astronomy ''the sun

THE MEMBERS OFSOLAR SYSTEM

SUN

The Sun is the heart of our Solar System.

Diameter: 865,278 miles or 1.9 million Km.Temperature:

6000 degrees Celsius – Visible part25,000,000 degree F

Regions:Photosphere(Solar Surface) – Consisting Hydrogen GasChromosphere(Sphere of Colour)

Corona or Crown- Upper layer

Sunspots- Usually appears black because they are cooler and less bright than the rest of the Photosphere.

The PlanetsThere are 8 Planets in our Solar System. Each planet has its own axis and revolves around the sun.

Planets Closest to the sun are Inner Planets or Terrestrial Planets.

Outer planets which are far from the sun are called Jovian Planets.

MERCURY

MERCURY, THE PLANET CLOSEST TO THE SUN, HAS

ALMOST NO ATMOSPHERE, AND ITS DUSTY

SURFACE OF CRATERS RESEMBLES THE MOON.

THE PLANET WAS NAMED FOR THE ROMAN GOD

MERCURY, A WINGED MESSENGER, AND IT

TRAVELS AROUND THE SUN FASTER THAN ANY

OTHER PLANET. MERCURY IS DIFFICULT TO SEE

FROM EARTH—IN FACT, THE FAMOUS

ASTRONOMER NICOLAUS COPERNICUS, FOR ALL

HIS YEARS OF RESEARCH AND OBSERVATION,

NEVER ONCE WAS ABLE TO SEE MERCURY.

Size: Two-fifths the size of Earth in diameter; second smallest in the solar system

Diameter: 3,032.4 miles (4,880 km)

Surface: Covered by a dusty layer of minerals (silicates), the surface is made up

of plains, cliffs, and craters

Atmosphere: A thin mixture of helium (95%) and hydrogen

Temperature: Mercury alternately bakes and freezes, depending on what side is

lit by the Sun. The sunlit side can reach up to 950° F (510° C) and the dark side

can drop as low as –346° F (–210° C)

Rotation of its axis: 59 Earth days

Rotation around the Sun: 88 Earth days

Your weight: If you weigh 100 pounds on Earth, you would weigh 38 pounds on

Mercury.

Distance from Earth: 57 million miles, at the closest point in its orbit

Mean Distance from Sun: 36 million miles (57.9 million km)

Satellites: 0

Rings: 0

Venus

Venus is often called Earth's twin because the two

planets are close in size, but that's the only similarity.

The thick clouds that cover Venus create a greenhouse

effect that keeps it sizzling at 864°F. Venus, named after

the Roman goddess of love and beauty, is also known as

the ―morning star‖ and ―evening star‖ since it is visible at

these times to the unaided eye. Venus appears as a

bright, white disk from Earth.

Size: About 650 miles smaller in diameter than Earth

Diameter: 7,519 miles (12,100 km)

Surface: A rocky, dusty, waterless expanse of mountains, canyons, and plains,

with a 200-mile river of hardened lava

Atmosphere: Carbon dioxide (95%), nitrogen, sulfuric acid, and traces of other

elements

Temperature: Ranges from 55°F (13°C) to 396°F (202°C) at the surface

Rotation of its axis: 243 Earth days



Venus.

Distance from Earth: At its closest, Venus is 26 million miles (41,840,000 km)

away

Mean Distance from Sun: 67.24 million miles (108.2 million km)

Satellites: 0

Rings: 0

EARTH IS NOT PERFECTLY ROUND; IT

BULGES AT THE EQUATOR AND IS

FLATTER AT THE POLES. FROM SPACE

THE PLANET LOOKS BLUE WITH WHITE

SWIRLS, CREATED BY WATER AND

CLOUDS.

Size: Four planets in our solar system are larger and four are smaller than Earth

Diameter: 7,926.2 miles (12,756 km)

Surface: Earth is made up of water (70%), air, and solid ground. It appears to be the only planet with water

Atmosphere: Nitrogen (78%), oxygen (21%), other gases

Rotation of its axis: 23 hours, 56 minutes, 4 seconds

Rotation around the Sun: 365.2 days

Satellites: 1


Rings: 0

Mars

Because of its blood-red color (which comes

from iron-rich dust), this planet was named for

Mars, the Roman god of war. Mars is the fourth

planet from the Sun, situated between Earth

and Jupiter. Three-quarters red, Mars also has

dark blotches on it and white areas at the

poles—these are white polar ice caps.

Size: About one-half the size of Earth in diameter

Surface: Canyons, dunes, volcanoes, and polar caps of water ice and carbon

dioxide ice


Atmosphere: carbon dioxide (95%)

Temperature: as low as –305°F (–187°C)

Rotation of its axis: 24 Earth hours, 37 minutes, 23 seconds



Mars.

Distance from Earth: 35 million miles (56 million km) at the closest point in its

orbit

Mean Distance from Sun:141.71 million miles (227.9 million km)

Satellites: 2

Rings: 0

JUPITER

A BELT OF ASTEROIDS (FRAGMENTS OF ROCK AND

IRON) BETWEEN MARS AND JUPITER SEPARATE

THE FOUR INNER PLANETS FROM THE FIVE OUTER

PLANETS.

