Chinese rocket's fall to earth: Why it's so hard to know where it will land

Astronomer Neil Norman watching out for the Chinese rocket stage. Picture: SARAH LUCY BROWN

Astronomer Neil Norman will be watching out for the re-entry of the Chinese rocket stage. Picture: SARAH LUCY BROWN - Credit: Archant

In his latest column, Suffolk astronomer Neil Norman gives his view on the Chinese rocket which is expected to fall back to earth this weekend - though nobody knows where.

We are all familiar with the International Space Station (ISS) passing over our skies on a regular basis, but it is soon to have competition from the Chinese space programme as they start construction on their very own version.

As I write this we are currently awaiting the re-entry of a Chinese rocket stage that was used on April 29 to send the first stage of the new space station into orbit.

Lots of media use the alarming headlines about it hurtling towards us at 17,000 mph and it will land on a populated area hurting dozens of people.

These facts are not (surprisingly!) true. The rocket stage is circling the Earth at 17,000 mph, not heading towards us at that speed.


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It is actually being pulled towards Earth at a rather leisurely 0.3mph, and this is why prediction of entry location is so hard because the exact point of our atmosphere getting a complete hold on it is hard to calculate.

Will it hit a populated area? Again, unknown. We can say that the chances are slim given that the vast majority of the planet is covered with oceans, but the risk is not ruled out completely.

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Will it cause damage should it hit a populated area? It certainly could. The stage is 18 tonnes in weight and a certain amount will land either on land or sea.

In fact, this is the largest item to make an unscheduled re-entry into the atmosphere in many years, and yes, you read that right, this is not planned.

The Chinese space agency has made a rather embarrassing blunder and should anything bad happen, consequences will have to be dealt with.

Satellites and rocket stages are normally deorbited in a controlled manner and the location they are aimed for is known as the satellite graveyard which is located in the Pacific ocean between Australia and New Zealand.

Interestingly though on any night you may yourself see a piece of man made space junk fall into the atmosphere before burning up and you can tell by the colour of it.

By now you are used to looking for meteor showers and occasionally you may have seen an extra bright fireball, did you notice the colour?

If it was yellow, it was iron and very likely a piece of asteroid.

A red one indicates a composition of nitrogen or oxygen, again another natural object, a purple colour is indicative of calcium, which again is natural but if you see meteors or fireballs that are coloured green/blue that indicates a composition of magnesium.

This has a high probability of being man made, perhaps something from a rocket stage, a bit of paint or maybe even a spanner or hammer lost by an astronaut on a space walk at some point in history.

Keep looking up and please do report any unusual fireballs or coloured meteors that you may see.

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