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 The
greatest distance astronomers can see into the
Universe is about 15,000 million light years,
although this is not necessarily the edge of the
universe.
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Our
own galaxy measures about 950,000 million km
across. It is only one among millions of other
galaxies. All the galaxies and the space
around make up the Universe.
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The
distances in the Universe are so great that it is
difficult to imagine them. If the Sun was the
size of a ball 1.8 m across, then Pluto, the most
distance planet would be the size of a pea 7.6 km
away. But our nearest star would be about
52,000 km or 32,313 miles away.
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All the members of the Solar System
move about other objects. The moons are
circling their parent planets, the planets circle
the Sun while each spins about its axis at the same
time. The Sun also spins and the whole
Solar System is moving around the galaxy it lies in.
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Views
from Earth, by far the brightest of the planets
visible tot he naked eye is Venus. It is often
called the "evening star." The
faintest planet is Pluto. It can only be seen
through a telescope.
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The
Earth is a very special planet because it is the
only place in the Solar System, and the only known
place in the entire Universe, to support life. If it
was closer to the Sun it would be too hot to support
life and if it was farther away it would be too
cold.
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The
Sun is a star, one of 100,00 0
million starts in our galaxy, the Milky Way.
Although it is a very ordinary star in the galaxy,
it is very important in our Solar System; without it
there would be no life on Earth.
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The
temperature in the middle of the Sun
 reaches
15 million o C (27 o F)
If a pinhead was this hot, it would set light to and
destroy everything for 60 miles around it.
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Just
one square centimeter of the Sun's surface shines
with the brightness of 232,500 candles.
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Eclipses
of the Sun take place when the Sun, Moon and Earth
are all lined up so that the Moon blocks out the
sunlight. In 585BC an eclipse happened in the
middle of a battle between the Lydians and
Medes. The armies made peace.
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 The
Moon is the closest planet to Earth. Its
average distance from Earth is only 384,000km or
239,000 miles. A train traveling at 161k/h
(100 miles per hour) would take 99.5 days to cover
the distance.
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The
Moon takes just over 27 days to travel around the
Earth. It always keeps the same half facing
the Earth. The far side of the Moon had never
been seen until the USSR spacecraft Luna 3 took the
first photographs in 1959.
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The
largest crater we can see on the Moon is called
Bailly and covers an area of about 67,300 square km
(26,000 square miles). If Bailly was brought
down to Earth, Scotland could sit comfortably inside
it.
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The
Moon has no atmosphere and contains no water.
Its soil is so dry that nothing will grow in
it. But scientists have found that with air
and water, plants can grow in Moon soil on Earth.
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The
Moon is a completely silent place. Noises
cannot be heard as there is no air to carry sound
from one place to another.
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Footprints
left on the Moon by the Apollo
astronauts will probably be visible for at least 10
million years.
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The
pull of gravity of the Earth on the Moon keeps the
Moon circling around the Earth. The Moon's
gravity also pulls the water in the Earth's seas
toward it, causing the Earth's tides. If the
Moon was closer to Earth the pull of its gravity
would be much stronger and the tides would flood the
coastlines of the world.
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Mercury,
Venus and Mars along with the Earth, form a group of
four rocky planets unlike the others. They are
known as the inner planets because they are the
nearest to the Sun.
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Although
Mercury is surrounded by a thin layer of helium gas,
there is so little of it that the amount collected
form a 6.4 km (4 mil) diameter sphere would be just
enough to fill a child's small balloon.
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Venus
rotates east to west, in the opposite direction to
all the other planets. This means that the Sun
rises in the west and sets in the east.
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Jupiter
and Saturn are members of a group of four planets,
known as the "gas giants", which are very
different from the inner planets. They are
rocky in the middle, surrounded by liquid hydrogen
and covered with thick cloudy atmospheres.
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 Jupiter
is so big that if a bicyclist set out to travel
non-stop once around it at a speed of 9.6 km/h
(6mph), the journey would take more than five years
(1,935 days) to complete.
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Saturn
is the second biggest planet in the Solar System and
it is 95 times heavier than Earth. The volume
of Saturn is 744 times that of Earth.
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Uranus
and Neptune are a second pair of "gas
giants", though smaller than Jupiter and
Saturn. Pluto is a small, solid planet,
probably more like the rocky inner planets (Mercury,
Venus, Earth, and Mars). They are all far too
cold for anything to live on their surfaces.
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People
used to think that the most distant planet in the
Solar System was Saturn. But in 1781 an
astronomer called Sir William Herschel discovered a
faint planet which was late named Uranus. It
was the first planet to be discovered since the
Ancient Greeks.
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The
average distance of Neptune from the Sun is 4,500
million km (2,800 million miles). This is 30
times the distance between Earth and the Sun.
If a plane flew at 1,770 km/h (1,100mph), it would
take 289 years to travel from Neptune to the Sun.
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Pluto
was discovered in 1930. With a diameter of
2,400 km (1,500 miles) it is smaller than our Moon,
making it the smallest and lightest planet in the
Solar System.
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A
baby born on Pluto (if that was possible) would have
to wait 248 Earth years before it reached its first
birthday.
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For
most of the time, Pluto is the most distant planet
from Earth. A plane moving at a speed of 1,810
km/h (1,125 mph) would take about 370 years to
travel from Earth to Pluto.
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The
stars you can see in the night sky are really
distant suns. Our sun is only one very
ordinary star among millions of others. The
next nearest star to our Solar System is called
Proxima Centauri and is 4.25 light years away.
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Stars
are born form the huge clouds of
gas and dust known as nebulae that float in the
Universe. They begin to grow when part of a
cloud forms into a small lump. This grows
smaller and hotter until a nuclear reaction starts
and the star is born.
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The
longest name for any star is "Shurnarkabtishashutu",
the Arabic for "under the southern horn of the
bull.
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Double,
or binary, stars consist of two stars which circle
around each other. Close pairs of stars may
take only a day or even less to complete their
circuits, but pairs that are far apart may take over
a hundred years.
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About
1,000 open clusters are in our galaxy. The
Pleiades is one such cluster, containing about 400
stars. It is also known as the Seven Sisters
and can easily be found in the night sky without a
telescope.
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Eclipsing
stars are not the only ones whose brightness goes up
and down. There are some stars called the
Cepheid variables that actually swell and shrink
regularly. As they throb in and out their
brightness also rises and falls.
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Although
the stars in the night sky look close together, they
are really separated by huge stretches of
space. This space contains very small gas and
dust particles known as interstellar matter.
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Stars
are not scattered randomly throughout the Universe,
but are grouped together in giant clouds known as
galaxies. The Milky Way is the name of the
galaxy our Solar System lies in, in one of the
spiral arms.
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Our
galaxy is so huge that a flash of light moving at
its natural speed of 1,100 million km (670 million
miles) per hour would take 100,000 years to go from
one side of the galaxy to the other.
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Some
astronomers believe that although the Universe is
expanding it always looks the same. This is
because new galaxies are formed in the middle to
replace those that are moving outward. This is
known as the Steady State theory.
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Radio
telescopes are designed to pick up radio waves
coming from distant radio sources. The first
true radio telescope was built in 1937. The
main type of radio telescope today looks like a
giant dish. The radio waves are focused onto
the telescope's receiver above or below the dish.
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The
closest star to our Solar System is over four light
years away. The journey in a rocket today
would take nearly 200,000 years. Future rocket
engines have been suggested that would use beams of
light for power. These rockets could nearly
reach the speed of light, so the same journey would
take just over four years.
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The
following facts were extracted from the Usborne
Book of Space Facts, Struan Reid. |
