☄ Halley 1P/Halley

How to follow comet Halley live

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

Comet fact sheet

About Halley

Comet 1P/Halley is the most historically documented periodic comet in human history. With an orbital period of roughly 75 to 76 years, it returns to the inner solar system often enough that a long-lived person can witness it twice in a lifetime. Chinese, Babylonian, Greek and medieval European civilizations all recorded its apparitions in clay tablets, chronicles and tapestries without knowing they were watching the same object. English astronomer Edmond Halley, in 1705, was the first to recognize this periodicity by comparing the orbits of the comets of 1531, 1607 and 1682, correctly predicting the 1758 return - though he did not live to see it.

Halley's legacy extends far beyond naked-eye apparitions: its debris produces two annual meteor showers, and ESA's Giotto mission in 1986 delivered the first direct images of a cometary nucleus in astronomical history. In 2061, the southern hemisphere will enjoy the best view in over a century, with the comet reaching magnitude -0.3.

History and discovery

The oldest accepted record dates to 240 BC in Chinese chronicles of the Shih Chi. The Bayeux Tapestry, woven around 1070, depicts the comet visible in April 1066 just before the Battle of Hastings - the Normans interpreted its appearance as an omen of conquest. The inscription beside the figure reads "isti mirant stellam" (these men wonder at the star). Halley published in 1705 the Astronomiae Cometicae Synopsis, demonstrating that the comets of 1531 (observed by Petrus Apianus), 1607 (observed by Johannes Kepler) and 1682 (observed by Halley himself) had nearly identical orbits. His prediction of a 1758 return was confirmed when the comet was spotted on December 25, 1758 by Johann Georg Palitzsch, a German farmer and amateur astronomer. Halley had died in 1742. The comet has borne his name by astronomical convention ever since.

The 1910 apparition was one of the most spectacular of the modern era - the comet briefly outshone Venus and its tail stretched over 100 degrees across the sky. The 1986 return was the weakest of the 20th century for naked-eye visibility, as Earth was poorly positioned relative to the comet and Sun. Even so, an international fleet of spacecraft visited the comet that year, marking the first direct scientific study of a cometary nucleus.

Orbit and returns

Halley follows a highly elongated elliptical orbit (eccentricity approximately 0.967), swinging from within Venus's orbit at perihelion (about 0.586 AU from the Sun) to beyond Neptune at aphelion, roughly 35 astronomical units away. Because it moves in a retrograde direction (opposite to the planets), it is classified as a short-period comet with a retrograde orbit - a trait suggesting origin in the Kuiper Belt or Oort Cloud.

The orbital period varies slightly from return to return, between 74 and 79 years, due to gravitational perturbations from Jupiter, Saturn, Uranus and Neptune. Over the last 30 documented centuries, the average period has hovered around 75 to 76 years. The last perihelion occurred on February 9, 1986, when the comet reached 0.587 AU from the Sun. The next is predicted for July 28, 2061, when geometry is expected to be far more favorable than in 1986. Updated 2025 estimates place peak magnitude around -0.3, making it considerably brighter than Saturn and visible to the naked eye for several weeks. The southern hemisphere will have a clear advantage, with the comet well elevated in the evening sky through August and September 2061.

Nucleus, coma and tail

Halley's nucleus is a dark, irregular object - Giotto's images revealed a shape resembling a lumpy potato or peanut: roughly 15 km long, 8 km wide and 8 km thick. Total mass is estimated at about 2.2 x 10¹⁴ kg. The surface is one of the darkest objects in the solar system, with an albedo of only 0.04 - darker than coal - absorbing 96% of incident sunlight. This extreme darkness is caused by an organic carbon-rich crust blanketing most of the icy interior.

As the comet approaches the Sun, solar energy sublimates ice beneath the crust, and gas and dust erupt in jets that form the coma (the cloud of gas and dust surrounding the nucleus) and the two tails. Halley displays two distinct tails: the plasma (or ion) tail, composed of ions and ionized molecules blown by the solar wind, always pointing directly away from the Sun and bluish in color; and the dust tail, composed of microscopic solid particles pushed by solar radiation pressure, slightly curved and whitish. In 1986, the plasma tail reached about 100 million km in length.

Halley's sublimation rate near perihelion is roughly 20 to 30 tonnes of gas and dust per second, meaning each pass strips away a layer several meters thick from the nucleus. The comet is estimated to survive another 2,000 to 3,000 orbits before completely disintegrating.

How to observe

At the 2061 apparition, Comet Halley will be visible to the naked eye for several weeks. The best viewing window for the southern hemisphere is forecast for August and September 2061, when the comet will be well elevated in the night sky and relatively close to Earth. For ideal observation: dark skies away from city lights, the comet at least 20 degrees above the horizon, and 7x50 or 10x50 binoculars to resolve the coma and distinguish the bluish ion tail from the whitish dust tail.

Between returns, Halley's legacy is permanently inscribed in the night sky through two annual meteor showers. The Eta Aquariids, active from late April through mid-May with a peak around May 6, are produced by debris Earth encounters while crossing the southern-ecliptic side of the comet's trail. Best observed from the southern hemisphere, where zenithal hourly rates can reach 50 to 85 meteors per hour. The Orionids, peaking around October 21, come from the northern side of the same trail, producing 20 to 30 meteors per hour under ideal conditions. Both showers feature fast meteors (around 66 km/s) with persistent trains.

For astrophotography of the 2061 comet, digital cameras with 50-200 mm lenses, ISO 1600 to 6400 and 5 to 30-second exposures on a fixed tripod will capture both tails in detail impossible to see with the naked eye.

Missions and scientific exploration

The 1986 return was the first to be explored by spacecraft - an international fleet of five missions, an unprecedented cooperative effort during the Cold War:

Giotto, approaching within 596 km of the nucleus, collected the most detailed data. Its cameras and spectrometers revealed the nucleus was far darker than expected, with jets of gas and dust erupting from just 10% of the Sun-facing surface. Most of the surface was covered by an inert dark crust. Giotto also detected large amounts of complex organic compounds in the coma.

No new mission to Halley has been approved as of 2026, though conceptual proposals from ESA and NASA for a rendezvous spacecraft that would accompany the comet for months have been discussed. A launch window for such a mission would fall between 2045 and 2050.

Trivia and records

• The nucleus is roughly 15 km long by 8 km wide, its irregular shape revealed by Giotto's images in 1986 - the first direct images of a cometary nucleus in history. Halley comet size dwarfs most asteroids of equivalent fame.
• The nucleus surface has an albedo of only 0.04 - darker than coal - absorbing 96% of sunlight rather than reflecting it.
• Mark Twain was born in 1835 (a Halley return year) and died in 1910 (the following return year). He predicted it himself: "I came in with Halley's Comet. I expect to go out with it." He died the day after the comet passed perihelion on April 20, 1910.
• In 1910, public panic broke out when astronomers detected cyanogen in the comet's tail and some scientists (incorrectly) speculated Earth could be poisoned when it passed through the tail. Entrepreneurs sold "anti-comet pills" as protection.
• Painter Giotto di Bondone witnessed the comet in 1301 and is believed to have depicted it as the Star of Bethlehem in his fresco Adoration of the Magi at the Cappella degli Scrovegni in Padua - which inspired ESA to name its 1986 probe "Giotto."
• When will Halley's comet return next? July 28, 2061. People born today in 2026 will be 35 years old and able to see it with the naked eye.
• The earliest reliable Japanese record dates to AD 684, described in the Nihon Shoki chronicles as "a long star in the eastern sky."

Other comets

See the full comet catalogue.