Highly magnetic dead stars may have solid surfaces, but you definitely wouldn’t want to walk on them

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 old. Since before recorded history, people have looked up at 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 out into the cosmos, identifying destinations, and then actually going there to walk on extraterrestrial 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 a star’s surface just got a little easier, thanks to a recent discovery published in the journal Science.

Scientists from the University of Padua and their colleagues used data from NASA’s Imaging X-Ray Polarimetry Explorer satellite. The IXPE is a collaboration between NASA and the Italian Space Agency that studies the polarization – the direction in which light waves twist – of X-ray light in the cosmos. The researchers used the instrument to observe a highly magnetized dead star, known as a magnetar, 13,000 light-years from Earth.

When stars several times more massive than the Sun die, they explode into a bright supernova of rapidly expanding gas. If the star is in the correct size range, a piece of it is left behind after the explosion, a very compact stellar remnant known as a neutron star. These super dense phantom stars already have incredibly strong magnetic fields, but some are even stronger than others and we call them magnetars. 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 strong magnetic fields, but it’s likely the result of the strange machinations going on inside the star. Matter is squeezed so tightly and experiences such immense forces and pressures that the interior of the star could become a superconducting fluidturning the entire star into a dynamo that generates the magnetic field.

Magnetars emit light in the X-ray portion of the spectrum and can be observed with X-ray telescopes. Researchers examined IXPE data from observations of magnetar 4U 0142+61, located in the constellation Cassiopeia, in the hope to determine the surface characteristics of the dead star. Looking at the measurements, the scientists found a lower amount of polarized light than they would have expected if the light passed through an atmosphere. If an atmosphere was present, it should have filtered the light more, but that doesn’t seem to be the case. Instead, they found that when light was at higher energies, the angle of polarization shifted 90 degrees from lower energies. These results are consistent with what we would expect to find if the star actually had a solid crust instead of a gaseous atmosphere.

The researchers suggest that the strong magnetic field turns the star’s gas into a solid, similar to how low temperatures cause liquid water to crystallize and turn it into ice. Instead of an amorphous cloud of hot gas, it becomes liquid or solid in a process known as magnetic condensation. The result is a surface crust made up of ions bound together in a crystal lattice stretched in the direction of the magnetic field.

Now that we know there are stars strong enough to walk on, it’s hard not to imagine what that might look like. A person – or non-human extraterrestrial intelligence – could walk on the surface of a neutron star, in theory, but the first step would be the last. Before you even get close to the star, once you reach a distance of about a thousand miles, the magnetic field would be so powerful that it would strip electrons from your body and reduce you to a puff of atoms that dissipates quickly.

If you could survive on the ground and reach the surface, you would never be able to leave. On neutron stars, matter is so dense that a lump 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, these are earthly books. On a magnetar, the same person would weigh nearly 26 trillion pounds. There may not be enough rocket fuel in the solar system to meet the escape velocity from the star’s surface, let alone materials or bodies strong enough to sustain the crash.