Closest Approaches to the Earth by Comets
The following table lists, in order of increasing geocentric distance, the closest known approaches to the earth by comets. In order to qualify for this listing, the approach must have occurred during an observed apparition, although in some cases the object was not under observation at the time of closest approach.
The dates of closest approach are given in Terrestrial Time (TT), although at the precision of this table they can be considered to be in Universal Time (UT).
For comparison, the mean distance of the moon is 0.0026 AU = 384400 km = 238900 miles.
(1 AU is approximately the mean distance of the earth from the sun = 149597870 km = 92955810 miles.)
Distance Date (TT). Permanent designation (AU).
0.0151 1770 July 1.7 D/1770 L1 (Lexell)
0.0229 1366 Oct. 26.4 55P/1366 U1 (Tempel-Tuttle)
0.0312 1983 May 11.5 C/1983 H1 (IRAS-Araki-Alcock)
0.0334 837 Apr. 10.5 1P/837 F1 (Halley)
0.0366 1805 Dec. 9.9 3D/1805 V1 (Biela)
0.0390 1743 Feb. 8.9 C/1743 C1
0.0394 1927 June 26.8 7P/Pons-Winnecke
0.0437 1702 Apr. 20.2 C/1702 H1
0.0617 1930 May 31.7 73P/1930 J1 (Schwassmann-Wachmann)
0.0628 1983 June 12.8 C/1983 J1 (Sugano-Saigusa-Fujikawa)
0.0682 1760 Jan. 8.2 C/1760 A1 (Great comet)
0.0787 2006 May 12.4 73P/Schwassmann-Wachmann
0.0839 1853 Apr. 29.1 C/1853 G1 (Schweizer)
0.0879 1797 Aug. 16.5 C/1797 P1 (Bouvard-Herschel)
0.0884 374 Apr. 1.9 1P/374 E1 (Halley)
0.0898 607 Apr. 19.2 1P/607 H1 (Halley)
0.0934 1763 Sept.23.7 C/1763 S1 (Messier)
0.0964 1864 Aug. 8.4 C/1864 N1 (Tempel)
0.0982 1862 July 4.6 C/1862 N1 (Schmidt)
0.1018 1996 Mar. 25.3 C/1996 B2 (Hyakutake)
0.1019 1961 Nov. 15.2 C/1961 T1 (Seki)
Note: This list is complete for comets discovered after 1700 that approached the earth to within 0.1020 AU. It also includes a number of well-documented earlier approaches by periodic comets. C/1491 B1 allegedly came to within 0.0094 AU on 1491 Feb. 20.0 TT, but the orbit of this comet is very uncertain.

The Outer Solar System

This animation shows the motions of objects in the outer solar system, beyond the orbit of Jupiter, over a 100-year period at 200-day intervals. The orbits and current locations of the Jovian planets (Jupiter, Saturn, Uranus and Neptune) are shown. The current location of Pluto is indicated by the large white crossed circle. High-eccentricity objects are shown with cyan triangles, Centaurs as orange triangles, Plutinos as white circles, "Classical" TNOs as red circles and Scattered-Disk Objects as magenta circles.

NOTE: The strange behavior exhibited by the comets (a general heading inwards prior to the mid 1990s and a general heading outwards post 2000) is a consequence of plotting only those comets currently observable (as of mid 2002). Around this date, all of the long-period comets would have been at or near perihelion. Fifty years either side of this date they are all far from the sun. If the full cometary catalogue had been plotted, this effect would not be so noticeable as there would be inbound and outbound comets visible on each pre-2002 frame.

This animation (prepared 2002 July 31) is available as:

• Animated GIF (961 x 961 pixels, 4.7 MB)
• Animated GIF (401 x 401 pixels, 1.2 MB)

A newer version (prepared 2011 April 17) is available as:

• Animated GIF (961 x 961 pixels, 2.7 MB)