The asteroid hunters: how new technology will help save Earth from a catastrophic collision

An asteroid was spotted curving towards Earth on 4 September , but was too puny to cause any damage.

The Philippines island of Luzon was in the line of fire, and there was nothing they could do about it.

Planetary defence is a field of applied science known as planetary defence.

While space agencies are building spacecraft and developing technology to deflect (or destroy) incoming asteroids, others have their eyes on the sky.

Nasa recently gave the green light to begin building Nasa 's NEO Surveyor mission.

Instead of using reflected starlight to find asteroids, it's going to seek out their heat signatures.

Using visible light to spy asteroids allows astronomers to catch sight of moving objects and get an estimate of their size.

But there is an issue with this method: a small asteroid that has a shiny rocky coating reflects as much light as a bigger asteroid with a dull, charcoal-like coating.

The world is besieged by conundrums: the climate crisis, war, poverty, political instability, pandemics, environmental destruction. Earth is a beautiful, troubled place. But, increasingly, it’s one protected from threats originating from beyond the firmament and for that, we can most certainly be thankful. Dr Robin George Andrews is the author of How to Kill an Asteroid: The Real Science of Planetary Defence ( WW Norton & Company , 19.99 ). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply.