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A little about our Solar System As you know, planets are

part of our solar system.

Comets, asteroids and

the planets' moons are

part of the solar system,

too. These things all orbitaround a star we call the

sun. And it's all held

together by gravity.

The planets are oftendivided into two

groups: the four innerplanets (Mercury,

Venus, Earth and

Mars) and the fiveouter planets (Jupiter,

Saturn, Uranus,Neptune and Pluto).

MERCURY The diameter of Mercury

is 3,031 miles.

It takes the planet 58.6days to rotate completely360 degrees.

It takes 88 Earth days forMercury to rotate aroundthe sun.

Mercury only weighs5.5% of what earthweighs.

Mercurys diameter is38% of what the earthsdiameter is.

More about Mercury

Mercury is the closestplanet to the sun.Because Mercury is soclose to the sun (and thesun's glare) it is difficult to

spot from Earth.

Mercury's gravity is lessthan half what we haveon Earth, so Mercury canhold onto only a small bitof an atmosphere. Sincethere's not muchatmosphere (which onEarth acts like a warmblanket) temperatures on

Mercury go crazy. It canbe a scorching 750degrees Fahrenheitduring the day, and minus320 at night!

VENUS

The Diameter of Venus is7,521 miles.

It takes 243 days to rotate360 degrees completely.

It Takes 225 Earth daysto orbit the sun.

It only has 82 % of the

mass earth has Its diameter is about 95%

of earths.

It is a 30 percent closer tothe sun that the earth.

More fun facts about Venus

The second planet from thesun bakes under twice asmuch solar radiation as Earth.Venus reaches temperaturesof 895 degrees Fahrenheit!

The thick clouds around Venusrotate much faster than theplanet itself -- once every fourdays. Not counting the moon,Venus is the brightest object inthe night sky.

The surface of Venus is mostlya rocky desert (there are manycomputer-generated that showlava flows around a placecalled Sif Mons). Like Mercury,Earth and Mars, Venus ismostly rock and metal.

While all of the planets orbit inan ellipse (something like theshape of an egg), Venus' orbitis the closest to a perfectcircle.

Because it is often brighterthan anything in the sky exceptthe moon, Venus is the causeof many UFO reports.

EARTH

The Diameter ofearth is 7,926 miles.

It takes 23 hours, 56

minutes for the

earth to rotatecompletely.

It takes 365.24 daysfor the earth to Orbit

around the sun.

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Cool facts about Earth Earth is the third planet from

the sun. Like the other threeplanets of the inner solarsystem (Mercury, Venus, andMars) our planet is made upmostly of rock and metal.

One of the most importantthings about Earth is thatthere's lots of water, whichis one important reason whylife got started long ago.We're also lucky that Earth'satmosphere has plenty ofnitrogen and oxygen, twoother things that life needs.

It may not feel like it butthe ground under yourfeet is actually movingvery, very fast. TheEarth's surface is rotatingabout its axis at 1,532feet per second at theequator, and the planetzips around the sun atmore than 18 miles persecond! So all of us aregoing incredibly fast --even when we're standingstill.

MARS The diameter of Mars is 4,217

miles.

It takes 24 hours and 37minutes for it to rotate 360degrees completely.

It takes 687 days for mars tocompletely orbit the sun.

It only has 5% of the mass thatthe earth has.

It has 53% of the earthsdiameter.

Its 150% further away fromthe sun than the moon is.

THE LOW DOWNON MARS

The fourth planet from the sunhas always made us humansdo a lot wondering and hoping.While scientists haven't proventhere's any life on Mars, thedusty red planet is still afascinating place.

The surface of Mars is moreinteresting than most. LikeMercury, Venus and Earth,Mars is mostly rock and metal,but it also has lots ofmountains and craters.

The dust that gives Mars thereddish color is made ofsomething called iron oxide.Temperatures on Mars can getas cold as -207 degreesFahrenheit and as high as 80degrees Fahrenheit onsummer days.

Mars was probably warm andwet about 3.7 billion years ago.Mars cooled and the waterfroze. Some of that water stillmay exist in ice caps at thepoles.

JUPITER

Jupiter weighs over 316times as much as theearth.

It is also 11.12 timeslarger than the earth.

The fifth planet from thesun is mostly a huge ballof gas. But at Jupiter'scenter is a core of rockmany times the mass ofEarth. The whole planetis so massive it couldhold all the other planetsput together!

