Researchers reveal structure of carbon's 'Hoyle state'

December 10, 2012
Researchers reveal structure of carbon's 'Hoyle state'
Alpha clusters in the Carbon-12 nucleus forming a "bent arm" shape.

(—A North Carolina State University researcher has taken a "snapshot" of the way particles combine to form carbon-12, the element that makes all life on Earth possible. And the picture looks like a bent arm.

Carbon-12 can only exist when three , or helium-4 nuclei, combine in a very specific way. This combination is known as the Hoyle state. NC State physicist Dean Lee and German colleagues Evgeny Epelbaum, Hermann Krebs and Ulf-G. Meissner had previously confirmed the existence of the Hoyle state using a numerical lattice that allowed the researchers to simulate how the protons and neutrons interact. When the researchers ran their simulations on the lattice, the Hoyle state appeared together with other observed states of carbon-12, proving the theory correct from first principles.

But they also wanted to find out how the nucleons (the protons and neutrons inside the nucleus of an atom) were arranged inside the nucleus of carbon-12. This would enable them to "see" the structure of the Hoyle state. Using the same lattice, the researchers, along with collaborator Timo Laehde, found that -12's six protons and six neutrons formed three "alpha clusters" of four nucleons each. At low energy, the alpha clusters tended to clump together in a compact triangular formation. But for the Hoyle state, which is an excited , the three alpha clusters combined in a "bent arm" formation.

The researchers' findings will appear this month in .

"It's interesting that a straight chain seems not to be the preferred configuration for the Hoyle state," Lee says. "A bend in the chain seems necessary. This work leads us to the question of what other nuclei have such alpha cluster shapes. These would be rather exotic structures in and open some really interesting questions regarding shape and stability. For example, can we have longer chains of alpha clusters? We are investigating these possibilities."

Explore further: Pinning Down a Proton: Researchers Develop Method to Describe Binding of Protons and Neutrons

More information: "Structure and Rotations of the Hoyle State" Physical Review Letters, 2012.

The excited state of the 12C nucleus known as the "Hoyle state" constitutes one of the most interesting, difficult and timely challenges in nuclear physics, as it plays a key role in the production of carbon via fusion of three alpha particles in red giant stars. In this letter, we present ab initio lattice calculations which unravel the structure of the Hoyle state, along with evidence for a low-lying spin-2 rotational excitation. For the 12C ground state and the first excited spin-2 state, we find a compact triangular configuration of alpha clusters. For the Hoyle state and the second excited spin-2 state, we find a "bent-arm" or obtuse triangular configuration of alpha clusters. We also calculate the electromagnetic transition rates between the low-lying states of 12C.

Related Stories

Fundamental question on how life started solved?

May 9, 2011

For carbon, the basis of life, to be able to form in the stars, a certain state of the carbon nucleus plays an essential role. In cooperation with US colleagues, physicists from the University of Bonn and Ruhr-Universitat ...

Carbon, carbon everywhere, but not from the Big Bang

May 11, 2011

As Star Trek is so fond of reminding us, we're carbon-based life forms. But the event that jump-started the universe, the Big Bang, didn't actually produce any carbon, so where the heck did it – and we – come from? ...

New picture of atomic nucleus emerges

March 2, 2012

( -- When most of us think of an atom, we think of tiny electrons whizzing around a stationary, dense nucleus composed of protons and neutrons, collectively known as nucleons. A collaboration between the U.S. ...

The atomic nucleus: fissile liquid or molecule of life?

July 30, 2012

A new view of the nucleus that unifies its liquid and molecule-like aspects has been put forward by a team of researchers from France.  By making an analogy with neutron stars, the researchers have for the first time ...

On the origin of life's most crucial isotope

October 12, 2012

Since the Big Bang, the universe has been evolving. From the formations of simple protons and neutrons to the wide breadth of elements and molecules known today, it is ever growing in complexity and variety. And now, nuclear ...

Recommended for you

Professor solves 140-year fluid mechanics enigma

October 7, 2015

A Purdue University researcher has solved a 140-year-old enigma in fluid mechanics: Why does a simple formula describe the seemingly complex physics for the behavior of elliptical particles moving through fluid?

Perfectly accurate clocks turn out to be impossible

October 7, 2015

Can the passage of time be measured precisely, always and everywhere? The answer will upset many watchmakers. A team of physicists from the universities of Warsaw and Nottingham have just shown that when we are dealing with ...

The topolariton, a new half-matter, half-light particle

October 7, 2015

A new type of "quasiparticle" theorized by Caltech's Gil Refael, a professor of theoretical physics and condensed matter theory, could help improve the efficiency of a wide range of photonic devices—technologies, such as ...

Fusion reactors 'economically viable' say experts

October 2, 2015

Fusion reactors could become an economically viable means of generating electricity within a few decades, and policy makers should start planning to build them as a replacement for conventional nuclear power stations, according ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.