Halley's Comet, officially designated 1P/Halley and also
referred to as Comet Halley after
Edmond Halley, is a
comet that can be
seen every 75-76 years. It is the most famous of all
periodic comets. Although in every century many long-period comets appear
brighter and more spectacular, Halley is the only short-period comet that is
visible to the naked eye, and thus, the only naked-eye comet certain to return
within a human lifetime.
Its many appearances over the centuries have had a notable effect on human
history, despite the fact that they were not recognized as the same object until
17th century. Halley's Comet last appeared in the inner
System in 1986, and will next appear in mid 2061.
The most standard pronunciation of "Halley" — and the pronunciation that the
astronomer himself probably used — is [hæli]
to rhyme with "valley". The once-standard alternate pronunciation [heɪli]
(to rhyme with "Bailey") led to
and roll singer Bill Haley
naming his band
Bill Haley and the Comets.
Edmond Halley's study
Halley's Comet was the first to be recognized as periodic. Having perceived
that the observed characteristics of the comet of 1682 were nearly the same as
those of two comets which had appeared in 1531 (observed by
Petrus Apianus) and 1607 (observed by
Johannes Kepler in
concluded that all three comets were in fact the same object returning every
76 years (a period that has since been amended to every 75–76 years). After a
rough estimate of the perturbations the comet would sustain from the attraction
of the planets, he predicted its return for 1757. Halley's prediction of the
comet's return proved to be correct, although it was not seen until
Johann Georg Palitzsch, a German farmer and amateur astronomer, and did not
pass through its
until March 1759; the attraction of
Saturn having caused a retardation of 618 days, as was computed by a team of
Joseph Lalande, and
Nicole-Reine Lepaute, previous to its return. Halley did not live to see the
comet's return, having died in 1742.
Halley's calculations enabled the comet's earlier appearances to be found in
the historical record.
||1758 (first predicted perihelion)
||Halley's Comet, 1P (see
||February 9, 1986
|Next perihelion (predicted):
- 240 BCE and earlier: Historical records show that Chinese astronomers
observed the comet's appearance in 240 BCE and possibly as early as 2467 BCE.
Habitual observations and calculations of appearances after 240 BC are recorded
by Chinese, Japanese, Babylonian, Persian, and other mesopotamian astronomers.
- 87 BCE: According to
researchers, the "Symbol on
Tigranes the Great's crown that features a star with a curved tail may
represent the passage of Halley's comet in 87 BC. Tigranes could have seen
Halley's comet when it passed closest to the Sun on Aug. 6 in 87 BC according to
the researchers, who said the comet would have been a 'most recordable event' --
heralding the New Era of the brilliant King of Kings.
- 12 BCE: Some
have suggested that the comet's appearance in 12 BC might explain the Biblical
story of the
Star of Bethlehem.
- 66 CE: In the
Talmud, it is mentioned that "There is a star which appears once in seventy
years that makes the captains of the ships err" (Horioth,
chap. III). It probably refers to the AD 66 perihelion.
- 837: In this year, it is calculated that Comet Halley may have passed as
close as 0.03 AU
(3.2 million miles) from
Earth, by far its
closest approach. Its tail may have stretched 90 degrees
across the sky.
- 1066: The comet was seen in England and thought to be a bad omen: later that
Harold II of England died at the
Battle of Hastings. It is shown on the
Bayeux Tapestry, and the accounts which have been preserved represent it as
having then appeared to be four times the size of
Venus, and to have shone with a light equal to a quarter of that of the
appearance of the comet is also noted in the
Anglo-Saxon Chronicle. Having first seen it as a young boy in 989,
Eilmer of Malmesbury declared prophetically in
1066: "You've come,
have you?...You've come, you source of tears to many mothers. It is long since I
saw you; but as I see you now you are much more terrible, for I see you
brandishing the downfall of my country" (William
of Malmesbury, Deeds of the English Kings, Ch. 225,
- Chaco Native Americans in New Mexico recorded this 1066 comet in their
- 1301: The artist
Giotto di Bondone could have observed the comet and his depiction of the
Star of Bethlehem in the
Arena Chapel cycle completed in 1305 is a candidate for an early depiction.
