Mystery of ‘Blue Ring Nebula’ found to be result of stellar merger

A study that was 16 years in the making has solved the mystery of an ultraviolet ring around a star in space.

Scientists found that the ring in question, nicknamed “the Blue Ring Nebula,” is the result of an interstellar collision and is “the base of a cone-shaped cloud of fluorescing debris,” said the report “Merging Stars Produce Glowing Blue Ring Nebula.”

The debris “formed after a sun-like star collided into, and engulfed, a smaller stellar companion,” the Caltech report said.

“In fact, the scientists say two cones of material were shot out in the collision, in opposite directions. Because one of the cones is pointed directly toward Earth, it appeared to GALEX (NASA’s former Galaxy Evolution Explorer mission) as a ring,” the report said.

“The event represents the first observation by astronomers of a rare, never-before-seen phase in the evolution of stellar mergers that occurs a few thousand years into the process and is estimated to last roughly thousands to hundreds of thousands of years, a relatively short period on the timescale of cosmic events.”

Astronomers from NASA’s GALEX saw the nebula 16 years ago from space telescope images, the Caltech report said. The image has been studied since that time, and the star was named TYC 2597-735-1, said the article “A blue ring nebula from a stellar merger several thousand years ago” in its abstract on the Nature website.

The abstract said that while stellar mergers are brief and common for binary star systems, they have astrophysical significance.

“For example, they may lead to the creation of atypical stars (such as magnetic stars, blue stragglers and rapid rotators), they play an important part in our interpretation of stellar populations and they represent formation channels of compact-object mergers,” the abstract said.

“Although a handful of stellar mergers have been observed directly, the central remnants of these events were shrouded by an opaque shell of dust and molecules, making it impossible to observe their final state (for example, as a single merged star or a tighter, surviving binary). Here we report observations of an unusual, ring-shaped ultraviolet (‘blue’) nebula and the star at its centre, TYC 2597-735-1. …

“TYC 2597-735-1 provides a look at an unobstructed stellar merger at an evolutionary stage between its dynamic onset and the theorized final equilibrium state, enabling the direct study of the merging process.”