There Could Be Carbon-Rich Exoplanets Made Of Diamonds

llustration of a carbon-rich planet with diamond and silica as main minerals. Water can convert a carbide planet into a diamond-rich planet. In the interior, the main minerals would be diamond and silica (a layer with crystals in the illustration). The core (dark blue) might be iron-carbon alloy. Credit: Shim/ASU/Vecteezy

Scientists are getting better at understanding exoplanets. We now know that they’re plentiful, and that they can even orbit dead white dwarf stars. Researchers are also getting better at understanding how they form, and what they’re made of.

A new study says that some carbon-rich exoplanets could be made of silica, and even diamonds, under the right circumstances.

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Carbon “Super Earths” – Diamond Planets

Iron, carbon, and oxygen subjected to intense temperatures and pressures form a pocket of iron oxide (bottom, center) and a darker pocket of diamond (bottom, right). Electron micrograph courtesy of Ohio State University

[/caption]During a laboratory experiment at Ohio State University, researchers were simulating the pressures and conditions necessary to form diamonds in the Earth’s mantle when they came across a surprise… A carbon “Super Earth” could exist. While endeavoring to understand how carbon might behave in other solar systems, they wondered if planets high in this element could be pressurized to the point of producing this valuable gemstone. Their findings point to the possibility that the Milky Way could indeed be home to stars where planets might consist of up to 50% diamond.

The research team is headed by Wendy Panero, associate professor in the School of Earth Sciences at Ohio State, and doctoral student Cayman Unterborn. As part of their investigation they incorporated their findings from earlier experiments into a computer modeling simulation. This was then used to create scenarios where planets existed with a higher carbon content than Earth..

The result: “It’s possible for planets that are as big as fifteen times the mass of the Earth to be half made of diamond,” Unterborn said. He presented the study Tuesday at the American Geophysical Union meeting in San Francisco.

“Our results are striking, in that they suggest carbon-rich planets can form with a core and a mantle, just as Earth did,” Panero added. “However, the cores would likely be very carbon-rich – much like steel – and the mantle would also be dominated by carbon, much in the form of diamond.”

At the center of our planet is an assumed molten iron core, overlaid with a mantle of silica-based minerals. This basic building block of Earth is what condensed from the materials in our solar cloud. In an alternate situation, a planet could form in a carbon-rich environment, thereby having a different planet structure – and a different potential for life. (Fortunately for us, our molten interior provides geothermal energy!) On a diamond planet, the heat would dissipate quickly – leading to a frozen core. On this basis, a diamond planet would have no geothermal resources, lack plate tectonics and wouldn’t be able to support either an atmosphere or a magnetic field.

“We think a diamond planet must be a very cold, dark place,” Panero said.

How did they come up with their findings? Panero and former graduate student Jason Kabbes took a miniature sample of iron, carbon, and oxygen and subjected it to pressures of 65 gigapascals and temperatures of 2,400 Kelvin (close to 9.5 million pounds per square inch and 3,800 degrees Fahrenheit – conditions similar to the Earth’s deep interior). As they observed the experiment microscopically, they saw oxygen bonding with iron to create rust… but what was left turned to pure carbon and eventually formed diamond. This led them to wonder about planetary formation implications.

“To date, more than five hundred planets have been discovered outside of our solar system, yet we know very little about their internal compositions,” said Unterborn, who is an astronomer by training.

“We’re looking at how volatile elements like hydrogen and carbon interact inside the Earth, because when they bond with oxygen, you get atmospheres, you get oceans – you get life,” Panero said. “The ultimate goal is to compile a suite of conditions that are necessary for an ocean to form on a planet.”

But don’t confuse their findings with recent, unrelated studies which involves the remnants of an expired star from a binary system. The OSU team’s finding simply suggest this type of planet could form in our galaxy, but how many or where they might be is still very open to interpretation. It’s a question that’s being investigated by Unterborn and Ohio State astronomer Jennifer Johnson.

Because diamonds are forever…

Original Story Source: Ohio State Research News.

Star Transforms Into A Diamond Planet

Schematic view of the Pulsar-Planet system PSR J1719-1438 showing the pulsar with 5.7 ms rotation period in the centre, and the orbit of the planet in comparison to the size of the sun (marked in yellow). Credit: Swinburne Astronomy Productions, Swinburne University of Technology


“Remember when you were young… You shone like the sun.” Four thousand light years away in the constellation of Serpens, a millisecond pulsar binary is pounding out its heartbeat. Meanwhile an international research team of scientists from Australia, Germany, Italy, the UK and the USA, including Prof. Michael Kramer from Max Planck Institute for Radio Astronomy in Bonn, German are listening in. Utilizing the 64-m radio telescope in Parkes, Australia, the team made a rather amazing discovery. The companion star could very well be an ultra-low mass carbon white dwarf… one that’s transformed itself into a planet made of pure diamond.

“The density of the planet is at least that of platinum and provides a clue to its origin”, said the research team leader, Prof. Matthew Bailes of Swinburne University of Technology in Australia. Bailes leads the “Dynamic Universe” theme in a new wide-field astronomy initiative, the Centre of Excellence in All-sky Astrophysics (CAASTRO). He is presently on scientific leave at Max Planck Institute for Radio Astronomy.

Like a lighthouse, PSR J1719-1438 emits radio signals which sweep around methodically. When researchers noticed a specific modulation every 130 minutes, they realized they were picking up a signature of planetary proportions. Given the distance of its orbit, the companion could very well be the core of a once massive star whose material was consumed by pulsar’s gravity.

“We know of a few other systems, called ultra-compact low-mass X-ray binaries, that are likely to be evolving according to the scenario above and may likely represent the progenitors of a pulsar like J1719-1438” said Dr. Andrea Possenti, of INAF-Osservatorio Astronomicodi Cagliari.

With almost all of its original mass gone, very little of the companion could be left save for carbon and oxygen… and stars still rich in lighter elements like hydrogen and helium won’t fit the equation. This leaves a density which could very well be crystalline – and a composition which closely resembles diamond.

“The ultimate fate of the binary is determined by the mass and orbital period of the donor star at the time of mass transfer. The rarity of millisecond pulsars with planet-mass companions means that producing such ‘exotic planets’ is the exception and not the rule, and requires special circumstances”, said Dr. Benjamin Stappers from the University of Manchester.

“The new discovery came as a surprise for us. But there is certainly a lot more we’ll find out about pulsars and fundamental physics in the following years”, concludes Michael Kramer.

Shine on, you crazy diamond…

Original Story Source: Max Planck Institut for Radio Astronomy and Transformation of a Star into a Planet in a Millisecond Pulsar Binary.