- 1456: The comet passed very close to the Earth; its tail extended over 60°
of the heavens and took the form of a sabre. According to one story, first
appearing in a posthumous biography in 1475 and later embellished and
Pope Callixtus III
excommunicated the 1456 apparition of the comet, believing it to be an ill
omen for the Christian defenders of
who were at that time being besieged by the armies of the
Ottoman Empire. However, no known primary source supports the authenticity
of this account.
An image of Halley's Comet from 1910
The most recent appearances have been in 1835, 1910, and 1986. Halley will
next return in 2061.
American satirist and writer
was born on
exactly two weeks after the comet's
In his biography, he said, "I came in with Halley's comet in 1835. It's coming
again next year (1910), and I expect to go out with it. The Almighty has said no
doubt, 'Now here are these two unaccountable freaks; they came in together, they
must go out together.' " Twain died on
1910, the day
following the comet's subsequent perihelion.
 The 1985 fantasy film
The Adventures of Mark Twain is inspired by this.
The April 1910 approach was notable for several reasons: it was the first
approach of which photographs exist, and the comet made a relatively close
approach, making it a spectacular sight. Indeed, on
May 18, the
transited the Sun's disk, and the Earth actually passed through its tail. At
the time, the comet's tail was thought to contain poisonous
and gas. The popular media picked up this fact and, despite the pleas of
astronomers, wove sensational tales of mass cyanide poisoning engulfing the
planet. In reality, the gas is so diffuse that the world suffered no ill-effects
from the passage through the tail.
Many people who claim to remember seeing the 1910 apparition are in fact
remembering a different comet, the
Great Daylight Comet of 1910, which surpassed Halley in brilliance and was
actually visible in broad daylight for a short time about four months before
Halley made its appearance.
The 1986 approach was the least favourable for Earth observers of all
recorded passages of the comet throughout history: the comet did not achieve the
spectacular brightness of some previous approaches, and with increased
light pollution from urbanization, many people never saw the comet at all.
Further, the comet appeared brightest when it was almost invisible from the
northern hemisphere in March and April, prompting many amateur astronomers to
travel to the southern hemisphere for a glimpse of the interloper. However, the
development of space travel allowed scientists the opportunity to study a comet
at close quarters, and several probes were launched to do so. Most
Giotto space probe, launched by the
European Space Agency, made a close pass of the comet's nucleus. Other
probes included the
joint projects Vega
1 and Vega 2,
and two Japanese
Sakigake. The probes were unofficially known as the
It was Stephen Edberg (then serving as the Coordinator for Amateur
Observations at NASA's
Jet Propulsion Laboratory (JPL)
and Charles Morris who were the first to observe Comet Halley with the naked eye
in its 1986 apparition.
The comet was also observed from space by the
International Cometary Explorer, which was in a solar orbit at the time.
Originally International Sun-Earth Explorer 3 (ISEE-3), it was renamed and
retooled after it was freed from its L1
Lagrangian point location to observe comet
Shuttle missions--the ill-fated
STS-61-E--were scheduled to observe Comet Halley from
low Earth orbit. 61-E, which would have been flown by
Challenger in March 1986, would have carried the
ASTRO-1 platform to study the comet, among other things. The Challenger
disaster thwarted all such plans. ASTRO-1 would not fly until late 1990 on
space station was unoccupied during Halley's 1986 visit, and
Mir, though launched
during the visit, did not have a crew during the time of the comet's stay.
Because its orbit comes close to Earth's orbit in two places, Comet Halley is
the parent body of two
Aquarids in early May, and the
The Eta Aquarids show orbital similarities approaching Earth as they do of Mars
and so a meteor shower at Mars is anticipated there as well
but this time appearing to come from Lambda Gemini.