Transcript Planets-in-solar

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Our Sun in Brief
The Sun is a star, a hot ball of glowing gases at the
heart of our solar system. Its influence extends far
beyond the orbits of distant Neptune and Pluto.
Without the Sun's intense energy and heat, there
would be no life on Earth. And though it is special to
us, there are billions of stars like our Sun scattered
across the Milky Way galaxy.
Mercury in a Brief
Sun-scorched Mercury is only slightly larger than Earth's Moon.
Like the Moon, Mercury has very little atmosphere to stop
impacts and it is covered with craters. Mercury's dayside is super
heated by the Sun, but at night temperatures drop hundreds of
degrees below freezing. Ice may even exist in craters. Mercury's
egg-shaped orbit takes it around the Sun every 88 days.
Featured Mission: MESSENGER
During a series of flybys, NASA's MESSENGER spacecraft has
revealed more of Mercury than has ever been seen before. The
spacecraft, the second to visit Mercury, will settle into orbit in
March 2011.
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Venus in Brief
Venus is a dim world of intense heat and volcanic
activity. Similar in structure and size to Earth, Venus'
thick, toxic atmosphere traps heat in a runaway
'greenhouse effect.' The scorched world has temperatures
hot enough to melt lead. Glimpses below the clouds
reveal volcanoes and deformed mountains. Venus spins
slowly in the opposite direction of most planets.
Featured Mission: Akatsuki
Japan's Akatsuki is the next planned mission to Venus.
The orbiter will follow Venus' thick cloud layers as they
are whipped around the planet by hurricane-force winds.
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Earth in Brief
Earth is an ocean planet. Our home world's
abundance of water - and life - makes it unique in
our solar system. Other planets, plus a few moons,
have ice, atmospheres, seasons and even weather,
but only on Earth does the whole complicated mix
come together in a way that encourages life - and
lots of it.
Featured Mission: Earth Science Missions
Orbiting spacecraft study our home world from
above as a whole system and aid in our
understanding how the planet is changing.
Earth's Moon in Brief
Our moon makes Earth a more livable planet by moderating
our home planet's wobble on its axis, leading to a relatively
stable climate, and creating a rhythm that have guided
humans for thousands of years. The Moon was likely formed
after a Mars-sized body collided with Earth and the debris
formed into the most prominent feature in our night sky.
Featured Mission: LADEE
LADEE will help determine the impact of increased human
activity on the Moon's thin exosphere. If scientists are ever to
know the lunar atmosphere in a relatively natural state, now
is the time to look.
The red planet Mars has inspired wild flights of
imagination over the centuries, as well as intense
scientific interest. Whether fancied to be the source of
hostile invaders of Earth, the home of a dying
civilization, or a rough-and-tumble mining colony of the
future, Mars provides fertile ground for science fiction
writers, based on seeds planted by centuries of scientific
observations.
Asteroids in Brief
Asteroids are rocky, airless worlds that orbit our Sun, but are
too small to be called planets. Tens of thousands of these
'minor planets' are gathered in the main asteroid belt, a vast
doughnut-shaped ring between the orbits of Mars and
Jupiter. Asteroids that pass close to Earth are called nearearth objects.
Featured Mission: Dawn
NASA's Dawn mission is on a 3-billion-kilometer (1.7billion-mile) journey to the asteroid belt to orbit asteroid
Vesta and dwarf planet Ceres. Scientists hope to characterize
the conditions of the solar system's earliest days by studying
these two very different worlds.
The most massive planet in our solar system, with four
planet-sized moons and many smaller moons, Jupiter
forms a kind of miniature solar system. Jupiter
resembles a star in composition. In fact, if it had been
about eighty times more massive, it would have become
a star rather than a planet. On January 7, 1610, using his
primitive telescope, astronomer Galileo Galilei saw four
small 'stars' near Jupiter. He had discovered Jupiter's
four largest moons, now called Io, Europa, Ganymede,
and Callisto. Collectively, these four moons are known
today as the Galilean satellites.
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Saturn was the most distant of the five planets
known to the ancients. Like Jupiter, Saturn is made
mostly of hydrogen and helium. Its volume is 755
times greater than that of Earth. Winds in the upper
atmosphere reach 500 meters (1,600 feet) per second
in the equatorial region. These super-fast winds,
combined with heat rising from within the planet's
interior, cause the yellow and gold bands visible in
the atmosphere.
