What is the Solar System
Content
What Is The Solar System?
The Solar System is made up of all the planets that orbit our Sun. In addition
to planets, the Solar System also consists of moons, comets, asteroids, minor
planets, and dust and gas.
Everything in the Solar System orbits or revolves around the Sun. The Sun
contains around 98% of all the material in the Solar System. The larger an
object is, the more gravity it has. Because the Sun is so large, its powerful
gravity attracts all the other objects in the Solar System towards it. At the
same time, these objects, which are moving very rapidly, try to fly away from
the Sun, outward into the emptiness of outer space. The result of the planets
trying to fly away, at the same time that the Sun is trying to pull them inward
is that they become trapped half-way in between. Balanced between flying
towards the Sun, and escaping into space, they spend eternity orbiting
around their parent star.
Solar System – Overview
Structure
At the heart of the solar system is our sun. The four planets nearest it are
rocky, terrestrial worlds— Mercury, Venus, Earth and Mars. After that are four
gas giants — Jupiter, Saturn, Uranus andNeptune. Between the orbits of Mars
and Jupiter lies the asteroid belt, which includes the dwarf planet Ceres.
Beyond the orbit of Neptune one finds the disk-shaped Kuiper belt, in which
dwarf planet Pluto resides, and far beyond that is the giant, spherical Oort
Cloud and the teardrop-shaped heliopause. See the structure of the solar
system (infographic).
Our solar system is a vast place,
with lots of mostly empty space
between planets. But out there are
comets, asteroids and more rocky,
frozen objects (including dwarf
planets) yet to be discovered in the
Kuiper Belt and Oort Cloud.
CREDIT: NASA
Discovery
For millennia, astronomers have
followed points of light that seemed
to move among the stars. The ancient Greeks named these planets, meaning
wanderers. Mercury, Venus, Mars, Jupiter and Saturn were known in
antiquity, and the invention of the telescope added the asteroid belt, Uranus
and Neptune, Pluto and many of these worlds' moons. The dawn of the space
age saw dozens of probes launched to explore our system, an adventure that
continues today. The discovery of Eris kicked off a rash of new discoveries of
dwarf planets, and more than 100 could remain to be found.
Sun
The sun is by far the largest object in our solar system, containing 99.8
percent of the solar system's mass. It sheds most of the heat and light that
makes life possible on Earth and possibly elsewhere. Planets orbit the sun
in oval-shaped paths called ellipses, and the sun is slightly off to the side of
the center of each ellipse.
Inner Solar System
Inner Planets
- The inner four
planets — Mercury, Venus, Earth
and Mars — are made up mostly
of iron and rock. They are known
as terrestrial or earthlike planets
because of their similar size and
composition.
Asteroid belt
- Asteroids are minor planets, most of which circle
the sun in a region known as the asteroid belt, between the orbits
of Mars and Jupiter. Scientists
estimate that there are more
than 750,000 asteroids in the
belt with diameters larger than
three-fifths
of
a
mile
(1
kilometer), and there are millions
of smaller asteroids. A number
have orbits that take them closer
into the solar system that
sometimes lead them to collide
with Earth or the other inner planets.
Outer Solar System
Outer Planets
The
outer
planets are giant worlds with thick
outer layers of gas. Nearly all their
mass is made up of hydrogen and
helium, giving them compositions
like that of the sun. Beneath these
outer layers, they have no solid
surfaces — the pressure from their thick atmospheres liquefy their
insides, although they might have rocky
cores. Rings of dust, rock, and ice encircle
all these giants, with Saturn's being the
most famous.
Comets
Comets are often known
as dirty snowballs, and consist mainly of ice
and rock. When a comet's orbit takes it
close to the sun, some of the ice in its central nucleus turns into gas
that shoots out of the comet's sunlit side, which the solar wind carries
outward to form into a long tail. Short-period comets that complete
their orbits in less than 200 years are thought to originate from the the
disk-shaped Kuiper belt, while long-period comets that take more than
200 years to return are thought to come from the spherical Oort cloud.
Formation
Many scientists think our 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. Other particles within the disk
collided and stuck together to form asteroid-sized objects named as
planetesimals, some of which combined to become the asteroids, comets,
moons and planets. The solar wind from the sun was so powerful that it
swept away most of the lighter elements, such as hydrogen and helium, from
the innermost planets, leaving behind mostly small, rocky worlds. The solar
wind was much weaker in the outer regions, however, resulting in gas giants
made up mostly of hydrogen and helium.
Trans-Neptunian Region
Astronomers had long suspected
that a band of icy material known as
the Kuiper belt existed past the orbit
of Neptune extending from about 30
to 55 times the distance of Earth to
the sun, and from the last decade of
the 20th century up to now, they
have found more than a thousand of
such objects. Scientists estimate the
Kuiper belt is likely home to
hundreds of thousands of icy bodies
larger than 60 miles (100 km) wide,
as well as an estimated trillion or
more comets.
Well past the Kuiper belt is the Oort cloud, which theoretically extends from
5,000 to 100,000 times the distance of Earth to the sun, and is home to up to
two trillion icy bodies. Past that is the very edge of the solar system, the
heliosphere, a vast, teardrop-shaped region of space containing electrically
charged particles given off by the sun. Many astronomers think that the limit
of the heliosphere, known as the heliopause, is about 9 billion miles (15
billion kilometers) from the sun.
Pluto is now considered a dwarf planet dwelling in the Kuiper belt. It is not
alone — recent additions include Makemake, Haumea and Eris. Another
object dubbed Sedna, which is about three-fourths the size of Pluto, might be
the first dwarf planet discovered in the Oort cloud.
