☄ Tempel 1 9P/Tempel 1

How to follow comet Tempel 1 live

The panel above recomputes the position of Tempel 1 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 Tempel 1 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 Tempel 1 with no math at all.

Comet fact sheet

About Tempel 1

Comet 9P/Tempel 1 is a short-period comet discovered in 1867, orbiting between Mars and Jupiter. It would be a relatively obscure object if not for NASA's Deep Impact mission, which in July 2005 launched a 370-kg copper impactor into its surface at roughly 10.2 km/s, creating a crater and exposing pristine interior material for the first time in the history of space exploration.

Six years later, a spacecraft that had already visited another comet was redirected to Tempel 1 to photograph the scar left by the impactor. The two visits combined produced the largest scientific dataset ever accumulated on a single short-period comet -- and revealed surprises that challenged decades of theory about Solar System formation.

History and discovery

Ernst Wilhelm Leberecht Tempel, a German-born astronomer working in Marseille (France) and later Milan (Italy), discovered the comet on April 3, 1867 during a systematic sky survey with a 108-mm refractor. It was the first of eleven comets he would discover during his career. Tempel was self-taught and worked professionally as a lithographer, with no formal academic training in astronomy.

The comet was lost after the 1879 apparition, partly due to gravitational perturbations from Jupiter. Reports of recovery in 1967 and subsequent confirmations linked it definitively to the original object, producing the designation 9P. Through the twentieth century the comet was monitored regularly without attracting public attention -- until NASA selected it as the target of a historic mission.

Deep Impact launched on January 12, 2005. The impactor struck the nucleus on July 4, 2005, at 05:52 UTC -- the date chosen deliberately to coincide with US Independence Day, earning the internal nickname "4th of July in space." In February 2011, the Stardust-NExT spacecraft (the same craft that had visited Wild 2) flew past at 181 km and photographed the crater.

Orbit and returns

Tempel 1 orbits the Sun with a period of approximately 5.5 years (with variations caused by Jupiter's gravity). Perihelion sits at about 1.5 AU from the Sun -- between Earth and Mars -- and aphelion reaches roughly 4.7 AU near Jupiter. The orbital inclination is only 10.5 degrees relative to the ecliptic, making it reachable by spacecraft using conventional chemical propulsion.

Nucleus, coma and tail

The nucleus of Tempel 1 measures approximately 7.6 by 4.9 km and has an irregular, flattened shape. Its geometric albedo is only 0.04 -- darker than charcoal -- typical of nuclei rich in carbonaceous material. Spacecraft imagery revealed radically different terrains: smooth plateaus, steep scarps up to 60 m high, and rough regions rich in fine granular material.

The coma in normal conditions is modest, with integrated magnitude between 9 and 11. The dust tail is faint and the ion tail nearly undetectable in typical returns. The comet emits primarily water, CO2, and CO in order of abundance, with water production rates on the order of 10 to 15 kg per second near perihelion.

How to observe

9P/Tempel 1 requires a telescope: in favourable returns it reaches magnitude 9, requiring a minimum aperture of 150 mm under a dark sky. In less favourable returns it may reach magnitude 11 or 12. It is not naked-eye visible under normal conditions and its tails are poorly developed.

To locate it, consult updated ephemerides (JPL Horizons or Heavens-Above) near the date of the next perihelion in 2027. The comet moves noticeably against the star background from night to night near perihelion. The best observing window is typically two to four weeks before and after closest solar approach.

Missions and notable observations

Tempel 1 is one of the most-visited comets in history. The table below summarises milestones from the two missions that studied it:

The 2005 impact ejected a cloud of material far denser and more extensive than models predicted, suggesting the nucleus material was extremely porous and fine -- comparable to talc. The Spitzer Space Telescope detected in the ejecta: crystalline silicates, carbonates, metal sulfides, smectite (clay), and polycyclic aromatic hydrocarbons. The presence of crystalline silicates was especially surprising, as these minerals form at high temperatures (above 1,000 K) -- incompatible with the cold environment of the Kuiper Belt where comets originate.

Trivia and records

• The impactor was made primarily of copper, chosen because it is spectrally neutral -- minimising contamination of the comet's chemical signatures in post-impact measurements.
• The relative impact velocity of 10.2 km/s released energy equivalent to roughly 4.7 tons of TNT.
• The initial flash saturated the mother spacecraft's own detectors; the ejecta cloud blocked the view of the newly formed crater -- which is why it took six years and the Stardust-NExT mission to confirm it.
• The crater identified in 2011 was only 49 metres in diameter -- far smaller than initial estimates of 100-250 m -- surrounded by a bright ejecta zone 85 to 120 m wide.
• Comparing 2005 and 2011 images revealed that the cometary terrain had changed independently of the impact: new material deposits, flows, and topographic alterations indicate comets are geologically more active than previously thought.
• Ernst Tempel discovered more than 20 comets and nebulae without ever attending a university or receiving formal astronomy training.
• The Stardust spacecraft, redirected to Tempel 1 after delivering Wild 2 samples to Earth, was renamed Stardust-NExT (New Exploration of Tempel) -- one of the rare examples of complete reuse of an interplanetary spacecraft.

Other comets

See the full comet catalogue.