September 24, 2021

I, Science

The science magazine of Imperial College

Like an oyster in the ocean, opening to reveal a pearl, new research has discovered stars can be stripped apart to reveal diamonds.

Nicknamed “The Dish”, the Australian CSIRO Parkes telescope stumbled on the discovery whilst searching for pulsars, as part of the “High Time Resolution Universe” survey. Pulsar J1719-1438 had a peculiar signal and upon closer inspection they discovered it was being orbited by a dense planet, five times the size of Earth and made entirely of diamond.

Pulsars are stars with a diameter of around 12 miles, about half the size of the Isle of Wight. Astronomers at CSIRO use these pulsars to study some of the fundamental laws of the universe. About 2-3 of them are discovered every month, so it’s hardly breaking news when they find one. However, only certain pulsars such as, J1719-1438, are classed as rarer milisecond pulsars. This means they spin much faster than others and are likely to have unique properties. In this case of this star, it’s uniqueness was found in it’s companion, dubbed The Diamond Planet.

Even more unusual, CSIRO’s Dr Michael Keith explained, is that “Although the composition of this “diamond planet” is not really similar to any planets in our solar system, it orbits the pulsar more like a planet than a star. Typically pulsars and their companions both move in similar sized orbits, however in this case the large difference in weights means the pulsar does a rather small wobble whilst the companion swings around in a wide, circular, orbit.”

All stars, when they become white dwarves, find the carbon they are made from is put under such great pressures that it crystallises into diamond. Even our Sun, when it finally burns out, will find a diamond at its centre. This is how the universe’s largest, trillion carat diamond ‘Lucy’ formed. However, the Diamond Planet, appears to have befallen a sadder fate and was stripped down by the pulsar to reveal the diamond core within. Now only the diamond core remains, orbiting the pulsar and providing it with the energy to spin faster.

When asked if it can really be called a planet, since it used to be a star Keith answered, “certainly the object began its life as something that is unquestionably a star, however it now is clearly “of planetary mass”. It’s not too hard to imagine a situation where a gassy planet similar to Jupiter accreted enough mass to start nuclear burning and become a star, so why not go the other way round and have a star lose enough mass to become a planet.”

It seems that this discovery really is a diamond in the rough for astronomy.

Quote from Dr Michael Keith: How it feels to discover a planet

Image: Swinburne Astronomy Productions