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1. Origin of the solar system
1. A cloud of interstellar gas and/or dust (the "solar nebula") is disturbed and collapses
under its own gravity. The disturbance could be, for example, the shock wave from a
nearby supernova.
2. As the cloud collapses, it heats up and compresses in the center. It heats enough for the
dust to vaporize. The initial collapse is supposed to take less than 100,000 years.
3. The center compresses enough to become a protostar and the rest of the gas orbits/flows
around it. Most of that gas flows inward and adds to the mass of the forming star, but the
gas is rotating. The centrifugal force from that prevents some of the gas from reaching the
forming star. Instead, it forms an "accretion disk" around the star. The disk radiates away
its energy and cools off.
4. First brake point. Depending on the details, the gas orbiting star/protostar may be
unstable and start to compress under its own gravity. That produces a double star. If it
doesn't ...
5. The gas cools off enough for the metal, rock and (far enough from the forming star) ice to
condense out into tiny particles. (i.e. some of the gas turns back into dust). The metals
condense almost as soon as the accretion disk forms (4.55-4.56 billion years ago
according to isotope measurements of certain meteors); the rock condenses a bit later
(between 4.4 and 4.55 billion years ago).
6. The dust particles collide with each other and form into larger particles. This goes on
until the particles get to the size of boulders or small asteroids.
7. Run away growth. Once the larger of these particles get big enough to have a nontrivial
gravity, their growth accelerates. Their gravity (even if it's very small) gives them an
edge over smaller particles; it pulls in more, smaller particles, and very quickly, the large
objects have accumulated all of the solid matter close to their own orbit. How big they
get depends on their distance from the star and the density and composition of the
protoplanetary nebula. In the solar system, the theories say that this is large asteroid
to lunar size in the inner solar system, and one to fifteen times the Earth's size in the outer
solar system. There would have been a big jump in size somewhere between the current
orbits of Mars and Jupiter: the energy from the Sun would have kept ice a vapor at closer
distances, so the solid, accretable matter would become much more common beyond a
critical distance from the Sun. The accretion of these "planetesimals" is believed to take a
few hundred thousand to about twenty million years, with the outermost taking the
longest to form.
8. Two things and the second brake point. How big were those protoplanets and how
quickly did they form? At about this time, about 1 million years after the nebula cooled,
the star would generate a very strong solar wind, which would sweep away all of the gas
left in the protoplanetary nebula. If a protoplanet was large enough, soon enough, its
gravity would pull in the nebular gas, and it would become a gas giant. If not, it would
remain a rocky or icy body.
9. At this point, the solar system is composed only of solid, protoplanetary bodies and gas
giants. The "planetesimals" would slowly collide with each other and become more
massive.
10. Eventually, after ten to a hundred million years, you end up with ten or so planets, in
stable orbits, and that's a solar system.

2. "Parts" of the Sun
The solar interior includes the core, radiative zone and convective zone. The photosphere is the
visible surface of the Sun. The solar atmosphere includes the chromosphere and corona.
Credit: SOHO (ESA & NASA)
What are the "parts" of the Sun? Scientists who study the Sunusually divide it up into three
main regions: the Sun's interior, the solar atmosphere, and the visible "surface" of the Sun
which lies between the interior and the atmosphere.
There are three main parts to the Sun's interior: the core,the radiative zone, and the convective
zone. The core is at the center. It the hottest region, where the nuclear fusion reactions that
power the Sun occur. Moving outward, next comes the radiative (or radiation) zone. Its name is
derived from the way energy is carried outward through this layer, carried by photons as
thermal radiation. The third and final region of the solar interior is named the convective (or
convection) zone. It is also named after the dominant mode of energy flow in this layer; heat
moves upward via roiling convection, much like the bubbling motion in a pot of boiling
oatmeal.
The boundary between the Sun's interior and the solar atmosphere is called the photosphere. It
is what we see as the visible "surface" of the Sun. The photosphere is not like the surface of a
planet; even if you could tolerate the heat you couldn't stand on it.
Did you know that the Sun has an atmosphere? The lower region of the solar atmosphere is called
the chromosphere. Its name comes from the Greek root chroma (meaning color), for it appears
bright red when viewed during a solar eclipse. A thin transition region, where temperatures rise
sharply, separates the chromosphere from the vast corona above. The uppermost portion of the
Sun's atmosphere is called the corona, and is surprisingly much hotter than the Sun's surface
(photosphere)! The upper corona gradually turns into the solar wind, a flow of plasma that moves
outward through our solar system into interstellar space. The solar wind is, in a sense,just an
extension of the Sun's atmosphere that engulfs all of the planets. Earth actually orbits within the
atmosphere of a star!