JUPITER, THE LARGEST PLANET IN OUR SOLAR

SYSTEM, WAS NAMED FOR THE MOST IMPORTANT

ROMAN GOD BECAUSE OF ITS SIZE. ABOUT 1,300

EARTHS WOULD FIT INTO IT. VIEWED THROUGH A

LARGE TELESCOPE, JUPITER IS STUNNINGLY

COLORFUL—IT IS A DISK COVERED WITH BANDS OF

BLUE, BROWN, PINK, RED, ORANGE, AND YELLOW.

ITS MOST DISTINGUISHING FEATURE IS ―THE

GREAT RED SPOT,‖ AN INTENSE WINDSTORM

LARGER IN SIZE THAN EARTH, WHICH HAS

CONTINUED FOR CENTURIES WITHOUT ANY SIGNS

OF DYING DOWN.

Size: 11 times the diameter of Earth


Surface: A hot ball of gas and liquid

Atmosphere: Whirling clouds of colored dust, hydrogen, helium,

methane, water, and ammonia. The Great Red Spot is an intense

windstorm larger than Earth.

Temperature: –234°F (–148°C) average

Rotation of its axis: 9 hours and 55 minutes

Rotation around the Sun: 12 Earth years

Your weight: If you weigh 100 pounds on Earth, you would weigh 265

pounds on Jupiter.

Distance from Earth: At its closest, 370 million miles (591 million km)


Satellites: 63

Rings: 4

SATURN

SATURN, THE SECOND-LARGEST PLANET,

HAS MAJESTIC RINGS SURROUNDING IT.

NAMED FOR THE ROMAN GOD OF FARMING,

SATURN WAS THE FARTHEST PLANET

KNOWN BY THE ANCIENTS. SATURN'S

SEVEN RINGS ARE FLAT AND LIE INSIDE

ONE ANOTHER. THEY ARE MADE OF

BILLIONS OF ICE PARTICLES.

Size: About 10 times larger than Earth in diameter


Surface: Liquid and gas

Atmosphere: Hydrogen and helium

Temperature: –288°F (–178°C)

Rotation of its axis: 10 hours, 40 min, 24 sec

Rotation around the Sun: 291/2 Earth years


Saturn.

Distance from Earth: 744 million miles at the closest point

Mean Distance from Sun: 887.14 million miles (1,427 million km)

Satellites: 31

Rings: 1,000?

URANUS

URANUS IS A GREENISH-BLUE PLANET,

TWICE AS FAR FROM THE SUN AS ITS

NEIGHBOR SATURN. URANUS WASN'T

DISCOVERED UNTIL 1781. ITS DISCOVEROR,

WILLIAM HERSCHEL, NAMED IT GEORGIUM

SIDUS (THE GEORGIAN STAR) AFTER THE

ENGLISH KING, GEORGE III. LATER ITS NAME

WAS CHANGED TO URANUS, AFTER AN

ANCIENT GREEK SKY GOD, SINCE ALL THE

OTHER PLANETS HAD BEEN NAMED AFTER

ROMAN AND GREEK GODS.

Size: 4 times larger than Earth in diameter


Surface: Little is known

Atmosphere: Hydrogen, helium, and methane

Temperature: uniform temperature of –353°F (–214°C)

Rotation of its axis: 17 hours

Rotation around the Sun: 30,685 days or 84 Earth years

Your weight: Not known

Distance from Earth: At the closest point, 1,607,000,000 miles

Mean Distance from Sun: 1,783.98 million miles (2,870 million km)

Satellites: 27

Rings: 11

NEPTUNE

NEPTUNE, NAMED FOR AN ANCIENT ROMAN SEA GOD, IS A

STORMY BLUE PLANET ABOUT 30 TIMES FARTHER FROM THE

SUN THAN EARTH. NEPTUNE WAS DISCOVERED WHEN

ASTRONOMERS REALIZED THAT SOMETHING WAS EXERTING

A GRAVITATIONAL PULL ON URANUS, AND THAT IT WAS

POSSIBLE THAT AN UNKNOWN PLANET MIGHT BE

RESPONSIBLE. THROUGH MATHEMATICAL CALCULATIONS,

ASTRONOMERS DETERMINED THERE WAS INDEED AN

UNDISCOVERED PLANET OUT IN SPACE—A YEAR BEFORE IT

WAS ACTUALLY SEEN FOR THE FIRST TIME THROUGH A

TELESCOPE (IN 1846).

