Astronomer captures Mercury's tail, resembling a comet's
On December 3, Steven Bellavia managed to photograph Mercury's massive sodium gas tail—stretching an incredible 24 million kilometers in general.
Predicted back in the 1980s, this glowing yellow tail shows up when sunlight hits Mercury's thin atmosphere and scatters sodium atoms.
Bellavia used a special filter to catch the effect clearly.
Why does Mercury have a tail?
Mercury's tail happens because intense sunlight pushes on its delicate atmosphere, sending sodium streaming far into space.
The brightness of this "tail" changes as Mercury moves around the Sun and peaks about 16 days before or after its closest approach—so December 9 is another great chance to spot it.
Observing this rare sight helps scientists understand how planets and comets interact in our Solar System.