Eta Carinae is noteworthy because it’s by far the brightest and largest star system within 10,000 light years of our own. It also deserves mention because it exploded in the 19th century. Twice. Astronomers still aren’t sure why, but a new series of 3-D models and images gives them unprecedented views of previously unseen features of the system.

“We are coming to understand the present state and complex environment of this remarkable object, but we have a long way to go to explain Eta Carinae’s past eruptions or to predict its future behavior,” said Goddard astrophysicist Ted Gull, who coordinates a research group that has monitored the star for more than a decade.

Eta Carinae is composed of two stars, and their orbits bring them atypically close together every 5.5 years or so. Located 7,500 light years away in the Carina constellation, they’re theoretically close enough for somewhat detailed study. In practice, gaseous solar winds emitted by both stars make observation difficult.

At periastron (the closest approach between the two stars), dramatic things happen including X-ray flares and changes in visibility as the smaller star loops around the larger. Three periastrons have occurred in the past 11 years, and NASA has developed a model based on the most common observations.

Much of the happenings, they say, can be explained by the interaction between the two stars’ solar winds. The primary star’s winds are dense and slower, expanding at a rate of about one million miles per hour. The secondary star’s winds carry less material, but move about six times as fast. 2014’s periastron closely resembles 2009’s, which tells scientists that the spiraling companion star’s winds are responsible for the X-ray flares.

With each periastron, the companion star’s winds carve a spiral-shaped cavity into those of the primary star as it approaches. These cavities expand, creating what one scientist likens to the shape of a blue crab. As expansion continues, shells of gas representing the crab’s “claws” race away from the system. Eventually, the primary star’s winds become so dense that the companion can no longer emit energy, and the crab shape disappears. Once the companion clears the primary, it returns.

These gas shells persist over thousands of times the distance between Earth and the sun,” Gull explained. “Backtracking them, we find the shells began moving away from the primary star about 11 years or three periastron passages ago, providing us with an additional way to glimpse what occurred in the recent past.”