Hubble Uncovers Mysterious Origins of a Milky Way Magnetar

Astronomers using the Hubble Space Telescope have uncovered a cosmic twist. A new study shows that the magnetar SGR 0501+4516, one of the most extreme types of neutron stars, likely didn’t form in a supernova as previously believed. Instead, its origin remains a mystery — challenging long-standing ideas about how magnetars are born.

This breakthrough became possible thanks to the combined power of Hubble’s infrared imaging and ESA’s Gaia spacecraft, which provides ultra-precise star maps. By tracking the magnetar’s movement across the sky, researchers ruled out any connection with nearby supernova remnants, including HB9.

A Magnetar That Doesn’t Fit the Mold

Magnetars are incredibly dense stars with magnetic fields billions of times stronger than those on Earth. These rare objects often produce gamma-ray and X-ray flares and rotate rapidly. NASA’s Swift Observatory first detected SGR 0501+4516 in 2008, placing it among just 30 known magnetars in the Milky Way.

Scientists typically link neutron stars — and by extension, magnetars — to supernova explosions. SGR 0501+4516 sits close to the supernova remnant HB9, which once seemed like its origin. But Hubble’s long-term imaging from 2010 to 2020, aligned with Gaia’s reference data, revealed something surprising: the magnetar’s path across the sky doesn’t match that of HB9 or any other known explosion.

“This movement is smaller than a single pixel in a Hubble image,” said Joe Lyman from the University of Warwick. “But it tells us the magnetar couldn’t have come from HB9.”

A New Theory Emerges

Without a nearby supernova origin, researchers propose two alternate formation theories. First, the magnetar may have formed through a neutron star merger. Second, it could have resulted from accretion-induced collapse — where a white dwarf gains too much mass from a companion star and collapses into a neutron star, instead of exploding.

This second theory could also explain the source of fast radio bursts (FRBs), which sometimes appear in older galaxies that no longer form massive stars. “We think this might be how SGR 0501 was born,” said Andrew Levan of Radboud University and the University of Warwick.

If confirmed, SGR 0501+4516 would become the first known magnetar in the Milky Way with no supernova link. “Understanding how magnetars form is one of the biggest open questions in astrophysics,” said Nanda Rea of the Institute of Space Sciences in Barcelona.

The team plans more observations with Hubble to study other magnetars and test whether similar formation paths exist elsewhere. This result shows how powerful collaborations between missions like Hubble and Gaia can solve long-standing cosmic puzzles.