Carl Sagan used to say that we are made of star stuff, but the similarity between humans and stars might not stop at the elements we are made of.
US researchers have discovered that a biological structure known as the endoplasmic reticulum found within human cells is remarkably similar to dense nuclear matter found in neutron stars. The helical structure looks like a multi-story parking garage, with evenly shaped sheets connected by what look like ramps.
Although remarkably similar in shape, the underlying physics is very different. Cell structures evolve to make biological processes better suited to the environment, while neutron stars are incredibly dense objects made of degenerate matter.
A study describing the findings is published in Physical Review C.
Helical structure is found both in cells (left) and neutron stars (right). UC Santa Barbara
“For neutron stars, the strong nuclear force and the electromagnetic force create what is fundamentally a quantum-mechanical problem,” study co-author Greg Huber of UC Santa Barbara explained in a statement. “In the interior of cells, the forces that hold together membranes are fundamentally entropic and have to do with the minimization of the overall free energy of the system. At first glance, these couldn’t be more different.”
The cell structures are about a nanometer in length, while the interactions that form the neutron stars are a million times smaller.
“Seeing very similar shapes in such strikingly different systems suggests that the energy of a system may depend on its shape in a simple and universal way,” co-author Charles Horowitz from Indiana University added.
The study highlights how several biological structures might have astrophysical counterparts. Computer simulations of the complex physics within neutrons stars have shown a variety of curious shapes commonly known as nuclear pasta. Among those, there are tubes (spaghetti), sheets (lasagne), and these curious “sheets with ramps” structures.
“They see a variety of shapes that we see in the cell,” Huber explained. “We see a tubular network; we see parallel sheets. We see sheets connected to each other through topological defects we call Terasaki ramps. So the parallels are pretty deep.”
The researchers add that they hope that this will start a deeper look at the connections between these two fascinating subjects.
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