Download Chapter One Technology, Science, and Scientific Measurement

Small Solar System Bodies
The term used to describe some types of
interplanetary material  a small solar system body
Definition: a category of celestial objects orbiting the Sun that
are not classified as planets, dwarf planets, or moons; this
includes objects known as asteroids, meteors, comets, and
some trans-Neptunian objects
Asteroids
An area called the asteroid belt is filled with a debris
field of rocky asteroids that also orbit the Sun
between a distance of 2.2 and 3.3 AU from the center
of the solar system.
Definition: a region in the solar system located between the
orbits of Mars and Jupiter where there are a high number of
asteroids
Definition: an object orbiting the Sun that is smaller than a
planet and has no atmosphere
Not all asteroids lie within the asteroid belt – some are
located inside the orbit of the Earth around the Sun (these
are called Aten asteroids).
Some asteroids are classified by their ability to
cross the Earth’s orbit (these are known as Apollo
asteroids).
– These are a concern to astronomers because they have the
potential to strike the Earth’s surface.
– Astronomers estimate that an asteroid strikes the Earth
once every 2,000 years.
Meteoroids
Smaller chunks of rock that are located in the solar
system are called meteoroids, meteors, and
meteorites.
Definition: small chunks of rock, no larger than a few feet
in diameter, that travel through space
Definition: a small chunk of rock, no larger than a few feet
in diameter, that is traveling through space and enters the
Earth’s atmosphere; commonly known as a shooting star
Definition: a meteor that does not burn up in the
atmosphere, and strikes the Earth’s surface
– Meteorites are grouped into three categories based on
their composition:
Stony meteorites are composed of silicate rock material.
Iron meteorites are composed of an iron-nickel alloy and are
very dense.
Stony-iron meteorites are composed of a mixture of silicate
rock and iron.
During certain times of the year, many meteors enter
the Earth’s atmosphere at once in an event called a
meteor shower.
Definition: an event that describes a group of meteors
entering and burning up in the Earth’s atmosphere
Comets
Once referred to as dirty snowballs, comets are
unique in their appearance.
Definition: a mixture of frozen compounds and rock that
orbits the Sun and which has a distinct tail composed of
vaporized gas and dust that always points away from the
Sun
– A comet consists of three parts: nucleus, coma, and tail
– A comet’s nucleus: the frozen compounds and rock
that form the core of a comet
– A comet’s coma: the dust and gas surrounding the
nucleus that was once held within the nucleus
– A comet’s tail: the vaporized gas and dust that trail
away from the nucleus of a comet
Most comets come from a region at the edge of the
solar system called the Oort cloud.
Definition: a hypothetical area that is located approximately
100,000 astronomical units from the orbit of the planet Pluto,
where comets are believed to originate
– There are two main types of comets, which are
classified based on their period of revolution around
the Sun.
Long-period comets take an extremely long time to orbit the
Sun, such as 30 million years.
Short-period comets orbit the Sun in periods less than 200
years.
Chapter Six
The Solar System and Its
Place in the Universe
Section One
Section Two
– The Solar System
– The Earth’s Place in the Universe
The Earth’s Place in the Universe
When viewed with very powerful telescopes, galaxies
are revealed to be some of the most beautiful objects
in space – the French astronomer Charles Messier was
the first scientist to begin to catalog these amazing
objects.
– Definition: a large grouping of stars
There are three types of galaxies: spirals, elliptical, and
irregular.
– SPIRAL: appears much like a rotating pinwheel
At the center of a spiral galaxy is the nucleus, which
is surrounded by many spiral arms.
The solar system is located is a spiral galaxy called
the Milky Way.
– Definition: the name for the galaxy of stars in which
our solar system is located
– ELLIPTICAL: have a nucleus and a halo of stars, but no
spiral arm.
Smaller elliptical galaxies are known as dwarf
elliptical.
Astronomers believe that elliptical galaxies are the
most common type of galaxy found in the universe.
– IRREGULAR: have no well-defined shape
Quasars
Besides galaxies, another structure is found out on
the edges of the universe – this is called a quasar.
Definition: a very high energy celestial object believed to
be a type of galaxy that is rapidly moving away from the
center of the universe
– Some quasars are moving away from the Earth at incredible
speeds of almost 90% of the speed of light – these are
the fastest objects yet discovered in the universe.