It’s a fate our sun will someday share.

As medium-size stars grow old, they run low on nuclear fuel, become unstable and shed their outer layers of gas into space. The common result is a stunning, brightly colored veil known as a planetary nebula.

Often nebula are symmetrical. But when more than one star is involved, they can become messy assemblages, taking odd or even familiar shapes such as a horse’s head or cat’s eye.

Now astronomers using the Gemini North observatory on Mauna Kea have stirred a debate about the formation of another complex and striking nebula called Sharpless 2-71. Found in the direction of the constellation Aquila, the Eagle, Sh 2-71 looks a bit like a brown blowfish face-on, its mouth open for a meal.

Inside the mouth are clues to the beast’s evolution that are intriguing scientists from Spain to Australia.

Since its discovery in 1946, many astronomers assumed that Sh 2-71 was formed from the death throes of a bright binary star system near its center. It appears as a single bright star near the center of the "mouth" in an image released Wednesday by the observatory.

But now the experts are not so sure.

That’s because the bright central star doesn’t appear to radiate enough ultraviolet light to cause the surrounding gas shell to glow as intensely as it does, much like a neon sign.

It’s possible that its unseen companion is providing the necessary juice. But another hypothesis is that a dim, bluish star just to the right is the nebula’s true parent.

"At the assumed distance to the nebula (about 3,260 light-years), the faint star has about the right brightness to be the fading remnant of the nebula’s progenitor star," says David Frew, an astronomer at Macquarie University in Sydney, who is studying the faint star with colleague Quentin Parker.

The odd shape of the nebula suggests a complicated, multistage evolution, argues Luis Miranda of the Astrophysics Institute of Andalucia in Granada, Spain.

"The nebula presents a multipolar structure and several pairs of bipolar lobes at different orientations," says Miranda. "These lobes most certainly formed at different times and likely involved a binary progenitor."

He adds, "The chaotic morphology of Sh 2-71 implies that very complex processes have been involved in its formation."

The Gemini Observatory, which has twin 8-meter telescopes on Mauna Kea and in central Chile, captured the image in mid-2011 using its Multi-Object Spectrograph filters, which selectively allow specific colors of visible light to reach the detector.

Travis Rector of the University of Alaska at Anchorage assembled the data from three filters to form the composite color image.

A lot more work is expected before the blowfish’s cloudy ancestry becomes clear.