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The most famous of all comets, Comet Halley is noted for producing spectacular displays when it passes near Earth on its 76-year trip around the sun. However, you don't have to wait until 2061 to see a piece of the comet -- you can do it this very week!
Halley's Comet leaves bits of itself behind -- in the form of small conglomerates of dust and ice called meteoroids -- as it moves in its orbit, which the Earth approaches in early May and mid-October. When it does, it collides with these bits of ice and dust, producing a meteor shower as the particles ablate -- or burn up -- many miles above our heads. The May shower is called the Eta Aquarids, as the meteors appear to come from the constellation Aquarius. The October shower has meteors that appear to come from the well-known constellation of Orion the Hunter, hence the name: Orionids.

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A celestial event seen by the ancient Greeks may be the earliest sighting of Halley's comet, new evidence suggests.
According to ancient writers, a large meteorite smacked into northern Greece between 466BC and 467BC.
The writers also described a comet in the sky at the time the meteorite fell to Earth, but this detail has received little attention, say the researchers.
Comet Halley would have been visible for about 80 days in 466BC, researchers write in the Journal of Cosmology.

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Halley's Comet or Comet Halley (officially designated 1P/Halley) is the most famous of the periodic comets, and is visible from Earth every 75 to 76 years. Many comets with long orbital periods may appear brighter and more spectacular, but Halley is the only short-period comet that is clearly visible to the naked eye, and thus, the only naked-eye comet that might appear twice in a human lifetime. During its returns to the inner solar system, it has been observed by astronomers since at least 240 BC, but it was only recognised as a periodic comet in the 18th century when its orbit was computed by English astronomer Edmond Halley, after whom it is named. Halley's Comet last appeared in the inner Solar System in 1986 and will next appear in mid-2061.

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Haley's Comet 100 Years Ago

One hundred years ago today, Haley's Comet passed the closest to the Earth since it's return on April 20, 1910.
The time before that, it appeared on November 30, 1835, on the night Samuel Langhorne Clemens, better known as Mark Twain, was born.

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Is Halley's comet an alien interloper?

Our sun may have stolen the vast majority of its comets from other stars.
Hal Levison of the Southwest Research Institute in Boulder, Colorado, and his colleagues say many of the Oort-cloud objects may have been stolen from other stars born in the same stellar nursery as the sun. Most stars like the sun form in clusters of between 10 and 1000 members. According to the team's simulations, encounters between stars in this crowded environment tend to disturb their scattered discs and detach objects from them, creating a reservoir of free-floating comets.
When stars later leave the cluster, some of these objects move along with them, getting captured into wide, Oort cloud-like orbits.

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Orbital Elements at Epoch 2449400.5 (1994-Feb-17.0) TDB
Reference: JPL J863/77 (heliocentric ecliptic J2000)
Element Value Uncertainty (1-sigma) Units
e 0.967142908462304 5.035e-09
a 17.8341442925537 3.8913e-08 AU
q 0.585978111516909 8.8924e-08 AU
i 162.262690579161 6.7791e-06 deg
node 58.42008097656843 9.0539e-06 deg
peri 111.3324851045177 1.1714e-05 deg
M 38.3842644764388 1.4226e-07 deg
tp 2446467.395317050925
(1986-Feb-05.89531706)
4.7896e-06 JED
period 27509.1290731861
75.32
9.0034e-05
2.465e-07
d
yr
n .01308656479244564 4.2831e-11 deg/d
Q 35.08231047359043 7.6546e-08 AU

Additional Model Parameters
Parameter Value Uncertainty (1-sigma)
A1 [EST] 2.696463929511566E-10 3.084E-11
A2 [EST] 1.554613388970244E-10 3.205E-15
S0 [EST] 861.6729585598083 16.03
Orbit Determination Parameters
# obs. used (total) 7428
data-arc span 57852 days (158.39 yr)
first obs. used 1835-08-21
last obs. used 1994-01-11
planetary ephem. DE405
SB-pert. ephem. SB405-CPV-2
fit RMS 1.0147
data source ORB
producer M.S.W. Keesey
solution date 2001-Aug-02 13:51:39

Additional Information
Earth MOID = .0637815 AU
T_jup = -0.605

Source

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On this day in 240 BC the first perihelion passage of Halley's Comet was recorded.

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Here is an animation of data from ESA's first interplanetary spacecraft, Giotto, launched to study Halley's comet during its 1986 apparition. These data are incredibly difficult to work with, but finally someone -- an amateur named Daniel Machácek -- came along who carefully reprojected each of the tiny postage stamp-sized images to create a window onto the comet, a window that jerks around more and more as the spacecraft gets hammered by Halley debris.
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Halley's Comet or Comet Halley (officially designated 1P/Halley) is the most famous of the periodic comets and can currently be seen every 75-76 years.
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May 19, 1910: Halley's Comet Brushes Earth With Its Tail
Earth passes through the tail of Halley's comet. The anticipation of its arrival creates quite a stir. In some circles, the comet's unusually close approach is seen as a sign of impending doom, a notion the down-market press does little to dispel.

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On Christmas Day, 1758, a German amateur astronomer and farmer named Johann Georg Palitzsch did something that would have made a great Christmas gift for English astronomer Edmond Halley. Johann "recovered" Halley's Comet, meaning he was the first to observe this previously observed "dirty snowball" as it returned to the inner solar system.

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