All that remains of a former giant red star is the coldest known object in the universe: the Boomerang Nebula. This frigid spindle of molecular gas and dust has somehow obtained a temperature of minus 458.5 degrees Fahrenheit, colder than deep space itself. But, just how that is possible has perplexed scientists for more than two decades since its discovery.
Now, with the help of the Atacama Large Millimeter/submillimeter Array (ALMA) based in Chilé, astronomers may have figured it out. The answer lies in a companion star lying squarely in the center of this nebula, that most likely plunged into the heart of it, forcing all the gas of the red giant to pour out violently. In fact, the outflows appear to be expanding 10 times faster than a single ordinary nebula could produce.
“These new data show us that most of the stellar envelope from the massive red giant star has been blasted out into space at speeds far beyond the capabilities of a single, red giant star,” said Raghvendra Sahai, an astronomer at NASA’s Jet Propulsion Laboratory in Pasadena, California, and lead author of the research, in a press release. “The only way to eject so much mass and at such extreme speeds is from the gravitational energy of two interacting stars, which would explain the puzzling properties of the ultra-cold outflow.”
But, the storm is about to quell. Scientists expect that the red giant will begin to shrink, heating up in the process to eventually transform into a planetary nebula. Though it won’t actually be a planet, it will look like one from the distant gaze of a telescope; a smooth orb of gas and dust.
For now, the Boomerang is a rare opportunity to see a nebula before it reaches planetary stage — the last stage before a star’s remnants loses its energy, flickers, and dies out, going completely dark.