New deep-sky images of the Milky Way’s central core reveal picturesque butterfly-shaped gas clouds left behind by dying stars called bipolar planetary nebulae. And all appear to be mysteriously aligned with one another.
Planetary nebulae form during the final life stages of sun-like stars when their fuel runs out. In some cases, jets of hi-speed gas from the dying star sculpt the expanding gas bubbles into a symmetrical hourglass-shape. This type of stellar remnant is referred to as a butterfly nebula.
Using both the Hubble Space Telescope and European Southern Observatory’s New Technology Telescope (NNT), researchers surveyed more than a hundred planetary nebulae in the Milky Way’s central core region, and found that bipolar-shaped nebulae display a surprising alignment with each other.
“This really is a surprising find and, if it holds true, a very important one,” said study co-author Bryan Rees, astronomer at the University of Manchester, in a press statement.
“Many of these ghostly butterflies appear to have their long axes aligned along the plane of our galaxy,” he added.
For Rees and his team, the particularly perplexing part is that for all these butterfly nebulae to exhibit this kind of alignment with each other—despite their individual, unique histories and properties—their progenitor stars would have to have all been rotating perpendicular to the clouds of gas and dust that gave birth to them.
“The alignment we’re seeing for these bipolar nebulae indicates something bizarre about star systems within the central bulge,” explained Rees.
One hypothesis for this surprising alignment is that it may be directly tied to the origin of the strong magnetic field emitted by the Milky Way’s bulge. Very little is known about how this magnetic field formed and evolved over time. As such, this quirky arrangement of planetary nebulae may very well help unlock some as yet unknown history of our own galaxy.