Some stars end their lives as white dwarfs — dense remnants the size of a planet. A small fraction of these objects have very strong magnetic fields, millions of times more powerful than a refrigerator magnet. Such stars are called magnetic white dwarfs.

Astronomers hunted for them in the vast LAMOST sky survey. They matched spectra, the "rainbows" of starlight, with data from other telescopes. What caught their eye was the splitting of spectral lines: under the influence of a magnetic field, one line splits into several. It's like iron filings lining up along a magnet's field lines.

The team measured the field strengths, which ranged from a few million to tens of millions of gauss. For comparison, Earth's magnetic field is less than one gauss. Such powerful fields can affect the light a star emits and even its shape.

These new objects will provide targets for future observations with more powerful telescopes. This will help us understand where stars get their magnetic fields and how they evolve over time.