A long-standing mystery of planetary astronomy appears to have been solved. An unusual meteor shower that was observed once over 60 years ago and didn’t occur again until recently may have been due to a spent comet.

The thrilling tale begins in December 1956, when Japanese researchers observed for the first time a meteor shower they hadn’t seen before. They called it Phoenicid, as it appeared to originate from the constellation of the Phoenix. However, when people looked for it the following year, it wasn’t there.

The enigma of the Phoenicid was born. Scientists had to try to answer two questions: What caused the meteor shower? And why did it only happen once? Two Japanese teams were able to find a solution to both queries.

Meteor showers are caused by the debris left over by comets crossing the orbit of our planet. Based on its orbit, a potential cause for the Phoenicid was Comet Blanpain. This comet appeared in 1819 and then disappeared. However, what interested the researchers wasn’t just the similar disappearing act. In 2003, an asteroid was discovered in the same orbit as Comet Blanpain. The team proposed that if this object was the leftover of the comet, it could be responsible for the meteor shower.

This hypothesis came with a prediction: The shower would reoccur again on December 1, 2014. The two teams went out to look for the meteors, with one team heading to North Carolina and the other going to Las Palmas, one of the Canary islands. They indeed saw Phoenicid meteors that night – 29 out of 138 bolides to be exact.

These observations strongly suggest that Comet Blanpain was to blame, and while mostly inactive, it must have released enough dust debris in the 20th century to create the 1956 shower. The teams not only solved the mystery, but they also estimated historical changes in a comet for the first time.

“We would like to apply this technique to many other meteor showers for which the parent bodies are currently without clear cometary activities, in order to investigate the evolution of minor bodies in the Solar System,” team leader Yasunori Fujiwara, a graduate student at the Department of Polar Science, SOKENDAI, said in a statement.

The paper from Fujiwara’s research will be published in the Publications of the Astronomical Society of Japan, and the other team’s work will soon be available in the journal Planetary and Space Science.