Size: Almost 4 times the size of Earth in diameter


Surface: A liquid layer covered with thick clouds and with constant, raging storms

Atmosphere: Hydrogen, helium, methane, and ammonia

Temperature: –353°F (–214°C)

Rotation of its axis: 16 hours and 7 minutes



Distance from Earth: 2,680,000,000 miles at closest point

Mean Distance from Sun: 2,796.46 million miles (4,497 million km)

Satellites: 13

Rings: 4

PLUTO

PLUTO, NAMED AFTER THE ROMAN AND GREEK GOD OF THE

UNDERWORLD, IS THE COLDEST, SMALLEST, AND

OUTERMOST PLANET IN OUR SOLAR SYSTEM. PLUTO AND ITS

MOON, CHARON, ARE CALLED ―DOUBLE PLANETS‖ BECAUSE

CHARON IS SO LARGE IT SEEMS LESS OF A MOON THAN

ANOTHER PLANET. PLUTO WAS PREDICTED TO EXIST IN 1905

AND DISCOVERED IN 1930. IT IS THE ONLY PLANET THAT HAS

NOT YET BEEN STUDIED CLOSELY BY A SPACE PROBE.

DURING EACH REVOLUTION AROUND THE SUN, PLUTO

PASSES INSIDE NEPTUNE'S ORBIT FOR 20 YEARS, MAKING

NEPTUNE THE OUTERMOST PLANET FOR THAT TIME. PLUTO

PASSED INSIDE NEPTUNE'S ORBIT IN 1979 AND REMAINED

THERE UNTIL 1999.

(AUGUST 24, 2006)

PLUTO DEMOTED!

Size: Less than one-fifth the size of Earth in diameter

Diameter: 1,423 miles? (2,290 km?)

Surface: A giant snowball of methane and water mixed with rock

Atmosphere: Methane

Temperature: between –369° and –387°F (–223° and –233°C)

Rotation of its axis: 6 days, 9 hours, 18 minutes



Distance from Earth: At the closest point, 2.67 billion miles

Mean Distance from Sun: 3,666 million miles (5,900 million km)

Satellites: 1

Rings: ?

THE MOON

At a distance of 384,400 km from the Earth, the Moon is our closest celestial neighbor and

only natural satellite. Because of this fact, we have been able to gain more knowledge about it

than any other body in the Solar System besides the Earth. Like the Earth itself, the Moon is

unique in some ways and rather ordinary in others.

The Moon is unique in that it is the only spherical satellite orbiting a terrestrial planet. The

reason for its shape is a result of its mass being great enough so that gravity pulls all of the

Moon's matter toward its center equally.

Another distinct property the Moon possesses lies in its size compared to the Earth. At 3,475

km, the Moon's diameter is over one fourth that of the Earth's. In relation to its own size, no

other planet has a moon as large.

For its size, however, the Moon's mass is rather low. This means the Moon is not very dense.

The explanation behind this lies in the formation of the Moon. It is believed that a large body,

perhaps the size of Mars, struck the Earth early in its life. As a result of this collision a great

deal of the young Earth's outer mantle and crust was ejected into space. This material then

began orbiting Earth and over time joined together due to gravitational forces, forming what is

now Earth's moon. Furthermore, since Earth's outer mantle and crust are significantly less

dense than its interior explains why the Moon is so much less dense than the Earth.

When viewed from Earth, the many impact craters fround on the Moon's surface are visible.

The reason for this is simple. Unlike the Earth, the Moon is not geologically active, and so it

does not possess an atmosphere nor does it possess volcanic activity. Consequently, the

Moon does not undergo resurfacing as does the Earth.

THE MOON'S PHASES The lunar month is the 29.53 days it takes to go from one new

moon to the next. During the lunar month, the Moon goes

through all its phases. You can see the phases drawn in the

image below. Just like the Earth, half of the Moon is lit by the Sun

while the other half is in darkness. The phases we see result

from the angle the Moon makes with the Sun as viewed from

Earth.

At new moon, the Moon is lined up between the Earth and the

Sun. We see the side of the Moon that is not being lit by the Sun

(in other words, we see no Moon at all, because the brightness

of the Sun outshines the dim Moon!) When the Moon is exactly

lined up with the Sun (as viewed from Earth), we experience an

eclipse.

As the Moon moves eastward away from the Sun in the sky, we see a bit more

of the sunlit side of the Moon each night. A few days after new moon, we see a

thin crescent in the western evening sky. The crescent

Moon waxes, or appears to grow fatter, each night. When half of the Moon's

disc is illuminated, we call it the first quarter moon. This name comes from

the fact that the Moon is now one-quarter of the way through the lunar

month. From Earth, we are now looking at the sunlit side of the Moon from off

to the side.

The Moon continues to wax. Once more than half of the disc is illuminated, it

has a shape we call gibbous. The gibbous moonappears to grow fatter each

night until we see the full sunlit face of the Moon. We call this phase the full

moon. It rises almost exactly as the Sun sets and sets just as the Sun rises the

next day. The Moon has now completed one half of the lunar month.

During the second half of the lunar month, the Moon grows

thinner each night. We call this waning. Its shape is still gibbous

at this point, but grows a little thinner each night. As it

reaches the three-quarter point in its month, the Moon

once again shows us one side of its disc illuminated and the

other side in darkness. However, the side that we saw dark at the

first quarter phase is now the lit side. As it completes its journey

and approaches new moon again, the Moon is a waning

crescent.

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