Many a time teachers and students of science
complain about lack of laboratory and learning resources. However night sky is
a fantastic laboratory and teaching learning resource freely available to all
of us. It is this laboratory which was used to a great extent by pioneers like
Aryabhatta, Aristarchus, Hypatia, Galileo,
Caroline Herchel, Tyco Brahe, Johannes Kepler, Halley and others. Many spectacular celestial events
occur regularly which gives learners an opportunity to observe, enjoy and
learn. Few recent magnificent astronomical events being the total solar eclipse
of year 2009 and the transit of Venus of year 2012. Planetary Superconjunctions
are rare astronomical events. Lunar and annular eclipses and super moon are
other regular important celestial events to watch. However nothing can match
the beauty of a comet. The arrival of the comet ISON into our horizon in late
November this year provided us an exciting opportunity to gear towards
involving children on a massive scale in a campaign to track the comet, and
participate in the unravelling of its progression towards the Sun. Further,
tracking the comet, which was visible in the early morning sky November 2013
onwards, served to excite and inspire
all curious beholder of nature. Comets are dirty snow ball made out of dust and
ice. The word "comet" comes from the Greek word for "hair.
Newton discovered that comets move in elliptical orbits around the Sun. He also
thought that comets were members of the Solar System, just like planets, and
that they could return over and over again. The appearance of comets became
predictable after Halley, an English scientist correctly predicted the
reappearance of the comet seen in 1683. Using the newly developed gravitational
theory of Newton, he predicted that this comet would return in 1758. The comet
indeed came as predicted and named as Halley’s comet. Comets come from two
places: The Kuiper Belt and the Oort Cloud. Comets are the most primitive
objects in the Solar System. Many scientists think that they have kept a record
of the physical and chemical processes that occurred during the early stages of
the evolution of our Sun and Solar System. A comet is an irregular body,
assembled from millimetre sized dust grains coated heavily with ices. This is
the nucleus of a comet. The most prominent ice is water ice, followed by carbon
dioxide ice, ammonia ice and methane ice. The dust and the ices are so loosely
held together that a comet has only the strength of a biscuit! Comets are named
after the observers who spot them first and report to a central agency. If two
observers spot them on the same night, it is named after both of them. Most
comets are observed by amateur astronomers. Vainu Bappu discovered a comet in a
routine photograph he was examining as a student. This comet was named Bappu -
Newkirk – Whipple. About twenty comets are seen by telescopes every year. About
5 to 7 may be new ones while others have been seen before. Of the comets
detected every year only 1 or 2 reach naked eye visibility. Comets are the
oldest and least processed bodies orbiting the Sun and therefore constitute a
unique source of knowledge about the birth and early evolution of our Solar
System. Asteroids, comets and other cosmic debris have also had a fundamental
impact on the development of planet Earth and the life on it, by bombarding it
periodically. Comets colliding with the early Earth may have seeded our world
with the chemicals necessary for life to begin. The icy nature of the comets
almost certainly contributed to the quota of water that now exists in Earth’s
oceans.
Comet ISON (C/2012 S1) was discovered by Eastern European and Russian
astronomers on September 24, 2012 using
the facilities of International Scientific Optical Network (ISON). Comet ISON swung close by the Sun at the end of November
and was expected to climb up the dawn sky in December. The comet performed remarkably close Sun graze at its perihelion on November 28th. It flew less than one solar diameter past the
Sun’s surface, with the dusty ice of its nucleus broiling violently. Astronomers
tracking the “comet of the century” last night believed it had flown too close
to the sun and had broken up. All the evidence suggests Ison's nucleus was torn
apart in the close pass, in the same way that Comet Lovejoy was disrupted.Now
it would not be visible by naked eye. Professional astronomers are trying to
track the fragments with a telescope. Just before performing Sun graze it was
observed by my friend Mr. Kulwant Singh an amateur astronomer from rural
Punjab. I don’t know whether anybody was lucky in our state.
Comets will stay in the news, however. Next
year, in October, Comet Siding Spring (C 2013 A1) will breeze past Mars at a
distance of little more than 100,000km. Our spacecraft Mangal yaan will
arrive at Mars one month before the comet's closest approach. And then in
November, the European Space Agency's Rosetta mission will attempt to place a
probe on the nucleus of Comet 67P/Churyumov-Gerasimenko.
