Stars heavier than about eight times the mass of the Sun end their lives in dramatic explosions when the nuclear furnaces at their cores run out of fuel and collapse into neutron stars or black holes.
The Hubble observations suggest the erstwhile star was a luminous blue variable, a massive star at least 50 times as heavy as the Sun that jettisons most of itself material into space in a series of outbursts. Eta Carinae, wedged between gigantic hourglass-shaped clouds of material that it sloughed off, is a classic example of this kind of star.
That classification was surprising, since luminous blue variables were not expected to explode. Stellar models predict that the stars should evolve further – into other stellar types, shedding all of the hydrogen on their surfaces and most of their mass, before running out of fuel and going supernova.But "our star when it exploded still had some of its hydrogen envelope. It seems to have exploded before its time," says team member Douglas Leonard of San Diego State University in California.
One possibility, Leonard says, is that the star was actually close to death at its core, and for some reason did not lose all the hydrogen on its surface, appearing 'healthy'.