Planets & Solar System: The Complete Manual. An essential guide to our solar system

132 Pages·16.815 MB·English

W
E Planets &
N
Solar System
The Complete Manual
An essential guide to our solar system
Over
500

amazing
facts

Welcome to
Planets &
Solar System
The Complete Manual
Throughout history, humankind has looked up at the stars
and wondered what they were. Playing a central role in
mythology, philosophy and superstition, it wasn’t until
the rise of astronomy that we began to understand these
celestial bodies. After Galileo Galilei’s incredible discovery,
we now know the role of the Sun as the centre of a system
of planets, dubbed the Solar System. As new technology
advances we discover more and more about our fellow
planets, Mercury, Venus, Mars, Jupiter, Saturn, Uranus,
Neptune and the dwarf planet Pluto. Read on to discover
just how much we’ve learned about our neighbours so far,
and how much more knowledge is still to come.

Planets &
Solar System
The Complete Manual
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Planets & Solar System The Complete Manual © 2016 Imagine Publishing Ltd
ISBN 978 1785 462 801
Part of the
bookazine series
CONTENTS
8 B irth of the Solar System 64 M ars
Travel back to where it all began and discover Could there have been life on Mars? We're
how our Solar System came to be curious to discover
20 I nside the Sun 80 J upiter
Find out what makes the centre of our This gas giant is the largest in our Solar
universe tick System, but it's special in more ways too
92 S aturn
The rings of Saturn are a mesmerising
phenomenon and continue to amaze us
24 Mercury 104 U ranus
The smallest planet in our system has its This ice-cold planet has many secrets
own unique story to tell hidden within its layers
36 V enus 112 N eptune
There's a reason this earth-like planet is The distance may make it hard to research,
named after the goddess of love but distance makes the heart grow fonder
48 E arth 122 P luto
You may think you know Earth, but why is it This dwarf planet may have lost its status,
the only planet to host life? but it won our hearts
6
7
Birth of
the
SOLAR
SYSTEM
How did our Solar System form? Astronomers
thought they knew. But now, new research is
turning many of the old ideas on their heads
Around 4.5 billion years ago, our Sun and but also that the young Solar System was rather
all the other objects that orbit around it different from that we know now.
were born from an enormous cloud of The so-called ‘nebular hypothesis’ – the idea
interstellar gas and dust, similar to the glowing that our Solar System arose from a collapsing
emission nebulae we see scattered across today’s cloud of gas and dust – has a long history. As
night sky. Astronomers have understood this early as 1734, Swedish philosopher Emanuel
basic picture of the birth of the Solar System for a Swedenborg suggested that the planets were
long time, but the details of just how the process born from clouds of material ejected by the Sun,
happened have only become clear much more while in 1755 the German thinker Immanuel Kant
recently – and now new theories, discoveries and suggested that both the Sun and planets formed
computer models are showing that the story is alongside each other from a more extensive cloud
still far from complete. Today, it seems that not collapsing under its own gravity. In 1796, French
only did the planets form in a far more sudden mathematician Pierre-Simon Laplace produced a
and dynamic way than previously suspected, more detailed version of Kant’s theory, explaining
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how the Solar System formed from an initially very centre of the system, spin much faster than
shapeless cloud. Collisions within the cloud it does? Solutions to these problems would not
caused it to flatten out into a spinning disc, while come until the late 20th Century, and some of
the concentration of mass towards the centre them are still causing doubts even today.
caused it to spin faster (just as a pirouetting ice Much of what we know about the birth of our
skater spins faster when they pull their arms Solar System comes from observing other star
inwards towards their bodies). systems going through the same process today.
In the broad strokes described above, Laplace’s Stars are born in and around huge glowing
model is now known to be more or less correct, clouds of gas and dust, tens of light years
but he certainly got some details wrong, and left across, called emission nebulae (well known
some crucial questions unanswered – just how examples include the Orion Nebula, and the
and why did the planets arise from the nebula? Lagoon Nebula in Sagittarius). The nebulae glow
And why didn’t the Sun, concentrating more than in a similar way to a neon lamp, energised by
99 per cent of the Solar System’s mass at the radiation from the hottest, brightest and most
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Planets & Solar System
massive stars within them, and remain active for Inside the nebula, stars are incubated in huge
perhaps a few million years, during which time opaque pillars of gas and dust. As these pillars
they may give rise to hundreds of stars forming a are eroded by outside radiation from massive
loose star cluster. Since the brilliant, massive stars stars that have already formed, they break apart
age and die rapidly, it’s only the more sedate, into isolated dark globules whose internal gravity
lower-mass stars like our own Sun that outlive is strong enough to hold them together – the
both the nebula and the slow disintegration of seeds of individual solar systems. Gas falling
the star cluster. towards the very centre of the globule becomes
Star birth nebulae develop from the vast concentrated, growing hotter and denser until
amounts of normally unseen, dark gas and dust eventually conditions are right for nuclear fusion,
that forms the skeleton of our Milky Way galaxy, the process that powers the stars, to begin. As
and subside as the fierce radiation from their the star begins to generate energy of its own,
most massive stars literally blows them apart. its collapse stabilises, leaving an unpredictable
The initial collapse that kick-starts formation can stellar newborn surrounded by a vast disc of gas
be triggered in several ways – for instance by a and dust that will go on to form its solar system.
shockwave from a nearby exploding supernova, But how?
or by tides raised during close encounters with The first person to put Laplace’s hypothesis
other stars. However, the biggest waves of star on a sound theoretical footing was Soviet
birth are triggered when material orbiting in our astronomer Viktor Safronov, whose work was
galaxy’s flattened outer disc drift through a spiral- first translated from Russian in 1972. Safronov’s
shaped region of compression that extends from modified ‘solar nebular disk model’ allowed the
the galactic hub and gives rise to our galaxy’s Solar System to form from much less material,
characteristic shape. helping to resolve the problem of the Sun’s slow
"Star birth nebulae develop from the vast amounts of
unseen, dark gas and dust that forms our Milky Way”
How stars are formed
Disturbed nebula Slow collapse Flattening disc
A star is born when a cloud of Denser regions in the nebula Collisions between randomly
interstellar gas and dust passes collapse under their own moving gas clouds and dust
through a galactic density gravity. As mass concentrates particles tend to flatten out
wave, or is compressed by towards their centres, they their motions into a narrow
shock from a nearby supernova begin to spin more rapidly, and plane, creating a disc that spins
or tides from a passing star their cores grow hotter ever more rapidly
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