A mysterious volcanic comet just woke up, setting off four major eruptions in less than 48 hours and spewing enough from its icy bowels to make the city-sized object appear nearly 300 times brighter than normal , say the researchers. The latest outbursts, which are the largest in more than three years, add to the growing confusion about when and why this explosive oddity blows its peak.

The cometknown as 29P/Schwassmann-Wachmann (29P), is a large icy object that stretches for about 37 miles (60 kilometers)—about three times the length of Manhattan. It is one of about 500 comets known as “centaurs” that spend their entire lives confined to inner solar system. However, 29P is also part of an even rarer group known as cryovolcanic or cold volcanic comets.