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Once considered one of the blander-looking planets,
Uranus (pronounced YOOR un nus) has been
revealed as a dynamic world with some of the
brightest clouds in the outer solar system and 11
rings. The first planet found with the aid of a
telescope, Uranus was discovered in 1781 by
astronomer William Herschel. The seventh planet
from the Sun is so distant that it takes 84 years to
complete one orbit. Uranus, with no solid surface, is
one of the gas giant planets (the others are Jupiter,
Saturn, and Neptune).
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The eighth planet from the Sun, Neptune was the first
planet located through mathematical predictions rather
than through regular observations of the sky. (Galileo
had recorded it as a fixed star during observations with
his small telescope in 1612 and 1613.) When Uranus
didn't travel exactly as astronomers expected it to, a
French mathematician, Urbain Joseph Le Verrier,
proposed the position and mass of another as yet
unknown planet that could cause the observed changes
to Uranus' orbit. After being ignored by French
astronomers, Le Verrier sent his predictions to Johann
Gottfried Galle at the Berlin Observatory, who found
Neptune on his first night of searching in 1846. Seventeen
days later, its largest moon, Triton, was also discovered.
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Pluto in Brief
Tiny, cold and incredibly distant, Pluto was discovered
in 1930 and long considered to be the ninth planet. But
after the discoveries of similar intriguing worlds even
farther out, Pluto was reclassified as a dwarf planet. This
new class of worlds may offer some of the best evidence
of the origins of our solar system.
Featured Mission: New Horizons
NASA's New Horizons will be the first spacecraft to visit
Pluto and the Kuiper Belt. The spacecraft's 9 and a half
year journey to the ice dwarf began in January 2006. The
spacecraft is will reach Pluto in 2015.
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Throughout history, people have been both awed
and alarmed by comets, stars with "long hair" that
appeared in the sky unannounced and
unpredictably. We now know that comets are dirtyice leftovers from the formation of our solar system
around 4.6 billion years ago. They are among the
least-changed objects in our solar system and, as
such, may yield important clues about the formation
of our solar system. We can predict the orbits of
many of them, but not all.
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The Kuiper (pronounced Ki-Per) Belt is often called
our Solar System's 'final frontier.' This disk-shaped
region of icy debris is about 4.5 to 7.5 billion km (2.8
billion to 4.6 billion miles), 30 to 50 Astronomical
Units (AU). from our Sun. Its existence confirmed
only a decade ago, the Kuiper Belt and its collection
of icy objects - KBOs - are an emerging area of
research in planetary science
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What constitutes a planet? The International
Astronomical Union (IAU) developed some
definitions in 2001, modified them again in 2003, and
as of August 24, 2006, the IAU has come up with
another definition. The IAU said in a statement that
the definition for a planet is now officially known as
"a celestial body that (a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome
rigid body forces so that it assumes a hydrostatic
equilibrium (nearly round) shape and (c) has cleared
the neighborhood around its orbit."
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The Oort Cloud is an immense spherical cloud
surrounding our Solar System. Extending about 30
trillion kilometers (18 trillion miles) from the Sun, it
was first proposed in 1950 by Dutch astronomer Jan
Oort. The vast distance of the Oort cloud is
considered to be the outer edge of the Solar System where the Sun's orb of physical and gravitational
influence ends.
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Moons in Brief
Many of the moons of our solar system are as intriguing
as the planets. Earth's Moon holds many clues to the
formation of our home world and rest of the solar system
and offers a potential starting point for humanity to
extend its reach deeper into space. Jupiter's Europa and
Ganymede harbor signs of possible subsurface oceans.
Saturn's large moon Titan is the only moon in the solar
system known to have clouds, a mysterious, thick,
planet-like atmosphere and surface lakes.
the planetary moons probably formed from the discs of
gas and dust circulating around planets in the early solar
system.
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In 1991, the worlds of our own solar system were the
only known planets. Astronomers did not believe
that our Sun's environment was the only planet
producer in the universe. But they had no evidence
of planets outside our solar system