14. Our solar system consists of the
sun, planets, dwarf planets (or
plutoids), moons, an asteroid
belt, comets, meteors, and other
objects. The sun is the center of
our solar system; the planets,
over 61 moons, the asteroids,
comets, meteoroids and other
rocks and gas all orbit the Sun.
17. The nine planets that orbit the
sun are (in order from the
Sun): Mercury, Venus, Earth,
Mars, Jupiter (the biggest
planet in our Solar System),
Saturn (with large, orbiting
rings), Uranus, Neptune, and
Pluto (a dwarf planet or
plutoid).
18.
19. A belt of asteroids (minor planets
made of rock and metal) orbits
between Mars and Jupiter. These
objects all orbit the sun in
roughly circular orbits that lie in
the same plane, the ecliptic
(Pluto is an exception; this dwarf
planet has an elliptical orbit tilted
over 17° from the ecliptic).
20.
21. The inner planets (those
planets that orbit close to
the Sun) are quite different
from the outer planets
(those planets that orbit far
from the Sun).
22. The inner planets are:
Mercury, Venus, Earth, and
Mars. They are relatively
small, composed mostly of
rock, and have few or no
moons.
23. The outer planets include:
Jupiter, Saturn, Uranus, and
Neptune. They are mostly
huge, mostly gaseous, ringed,
and have many moons (plus
Pluto, which is a dwarf planet
that has one large moon and
two small moons).
33. Our sun is a star located at
the center of our Solar
System. It is a huge,
spinning ball of hot gas and
nuclear reactions that lights
up the Earth and provides us
with heat
37. The Sun's core can reach 10 to 22.5
million°F. The surface temperature is
approximately 9,900°F (5,500°C). The
outer atmosphere of the Sun (which we
can see during a solar eclipse) gets
extremely hot again, up to 1.5 to 2 million
degrees. At the center of big sunspots the
temperature can be as low as 7300 °F
(4300 K, 4000 °C). The temperature of the
Sun is determined by measuring how
much energy (both heat and light) it
emits.
42. Astronomers study the Sun using
special instruments. Scientists
analyze how and why the amount of
light from the Sun varies over time,
the effect of the Sun's light on the
Earth's climate, spectral lines, the
Sun's magnetic field, the solar wind,
and many other solar phenomena.
The outer regions of the Sun (the
corona) are studied during solar
eclipses.
48. A star is born when an enormous cloud of
hydrogen gas collapses until it is hot enough to
burn nuclear fuel (producing tremendous
amounts heat and radiation). As the nuclear fuel
runs out (in about 5 billion years), the star
expands and the core contracts, becoming a
giant star which eventually explodes and turns
into a dim, cool object (a black dwarf, neutron
star, or black hole, depending on its initial
mass). The largest stars have the shortest life
span (still billions of years); more massive stars
burn hotter and faster than their smaller
counterparts (like the Sun).
52. Stars are giant nuclear reactors. In the
center of stars, atoms are taken apart by
tremendous atomic collisions that alter the
atomic structure and release an enormous
amount of energy. This makes stars hot and
bright. In most stars, the primary reaction
converts hydrogen atoms into helium atoms,
releasing an enormous amount of energy.
This reaction is called nuclear fusion
because it fused the nuclei (center) of atoms
together, forming a new nucleus. The
process of forming a new nucleus (and
element) is nucleosynthesis.
54. The closest star to us is the sun!
Other than that, the closest star
is Proxima Centauri, aka Alpha
Centauri C (the dimmest star in
the Alpha Centauri system).
Proxima Centauri is 4.3 light-
years from the Sun. It has an
absolute magnitude of 15.5.
56. The scientific name for the
twinkling of stars is stellar
scintillation (or astronomical
scintillation). Stars twinkle when
we see them from the Earth's
surface because we are viewing
them through thick layers of
turbulent (moving) air in the
Earth's atmosphere.
