Lesson 1.3

Question 1

● This indicates that stars originate from interstellar gas and dust.

Answer 1

Nebular Theory

Question 2

● There are three major steps on how the solar system was formed according to nebular
theory

Answer 2

○ cloud collapse,
○ formation of the protoplanetary disk,
○ and the growth of planets.

Question 3

Cloud Collapse

Answer 3

● The origin of the planets and sun in the solar system is a huge cloud of molecular gas
and dust. Then, something occurred that made the cloud collapse.
● Possible reasons are shockwaves from a supernova or the effect of a passing star.
● Whatever the reason, the result was a collapse at the center of the cloud due to gravity.
● In relation to the nebular theory, the collapsed cloud of interstellar gas and dust results in
a smaller radius which means it will spin faster.
● This resulted in a flattened disk of cloud with a central bulge.

Question 4

Formation of Protoplanetary Disk

Answer 4

Formation of Protoplanetary Disk
● Metals and silicates could exist near the sun because these compounds have higher
boiling points.
● As a result, terrestrial planets including Mercury, Venus, Earth, and Mars were eventually
formed containing a high concentration of these compounds.
● The terrestrial planets could not grow in huge diameters because of the limited reserve
of metallic elements in the solar nebula.
● Jovian planets composed of Jupiter, Saturn, Uranus, and Neptune are huge planets
made up of gasses without land surfaces.
● These planets were formed farther from the sun because the temperature is cool enough
for the gasses to condense, forming these massive, but low-density planets.

Question 5

terrestrial planets including

Answer 5

Mercury, Venus, Earth, and Mars

Question 6

_______ could not grow in huge diameters because of the limited reserve
of metallic elements in the solar nebula.

Answer 6

terrestrial planets

Question 7

Jovian planets composed of _____ are huge planets
made up of gasses without land surfaces.

Answer 7

Jupiter, Saturn, Uranus, and Neptune

Question 8

Growth of Planets

Answer 8

● dust and grains surrounding the sun eventually formed clumps. These clumps then
accreted forming planetesimals.
● Planetesimal is a small celestial body that once collides together, it tends to fuse to form
the planets of the solar system.

Question 9

is a small celestial body that once collides together, it tends to fuse to form
the planets of the solar system.

Answer 9

Planetesimal

Question 10

Proponents of the Nebular Theory

Answer 10

The nebular theory is credited to Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon
Laplace.

Question 11

proposes that the planets were formed from the material ejected
from the sun during an encounter with another celestial object.

Answer 11

encounter theory

Question 12

Encounter Theory ● This celestial object could have been another ___.

Answer 12

star

Question 13

The encounter theory has several forms, including the

Answer 13

planetesimal theory and the tidal
theory.

Question 14

1. Planetesimal Theory

Answer 14

a. According to the planetesimal theory, a passing star termed an intruding star
nearly collided with the protosun.
b. The massive gravitational pull of the intruding star causes the protosun to eject
filaments of material.
c. These materials condensed into planetesimals from which the planets were
formed through accretion.

Question 15

a passing star termed an ____

Answer 15

intruding star

Question 16

Unlike the nebular theory which describes Earth starting from ___ , the
planetesimal theory describes Earth starting from a solid mass smaller
than its present size.

Answer 16

molten mass

Question 17

Unlike the nebular theory which describes Earth starting from molten mass, the
planetesimal theory describes Earth starting _______

Answer 17

from a solid mass smaller
than its present size.

Question 18

The oceans and the atmosphere were formed on Earth through

Answer 18

volcanic activities.

Question 19

he planetesimal theory was proposed by an American geologist ____, and an American astronomer ____ in ___.

Answer 19

Thomas Chrowder Chamberlain
Forest Ray Moulton
1905.

Question 20

The initial phase of the Sun is called the ___
and it was stationary and rotated on its axis.

Answer 20

Primitive Sun:

Question 21

stationary and rotated on its axis.

Answer 21

Primitive Sun

Question 22

It was much larger in size than the primordial Sun.

Answer 22

Intruding Star: