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Outer Space
An E-Book by Peri Michael and Steven Piselli
Massachusetts Academy of Math and Science
Table of Contents
The Universe
Page 2
The Big Bang Theory
Page 3
Page 4
Page 5
The Solar System
Page 6
Page 7
Page 10
Page 11
Page 12
Black Holes
Page 13
Page 14
Page 15
Page 18
Image Credits
Page 20
About the Authors
Page 21
The Universe
The Universe is the biggest thing that scientists know
to exist. It goes on forever in every direction while
constantly growing. The universe contains the celestial
bodies that make up space, such as solar systems,
galaxies, stars, and nebulae. Some organize space into
a hierarchy of bodies, with the universe as the top, or
largest system. The order is typically planets, solar
systems, galaxies, galaxy clusters, and the universe.
Sometimes the space part of the hierarchy is included
in a longer list that starts with things as small as
The Big Bang Theory
The Big Bang Theory is the common theory of how
the universe was created. Scientists cannot prove that
the universe was created this way, but the vast
majority accept the Big Bang. They also do not know
what was there before the universe was made, or if
there really was anything at all. The Big Bang Theory
says that our universe started out as an extremelyinfinitely- small, dense, and hot object, or what
scientists call a “singularity”.
Over time, it grew bigger
and cooler. It expanded
out and became less
dense and hot. The Big
Bang was not one huge
explosion, but rather an
event that occurred over time. Scientists believe that
the universe continues to expand and get cooler even
today. Everything in the universe moves away from
everything else constantly because the universe
expands like a sponge.
In our solar system, everything revolves around the
sun. The sun is so large that it pulls everything around
it in because of gravity. Gravity occurs when an object
attracts another because of their masses. Very large
objects, such as those in space, have a gravitational
pull on other objects.
On Earth, gravity is
what keeps everything
on the ground, such as
people, buildings, and
the oceans.
It also keeps the moon and the
atmosphere around the Earth. Weight
Gravity is like
depends on the gravity at some
the glue of the
location, but mass does not because it
universe! It is
only measures amount of matter. A
the reason
rock with a certain mass on Earth has
everything stays
different weights on different planets
because of different accelerations of
Inertia keeps all objects in the universe moving
because objects in motion stay in motion. While
gravity pulls space objects toward the sun, inertia
makes them fly outward; when gravity pulls objects in,
inertia keeps them moving away. All celestial bodies
will keep moving until a force stops them.
Law of Inertia
Sir Isaac Newton’s First
Law of Motion, the law
of inertia, states that all
objects at rest stay at
rest and objects in
motion stay in motion
until a force changes
their movement.
The balance between gravity and inertia makes
planets and other celestial bodies stay in their orbits.
Gravity and inertia work together to keep all of the
planets around the sun and solar systems around the
The Solar System
Within the universe there are groups of space objects
called solar systems. A Solar System is a collection of
planets that orbit around a central gravitational
source. This source can be one or even two stars.
Others objects in the solar system include asteroids,
meteoroids, and comets.
In our solar system, there are eight planets that
revolve around the sun, which is a star.
Planets are large bodies made of either rock or gas
that orbits a star. Celestial bodies in our solar system
need to meet several requirements for scientists to
consider them planets. They need to orbit the sun, be
spherical in shape because of their own gravitational
pull, and clear their orbital path. That’s an expression
that means if the object really is a planet, over time it
would have either attracted any smaller solar bodies
and debris in its path of orbit, or have pushed them
The planets are
grouped into three
Terrestrial, Gaseous,
and Dwarf.
Our solar system has eight planets, which excludes
Pluto because it is actually a dwarf planet.
A Terrestrial Planet is a planet that is made of rock. Its
core usually consists of a molten metal. They are made
from the dust produced by a recently exploded star
over the span of billions of years. Terrestrial planets
can have features such as canyons, volcanoes,
mountains, and valleys.
Earth is the most common example of a terrestrial
planet. The Earth is the only planet in our solar system
that can support life. The other three inner planetsMercury, Venus, and Mars- are also terrestrial planets.
Gaseous Planets are planets made mostly of gases.
They also have metal or rock cores. The outer ring
planets of our solar system are gaseous planets.
Gaseous planets form over billions of years from the
condensing gases of a nebula.
The gaseous planets in our solar system, also called
the Gas Giants, are the outer planets: Jupiter, Saturn,
Uranus, and Neptune. Uranus and Neptune are also
known as the Ice Giants because they mostly consist of
ice and other gaseous chemicals.
Dwarf Planets are similar to
terrestrial planets but are
not large enough to clear
all the space debris around
them. There are currently
five known dwarf planets:
Ceres, Pluto, Haumea,
Makemake, and Eris.
Pluto is a dwarf planet. It
was discovered in 1930
and was thought to be a
terrestrial planet, but
when scientists looked
back at it in 2006, they
They then demoted it to a
dwarf planet.
Asteroids are large chunks of space rock that orbit
around the sun. They are not big enough to be moons
or planets. Their size can range from the size of dust
particles to around 600 miles across.
In our solar system, there are two large rings orbiting
the sun. These Asteroid Belts are large collections of
asteroids that orbit the sun. The first belt is between
the planets Mars and Jupiter. All of the planets inside
the belt are known are inner planets. The planets
outside of the belt are called outer planets. The second
belt starts after passing Neptune. When an asteroid
enters the Earth’s atmosphere it becomes a
Comets are large bodies made of ice and space dust.
Because their orbits are ovular, comets “grow” a tail
when they get closer to the sun.
Halley’s Comet
Halley’s Comet is
the most wellknown comet. It is
visible from Earth
by the naked eye
and passes by
every 75-76 years.
As the comet moves away from
the sun, the tail shrink and the
comet refreezes into a giant ball
of ice. Because of the large
distances comets travel, they are
only seen periodically.
Galaxies are clusters of stars, planets, and solar
systems revolving around a single black hole. The
galaxy our solar system is in is called the Milky Way
Galaxy. It contains about 400 billion stars and is just
under 100,000 light years wide. A Light Year is the
distance that light travels in one calendar year. That is
approximately 9.460 quadrillion meters, so our solar
system is 946.07 quintillion meters wide.
Galaxies can attract each
other to form what are
known as Galaxy Clusters.
They can contain up to 1,000
galaxies bound together by
A large portion of these clusters is dark matter. Dark
matter is what scientists believe makes up most of the
universe. It does not absorb light or radiation so
telescopes cannot see it; however, astronomers
speculate that dark matter has gravitational effects on
visible matter.
Black Holes
A Black Hole is an extremely dense region of space
where the gravity is so high that no light can escape.
Black holes are often located at the centers of
galaxies. They are created from densely compact
stars after their life as normal stars finishes. The
gravitational force that black holes create is strong
enough to hold billions of billions of stars and planets
in a very large range that can be over 10,000 light
years in diameter. Really large black holes are
classified as Supermassive Black Holes.
Some of the most beautiful structures in the universe
are nebulae. Nebulae are large clouds of cosmic dust,
hydrogen, helium, and gases. They occur after a star
explodes in a supernova. After billions of years, the
gravitational forces acting on the nebula would pull it
all back together resulting the creation of a star or
Planetary Nebulae are
clouds made mostly of
hydrogen that surrounds
really hot stars such as
white dwarfs, red giants,
and supergiants.
They are more dense than the common nebulae made
from an exploding supernova.
A Stellar Nursery is a nebula where stars are forming.
They often have lots of ultraviolet (UV) light because
of the stars forming inside.
Stars are giant balls of gas that produce light when
they burn. Much like people and animals, stars have
life cycles, but their life spans are much longer. All
stars are born from nebulae. Many stars seen from
Earth are Main Sequence Stars, which are stars in the
middle of their life. Gravity holds together the gases
that make up the stars. They have a nuclear fusion
process where hydrogen atoms become helium atoms
and energy makes light and heat.
Stars become Supergiants, or Red Giants, when they
start to burn out. The stars are much cooler than they
were before. When stars burn out, they usually
explode and turn into a white dwarf, neutron star, or
black hole.
A Supernova is a giant
explosion created by a dying
star. As the star starts to
decay, the outer shell grows
larger and larger. The core of
the star cannot hold the rest
of it together.
The star then violently explodes, and the burning
gases shoot across space. The supernova releases
about the amount of energy that our sun will produce
in its entire lifetime.
Not all stars become a
supernova. The star
has to have enough
mass to expand, which
is about the mass of 1.4
of our suns.
White Dwarfs are the cores of remaining stars after a
supernova explosion. The mass that a white dwarf has
is about the same as the mass of our sun. However,
the density is high so the star is about the same size as
Earth. Eventually, even white dwarfs burn out and
become black dwarfs.
When a huge star about 8 times the mass of our sun
explodes, the result is usually a Neutron Star or a
black hole.
With either type of star, the supernova also creates
cosmic dust, which forms a nebula. In ten thousand
years, the nebula will form a new star.
Asteroid Belt- a large collection of asteroids
Asteroids- a large chunk of space rock that orbits
around the sun
Big Bang Theory- the common theory of how the
universe was created, which says that the universe
expands from a point
Black Hole- an extremely dense region of space where
the gravity is so high that no light can escape
Comet- a large body made of ice and space dust
Dwarf Planet- a planet that is not large enough to
clear all the space debris in its orbit
Galaxy- a cluster of stars, planets, and solar systems
revolving around a black hole
Galaxy Cluster- a group of galaxies
Gaseous Planet- a planets made of mostly gases
Gravity- when an object attracts another because of
their masses
Inertia- objects in motion stay in motion
Meteoroid- an asteroid that enters the Earth’s
Nebula- a large cloud of cosmic dust, hydrogen,
helium, and other gases
Neutron Star- a result of a explosion of a huge star,
formed in the core of the supernova
Planetary Nebula- a cloud made mostly of hydrogen
that surrounds really hot stars
Planet- a large body made of either rock or gas that
orbits a star
Solar System- a collection of planets that orbit around
a central gravitational source
Star- a giant ball of gas that produces light when it
Stellar Nursery- a nebula where stars are forming
Supermassive Black Hole- a very large black hole
Supernova- a giant explosion created by a dying star
Terrestrial Planet- a planet that is made of rock
White Dwarf Star- stars formed after a supernova
explosion of most medium size stars
Image Credits
In-Text Images
Pg. 1-2
20-21 loads/2010/09/supernova_3-1024x768.jpg
About the Authors
Peri Michael and Steven Piselli are students at the
Massachusetts Academy of Math and Science.
Steven is currently a resident
of Millbury, Massachusetts.
He participates in multiple
musical groups affiliated with
Millbury High School. He will
be a Senior at Mass Academy
next year enrolling in Musical
Fundamentals of Music.
Peri lives in Ashburnham,
Massachusetts, and she will
be a senior next year. She
sketching, pottery, jewelry
making, and painting. In her
spare time, she enjoys
drawing and listening to