Explosive green 'Mother of Dragons' comet now visible in the Northern Hemisphere

A rare, formerly-horned comet that astronomers have dubbed the "Mother of Dragons" is now visible after dusk in the Northern Hemisphere.

This "Halley-type" comet, officially known as Comet 12P/Pons-Brooks, completes a single orbit around the sun once every 71 years. The last time it passed by Earth was in 1954, according to a statement from the European Space Agency (ESA).

The city-size comet has a nucleus measuring 10.5 miles (17 kilometers) wide and orbits the sun in an elliptical shape. Recent observations of the comet have revealed a hidden spiral of light surrounding its frigid heart.

Like most comets, 12P/Pons-Brooks is composed of ice, dust and rock and its head also has a green appearance. This is due to comets containing diatomic carbon molecules — duos of carbon atoms stuck together — that emit emerald light when exposed to the sun.

However, what makes this celestial object stand out is that it's a cryvolcanic, or cold volcano comet, meaning that it regularly erupts, spewing the contents of its icy core into space, making the comet look brighter than normal. Last July, scientists spotted the comet erupting for the first time in 69 years, and at the time, it sprouted horns that earned it the nickname "devil comet."

Related: Exploding, green 'devil comet' could photobomb April 8 total solar eclipse — and it might be visible with the naked eye

The comet has erupted frequently since then, and has earned a reputation for its "spectacular outbursts of gas and dust," according to the ESA statement.