Life on earth could be wiped out entirely if any of these cosmic catastrophes ever get to happen.
Dangerous impact. Credit: Don Davis/NASA
If you ask yourself what the biggest threat to human existence is
you'd probably think of nuclear war, global warming or a large-scale
pandemic disease. But assuming we can overcome such challenges, are we
really safe?
Living on our blue little planet seems safe until you are aware of
what lurks in space. The following cosmic disasters are just a few ways
humanity could be severely endangered or even wiped out. Happy reading!
1. High energy solar flare
Our sun is not as peaceful a star as one might initially think. It
creates strong magnetic fields that generate impressive sun spots,
sometimes many times larger than Earth. It also ejects a stream of
particles and radiation – the solar wind. If kept in check by Earth’s
magnetic field, this wind can cause beautiful northern and southern
lights. But when it becomes stronger, it can also influence radio
communication or cause power outages.
The most powerful magnetic solar storm documented hit Earth in
1859. The incident, called the Carrington Event, caused huge
interference with rather small scale electronic equipment. Such events
must have happened several times in the past, too, with humans
surviving.
But only in recent years have we become entirely dependent on
electronic equipment. The truth is we would suffer greatly if we
underestimate the dangers of a possible Carrington or even more powerful
event. Even though this would not wipe out humanity instantly, it would
represent an immense challenge. There would be no electricity, heating,
air conditioning, GPS or internet – food and medicines would go bad.
2. Asteroid impact
We are now well aware of the dangers asteroids could pose to
humanity – they are, after all, thought to have contributed to the
extinction of the dinosaurs. Recent research has made us aware of the
large host of space rocks in our solar system that could pose danger.
We are at the starting point of envisaging and developing systems
for protecting us against some of the smaller asteroids that could
strike us. But against the bigger and rarer ones we are quite helpless.
While they would not always destroy Earth or even make it uninhabitable,
they could wipe out humanity by causing enormous tsunamis, fires and
other natural disasters.
3. Expanding sun
Where the previous cosmic dangers occur at the roll of a dice with a
given probability, we know for certain that our sun will end its life
in 7.72 billion years. At this point, it will throw off its outer
atmosphere to form a planetary nebula, ending up as a stellar remnant
know as a “white dwarf”.
But humanity will not experience these final stages. As the sun
becomes older, it will become cooler and larger. By the time it becomes a
stellar giant it will be big enough to engulf both Mercury and Venus.
Earth might seem safe at this point, but the sun will also create an
extremely strong solar wind that will slow down the Earth. As a result,
in about 7.59 billion years, our planet will spiral into the outer
layers of the hugely expanded dying star and melt away forever.
4. Local gamma ray burst
Extremely powerful outbursts of energy called gamma ray bursts can
be caused by binary star systems (two stars orbiting a common centre)
and supernovas (exploding stars). These energy bursts are extremely
powerful because they focus their energy into a narrow beam lasting no
longer than seconds or minutes. The resulting radiation from one could
damage and destroy our ozone layer, leaving life vulnerable to the sun’s
harsh UV radiation.
Astronomers have discovered a star system – WR 104 – that could
host such an event. WR 104 is about 5,200-7,500 light years away, which
is not far enough to be safe. And we can only guess when the burst will
happen. Luckily, there is the possibility that the beam could miss us
entirely when it does.
5. Nearby supernovas
Supernova explosions, which take place when a star has reached the
end of its life, occur on average once or twice every 100 years in our
Milky Way. They are more likely to occur closer to the dense centre of
the Milky Way and we are about two-thirds of the way from the middle –
not too bad.
So can we expect a nearby supernova anytime soon? The star
Betelgeuse – a red super giant nearing the end of its life – in the
constellation of Orion is just 460-650 light years away. It could become
a supernova now or in the next million years. Luckily, astronomers have
estimated that a supernova would need to be within at least 50 light
years of us for its radiation to damage our ozone layer. So it seems
this particular star shouldn’t be too much of a concern.
6. Moving stars
Meanwhile, a wandering star on its path through the Milky Way might
come so close to our sun that it would interact with the rocky “Oort
cloud” at the edge of the solar system, which is the source of our
comets. This might lead to an increased chance of a huge comet hurtling
to Earth. Another roll of the dice.
The sun itself follows a path through the Milky Way that takes us
through more or less dense patches of interstellar gas. Currently we are
within a less dense bubble created by a supernova. The sun’s wind and
solar magnetic field help create a bubble-like region surrounding our
solar system – the heliosphere – which shields us from interacting with
the interstellar medium. When we leave this region in 20,000 to 50,000
years (depending on current observations and models), our heliosphere
could be less effective, exposing Earth. We would possibly encounter
increased climate change making life more challenging for humanity – if
not impossible.
And life goes on…
The end of humanity on Earth is a given. But this is not something
to make us crawl under a table. It is something that we cannot change,
similar to our lives having a definite start and end. This is what
defines us and makes us realise that the only thing we can do is make
the most of our time on Earth. Especially when we know that Earth needs a
careful balance to sustain humanity.
All the above scenarios harbour possible destruction, but in every
instance they also offer beauty and wonder. In many cases, they produce
what allowed us to be created. So rather than looking into the night sky
and wondering what will kill us next, we should marvel at the depth of
space, the wonders therein and the sublime nature of the universe. Be
inspired by space. It offers future and meaning.
Daniel Brown, Lecturer in Astronomy, Nottingham Trent University.
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