This 1986 photograph of Halley’s comet, taken from Easter Island on March 8 of that year, is likely the best view we’ll have until the comet returns to the inner Solar System in 2061. As of December 9, 2023, the comet now heads back into the inner Solar System, having just passed aphelion in its orbit. (Credit: NASA/W. Liller)
On December 9, 2023, Halley’s Comet reached aphelion: its farthest point from the Sun. As it returns, here are 10 facts you should know.
On December 9, 2023, Halley’s comet achieved aphelion, reaching its greatest distance.
This 1910 photograph of Halley’s comet represents the best display seen by human eyes since the development of photography as applied to astronomy. Although comets are usually visible near perihelion, or closest approach to the Sun, they can be billions of times fainter near aphelion, when farthest away. (Credit: Harvard College Observatory)
These 10 fantastic facts celebrate its impending return.
This simulated sky view shows the skies over London, England in the spring of 1066: when Halley’s comet returned. Although this event was recorded in numerous places, its identification with the return of Halley’s comet would require several hundred years to pass. (Credit: Morn/Stellarium)
1.) Its first recording was 240 B.C.E.
This ancient tablet is more than 2000 years old, and records the event of Halley’s comet as follows: “In the 7th year of Emperor Qin Shihuang of the Warring States, a broom star first appeared in the east, then it appeared in the north.” (Credit: Xu, Zhentao, David W. Pankenier, and Yaotiao Jiang. East Asian Archaeoastronomy: Historical Records of Astronomical Observations of China, Japan and Korea, 2000)
This Babylonian tablet records the appearance of Halley’s comet dating to late September, 164 BCE. There is evidence that Halley’s comet dates to prehistoric times, but this and the Chinese record one orbit prior are the first reliable, verifiable records of Halley’s comet as seen from Earth. (Credit: Linguica/English Wikipedia)
2.) Halley’s questioning Newton led to the Principia.
There may never be another Einstein or another Newton, but we can all learn to utilize their equations under the right physical circumstances. We can become excellent at physics they same way they did: by solving problems quantitatively. (Credit: Orrin Turner (L), Godfrey Kneller (R))
Newton offhandedly told Halley a central, ~1/r² force law would create elliptical orbits, then proved it.
The orbits of the planets in the inner Solar System aren’t exactly circular, but are elliptical, as are the orbits of all bodies gravitationally bound to the Sun. Planets move more quickly at perihelion (closest to the Sun) than at aphelion (farthest from the Sun), conserving angular momentum and obeying Kepler’s laws of motion, which were put on a more solid, generalized mathematical footing by Newton. (Credit: NASA/JPL)
3.) Halley identified 3 prior returns.
This diagram shows Halley’s comet’s orbit, neglecting the gravitationally perturbative effects of the planets. Halley’s comet spends most of its time near aphelion, near the orbit of Neptune and beyond, but plunges into the inner Solar System once every 74–79 years. (Credit: nagualdesign/Wikimedia Commons)
The original publication of Edmond Halley’s wherein he first identified the thrice-recorded comets of 1531, 1607, and 1682 as the same object: Halley’s comet, with a predicted return in 1758. (Credit: Hook & Norman, The Haskell F. Norman Library of Science & Medicine (1991) no. 978)
