☄ Tuttle 8P/Tuttle

How to follow comet Tuttle live

The panel above recomputes the position of Tuttle every second in your browser: its distance from the Sun and from Earth, its position in the sky (right ascension and declination). 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 Tuttle 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 Tuttle with no math at all.

Comet fact sheet

About Tuttle

8P/Tuttle occupies a peculiar position among short-period comets: with a 13.5-year orbit it sits at the upper boundary of what is conventionally called the Halley family, though many texts classify it as an intermediate-period comet. Its closest approach to the Sun is just 1.03 AU, essentially at Earth's orbital distance, while its farthest point reaches 10.4 AU, near the limit of Saturn's orbit. Discovered in 1858 by Horace Tuttle, it is best known today for the debris trail that produces the Ursids every December, the meteor shower of the northern winter solstice.

In 2008, the Arecibo Observatory radar revealed a surprise: the nucleus of 8P/Tuttle is not a uniform sphere but a contact-binary object roughly 10 km long, two distinct lobes joined by a narrow neck. This structure is identical in type to comet 67P/Churyumov-Gerasimenko, explored in detail by ESA's Rosetta spacecraft.

History and discovery

Horace Parnell Tuttle was an astronomer at the United States Naval Observatory when he discovered the comet on January 4, 1858. Tuttle was one of the most productive observers of his era, co-discoverer of several other comets and minor objects. 8P received only his surname, following the convention of the time. Notably, the same Horace Tuttle co-discovered 109P/Swift-Tuttle, the giant parent body of the Perseids, one of the most abundant annual meteor showers.

The comet was tracked through several consecutive perihelia in the nineteenth and early twentieth centuries, then lost and recovered multiple times. Its cometary nature is well established: each close solar passage sublimates part of the icy nucleus. The connection to the Ursids was established in the twentieth century when orbital calculators showed that the shower radiant matched the trajectory of debris left behind by 8P.

Orbit and returns

8P/Tuttle has a period of 13.5 years, setting it apart from typical Jovian comets (periods of 3 to 9 years) and placing it near the Halley-type class (periods of 20 to 200 years). Its perihelion at 1.03 AU falls almost exactly at Earth's orbital distance, meaning that at each pass the comet crosses the habitable zone of the Solar System.

The aphelion at 10.4 AU means the comet spends a significant fraction of each cycle beyond Saturn, in a zone of very low temperatures where the nucleus lies nearly dormant. The last perihelion was on August 27, 2021. The next perihelion is forecast for April 18, 2035, when the comet may reach magnitude 7 to 8 under favorable conditions.

Nucleus and family

Radar observations carried out by the Arecibo Observatory in January 2008 (published in Icarus in 2010 by Harmon and collaborators) revealed that the nucleus of 8P/Tuttle is a contact-binary object roughly 10 km long on its major axis and 4 km across the short dimension. The rotation period is 11.4 hours. The bilobed structure is identical in type to that of comet 67P/Churyumov-Gerasimenko, explored in detail by ESA's Rosetta spacecraft between 2014 and 2016.

The Arecibo radar also detected a separate echo from large (centimeter-scale) grains moving slowly away from the nucleus, exactly the type of material expected to contribute to a meteor shower like the Ursids. These large grains produce the brightest meteors and leave long-lasting luminous trails in the sky.

• Nucleus structure: contact binary (two lobes joined by a neck)
• Total length: ~10 km
• Short dimension: ~4 km
• Rotation period: 11.4 hours
• Orbital class: Halley-type (intermediate period)
• Structural analog: same bilobed type as 67P/Churyumov-Gerasimenko (Rosetta)

How to observe

The next favorable perihelion of 8P/Tuttle will be in April 2035. At its best approaches the comet can reach magnitude 7 to 8, theoretically visible to the naked eye under excellent dark skies, though binoculars or a small telescope are a more reliable bet. The geometry of the next pass is still being refined; observers should consult JPL Horizons from 2033 onward to plan observations.

To observe the Ursids, the ideal window is December 13 to 24, peaking typically around December 22, near the northern winter solstice. The radiant lies in Ursa Minor, close to the star Beta Ursae Minoris (Kochab). The normal rate is 5 to 10 meteors per hour, but outbursts can raise that figure considerably. The shower is best observed from the northern hemisphere.

• Ursid radiant: Ursa Minor, near Kochab (beta UMi)
• Activity window: December 13 to 24
• Peak: around December 22 (near winter solstice)
• Normal ZHR: 5 to 10 meteors/hour
• Historical outburst ZHR: above 100 (1945, 1986, 2000)
• Next 8P perihelion: April 18, 2035

Ursids and science

The Ursids (IAU code URS) are active from December 13 to 24, peaking typically around December 22, near the northern winter solstice. The radiant lies in Ursa Minor, close to the star Beta Ursae Minoris (Kochab). The normal rate is 5 to 10 meteors per hour, but outbursts can raise that figure considerably. Documented outbursts occurred in 1945 (estimated ZHR above 100), 1986, and 2000.

The link between 8P/Tuttle approaching perihelion and Ursid outbursts is well established: when the comet is near perihelion the density of material in Earth's crossing zone increases and rates climb. The 13.5-year period means intense outbursts tend to recur every one or two cycles, but precise prediction is difficult because debris is unevenly distributed along the trail. The last perihelion (2021) was potentially associated with elevated Ursid activity in December 2021, and the same pattern may recur with the 2035 perihelion.

Facts

• Horace Tuttle also co-discovered comet Swift-Tuttle (109P), parent body of the Perseids, one of the most abundant annual meteor showers, making him indirectly responsible for two yearly showers of major observer interest.
• The nucleus of 8P/Tuttle is a contact binary ~10 km long, revealed by Arecibo radar in 2008, with a structure identical in type to comet 67P/Churyumov-Gerasimenko explored by ESA's Rosetta.
• With a perihelion nearly identical to Earth's orbital distance (1.03 AU), 8P is one of the few intermediate-period comets that approaches the planet so closely, which makes the Earth's crossing of the Ursid debris trail particularly dense.
• The name "Ursids" comes from Ursa Minor, the constellation of the radiant, not from polar bears, though that confusion appears regularly in popular science writing.
• ESA considered 8P/Tuttle as a potential backup target for the Comet Interceptor mission, launched in 2028 to intercept a dynamically new or interstellar comet.
• The 1945 Ursid outburst was observed during World War II and is one of the few high-intensity meteor events of that decade with reliable records.

Other comets

See the full comet catalogue.