ALMA captures a bubble of ejected material around U Antliae, an ageing star

This ALMA image reveals much finer structure in the U Antliae shell than has previously been possible. Around 2700 years ago, U Antliae went through a short period of rapid mass loss. During this period of only a few hundred years, the material making up the shell seen in the new ALMA data was ejected at high speed. Examination of this shell in further detail also shows some evidence of thin, wispy clouds known as filamentary substructures.

Astronomers have used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to capture a breathtaking image of a shell of ejected material around U Antliae, star about 900 light years away from the Earth. The star actually has two shells of ejected material from two events where the ageing star rapidly expelled large amounts of matter. The material that makes up the shell was ejected at high speeds around 2700 years ago.

Researchers can study the thin and delicate shell with precision because the ALMA astronomical instrument not only captures images, but also produces a three dimensional dataset known as a data cube. Each slice in the cube represents observations in slightly different wavelengths. The slices show gases moving away or towards the observer at different speeds, and allow scientists to create a 3D map of the shell, similar to the computer tomography of the human body using X-Ray or Ultrasound machines.

The shell is remarkably symmetrical and very thin. The shell has a number of chemical compounds based on carbon and other elements. The bubbles of ejected material like the one seen around U Antliae help recycle matter and contribute up to 70 percent of the dust in the interstellar medium. The observations allow scientists to figure out how stars evolved in the early universe, as well as the evolution of galaxies.


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