Boomerang Nebula: Coldest Region in Space is not What it Looks Like

It's so cold that it's colder than the darkest voids of space, and scientists studying the Boomerang Nebula have now discovered that the nebula's ghostlike shape is not what it once seemed.

The Boomerang Nebula, located around 5,000 light-years away, is the coldest object in space, sitting at a crisp minus 458 degrees Fahrenheit, or one degree Kelvin. The object was first spotted through the Hubble telescope, and appeared to have an hourglass shape. Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope, however, have found that the hour glass's waist is actually much broader that initially observed.

"This ultra-cold object is extremely intriguing and we're learning much more about its true nature with ALMA," said Raghvendra Sahai, a researcher and principal scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "What seemed like a double lobe, or 'boomerang' shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space."

The Boomerang Nebula is a pre-planetary nebula, a stage in a star's life preceding the planetary nebula, one of the last stages in a star's life when most of the outer layers have been shed. The Boomerang Nebula's distinct glow can be attributed to a special effect where light is absorbed by particles such as tiny dust grains, then reemitted into space.

"When astronomers looked at this object in 2003 with Hubble, they saw a very classic 'hourglass' shape," Sahai said. "Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant."

"This is important for the understanding of how stars die and become planetary nebulae," Sahai says. "Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star."

You can read the full published findings in The Astrophysical Journal.