Samriddhi Mathur
Friday, 26 December 2014
Some information on : The Sun
Introduction:
The sun lies
at the heart of the solar system, where it is by far the largest object.
It holds 99.8 percent of the solar system's mass and is roughly 109 times the
diameter of the Earth — about one million Earths could fit inside the sun.
The visible
part of the sun is about 10,000 degrees Fahrenheit (5,500 degrees Celsius),
while temperatures in the core reach more than 27 million F (15 million C),
driven by nuclear reactions. One would need to explode 100 billion tons of dynamite
every second to match the energy produced by the sun, according
to NASA.
The sun is
one of more than 100 billion stars
in the Milky Way. It orbits some 25,000 light-years from the galactic
core, completing a revolution once every 250 million years or so. The sun is
relatively young, part of a generation of stars known as Population I, which
are relatively rich in elements heavier than helium. An older generation of
stars is called Population II, and an earlier generation of Population III may
have existed, although no members of this generation are known yet.
Formation & evolution:
The sun was
born about 4.6 billion years ago.
Many scientists think the sun and the rest of the solar system formed from
a giant, rotating cloud of
gas and dust known as the solar nebula. As the nebula collapsed because of its
gravity, it spun faster and flattened into a disk. Most of the material was
pulled toward the center to form the sun.
The sun has
enough nuclear fuel to stay much as it is now for another 5 billion years.
After that, it will swell to become a red giant. Eventually, it will shed its
outer layers, and the remaining core will collapse to become a white dwarf.
Slowly, this will fade, to enter its final phase as a dim, cool theoretical
object sometimes known as a black dwarf.
Internal structure and atmosphere:
The sun and
its atmosphere are divided into several zones and layers. The solar interior,
from the inside out, is made up of the core, radiative zone and the convective
zone. The solar atmosphere above that consists of the photosphere,
chromosphere, a transition region and the corona. Beyond that is the solar wind, an outflow of gas from the
corona.
The core
extends from the sun's center to about a quarter of the way to its surface.
Although it only makes up roughly 2 percent of the sun's volume, it is almost
15 times the density of leadand holds nearly half of the sun's mass. Next is
the radiative zone, which extends from the core to 70 percent of the way to the
sun's surface, making up 32 percent of the sun's volume and 48 percent of its
mass. Light from the core gets scattered in this zone, so that a single photon
often may take a million years to pass through.
The
convection zone reaches up to the sun's surface, and makes up 66 percent of the
sun's volume but only a little more than 2 percent of its mass. Roiling
"convection cells" of gas dominate this zone. Two main kinds of solar
convection cells exist — granulation cells about 600 miles (1,000 kilometers)
wide and supergranulation cells about 20,000 miles (30,000 kilometers) in
diameter.
Chemical composition:
Just like
most other stars, the sun is made up mostly of hydrogen, followed by helium.
Nearly all the remaining matter consists of seven other elements — oxygen,
carbon, neon, nitrogen, magnesium, iron and silicon. For every 1 million atoms
of hydrogenin the sun, there are 98,000 of helium, 850 of oxygen, 360 of
carbon, 120 of neon, 110 of nitrogen, 40 of magnesium, 35 of iron and 35 of
silicon. Still, hydrogen is the lightest of all elements, so it only accounts
for roughly 72 percent of the sun's mass, while helium makes up about 26
percent.
Friday, 31 October 2014
THE ADDRESS
I read the story 'The Address' it’s a story about Mrs S’s
daughter who after the war, comes back to Mrs Dorling’s house to take her mother’s
belongings back. But she decides to
leave them all behind and resolves to move on. I really liked the story, its
very emotional and sensitive and tells about the destructions caused by the
wars.
ALBERT EINSTEIN AT SCHOOL
I read the story 'Albert Einstein at school' by Patrick
Pringle. It’s a story which describes the childhood of sir Einstein.The writer
also talked about sir Einstein’s friend Yuri who helped him to get a doctor who
can give him a certificate in which Einstein has a nervous breakdown and cannot
go to school for 6 months will be written. I think everybody wishes to have
such a loyal and honest friend in their life.
RANGA'S MARRIAGE
I read the story ‘Ranga’s Marriage’ by Mast Venkatesha Iyengar. I liked the start of the
story when writer talks about the village Hosahalli and the mangoes. Ranga is
the accountant’s son, he is the one of the rare people in the village who went
to city to pursue their studies and knows English. His ideas about marriage were
quite different than the thoughts of villagers. But finally he marries to
Ratana. I liked that inspite of his leaving the village Ranga did’nt
forget his values.
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