Exploring a neutron star

If we could be transported to the surface of a neutron star, we would be destroyed down to the atomic level or beyond before we even knew we'd arrived.

The environment is so hostile that nothing familiar to us could survive there. Pulsars, cosmic radio sources discovered in the 1960s, are believed to be rapidly rotating neutron stars.

We are familiar with the idea that atoms consist of a nucleus, containing a collection of protons and neutrons, which is surrounded by a cloud of electrons.

Compared with the diameter of the atom, the nucleus and electrons are tiny. Atoms are almost entirely empty space.

However, despite their apparent emptiness, atoms are highly resistant to compression, which is why we can walk on the ground without falling through, and can pick things up and interact with our environment.

However, in the explosion at the end of the life of a giant star, the shock waves can be intense enough to compress the star's core so hard the atoms themselves collapse. The electrons are jammed into the nucleus where they meld with the protons to make neutrons.

The result is that the core of the star becomes a lump of neutrons, occupying vastly less space. This is a possible fate for stars around 1.4 times the mass of the Sun, or larger.

The compression that occurs when the atoms collapse takes us from a star maybe two million kilometres in diameter down to a ball of neutrons 20 km or so across.

If one could bring a teaspoonful of neutron star material to Earth, it would weigh about a billion tonnes. On a neutron star, we would weigh about 100 billion times what we weigh on Earth.

The temperature would thousands of degrees Celsius, and the air we'd be breathing would include vaporized metals.

Stars contain a large amount of magnetism. When they are compressed into neutron stars the magnetic fields are compressed, too. The result is that on the surface the magnetic fields are billions of times stronger than the strongest laboratory magnetic fields we can make on Earth.

This means that if we were wandering around on the surface of a neutron star and not being crushed or roasted, we would find something really odd. There is an easy direction to walk and a hard one. Just as beads slide easily along a string, we would find it easy to walk back and forth along the magnetic field.

However, walking at right angles would mean crossing the magnetic field, which would be really hard. The Earth's magnetic field is so weak by comparison we don't notice this effect.

When a spinning star collapses to a smaller diameter, the rotation speeds up, so our neutron star could be rotating many times a second.

The intense magnetic field reaches far out into space and gets connected to nearby clouds of material that are not rotating as quickly, so the magnetic fields get wound up, snap, and release energy, producing intense X-rays, other radiation, and radio emissions.

Assuming we are surviving the radiation too, it would be worth looking at the ground we are walking on. It would be glowing, because it is hot, but also it would not be like the ground here on Earth.

It would be fibrous, like a doormat, or grainy, like wood. This is because the lines of magnetic force extend into the ground, forcing the material to coagulate along the direction of the magnetic field rather than across it.

Gardening would be no fun because the magnetic fields would make it extremely hard to turn the soil over. It is unlikely we will ever even get close to a neutron star, or even try to.

These are objects we will continue to observe from a safe distance and comprehend through physics.

About 2,000 neutron stars have been discovered scattered around our galaxy, the Milky Way.

• Mars is now lost in the sunset glow.
• Jupiter and Saturn rise around midnight and will lie low in the south at dawn.
• The Moon will be Full on the 24th.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.