An odd “zombie” star has grabbed its companion in a magnetic embrace. It keeps the two stars synchronized, and it pulls gas from the companion.

The system is A-M Herculis. It’s almost 300 light-years away, in the constellation Hercules.

The main star in the system is a white dwarf — the corpse of a once-normal star. It’s about two-thirds as massive as the Sun, but only about as big as Earth. That means it’s extremely dense, so its gravity is strong.

The star’s magnetic field is millions of times stronger than the Sun’s. And that’s bad for the companion – a cool, faint ember known as a red dwarf. The stars are so close that they orbit each other every three hours. At that range, the magnetic field of the white dwarf exerts a powerful pull. It’s made the two stars rotate in such a way that the same hemisphere of each star always faces the other – just as the same hemisphere of the Moon always faces Earth.

The field also pulls gas from the companion. In most systems like this, the infalling gas forms a wide, spinning disk. But in the case of A-M Herculis, it plunges directly onto the white dwarf, guided by the magnetic field. The streamer varies – thicker at some times, thinner at others. But it piles onto the poles of the white dwarf, making the star hotter and brighter – renewed vigor for a stellar zombie.

Hercules is high in the sky at dawn. But A-M Herc is much too faint to see without a telescope.

Script by Damond Benningfield