SATURN

Diameter: 74,900 miles Time to rotate completely: 10

hours, 39 minutes It takes 29.5 years for saturn

to orbit the sun. The sixth planet from the sun

has a rocky core and a lot ofgas on its surface. But Saturnis known for its rings. Themile-thick rings are made oftons and tons of ice that orbitthe planet. Some of the icebits are smaller than marbles,some are bigger than yourcomputer.

Saturn has 18 known moons,each made mostly of ice androck.

URANUS

The diameter of Uranus is 31,763 miles long.

It takes the planet 17 hours and 54 minutes to turn 360 degrees.

It takes 84 years for uranus to orbit the sun.

It weighs 14.5 times as much as the earth

It is 4.1 times heavier than the earth

The seventh planet from the sun is a lot like its neighbors, with a cloudy

surface, rapid winds, and small rocky core.

Uranus rotates at an extreme tilt of 98 degrees, sort of on its side. Thiscauses one pole to point toward the sun for decades, giving the planet

strange seasons. Scientists think the planet might be on its side because

some other large object crashed into it a long time ago.

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NEPTUNE The eighth planet from the sun

(well, some of the time it's eighth,but more on that later) has a rockycore surrounded by ice, hydrogen,helium and methane.

Like the other gas planets,Neptune has rapidly swirlingwinds. Its quick rotation causesfierce winds and some very strongstorms. The planet has eightknown moons. Like Saturn,Neptune has rings. But Neptune'srings are not as thick, and they arehard to spot.

Neptune was discovered in 1846.

PLUTO The mass of pluto is .2% of the earth.

The diameter is only 18% of what theearths is.

Pluto, which is smaller than our moon,is a cold, dark, frozen place. We don'tknow very much about the tiny planet.Scientists think it is made of rock andice. It might have a thin atmosphere ofnitrogen, carbon monoxide andmethane.

Some astronomers think Pluto mayhave wandered into the system from amore distant place called the KuiperBelt. In the Kuiper Belt, Pluto-likeobjects and comets orbit the sun. Somaybe Pluto is not a planet at all, butmore like a large asteroid or comet.Some scientists say Pluto may be anold moon of Neptune that escaped.

Pulsar

A neutron star thatproduces radio waves

Nebula

A large amount of gasand dust in space

spreaded out in animmense volume

Protostar

A contracting cloud ofgas and dust the

earliest stage of astars life.

White Dwarf

The remaining hotcore of a star after its

outer layers haveexpanded and drifted

out into space.

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Supernova The explosion of a

dying giant or

supergiant star.

Neutron StarA tiny star that remains

after a supernova

explosion.

Black Hole

The remains of an

extremely massive

star pulled into a

small volume by

the force of

gravity.

A distant galaxy witha black hole at its

center.

Quasar

Binary Star

A star system thatcontains two stars.

Eclipsing Binary

A star system inwhich one star

periodically blockslight from another.

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Spiral Galaxy A galaxy whose arms

curve outward in a

pinwheel pattern

Elliptical Galaxy A galaxy shaped like

a flattened ball

containing only oldstars.

Irregular Galaxy

A galaxy that doesnot have a regular

shape.

In one version, from the Greeks is, Artemis, the goddess of hunting and the moon fell in

love with Orion. She was so entranced by him, she forgot her divinely duty of illuminating

the night sky. Her twin brother Apollo, seeing Orion swimming in the sea, dared his sisterto strike what only appeared to be a spot on the waves. Not knowing it was Orion,

Artemis shot an arrow and killed him. Later, when she found out what she did, she placed

his body among the stars. The grief she felt explains why the moon looks so sad at night.

Virgo sometimes she has been known as Astraeia,

daughter of Astraeus and Eos. She was the Roman

goddess of justice, who finally sickened of the wars of men

and left for the heavens.

Little bear has a long tail because of its

being held by the tail and spun around thepole.

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Heracles, the most famous Greek hero. The ancient Romans called him Hercules. Heracles was acourageous and very strong man. Unfortunately, Heracles had a terrible enemy: the goddess Hera.

Hera was so annoyed by Heracles' strength and fame that she cast a spell over him. As a result, he

committed a terrible crime. Seeking forgiveness, Heracles was told to perform twelve very difficulttasks for the king

This constellation is called The Big Dipper or in

our country The Plough.

Leo the Lion Cygnus the Swan

Delphinus the Dolphin