Swift-Tuttle is the parent of the Perseids, the most watched meteor shower of the year. Its 26-km nucleus is the largest of any known periodic comet that repeatedly crosses Earth’s orbit, and it swings past only once every 133 years - the next visit comes in 2126.
Its debris causes the Perseid meteor shower every August.
Its 26-km nucleus is roughly twice the size of the impactor that ended the dinosaurs.
It returns in July 2126, when it should be a bright naked-eye comet.
How a comet makes a meteor shower
Every time Swift-Tuttle rounds the Sun it sheds dust, and over thousands of years that dust spreads out into a river of debris tracing the whole orbit. Every August Earth ploughs through that river; sand-grain-sized particles hit the atmosphere at ~59 km/s and vaporise in streaks of light - the Perseids. A meteor shower is a comet’s orbit made visible.
Physical characteristics
Diameter
26 km
Geometric albedo
0.04
Atmosphere and composition
Atmosphere
None at rest; it grows a bright coma and tails during its rare visits to the inner Solar System.
Composition
Presumed classic mix of water ice, frozen gases and dark dust; its interior has never been probed.
Orbit and activity
Perihelion distance
0.96 AU
Aphelion distance
51.2 AU
Origin
Halley-type comet
Last perihelion
11 Dec 1992
Next perihelion
12 Jul 2126
Associated meteor shower
Perseids (August)
Discovery
Discovered by
Lewis Swift & Horace Tuttle
Year
1862
How
independent visual discoveries three days apart
What is still uncertain
Nucleus albedo is an assumed comet-typical value; only the diameter is reasonably well constrained.