☄ Schwassmann-Wachmann 3 73P/Schwassmann-Wachmann 3

How to follow comet Schwassmann-Wachmann 3 live

The panel above recomputes the position of Schwassmann-Wachmann 3 every second in your browser: its distance from the Sun and from Earth, its position in the sky (right ascension and declination), and a live countdown to the next perihelion. It runs on the same kind of engine observatories use, a Kepler solver applied to the JPL osculating orbital elements, so the numbers are not a static snapshot, they keep ticking.

Just below, the top-down map of the Solar System shows exactly where Schwassmann-Wachmann 3 is right now among the planets. You can fast-forward time with the day slider, zoom and pan, compare its distance to another body with a click, and press "Next event" to jump straight to perihelion. It is the most direct way to grasp the orbit of Schwassmann-Wachmann 3 with no math at all.

Comet fact sheet

About Schwassmann-Wachmann 3

73P/Schwassmann-Wachmann 3 (abbreviated SW3) is a short-period Jupiter-family comet that became a natural laboratory for the study of cometary disruption. Discovered in 1930 as an apparently ordinary object, it remained relatively obscure until 1995, when it surprised astronomers by spontaneously splitting into at least four fragments during a brightness outburst of factor 400. Each subsequent return revealed more fragmentation, and in 2006 the comet approached Earth as a procession of dozens of separate nuclei, photographed by the Hubble Space Telescope in real time.

SW3 became the definitive case study for how comets die. Its progressive disintegration revealed details about the internal mechanical strength of cometary material, its heterogeneous composition, and the processes that eventually dissolve comets into debris streams -- like the one that produced the 2022 Tau Herculids storm.

History and discovery

Arnold Schwassmann and Arno Arthur Wachmann discovered the comet on May 2, 1930, at Hamburg-Bergedorf Observatory in Germany during a long photographic exposure aimed at a different target. At discovery the object was near its closest Earth approach that cycle and reached magnitude 8 -- relatively bright for a short-period comet. The periodic orbital character was quickly calculated, with a period of about 5.36 years.

After discovery the comet was lost and only recovered in 1979, nearly 50 years later, thanks to refined orbital calculations. Returns in 1979, 1985, and 1990 passed without notable incidents. In September and October 1995, during what should have been a routine return, the comet displayed a brightness outburst of factor 400 -- far beyond normal activity variation -- and was detected split into at least four pieces labelled A, B, C, and D. From that moment, the story of SW3 became the story of its progressive fragmentation.

Orbit and returns

The orbit of 73P has an eccentricity of 0.6938 and an inclination of 11.4 degrees. Perihelion is at 0.939 AU, slightly inside Earth's orbit, and aphelion at 5.19 AU near Jupiter. The orbital period is 5.36 years. This geometry places the comet in a potential meteor shower position every time Earth crosses the debris trail at the same time of year.

Nucleus, coma and tail

The original SW3 nucleus, before the 1995 fragmentation, was estimated at 1.1 km in diameter -- small for a short-period comet but sufficient to maintain significant activity at each passage. Fragmentation revealed the interior was heterogeneous: distinct fragments released different quantities of CO2, water, and organic compounds, suggesting different regions of the original nucleus had varying compositions and internal structures.

The 2006 data allowed estimation of the cometary material's tensile strength at very low values: on the order of 1 to 10 kPa -- similar to fresh snow or polystyrene foam. This explains why such a small object could fragment spontaneously without any external impact: subtle tidal forces, internal gas pressure variations, and thermal cycles are sufficient to tear apart a nucleus so weakly cohesive.

The tails of the main fragments (B and C) in 2006 were visible in long-exposure photographs, with a moderate dust tail and detectable ion tail. Some sub-fragments created in real time (observed by Hubble) did not develop individual tails before dispersing.

How to observe

In 2006 several SW3 fragments reached magnitude 5 to 7, making them visible in binoculars. Fragment C was the most active and brightest, displaying multiple sub-fragments and a well-developed coma. In earlier and later returns fragments stay between magnitude 9 and 14, requiring a telescope. Fragment B, the second most active in 2006, was tracked by amateur observers with 150-mm telescopes.

The 2022 return was favourable for observation (minimum distance 0.39 AU), but most fragments were below magnitude 10. The Tau Herculids meteor shower associated with SW3 occurs around May 30 each year -- in 2022 the intensity was exceptionally high. Monitoring the Tau Herculids calendar is an indirect way to follow the comet's evolution without a telescope.

Missions and notable observations

SW3 was not the target of a dedicated spacecraft, but was studied by some of the most powerful observational tools available during the 2006 return. The table below summarises the most relevant observations:

Trivia and records

• The Tau Herculids shower of May 30, 2022, produced up to 250 meteors per hour in some regions -- 25 times above conservative forecasts of fewer than 10 per hour. The meteors were debris ejected during the 1995 fragmentation, not the 2006 one.
• In 2006 Hubble photographed the active sub-fragmentation of fragment B in real time -- one of the few times in history that a comet's disintegration process was captured while happening.
• The Spitzer Space Telescope detected 55 fragments in the 2006 return, spread along the comet's orbit, indicating that the 1995 fragmentation had already created a debris stream occupying an extensive orbital arc.
• The original SW3 nucleus, estimated at 1.1 km, was smaller than many famous comets -- but Earth's proximity in 2006 (0.0794 AU, the eighth closest cometary approach in the modern era) made the fragmentation exceptionally well documented.
• The estimated tensile strength of SW3 material is 1 to 10 kPa -- comparable to fresh snow. This suggests cometary nuclei are extremely fragile structures capable of disintegrating under minimal forces.
• If all 2006 fragments were recombined, the total volume would still be smaller than the original pre-fragmentation nucleus -- the difference represents material that evaporated or dispersed into particles below the detection threshold.
• Arnold Schwassmann and Arno Wachmann, the co-discoverers, worked together for decades in Hamburg. Wachmann outlived Schwassmann by many years and witnessed the growing scientific interest in the comet carrying both their names.

Other comets

See the full comet catalogue.