Astronomers revealed mysterious star formation by hearts of molecular clouds

Data from the world's largest radio telescopes holds clues.

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Typically, new stars form when diffuse atomic gas condenses into concentrations of molecular gas, forming molecular clouds. The high-density cores within these molecular clouds act as triggers for star formation. While this process is common in the inner regions of galaxies, it becomes less common toward the outer edges of galaxies.

A team of astronomers has discovered unusual star formation at the outer edge of the galaxy M83. The study utilized various instruments, including ALMA, VLA, GBT from NRAO, Subaru Telescope from NAOJ, and GALEX from NASA.

The team identified 23 molecular clouds exhibiting a distinct type of star formation at the outer edges of the galaxy M83. Unlike typical molecular clouds, only the star-forming dense cores of these clouds were observed. This discovery provides valuable insights into the physical processes involved in star formation at the far edges of galaxies.

Astronomer Jin Koda of Stony Brook University, who led this research, said, “The star formation at galaxy edges has been a nagging mystery since their discovery by the NASA GALEX satellite 18 years ago.”

David Thilker of Johns Hopkins University commented, “Previous searches for molecular clouds in this environment were unsuccessful. Seeing the search for dense clouds associated with the outer disk finally come to fruition has been gratifying, revealing a characteristically different observational fingerprint for the molecular clouds.”

The discovery of these molecular clouds has revealed a connection to a vast reservoir of diffuse atomic gas. While it is common for atomic gas to condense into dense molecular clouds, where even denser cores lead to star formation, the conversion of atomic gas to molecular clouds at the edges of galaxies was not previously evident and still needs to be solved.

It’s remarkable that an undergraduate student, Amanda Lee, played a significant role in processing data from the Green Bank Telescope (GBT) and Very Large Array (VLA) for these findings. