 2014-08-08.
  5. ^ Using the volume of an ellipsoid of 8x4x4km * a rubble pile density of 0.3 g/cm³ yields a mass (m=d*v) of 2.0E+13 kg.
  6. ^ D. T. Britt; G. J. Consol-magno SJ; W. J. Merline (2006). "Small Body Density and Porosity: New Data, New Insights" (PDF). Lunar and Planetary Science XXXVII. Archived (PDF) from the original on 17 December 2008. Retrieved 2008-12-16.
  7. ^ Robert Roy Britt (2001-11-29). "Comet Borrelly Puzzle: Darkest Object in the Solar System". Space.com. Archived from the original on 22 January 2009. Retrieved 2008-12-16.
  8. ^ Beatty, Kelly (25 June 2004). "Meet Comet Borrelly". Sky & Telescope. Retrieved 27 January 2021.

External linksEdit

Numbered comets
19P/Borrelly Next