According to the nebular hypothesis: - The Sun and planets formed from a giant cloud of dust and gas that collapsed due to some event around 4.57 billion years ago. - As the cloud collapsed and began rotating faster, it flattened into a disk with the Sun forming at the center. - The terrestrial planets like Earth formed closer to the Sun from metals and rocks, while the gas giants formed beyond the frost line where ices could also form, allowing them to grow larger. - Leftover debris that did not form planets remains in regions like the Asteroid Belt and Kuiper Belt today.

2. • Provide the scientific explanation
for the origin of the Universe and
the elements in it
• describe how the Earth formed
according to the nebular theory
• create a model of the basic
internal layers of the earth

3. any massive self-luminous
celestial body of gas that
shines by radiation
derived from its internal
energy sources

4. either of two general
types of stellar
assemblages held
together by the mutual
gravitational attraction of
its members

6. • also known as galactic clusters,
do not have a distinct shape;
• their stars are loosely clustered
together in an amorphous
gravitationally bound group.

7. • globular clusters look like faint
smudges of light against the
darkness of space.
• But a telescope reveals their true
form: thousands to millions of
stars form a spherical shape with
a bright, dense core.

8. Galaxies are vast cosmic
islands of stars, gas, dust,
and dark matter held
together by gravity.

9. • ELLIPTICAL
• SPIRAL
• IRREGULAR

10. ELLIPTICALS
account for about
one-third of all
galaxies, vary from
nearly circular to very
elongated
possess
comparatively little
gas and dust, contain
older stars and are
not actively forming
stars anymore

11. SPIRALS
appear as flat, blue-
white disks of stars,
gas and dust with
yellowish bulges in
their centers
divided into two
groups: normal
spirals and barred
spirals

12. IRREGULARS
have very little dust,
are neither disk-like
nor elliptical
These galaxies are
abundant in the
early universe,
before spirals and
ellipticals
developed

13. • A planet is a celestial body that:
⚬ (a) is in orbit around the Sun,
⚬ (b) has sufficient mass for its self-gravity to overcom
rigid body forces so that it assumes a hydrostatic
equilibrium (nearly round) shape, and
⚬ (c) has cleared the neighborhood around its orbit.

14. • A "dwarf planet" is a celestial body that
⚬ (a) is in orbit around the Sun,
⚬ (b) has sufficient mass for its self-gravity to overcome
rigid body forces so that it assumes a hydrostatic
equilibrium (nearly round) shape,
⚬ (c) has not cleared the neighborhood around its orbit,
⚬ (d) is not a satellite.

15. • All other objects, except satellites, orbiting
the Sun shall be referred to collectively as
"Small Solar System Bodies".

16. Our planetary system is
located in an outer spiral
arm of the Milky Way
galaxy.

17. There are many planetary systems like ours in the
universe, with planets orbiting a host star. Our planetary
system is called “the solar system” because we use the
word “solar” to describe things related to our star, after
the Latin word for Sun, "solis."

19. • speculates that the Universe
goes through repeated cycles of
the big bang and subsequent
expansions
• ‘big bang’ was not the
beginning of the Universe but
rather a transition phase

20. • A study conducted by a group
of researchers in 2013
speculated that our Universe
might have originated from the
debris spewed out of a
collapsed four-dimensional star
or a black hole.

21. • The plasma cosmology (or
plasma universe theory)
speculates that electromagnetic
forces and plasma play a much
more important role in the
Universe instead of gravity.

22. • the basic idea is that the
Universe has no beginning
and no future. Instead of
a hot Big Bang, the theory
advocates for a cold and
slowly evolving Universe.

23. • the Universe follows an infinite cyclic
model. It means that our current Universe
will be replaced by an endless number of
universes.
• Each iteration of the Universe is divided
into two phases, ‘Kalpa’ (or the day of
Brahma) and ‘pralaya’ (the night of
Brahma), and each is 4.32 billion years
long.

24. • asserts that the observable Universe
remains the same at any place and
time. In the Universe, which is
forever expanding, matter is
continuously created to fill the
space.

25. • the universe as we know it started
with an infinitely hot and dense
single point that inflated and
stretched — first at unimaginable
speeds, and then at a more
measurable rate — over the next
13.8 billion years to the still-
expanding cosmos that we know
today

29. According to this theory, the
Sun and all the planets of our
Solar System began as a giant
cloud of molecular gas and
dust.
Then, about 4.57 billion
years ago, something
happened that caused the
cloud to collapse.

30. From this collapse, pockets of
dust and gas began to collect
into denser regions.
as the denser regions pulled in
more and more matter,
conservation of momentum
caused it to begin rotating,
while increasing pressure
caused it to heat up

31. Most of the material ended
up in a ball at the center while
the rest of the matter
flattened out into disk that
circled around it.
While the ball at the center
formed the Sun, the rest of the
material would form into the
protoplanetary disc.

33. Due to their higher boiling
points, only metals and silicates
could exist in solid form closer
to the Sun, and these would
eventually form the terrestrial
planets of Mercury, Venus,
Earth, and Mars.
The planets formed by
accretion from this disc, in
which dust and gas
gravitated together and
coalesced to form ever larger
bodies.

34. Because metallic elements only
comprised a very small fraction
of the solar nebula, the
terrestrial planets could not
grow very large.

35. The giant planets (Jupiter,
Saturn, Uranus, and Neptune)
formed beyond the point
between the orbits of Mars
and Jupiter where material is
cool enough for volatile icy
compounds to remain solid (i.e.
the Frost Line)

36. The ices that formed these
planets were more plentiful
than the metals and silicates
that formed the terrestrial
inner planets, allowing them
to grow massive enough to
capture large atmospheres of
hydrogen and helium.

37. Leftover debris that never
became planets congregated
in regions such as the
Asteroid Belt, Kuiper Belt,
and Oort Cloud