☄ Kopff 22P/Kopff

How to follow comet Kopff live

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

Comet fact sheet

About Kopff

22P/Kopff was discovered on 22 August 1906 by German astronomer August Kopff at Heidelberg Observatory, using photographic plates. It is a short-period comet whose orbit is confined almost entirely between Jupiter and the Sun, placing it firmly in the Jupiter-family comet group.

Classic estimates put the nucleus at roughly 3.4 km in diameter, but Hubble Space Telescope images from 1996 (Lamy et al.) revised this to an effective radius of 1.67 to 1.8 km. It is not large by cometary standards, but it compensates with regular, predictable returns. Every perihelion since discovery has been observed, building a continuous record spanning more than a century.

History and discovery

August Kopff was working on the Heidelberg Observatory photographic programme when he identified the comet on plates taken in August 1906. The orbit was calculated quickly and confirmed the object had been gravitationally captured by Jupiter at some point in the geologically recent past. Kopff was a prolific observer: beyond the comet, asteroid (1102) Peppina and other objects carry his credit.

Over the following decades each return was reobserved with progressively larger telescopes. Modern ephemerides computed by NASA/JPL from multiple apparitions have sub-arcsecond accuracy, allowing amateur observatories to track it with modest equipment. The 1996 return was the first covered systematically with high-sensitivity CCD cameras, opening a new era of detailed light curves.

Orbit and returns

The current orbital period is approximately 6.44 years. Perihelion lies at about 1.58 AU from the Sun (between Earth and Mars), and aphelion at about 5.3 AU, near Jupiter's orbit. This geometry is typical of Jupiter-family comets: the Tisserand parameter with respect to Jupiter (T_J) is around 2.8, within the defining range for the group.

Jupiter has altered the orbit on several occasions. Close encounters with Jupiter in 1954 and 2008 produced measurable perturbations. The perihelion passage in the 2022-2023 cycle occurred in October 2022, with visual magnitude around 9, within reach of 10x50 binoculars under a dark sky. The next perihelion is expected around 2029.

Nucleus and dynamic family

The nucleus of 22P/Kopff reflects only about 4% of incoming sunlight, making it darker than coal in terms of geometric albedo. That very low value is typical of cometary nuclei, whose surfaces are coated with dark, refractory organic crust. Hubble images obtained by Lamy et al. in 1996 measured an effective nuclear radius of 1.67 to 1.8 km, refining earlier estimates of up to 3 km in diameter.

22P belongs to the Jupiter family (JF), the largest known dynamical group of comets, with more than 400 catalogued members. JF comets have a Tisserand parameter T_J between 2 and 3, low-inclination orbits, and typical periods between 3 and 20 years. Most are thought to have migrated from the Kuiper Belt and been captured by Jupiter over millions of years. Each perihelion passage vaporises a layer of ice; over thousands of orbits this erosion gradually whittles down the nucleus.

How to observe

On favourable returns 22P/Kopff reaches magnitude 8 to 10, putting it within range of sturdy binoculars and amateur telescopes from 80 mm aperture upward. The coma is usually diffuse with little central condensation, and the gas tail (type I, ionised) only shows up in long-exposure images.

To locate the comet, use ephemerides from JPL Horizons (horizons.jpl.nasa.gov) or the Stellarium app, which includes trajectories for catalogued comets. On returns with moderate brightness (magnitude 9 to 10), a moonless sky and a zenith distance below 45 degrees make a significant difference. Narrowband filters (OIII, UHC) do not help for comets since the emission is broadband; observe without a filter.

• Minimum recommended aperture: 80 mm (binocular or reflector)
• Best magnification: 30x to 60x to take in the full coma
• Sky condition: visual limiting magnitude above 5.5
• Ephemeris tools: JPL Horizons or Heavens-Above.com

Science and notable observations

22P/Kopff was listed as a candidate spacecraft rendezvous target in ESA studies during the 1990s and 2000s. NASA also studied it as an alternative target for the CRAF (Comet Rendezvous Asteroid Flyby) mission, cancelled in 1992 due to budget constraints. Although no spacecraft has visited Kopff, the scientific interest generated detailed published light curves and coma composition work.

Spectroscopic observations have detected CN, C2 and OH emissions, classic indicators of nucleus volatility and water production rate. Measurements at the 2009 return estimated water production at around 10^27 to 10^28 molecules per second at perihelion. In the infrared, crystalline silicates were identified in the coma during the 1996 apparition, indicating that some material was thermally processed before being ejected.

Facts worth knowing

• 22P/Kopff is one of the few Jupiter-family comets observed continuously since discovery, covering more than sixteen complete orbits.
• NASA cancelled its CRAF mission to 22P/Kopff in 1992 due to budget cuts; ESA's Rosetta was later sent to 67P/Churyumov-Gerasimenko instead.
• The nucleus reflects only about 4% of incoming sunlight, an albedo equivalent to wet asphalt.
• That low albedo means the nucleus absorbs 96% of the solar radiation it receives, heating up enough to sublimate ice even at moderate distances from the Sun.
• Each perihelion strips away a layer of ice; over thousands of orbits the nucleus can fragment, as happened to Comet Shoemaker-Levy 9 after a close Jupiter encounter.
• Asteroid (1102) Peppina was also discovered by August Kopff, in 1928, named after his wife.

Other comets

See the full comet catalogue.