☄ Honda-Mrkos-Pajdusakova 45P/Honda-Mrkos-Pajdusakova

How to follow comet Honda-Mrkos-Pajdusakova live

The panel above recomputes the position of Honda-Mrkos-Pajdusakova 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 Honda-Mrkos-Pajdusakova 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 Honda-Mrkos-Pajdusakova with no math at all.

Comet fact sheet

About Honda-Mrkos-Pajdusakova

45P/Honda-Mrkos-Pajdusakova combines three discoverers from three countries in a name astronomers usually shorten to "45P/HMP." Japanese astronomer Minoru Honda detected it on 3 December 1948; Czech astronomer Antonin Mrkos and Slovak astronomer Ludmila Pajdusakova made independent discoveries days later. Orbital calculations showed the same object, producing the triple name.

With an orbital period of about 5.26 years, it is one of the Jupiter-family short-period comets that approaches Earth most closely. On favourable returns the minimum Earth distance drops below 0.1 AU, under 15 million kilometres, a rarity among catalogued comets. Ludmila Pajdusakova was one of the first women to have her name on a comet through her own discovery work.

History and discovery

Minoru Honda, a Japanese astronomer and photographer from Kurashiki, discovered the comet on 3 December 1948 with a wide-field photographic camera. In the following days, Antonin Mrkos at Skalnate Pleso Observatory in Czechoslovakia and Ludmila Pajdusakova at the same observatory made independent observations. Pajdusakova worked at Skalnate Pleso from 1947 to 1979 and discovered or co-discovered several comets and asteroids, being one of the first women to have her name on a comet through her own discovery work rather than as a posthumous honour.

The link between the three detections was established through orbital calculations showing agreement within the measurement errors of the time. The comet was numbered 45P in the IAU periodic comet list. Honda was already known for his persistence as a sky sweeper: over his career he discovered or co-discovered dozens of novae and several comets.

Orbit and proximity to Earth

45P/HMP's perihelion lies at 0.53 AU from the Sun, inside Venus's orbit, while aphelion reaches about 5.5 AU. The orbital inclination is only 4.3 degrees, nearly in the ecliptic plane. The Tisserand parameter T_J is 2.57, near the lower boundary of the Jupiter-family criterion.

The combination of an interior perihelion and a nearly coplanar orbit means that on certain returns Earth and the comet draw very close. In February 2017 the minimum distance was only 0.0832 AU (12.4 million km), making the comet visibly fast: it was moving more than 10 degrees per day against background stars. Magnitude reached 7 to 8, within binocular range. The next favourable perihelion is in August 2026.

Nucleus and dynamic family

The nucleus of 45P/HMP is estimated between 0.8 and 1.3 km in diameter, making it one of the smallest nuclei of periodic comets with a well-determined orbit. That small size, combined with perihelion at 0.53 AU, produces a high sublimation rate per unit of nuclear surface area during each close solar passage.

With T_J of 2.57, the comet is near the lower boundary of the Jupiter family range (2 < T_J < 3), indicating its orbit was strongly perturbed by Jupiter. The 4.3-degree inclination is typical of young family members not yet redistributed in inclination by successive encounters. The combination of small nucleus and low-inclination orbit makes 45P/HMP one of the catalogued comets with the highest potential for future close Earth approaches.

How to observe

On typical returns 45P/HMP reaches magnitude 10 to 12, requiring an amateur telescope of 100 to 150 mm. On close approaches such as 2017 it can reach magnitude 7 and be seen in sturdy 7x50 or 10x50 binoculars under a moderately dark sky.

A particular challenge of observing 45P during peak approaches is its apparent speed: in February 2017 the comet was moving more than 10 degrees per day, leaving a visible streak in 60-second exposures without precise tracking. For the August 2026 return, exact geometry will determine the magnitude; check JPL Horizons for updated ephemerides.

• Typical magnitude: 10 to 12 (normal return)
• Close-approach magnitude: up to 7 to 8
• Peak apparent speed: more than 10 degrees per day (2017)
• Next perihelion: August 2026

Science and notable observations

The comet was studied by coordinated observing campaigns in 2017 using telescopes in Hawaii, Chile and from space (NASA's Swift). Ultraviolet spectra revealed production rates of OH (a water proxy), CO and CN. Water production at perihelion was estimated at about 3 x 10^27 molecules per second, comparable to other similarly sized Jupiter-family comets.

Goldstone radar observations (JPL/NASA) in February 2017 imaged the nucleus, confirming an effective size of about 0.8 to 1.3 km. A study published in the Planetary Science Journal in 2022 (Schleicher et al.) identified recurring gas ejection events in the nucleus, periodic activity patterns possibly tied to rotation and the position of specific active regions on the surface.

Facts worth knowing

• Ludmila Pajdusakova was one of the first women in the twentieth century to have her name on a comet through her own discovery, not as a posthumous honour.
• In 2017 the apparent sky speed of 45P/HMP was so high that standard 60-second exposures showed the comet as a streak rather than a fuzzy patch.
• The nucleus is estimated at 0.8 to 1.3 km in diameter, one of the smallest nuclei of periodic comets with a well-determined orbit.
• The comet holds one of the lowest Earth-approach distances among known non-asteroid periodic objects, with historical minima of 0.06 AU in some passages.
• Minoru Honda was also a dedicated astronomical photographer who captured novae and supernovae in addition to comets, making him one of the most prolific amateur observers of the twentieth century.
• The next favourable perihelion is in August 2026; the degree of Earth approach on that return will depend on the exact geometry calculated in the months beforehand.

Other comets

See the full comet catalogue.