23Apr2017

Outer Space Is Heavy

Do we mean how heavy something is, or how big it is? Maybe it is how much material it contains? To understand we have to know a few things.

Like the difference between “weight” and “mass” and how they relate to each other. Weight is the measure of how strongly gravity pulls downwards on an object but mass is a measure of how much matter something contains.

So an objects weight is how hard gravity is pulling on it and on Earth if something has a mass of 100Kg then the force of gravity will cause it to have a weight of 100Kg. We think the weight is the same everywhere … because we all live on the surface of the planet Earth but in orbit the object would not push on the scales at all.

The scales would show 0Kg but the mass would stay the same. On the Moon an object with a weight of 100Kg on Earth would weigh just 16.6Kg but its mass would remain the same! Another factor we need to take into account when measuring an object is density. The density of a substance is the relationship between the mass of the substance and how much space it takes up (volume). The mass of atoms, their size, and how they are arranged determine the density of a substance.

So why is all this of interest? Well when a large star (about twice the size of our Sun) reaches the end of its life it begins to expand before exploding in a cataclysmic supernova.

The outer layers are blown out into space while at the core, nuclear fusion ceases and because there is no longer any outward pressure to balance the force of gravity the star rapidly condenses and collapses in on itself and it becomes a neutron star and the thing about neutron stars is that they have a small diameter (around 20Km) but a mass of about 1.5 times our Sun and are incredibly dense!

Neutron Star Collision

A tea spoon of neutron star matter would weigh about one hundred million tons on Earth. Now that is heavy! The core of a neutron star is under immense pressure which may be similar to that which existed at the time of the Big bang.

When neutron stars form they begin to rotate and as they compress and shrink they begin to spin faster and faster, just like an pirouetting ice skater speeds up they draw in their arms. This is due to the conservation of angular momentum. Most neutron stars will slow down over time but some will continue to spin rapidly and will emit radiation, that when seen from Earth, resembles a light house flashing its light.

These stars are given the name “Pulsars” but even they will eventually slow down and become regular neutron stars. Very few neutron stars become pulsars and we believe there are only about 1000 known pulsars compared to the billions of old neutron stars.  Express&Echo

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