220P/McNaught, is a Jupiter-family comet with a 5.5-year orbit around the Sun. It is one of several comets discovered by Australian astronomer, Robert H. McNaught. It reached perihelion on 14 June 2026, two weeks after a large outburst in which the comet brightened as much as 8,000 times. In August 2026 there was a second outburst brightening by a factor of about 600.
Discovery
Robert McNaught discovered the comet in images obtained by the Uppsala Southern Schmidt Telescope in Siding Spring Observatory, Australia, on 20 May 2004. The comet in the CCD images had an estimated magnitude of 17.7. The discovery of the comet was confirmed by J. Young at Table Mountain Observatory on May 25. The comet had a coma 8–10 arcseconds across without central concentration and a narrow tail 20 to 30 arcseconds long.
The comet was recovered by Spacewatch on 28 April 2009 and independently by G. Muler, J. M. Ruiz and R. Naves with the 0.30-m Schmidt-Cassegrain telescope at the Nazaret Observatory on May 1. The comet had an apparent magnitude of 20.2. The comet appeared stellar in the single 120s exposure by Spacewatch. Afterwards, the comet was given the permanent number 220P.
2026 outbursts
On 1 June 2026, Mike Kelley reported on the comet mailing list that 220P/McNaught had undergone a large outburst. Using data from the Zwicky Transient Facility, he noted the comet brightened by about 7 magnitudes (from roughly magnitude 18 to 11), more than a 600-fold increase in brightness. The outburst occurred within a window between May 30 at 14:05 and May 31 at 03:37 UTC. Other observations reported the comet reached a peak magnitude of 8.2, which would represent up to an 8,000-fold increase in brightness. The comet on June 3 had a coma 6.5 arcminutes across and a tail about 2 arcminutes long, while deeper exposures revealed a fain ion tail about two degrees long on June 2. Visually, the coma was about 3 arcminutes across despite bright moonlight. Follow-up measurements from the TRAPPIST-North Telescope (Z53) noted a significant drop in dust production rate after the outburst, which appeared to be enriched in in relation to CN, likely indicating that a fragmentation event has occurred. By mid-June the comet had faded to about magnitude 12. On 5 August 2026 the comet outburst a second time by a factor of about 600 surging from magnitude 14 to magnitude 7.
For comparison, in 2007, Comet 17P/Holmes brightened as much as a million-fold, jumping from magnitude 17 to about magnitude 2.8.
+Notable Comet Outbursts Comet Date Distancefrom Sun Change in magnitudeand brightness 220P/McNaught 2026-05-30 1.6 AU 9.5 magnitudes (7000x) 17P/Holmes 2007-10-23 2.4 AU 14.2 magnitudes (500000x) 41P/Tuttle–Giacobini–Kresák 1973-05-26 3.9 AU 10 magnitudes (10000x) 289P/Blanpain 2013-07-04 3.9 AU 9 magnitudes (4000x) 29P/Schwassmann–Wachmann 10/year 6.0 AU 3 magnitudes (20x)
These outbursts are caused by the sudden release of heated gases breaking through the crust and creating a massive dust plume that significantly increases the coma's column density and surface area.
Orbit The comet takes 5.5 years to orbit the Sun. It has an Earth–Minimum orbit intersection distance (E–MOID) of and on 20 August 2048 will pass from Earth. Several close approaches to Jupiter between 1956 and 2170 are expected, the closest of which (0.62 AU) will occur in 2063.
Notes
References
External links
at the Minor Planet Center database 220P/McNaught at Seiichi Yoshida's website 220P/McNaught at Gideon van Buitenen's website