3. What is moon ?
The Moon is an astronomical body that orbits planet Earth, being Earth's only permanent natural
satellite.
Phases ofthe Moon
The phases of the Moon are the different ways the Moon looks from Earth over about a month.
As the Moon orbits around the Earth, the half of the Moon that faces the Sun will be lit up. The
different shapes of the lit portion of the Moon that can be seen from Earth are known as phases of
the Moon. Each phase repeats itself every 29.5 days.
The same half of the Moon always faces the Earth, so the phases will always occur over the same
half of the Moon's surface
There are 8 phases that the moon goes through.
 A new moon is when the Moon cannot be seen because we are looking at the unlit half of the
Moon. The new moon phase occurs when the Moon is directly between the Earth and Sun.
A solar eclipse can only happen at new moon.
 A waxing crescent moon is when the Moon looks like crescent and the crescent increases
("waxes") in size from one day to the next. This phase usually is only seen in the west.
 The first quarter moon (or a half moon) is when half of the lit portion of the Moon is visible after
the waxing crescent phase.
 A waxing gibbous moon occurs when more than half of the lit portion of the Moon can be seen
and the shape increases ("waxes") in size from one day to the next. The waxing gibbous phase
occurs between the first quarter and full moon phases.
 A full moon is when we can see the entire lit portion of the Moon. The full moon phase occurs
when the Moon is on the opposite side of the Earth from the Sun, called opposition. A lunar
eclipse can only happen at full moon.
 A waning gibbous moon occurs when more than half of the lit portion of the Moon can be seen
and the shape decreases ("wanes") in size from one day to the next. The waning gibbous phase
occurs between the full moon and third quarter phases.
 The last quarter moon (or a half moon) is when half of the lit portion of the Moon is visible after
the waning gibbous phase.
 A waning crescent moon is when the Moon looks like the crescent and the crescent decreases
("wanes") in size from one day to the next.
"Blue moonA second full moon in one calendar month is usually called a "blue moon" and this
occurs approximately every 3 years. The saying "Once in a blue moon" refers to something that
does not happen often (like a blue moon.)

4. ECLIPSE
An eclipse is an astronomical event that occurs when an astronomical object is temporarily
obscured, either by passing into the shadow of another body or by having another body pass
between it and the viewer. This alignment of three celestial objects is known as a syzygy.[1]
Apart
from syzygy, the term eclipse is also used when a spacecraft reaches a position where it can
observe two celestial bodies so aligned. An eclipse is the result of either an occultation (completely
hidden) or a transit (partially hidden).
The term eclipse is most often used to describe either a solar eclipse, when the Moon's shadow
crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the Earth's shadow.
However, it can also refer to such events beyond the Earth–Moon system: for example, a planet
moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its host
planet, or a moon passing into the shadow of another moon. A binary star system can also produce
eclipses if the plane of the orbit of its constituent stars intersects the observer's position.
For the special cases of solar and lunar eclipses, these only happen during an "eclipse season", the
two times of each year when the plane of the Earth's orbit around the Sun crosses with the plane of
the Moon's orbit around the Earth. The type of solar eclipse that happens during each season
(whether total, annular, hybrid, or partial) depends on apparent sizes of the Sun and Moon (which is
a function of the elliptical distance in the Earth from the Sun and the Moon from the Earth,
respectively, as seen from the Earth's surface). If the orbit of the Earth around the Sun, and the
Moon's orbit around the Earth were both in the same plane with each other, then eclipses would
happen each and every month. There would be a lunar eclipse at every full moon, and a solar
eclipse at every new moon. And if both orbits were perfectly circular, the each solar eclipse would be
the same type every month. It is because of the non-planar and non-circular differences that eclipses
are not a common event. Lunar eclipses can be viewed from the entire nightside half of the Earth.
But solar eclipses, particularly a total eclipse, as occurring at any one particular point on the Earth's
surface, is a rare event that can span many decades from one to the next.