The Solar System is made up of all the planets that orbit our Sun. In addition
to planets, the Solar System also consists of moons, comets, asteroids, minor
planets, and dust and gas.
Everything in the Solar System orbits or revolves around the Sun. The Sun
contains around 98% of all the material in the Solar System. The larger an
object is, the more gravity it has. Because the Sun is so large, its powerful
gravity attracts all the other objects in the Solar System towards it. At the
same time, these objects, which are moving very rapidly, try to fly away from
the Sun, outward into the emptiness of outer space. The result of the planets
trying to fly away, at the same time that the Sun is trying to pull them inward
is that they become trapped half-way in between. Balanced between flying
towards the Sun, and escaping into space, they spend eternity orbiting
around their parent star.
Solar System – Overview
Structure
At the heart of the solar system is our sun. The four planets nearest it are
rocky, terrestrial worlds— Mercury, Venus, Earth and Mars. After that are four
gas giants — Jupiter, Saturn, Uranus andNeptune. Between the orbits of Mars
and Jupiter lies the asteroid belt, which includes the dwarf planet Ceres.
Beyond the orbit of Neptune one finds the disk-shaped Kuiper belt, in which
dwarf planet Pluto resides, and far beyond that is the giant, spherical Oort
Cloud and the teardrop-shaped heliopause. See the structure of the solar
system (infographic).
Our solar system is a vast place,
with lots of mostly empty space
between planets. But out there are
comets, asteroids and more rocky,
frozen objects (including dwarf
planets) yet to be discovered in the
Kuiper Belt and Oort Cloud.
CREDIT: NASA
Discovery
For millennia, astronomers have
followed points of light that seemed
to move among the stars. The ancient Greeks named these planets, meaning
wanderers. Mercury, Venus, Mars, Jupiter and Saturn were known in
antiquity, and the invention of the telescope added the asteroid belt, Uranus
and Neptune, Pluto and many of these worlds' moons. The dawn of the space
age saw dozens of probes launched to explore our system, an adventure that
continues today. The discovery of Eris kicked off a rash of new discoveries of
dwarf planets, and more than 100 could remain to be found.
Sun
The sun is by far the largest object in our solar system, containing 99.8
percent of the solar system's mass. It sheds most of the heat and light that
makes life possible on Earth and possibly elsewhere. Planets orbit the sun
in oval-shaped paths called ellipses, and the sun is slightly off to the side of
the center of each ellipse.
Inner Solar System
Inner Planets
- The inner four
planets — Mercury, Venus, Earth
and Mars — are made up mostly
of iron and rock. They are known
as terrestrial or earthlike planets
because of their similar size and
composition.
Asteroid belt
- Asteroids are minor planets, most of which circle
the sun in a region known as the asteroid belt, between the orbits
of Mars and Jupiter. Scientists
estimate that there are more
than 750,000 asteroids in the
belt with diameters larger than
three-fifths
of
a
mile
(1
kilometer), and there are millions
of smaller asteroids. A number
have orbits that take them closer
into the solar system that
sometimes lead them to collide
with Earth or the other inner planets.
Outer Solar System
Outer Planets
The
outer
planets are giant worlds with thick
outer layers of gas. Nearly all their
mass is made up of hydrogen and
helium, giving them compositions
like that of the sun. Beneath these
outer layers, they have no solid
surfaces — the pressure from their thick atmospheres liquefy their
insides, although they might have rocky
cores. Rings of dust, rock, and ice encircle
all these giants, with Saturn's being the
most famous.
Comets
Comets are often known
as dirty snowballs, and consist mainly of ice
and rock. When a comet's orbit takes it
close to the sun, some of the ice in its central nucleus turns into gas
that shoots out of the comet's sunlit side, which the solar wind carries
outward to form into a long tail. Short-period comets that complete
their orbits in less than 200 years are thought to originate from the the
disk-shaped Kuiper belt, while long-period comets that take more than
200 years to return are thought to come from the spherical Oort cloud.
Formation
Many scientists think our 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. Other particles within the disk
collided and stuck together to form asteroid-sized objects named as
planetesimals, some of which combined to become the asteroids, comets,
moons and planets. The solar wind from the sun was so powerful that it
swept away most of the lighter elements, such as hydrogen and helium, from
the innermost planets, leaving behind mostly small, rocky worlds. The solar
wind was much weaker in the outer regions, however, resulting in gas giants
made up mostly of hydrogen and helium.
Trans-Neptunian Region
Astronomers had long suspected
that a band of icy material known as
the Kuiper belt existed past the orbit
of Neptune extending from about 30
to 55 times the distance of Earth to
the sun, and from the last decade of
the 20th century up to now, they
have found more than a thousand of
such objects. Scientists estimate the
Kuiper belt is likely home to
hundreds of thousands of icy bodies
larger than 60 miles (100 km) wide,
as well as an estimated trillion or
more comets.
Well past the Kuiper belt is the Oort cloud, which theoretically extends from
5,000 to 100,000 times the distance of Earth to the sun, and is home to up to
two trillion icy bodies. Past that is the very edge of the solar system, the
heliosphere, a vast, teardrop-shaped region of space containing electrically
charged particles given off by the sun. Many astronomers think that the limit
of the heliosphere, known as the heliopause, is about 9 billion miles (15
billion kilometers) from the sun.
Pluto is now considered a dwarf planet dwelling in the Kuiper belt. It is not
alone — recent additions include Makemake, Haumea and Eris. Another
object dubbed Sedna, which is about three-fourths the size of Pluto, might be
the first dwarf planet discovered in the Oort cloud.
