All the cosmic objects in this universe arouse deep interest and curiosity in our minds, whether it is a star in the distant sky or a planet moving slowly with steady light or a galaxy forming an illuminated path. But may be the comet, the momentary guest at earth's sky in respect of time, is a little bit ahead among all. Putting aside human social beliefs, comets are several steps ahead of other cosmic bodies as a source of newly discovered knowledge for scientists. Today we will discuss about the most famous astronomical object in space science as well most discussed heavenly body among the common people, the Halley's Comet.
Halley's Comet is such a short-period comet that humans can see it with the naked eye twice, if not more, in its lifetime. If we talk about the history of this comet, we have to go back to the Greek civilization of ancient Europe. A mysterious line of light is mentioned in documents from 468 to 466 BC. Some Mesopotamian astronomers also mentioned this mysterious line of light. There, they reported that after the interval of 75 to 79 years, a bright light appeared in the sky for a few days, for which the sailors of the ship could not determine the right direction in the sea at night and lost their way and faced great problems. After a few days, when the star disappeared, everything would be fine again. The first documented history of Halley's Comet is found in our neighboring country China. According to that document, the comet was visible from Earth's sky from 15th to 25th day of the month of May of 240 BC. Halley's Comet was last seen from Earth in 1986. Till date, it has appeared before us a total of 30 times since the first recorded history of appearing. The first photographs of Haley's comet were made on 20th April 1910, and another striking fact is that the comet reached the closest point to Earth in 837 AD. At that time the distance between the comet and the earth was less than 50,000 km.
Edmund
Haley, a friend, publisher and editor of Sir Isaac Newton, one of Europe's
foremost scientists, witnessed the comet's appearance in the earth's sky on
15th September 1682, with many people around the world. He then went on to
study Newton's mathematical theory and found 24 comets that repeatedly appeared
in the earth's sky and disappeared again. From that source, Edmund Haley found
a bright astronomical orbit that closely resembled the orbit of 1605, visible
in the earth's sky. After completing the complex mathematical
steps, he understood that, before this incident, this comet came to the earth's
sky many times and in future it would come in every 75 to 76 years
interval. As early as 1705, Edmund Haley
predicted that the comet would reappear in 1758, exactly seventy six years
after its next orbit around the Sun, and in fact, practically this happened.
Unfortunately,
when Edmund Haley died in 1742, he could no longer to see the truth of his
calculations with his own eyes. French astronomer Nicolas Louis de Lacaille
later named that particular periodic comet Haley's Comet in honor of Edmund
Haley.
The orbits of Halley's comet are highly elliptical. At the time of orbiting the sun, when the comet comes closest to the sun (Perihelion), the distance from the Sun to the comet is 0.6 AU (The average distance from the sun to earth is 1 AU or 1 astronomical unit). The location of that place in the solar system is a place between the orbits of Mercury and Venus. According to the law of rotation, when a comet is in the farthest place from the Sun (Aphelion), the distance of the comet from the sun is 35 AU. In other words, it is place which is located at 35 times more distant than the average distance between the earth and the sun. In terms of location, this place is very close to sun's nearest dwarf planet Pluto. Halley's Comet is a comet which orbits in retrograde orbit, meaning that most of the cosmic objects in the solar system are orbiting the sun in the same direction, while Halley's Comet is orbiting the sun in the completely opposite direction. In the past, when the comet came close to Earth, its speed was measured at 70.56 km per second or 2,54,016 km per hour. However, this velocity is not the highest or the lowest of a comet because, according to the cosmic law, when an object is in the perihelion state, its velocity reaches the final stage, and when the object is in the aphelion state, it attains the lowest velocity. Since the position of the Earth is not in the position of perihelion state or aphelion state of the comet, it is normal for the speed of Haley's comet to increase or decrease. Once Halley's Comet orbits the sun, it orbits the Earth twice, and twice meteors fall on the Earth's sky. These meteor showers are known to us by different names such as Eta Aquarids and Orionides
Comets
that complete their orbit around the Sun in 200 years or less are called
short-period comets. Halley's Comet is one such comet. Halley's comet is
thought to have been born 1 crore or 10 million years ago today, and its source
was the giant Oort cloud which is surrounding the solar system. (Oort Cloud: A
region of asteroids and comets orbiting at a distance of 2000-2,00,000 AU from
the Sun for which there is no evidence of existence, but theoretically and the
surrounding conditions claim the presence of this region.) A long time ago
this comet was the long-period comet. But due to the intense gravitational
force of a giant planet, its orbit has become shorter. Haley's current orbit
around the Sun is estimated to have been between 16,000 and 2,00,000 years ago.
