Her work helped her boss win the Nobel Prize. Now the spotlight is on her

Scientists have long studied the work of Subrahmanyan Chandrasekhar, the Indian-born American astrophysicist who won the Nobel Prize in 1983, but few know that his research into stellar and planetary dynamics owes a deep debt of gratitude to an almost forgotten woman: Donna DeEtte Elbert.

From 1948 to 1979, Elbert worked as a “computer” for Chandrasekhar, tirelessly devising and solving mathematical equations by hand. Although she shared authorship with the Nobel laureate on 18 papers, and Chandrasekhar enthusiastically acknowledged her seminal contributions, her greatest achievement was not recognized until a postdoctoral fellow at UCLA connected threads of Chandrasekhar’s work that all led back to Elbert.

Elbert’s performance? Before anyone else, she predicted the conditions claimed to be optimal for a planet or star to generate its own magnetic field, said scholar Susanne Horn, who has spent half a decade building on Elbert’s work.

Now, Horn and UCLA professor of earth, planetary and space sciences Jonathan Aurnou have published a paper in Proceedings of the Royal Society A where they present the newly named “Elbert area,” which details their predictions about the range of combinations that rotation, convection, and magnetism can assume to best generate a planet-wide magnetic field.

The work, the authors say, will help researchers in a variety of disciplines to better understand conditions in Earth’s interior and within other planets, and to identify planets outside our solar system with the potential to host life.

“Elbert had no formal math training, but what she did most people couldn’t do today. It’s really hard math that’s usually done using modern electronic computers,” says Horn, now an associate professor at the Fluid Research Center and Complex Systems at Coventry University in Great Britain. “Chandrasekhar says in footnotes that the subtle and elegant ways of solving particular problems were actually put forward by Elbert. She is all over his treatise on geophysical and astrophysical fluid dynamics, but is not the author. Today she would be considered a mathematician in her own right, but in the 50s and 60s it was hard for a woman to get more credit than a footnote.”

And because Elbert’s discovery of the generation of planetary magnetic fields remained embedded in her employer’s work, the discovery has generally been attributed to Chandrasekhar, who shared the Nobel in Physics for discoveries related to stellar evolution and massive stars.

Horn said she hopes the work she and Aurnou have undertaken to refine and expand on Elbert’s original predictions provides a fitting — if belated — tribute to Elbert, who died in 2019 at age 90.

The Elbert Series: How Planets and Stars Create Magnetic Fields

Planets generate their own magnetic fields through the internal circulation of heated, electrically conductive fluids such as liquid metals or very salty oceans. As a planet rotates on its axis, the motion of these fluids becomes organized, generating planetary magnetic fields along the way. Scientists believe that planets with magnetic fields are more likely to sustain life because the magnetic field acts as a kind of cocoon that protects the planet from the surrounding, often hostile space environment, Aurnou said.

“The key is that you have all these fluid motions. Earth’s core is predominantly liquid iron. As the planet slowly cools to space, the cooler upper part of the liquid core sinks and the hotter iron rises with depth,” he explained.

The motion caused by this sinking and rising is known as convection. Convection movements in electrically conductive materials, such as the liquid iron in Earth’s core, can create electrical currents that can then generate a planet’s global magnetic field.

“It is not clear whether convective turbulence alone will generate a planetary-scale magnetic field,” Aurnou noted, “but we know that planetary rotation organizes the turbulence into patterns of motion that can.” In other words, he said, rotational forces called Coriolis forces move fluids in predictable ways as the planet rotates. “Elbert was the first to point out that when these rotational forces are comparable in strength to magnetic forces, then convection will begin to organize on the scale of the planet. It’s such a simple, sensible system.”

Elbert discovered this principle firsthand while Chandrasekhar was on a summer lecture tour and presented it to him when he returned. He incorporated Elbert’s discovery into his own work, crediting her in a footnote without elaborating on its significance.

But Horn jumped from Elbert’s work.

“What we did was look for how the convection patterns in liquid metals and their evolution vary when subjected to both rotation and magnetic fields,” Horn said. “We found that there are different regimes of convective behavior, and we mapped where those exact regimes are. This work makes a whole series of new predictions that we will use to build future laboratory and numerical models of planetary and stellar magnetic field generation.”

The open-access paper, “The Elbert range of magnetostrophic convection. I. Linear theory,” is the first in a series of three papers Horn and Aurnou plan to publish that build on Elbert’s work.

More information:
Susanne Horn et al., The Elbert series of magnetostrophic convection. I. Linear theory, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences (2022). DOI: 10.1098/rspa.2022.0313