Silent Explosion: The Faintest Supernova in the Galaxy ⚡ экспресс
The Pa 30 nebula, source of an ultra-fast wind (16,000 km/s), is thought to be the remnant of a white dwarf merger in 1181. First deep radio observations found no emission: upper limits of 0.84 mJy at 1.5 GHz and 0.29 mJy at 6 GHz. Its radio brightness is a thousand times fainter than typical supernova remnants. If Pa 30 is a remnant, its kinetic energy is thousands of times lower than normal, making it the dimmest known in radio. It's like hearing silence where you expected a roar: either the Galaxy hides a whole population of 'quiet' remnants, or Pa 30 is no remnant at all.
In 1181, in the constellation Cassiopeia, a "guest star" blazed into view — a bright spot that rivaled other luminaries for half a year. Most likely, it was the merger of two white dwarfs, the burned-out remnants of stars like our Sun. What remains is nebula Pa 30: a cloud of tenuous gas and cosmic dust, expanding at a breakneck pace — nearly 5% the speed of light. Yet modern radio telescopes pick up only a faint whisper instead of the expected roar.
Typically, a supernova's shockwave accelerates charged particles to near-light speeds, making them "scream" in radio waves. Pa 30 is silent — its radio emission is a thousand times weaker than that of the Crab Nebula with a neutron star inside. This means either the explosion was surprisingly sluggish, or particle acceleration works differently. It’s precisely this scenario — a white dwarf merger without a powerful radio echo — that Subrahmanyan Chandrasekhar predicted back in the 1930s while studying the mass limit of these objects.
The most unexpected conclusion: our Galaxy may be littered with dozens of such invisible ghosts. We simply hadn't noticed them, and now we’ll have to rewrite the history of stellar explosions in the Milky Way.
🎯 Pa 30 is one of the few nebulae that can be linked to historical records: its outburst was observed in 1181 in the constellation Cassiopeia, and it hung in the sky for nearly half a year.