29P/Schwassmann–Wachmann

Discovery

It was discovered photographically, when the comet was in outburst and the magnitude was about 13. Precovery images of the comet from March 4, 1902, were found in 1931 and showed the comet at 12th magnitude.

Orbit and physical properties

The comet reached its most recent perihelion on March 7, 2019. It spends its entire orbit just beyond Jupiter at 5.8-6.3 AU from the Sun where the comet remains active with a coma as it is close to the snow line. It will reach aphelion on 30 September 2026.

The comet is a member of a class of objects called "centaurs", of which at least 500 are known. These are small icy bodies with orbits between those of Jupiter and Neptune. The centaurs have been recently perturbed inward from the Kuiper belt, a disk of trans-Neptunian objects occupying a region extending from the orbit of Neptune to approximately 50 AU from the Sun. Frequent perturbations by Jupiter will likely accumulate and cause the comet to migrate either inward or outward by the year 4000. A number of centaurs appear to be dynamically and perhaps even physically related to 29P; such objects may traverse the coma of 29P when in outburst.

The comet nucleus is estimated to be in diameter.

Outbursts

The comet is unusual in that while normally hovering at around 16th magnitude, it suddenly undergoes an outburst. This causes the comet to brighten by 1 to 5 magnitudes. Outbursts are very sudden, rising to maximum in about 2 hours, which is indicative of their cryovolcanic origin; and with the times of outburst modulated by an underlying 57-day periodicity possibly suggesting that its large nucleus is an extremely slow rotator.

2025 During 2025 there where 8 notable outbursts with them being twinned events. The outbursts occurred on January 2/6, February 1/2, May 13/25, and December 4/11. The December outburst reached about magnitude 13.

References

|access-date=2009-04-30 |url-status=dead |archive-url=https://web.archive.org/web/20150623181807/http://home.surewest.net/kheider/astro/29P4000-clones.gif |archive-date=June 23, 2015

|archive-url=https://web.archive.org/web/20220617145415/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%2790000394%27&START_TIME=%272035-02-10%27&STOP_TIME=%272035-03-01%27&STEP_SIZE=%273%20hours%27&QUANTITIES=%2719%27 |archive-date=2022-06-17 |url-status=live

References

1. [http://www.aerith.net/comet/catalog/0029P/2019.html Yoshida: 29P (2012-2026)]
2. [http://jcometobs.web.fc2.com/pcmtn/0029p.htm 29P past, present and future orbital elements]
3. Lin, Zhong-Yi. (15 January 2021). "ATel #14323: Outburst of comet 29P/Schwassmann–Wachmann 1". [[The Astronomer's Telegram]].
4. (1 July 2016). "Discrete sources of cryovolcanism on the nucleus of Comet 29P/Schwassmann–Wachmann and their origin". Icarus.
5. Trigo-Rodriguez et al., Outburst activity in comets, I. Continuous monitoring of comet 29P/Schwassmann–Wachmann 1 [http://www.aanda.org/articles/aa/pdf/2008/26/aa8666-07.pdf]
6. Trigo-Rodriguez et al., Outburst activity in comets, II. A multi-band photometric monitoring of comet 29P/Schwassmann–Wachmann 1 {{ArXiv. 1009.2381
7. [https://groups.io/g/29P-ml/topic/29p_twin_strong_outbursts/116728321 29P: Twin strong outbursts] (11 Dec 2025)
8. Trigo-Rodríguez. (2008). "A continuous follow-up of Centaurs, and dormant comets: looking for cometary activity.". European Planetary Science Congress.
9. "JPL Small-Body Database Search: orbital class (CEN)". Jet Propulsion Laboratory.