x Abu Dhabi, UAESaturday 25 November 2017

Astronomers look to have made a golden neutron star discovery

A US observatory is rumoured to have witnessed a collision between two of these mind-boggling stars, which would have produced ripples in spacetime and could lead to the answer to the mystery of the origin of gold

ACKD0T "LIGO Facility near Richland Washington USA on the Hanford Reservation". Image shot 04/2007. Exact date unknown.
ACKD0T "LIGO Facility near Richland Washington USA on the Hanford Reservation". Image shot 04/2007. Exact date unknown.

The rumours began late last month with an enigmatic tweet from a scientist at the University of Texas. It read: “New LIGO. Source with optical counterpart. Blow your sox off!”

In an instant, astronomers around the world knew what this meant – a discovery of huge proportions.

LIGO stands for the US-based Laser Interferometer Gravitational-Wave Observatory, which made global headlines last year by detecting ripples in the fabric of space and time caused by the collision of two black holes.

Since then, astronomers have been waiting for LIGO to detect other cosmic cataclysms.

Now the word is that it’s succeeded – and this time the culprit is even more bizarre than a black hole.

There are some pretty weird things in our universe, from giant black holes that devour entire stars to invisible forces propelling the universe. Yet there’s nothing quite as mind-boggling as the object at the centre of the current rumours: a neutron star.

Predicted by theorists in the 1930s and discovered almost exactly 50 years ago, neutron stars are the stuff of nightmares.

Born during the death-throes of giant stars at least 10 times more massive than our sun, they consist of matter crushed to the point where everything turns into the eponymous sub-atomic particle.

That requires unimaginably high pressures – and leads to neutron stars cramming the mass of a couple of suns into a ball smaller than Dubai’s coastline.

Not that you’d want to get anywhere near one of these things: they have a surface temperature of at least 1,000,000C, and magnetic fields 100 million times stronger than the Earth’s.

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But just supposing it were possible to get close enough to examine one, you would be in for the biggest surprise of all. Neutron stars have an incredibly smooth surface made from solid iron.

It’s an outrageous mix of properties that has often sprung surprises on astronomers.

When the first one was discovered in the summer of 1967 by British graduate student Jocelyn Bell, its tell-tale radio bursts were so regular that she and her colleagues initially suspected they had made contact with aliens. They even called the source LGM-1 – for “Little Green Man”.

Announcing the discovery, Bell and her colleagues suggested the source might be some kind of vibrating star. But theorists realised the answer was far stranger: a spinning neutron star whose magnetic field focused radio waves like the beam of a lighthouse.

The discovery led to a Nobel Prize for Bell’s supervisor (controversially, Bell herself was ignored), and neutron stars have been a source of Nobel prize-winning insights ever since.

A pair of pulsars found orbiting each other turned out to be spiralling in towards one another and emitting gravitational waves. While the waves couldn’t be detected – LIGO was still decades in the future - the rate of orbital decay agreed with Einstein’s theory of gravity, and won its discoverers another Nobel prize.

Now astronomers at LIGO may be about to make a bid for their own neutron star-related Nobel.

Following last month’s tweet, reports have been circulating that the gigantic instruments at LIGO have detected ripples in spacetime produced by a collision between two neutrons stars.

While officials at LIGO refuse to confirm the rumours, publicly available records show that at least three orbiting telescopes have been turned towards the same patch of sky.

Tellingly, these telescopes are normally used to study events emitting gamma rays, X-rays and ordinary light – and neutron star collisions are expected to produce all three.

One image taken by the Hubble Space Telescope even carried a caption saying it showed a “BNS-MERGER”, the technical name for a binary neutron star collision.

If the rumours are true, then astronomers may be about to get their first detailed insights into the life and death of these bizarre objects. They may also be able to give Einstein’s theory of gravity its best work-out yet.

Combined with their celebrated discovery of gravitational waves from colliding black holes, doing the same for neutron stars would more or less guarantee a Nobel for the founders of LIGO, who were surprisingly overlooked last October.

And there may also be something in the discovery for the rest of us: the answer to a

long-standing mystery about the origin of gold.

Most chemical elements are created in the furnaces of exploding stars but the sheer rarity of gold suggests it’s an exception. As we reported in 2012, scientists now think that there’s only one event extreme enough to create this precious metal: the collision of neutron stars.

The data now being pored over by astronomers may be about to make this coveted metal seem even more special.

Robert Matthews is Visiting Professor of Science at Aston University, Birmingham, UK