Highly magnetic dead stars might have solid surfaces, but you sure wouldn't want to walk on 'em

Apollo 11 was the culmination of NASA’s crewed space operations in the 1960s, but more than that, it was the realization of a dream thousands of years in the making. Since before recorded history, people have looked to the sky and imagined what it might be like to touch the Moon and see the stars. Apollo 11 (seen from the inside in the 2019 documentary Apollo 11) proved that we were capable of looking into the cosmos, identifying destinations, and then actually going there to walk upon alien surfaces.

Our potential exploratory targets have always been limited to rocky planets and moons, as the gaseous surfaces of stars and gas giants kept them perpetually beyond our reach. Now, the prospect of walking on the surface of a star just got a little bit easier, thanks to a recent discovery published in the journal Science.

Scientists from the University of Padova, and colleagues, used data from NASA’s Imaging X-Ray Polarimetry Explorer satellite. The IXPE is a collaboration between NASA and the Italian Space Agency looking at the polarization – the direction the light waves are wiggling – of X-ray light in the cosmos. Researchers used the instrument to observe a highly magnetized dead star, known as a magnetar, 13,000 lightyears from Earth.

When stars several times more massive than the Sun die, they explode into a brilliant supernova burst of rapidly expanding gas. If the star is in the right size range, a piece of it is left behind after the explosion, a highly compacted stellar remnant known as a neutron star. These super dense ghost stars already have incredibly powerful magnetic fields, but some are even stronger than others and we call them magnetars. The fields around some magnetars have been measured at 1,000 times the strength of a typical neutron star and a trillion times stronger than Earth’s magnetic field.

It’s unclear why magnetars have such aggressively powerful magnetic fields, but it’s probably the result of the strange machinations happening inside the star. Matter is pressed so closely together and is under such immense forces and pressures that the star’s interior might become a superconducting fluid, turning the entire star into a dynamo which generates the magnetic field.

Magnetars emit light in the X-ray part of the spectrum and can be observed with X-ray telescopes. Researchers looked at the IXPE data from observations of magnetar 4U 0142+61, located in the constellation Cassiopeia, in the hope of determining the surface features of the dead star. When looking at the measurements, scientists found a lower amount of polarized light than they would have expected if the light was passing through an atmosphere. Were an atmosphere present, it should have filtered out more of the light, but that didn’t appear to be the case. Instead, they found that when the light was at higher energies, the angle of polarization shifted 90 degrees as compared with lower energies. Those findings are consistent with what we would expect to find if the star actually had a solid crust instead of a gaseous atmosphere.

Researchers suggest that the powerful magnetic field transforms the star’s gas into a solid, in the same way that low temperatures cause crystallization in liquid water and turn it into ice. Instead of an amorphous cloud of hot gas, it becomes a liquid or solid in a process known as magnetic condensation. The result is a surface crust made of ions bound together in a crystalline lattice all stretched in the direction of the magnetic field.

Now that we know there are stars out there which are solid enough to walk on, it’s difficult not to imagine what that might be like. A person – or non-human alien intelligence – could step on the surface of a neutron star, in theory, but the first step would be your last. Before you even got close to the star, once you reached a distance of about a thousand kilometers away, the magnetic field would be so powerful that it would strip electrons away from your body and reduce you to a rapidly dissipating puff of atoms.

If you could survive the field and actually reach the surface, you would never be able to leave. On neutron stars, the matter is packed so densely that a piece the size of a sugar cube would weigh about the same as a typical mountain on Earth. According to the CDC, the average person in the United States weighs 185 pounds. Of course, that’s Earth pounds. On a magnetar, the same person would weigh in at nearly 26 trillion pounds. There might not be enough rocket fuel in the solar system to achieve escape velocity from the star’s surface, let alone materials or bodies strong enough to endure the crush.