Mark Thompson - 101 Facts You Didnt Know About Space

101 FACTS

YOU DIDNT KNOW ABOUT

SPACE

MARK THOMPSON

First published in Great Britain in 2020 by White Owl

An imprint of

Pen & Sword Books Ltd

Yorkshire Philadelphia

Copyright Mark Thompson, 2020

ISBN 9781526744579

ePUB ISBN 9781526744586

Mobi ISBN 9781526744593

The right of Mark Thompson to be identified as Author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

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Design by Paul Wilkinson

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The Sun is at the very heart of our Solar System and on average 150 million kilometres away from us. It rises in the east and sets in the west, has been there since we were born and should be there until the day we die! To many it never seems to change, but get close up and personal with the Sun and you begin to appreciate that it is so much more than just a glowing ball of light in the sky that makes us warm on a sunny day.

The Sun is a massive ball of gas, more accurately a ball of plasma, which is an electrically charged gas. It has a visible surface which we call the photosphere, where temperatures vary between 4,500 K and 6,000 K (kelvin scale of temperature measurement) and it is here where sunspots can be seen. Directly below the photosphere is the convective zone, which is 200,000 km thick, and it is here that energy from the core of the Sun is transferred through convection (the process where warmer material is less dense and rises while cooler material is more dense and sinks). Below the convective zone is the radiative zone, which is 300,000 km thick, and where the process of radiation transfers the heat. Beneath the radiative zone is the core of the Sun and it is here that the energy is actually produced. The core of the Sun has a radius of 153,000 km and the temperatures soar to a toasty 15 million K!

The process by which the Sun creates its energy is through fusion, the joining of hydrogen molecules to create helium molecules. It is actually a little more complex than that but it takes four hydrogen molecules to fuse together to produce a helium molecule, and when they do, they give off a little bit of energy. This energy is the heat and light we experience from the Sun but the figures are vast and almost incomprehensible. Every second, the fusion process converts around 700 million tonnes of matter from hydrogen into helium, but 5 million tonnes gets converted into energy (in accordance with Einsteins famous equation E=mc2).

The nuclear fusion happens in the core, which as we have seen is 306,000 km in diameter, but the Sun itself is 1.39 million km in diameter so the vast majority of energy production happens in a relatively small volume. The power output of the core is estimated to be 276 watts per cubic metre which, when compared to a typical household light bulb of 60 or 100 watts is not a great deal and is around the same as a fairly typically sized compost heap!

Surprising? Even though the power output is 276 watts per cubic metre there are LOTS of cubic metres in the Sun, 15 million billion cubic metres to be exact, so if you multiply the 276 watts per cubic metre you can understand how the power output volume for volume can be less than a compost heap, but the overall output of the Sun is much greater.

The Sun as seen by the SOHO (Solar and Heliospheric Observatory) spacecraft, revealing detail in the solar chromosphere. (NASA)

FACT 2

Venus smells like rotten eggs

What does Earth smell like? It is pretty tricky to name one smell because it largely depends where you are and even on the weather. For example cities and towns smell of many different things including traffic fumes whereas a forest has that lovely green smell we associate with nature. If it rains then the impact of drops of water on soil can release aerosol gasses giving rain that fresh smell. Other planets have smells too but until human visitors can breathe in their air (which is highly unlikely due to their atmospheric composition) we can only guess what they smell like.

Consider Venus. Whilst Venus is the second planet from the Sun it surprises most that it is hotter than Mercury, which is closer. The conditions on Venus are really quite hostile thanks to the greenhouse effect. You will have heard that phrase before and it originates from the way certain gasses cause a planet to warm up. The warmth you feel on a sunny day isnt solely because energy from the Sun hits your body and warms you up, instead, energy from the Sun traverses through our atmosphere, warms the ground, which then re-radiates the energy back into the atmosphere, which makes the lower atmosphere where we live nice and warm. A lot of the re-radiated energy then escapes out into space, moderating the temperature. The presence of greenhouse gasses can stop the energy radiating out into space just like glass stops heat escaping from a greenhouse.

Venus has suffered from the greenhouse effect for millions of years due to its proximity to the Sun and to significant volumes of carbon dioxide, a greenhouse gas, being released into its atmosphere. The Venusian atmosphere is almost entirely carbon dioxide and, with the release of sulphuric acid from volcanoes and atmospheric chemical reactions it even rains sulphuric acid from the thick dense clouds. The temperature in the atmosphere means the raindrops evaporate before they hit the ground. Thanks to spacecraft that have visited Venus such as Vanera and Mariner we now have a very good model of its atmosphere and can infer that the presence of sulphuric acid and hydrogen sulphide will cause the spacecraft of anyone brave enough (or stupid enough) to venture to Venus to fill with the rather pungent smell of rotten eggs as you prepare for landing!

Visible light image of Venus showing the tops of its thick dense atmosphere. (NASA)

FACT 3

You are made of stardust

Look around you, what can you see? If you are at home then you might see other members of your family, a sofa and perhaps a TV, or if you are sat in a coffee shop you might see a street scene with cars and buses. Everything you can see is made up of a multitude of different atoms from iron to carbon, but when the Universe formed over 13 billion years ago the first atoms were mostly hydrogen and helium. Somehow, something happened, some physical process turned hydrogen and helium into the stuff we see in the Universe today.