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ALMA Returns to Boomerang Nebula, 'Coldest Object in the Universe'

ALMA Returns to Boomerang Nebula, 'Coldest Object in the Universe'

Composite image of the Boomerang Nebula, a pre-planetary nebula produced by a dying star. ALMA observations (orange) showing the hourglass-shaped outflow, which is embedded inside a roughly round ultra-cold outflow. The hourglass outflow stretches more than three trillion kilometers from end to end (about 21,000 times the distance from the Sun to the Earth), and is the result of a jet that is being fired by the central star, sweeping up the inner regions of the ultra-cold outflow like a snow-plow. The ultra-cold outflow is about 10 times bigger. The ALMA data are shown on top of an image from the Hubble Space Telescope (blue).