The
central part of Haley's comet is much smaller than its tail. Its length is 15
km, width and thickness is 8 km. and weigh is 22,00,00,00,00,00,000 kilogram.
The main constituents are silicate and carbonaceous substances. When the comet
came close to Earth in 1986, it was discovered that the comet has rotated once
around its axis in 7.4 earth-day. At this time, various spacecraft took
pictures of the comet, in which only 25 percent of surface came to light. By
analyzing this little image, scientists can understand that this comet has
mountains, valleys, craters all like our earth. By analyzing its density,
scientists have come to the conclusion that the center of the comet is made up
of more than one small piece of loose matter. As the comet moves closer to the
sun, the length of its tail increases. In the case of Haley's comet, this
bright tail is made up of carbon dioxide, carbon monoxide, water vapor, and
other substances that can travel from 1,00,00,000 km to 10,00,00,000 km, and
contains a maximum of 80 percent water vapor. Apart from this tail, as the
comet moves towards the sun, another tail is formed this is ion-tail due to ion
particles of sun.
When
Haley's comet appeared in the Earth's sky in 1986, the comet's shortest
distance from Earth was 6,30,00,000 km and the date was 11th April 1986. During
this time many space agencies from different countries of the world launched a
number of observational spacecraft to observe the comet. Notable among them was
Sakigake and Suisei of the Japan Space Research Organization (JEXA), Vega-1 and
Vega-2 made by the Russian Space Research Organization (Roscosmos) and Geotto
of the European Space Research Organization (ESA). The Vega and Geotto
spacecraft have given us the most information about comets. The Giotto
spacecraft made its flyby over the comet from the distance of 596 km. (Flyby:
In the terminology of space science, the shortest distance an observer passes
over a planet, satellite, comet or asteroid).
At
present, Haley's comet is not visible from the earth and its position is not
close to the earth, but our eyes are always fixed on it. Now the comet is out
of Neptune's orbit and will gradually move away from the sun in the next two
years, touching the orbit of Pluto and will start moving towards the Sun again
from 2023. In this way, on July 26, 2061, Halley's Comet will come closest to
the sun. However, a few days before and after the comet from the earth's sky
will be seen quite bright and clear. Earthlings will then witness again this
cosmic event around 27th March 2134.
Of
course, Halley's Comet will not continue to appear in the earth's sky in this
way for ages to increase the curiosity of scientists from ordinary people. The
eminent British astronomer David Hughes has concluded from his long research
that the central part of Halley's Comet has shrunk the most in the last 2,000
to 3,000 years, and that it has been extremely rapid. During this time the
original size of the comet was reduced by 80 to 90 percent. If this kind of
pace continues in nature, then the fate of Haley's comet awaits any one of
three possible consequences. First, the comet might completely evaporate within
a few thousand years and disappear from the solar system. Second, it would
split into two or more smaller fragments, or third, the final result may be
that millions of years later, due to natural cause, the speed of the comet will
increase and it will fall out of the solar system forever and go to an unknown
destination.
Today
we know that in the coming days our earth will have no existence, the solar
system will change radically and finally the life of the sun will also come to
an end. So thousands of comets in this solar system will disappear due to
natural causes, which is a very natural phenomenon and they were visible from
the earth during their lifetime when they accidentally came close to the earth
as they rotated around the sun. There are no abnormalities or miracle in it. So
there is no scientific basis for raising the issue of good luck or bad luck
with the sight of a comet. Therefore, with the proper management of all the
cosmic events those are happening or will happen in the future, to get rid of
all these unscientific, unrealistic, bizarre imaginary thoughts, to know the
unknown with an open mind, to know science and to experience the unearthly
cosmic beauty we should try to observe deeply and find out the reason.
DECLARATION:
All The Images Have Been Sourced From Google.
