Download Halley`s Comet is arguably the most famous comet. It is a "periodic

Halley's Comet is arguably the most famous comet. It is a "periodic" comet and returns
to Earth's vicinity about every 75 years, making it possible for a human to see it twice in
his or her lifetime. The last time it was here was in 1986, and it is projected to return in
2061.
The comet is named after English astronomer Edmond Halley, who examined reports of
a comet approaching Earth in 1531, 1607 and 1682. He concluded that these three
comets were actually the same comet returning over and over again, and predicted the
comet would come again in 1758.
Halley didn't live to see the comet's return, but his discovery led to the comet being
named after him. (The traditional pronunciation of the name usually rhymes with valley.)
Halley's calculations showed that at least some comets orbit the sun.
Further, the first Halley's Comet of the space age – in 1986 – saw several spacecraft
approach its vicinity to sample its composition. High-powered telescopes also observed
the telescope as it swung by Earth.
Halley's in history
The first known observation of Halley's took place in 239 B.C., according to the
European Space Agency. Chinese astronomers recorded its passage in the Shih Chi
and Wen Hsien Thung Khao chronicles.
When Halley's returned in 164 B.C. and 87 B.C., it probably was noted in Babylonian
records now housed at the British Museum in London. "These texts have important
bearing on the orbital motion of the comet in the ancient past," noted a Nature research
paper about the tablets.
Halley's most famous appearance occurred shortly before the 1066 invasion of England
by William the Conquerer. It is said that William felt the comet heralded his success. In
any case, the comet was put on the Bayeux Tapestry – which chronicles the invasion –
in William's honor.
Another appearance of the comet in 1301 possibly inspired Italian painter Giotto's
rendering of the Star of Bethlehem in "The Adoration of the Magi, "according to the
Britannica encyclopedia.
Astronomers in these times, however, saw each appearance of Halley's Comet as an
isolated event. Comets were often foreseen as a sign of great disaster or change.
Even when Shakespeare wrote his play "Julius Caesar" around 1600, just 105 years
before Edmond Halley calculated that the comet returns over and over again, one
famous phrase spoke of comets as heralds: "When beggars die there are no comets
seen; the heavens themselves blaze forth the death of princes."
Discovery of Halley's recurrence
Astronomy began changing swiftly around the time of Shakespeare, however. Many
astronomers of his time held that Earth was the center of the solar system, but Nicolaus
Copernicus – who died about 20 years before Shakespeare's birth – published findings
showing that the center was actually the sun.
It took several generations for Copernicus' calculations to take hold in the astronomy
community, but when they did, they provided a powerful model for how objects move
around the solar system and the universe.
Edmond Halley
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Edmond Halley published "A Synopsis of the Astronomy of Comets" in 1705,
cataloguing what he had found from searching historical records of 24 comets
appearing near Earth between 1337 to 1698. Three of those observations appeared to
be very similar in terms of orbit and other parameters, leading Halley to propose that
one comet might be visiting Earth again and again.
The comet appeared in 1531, 1607 and 1682. Halley suggested the same comet could
return to Earth in 1758. Halley did not live long enough to see its return – he died in
1742 – but his discovery inspired others to name the comet after him.
On each successive journey to the inner solar system, astronomers on Earth turned
their telescopes skyward to watch Halley's approach.
The comet's pass in 1910 was particularly spectacular, as the comet flew by about 13.9
million miles (22.4 million kilometers) from Earth, which is about 1/15 the distance
between Earth and the Sun. On that occasion, Halley's was captured on camera for the
first time.
According to biographer Albert Bigelow Paine, the writer Mark Twain said in 1909, "I
came in with Halley's Comet in 1835. It is coming again next year, and I expect to go out
with it." Twain died on April 21, 1910, one day after perihelion, when the comet emerged
from the far side of the sun.
Halley's in the Space Age
When Halley's Comet came by Earth in 1986, it was the first time we could send
spacecraft up to look at it.
That was a fortunate occurrence, as the comet ended up being underwhelming in
observations from Earth. When the comet made its closest approach to the sun, it was
on the opposite side of that star from the Earth – making it a faint and distant object,
some 39 million miles away from Earth.
Several spacecraft successfully made the journey to the comet. This fleet of spaceships
is sometimes dubbed the "Halley Armada." Two joint Soviet/French probes (Vega 1 and
2) flew nearby, with one of them capturing pictures of the heart or nucleus of the comet
for the first time.
The European Space Agency's Giotto got even closer to the nucleus, beaming back
spectacular images to Earth. Japan sent two probes of its own (Sakigake and Suisei)
that also obtained information on Halley.
Additionally, NASA's International Cometary Explorer (already in orbit since 1978)
captured pictures of Halley from 17.3 million miles (28 million kilometers away.)
"It was inevitable that this most famous of all comets would receive unprecedented
attention, but the actual magnitude of the effort has surprised even most of those
involved in it," NASA noted in an account of the event.
Sadly, the astronauts aboard Challenger's STS-51L mission were also scheduled to
look at the telescope when they arrived in the orbit, but they never got the chance. The
shuttle exploded about two minutes after launch on Jan. 28, 1986, due to a rocket
malfunction.
It will be many decades until Halley's gets close to Earth again, but in the meantime you
can see its remnants every year. The Orionid meteor shower, which is spawned by
Halley's fragments, occurs annually in October. Halley's also produced a shower in
May, called the Eta Aquarids.
When Halley's sweeps by Earth in 2061, the comet will be on the same side of the sun
as Earth and will be much brighter than in 1986.
One astronomer predicted it could be as bright as apparent magnitude -0.3. This is
relatively bright, but well below that of the brightest star in Earth's sky: Sirius, at
magnitude -1.4 as seen from Earth.
— Elizabeth Howell, SPACE.com Contributor
Source: http://www.space.com/19878-halleys-comet.html
Use the information provided in the article to develop a graph displaying the
frequency of Halley’s Comet being visible from Earth. There is no “right or
wrong” answer to this, but reason through the information provided to create a
graphic representation. (Hint: Highlight/underline numbers or mathematical
references throughout the passage)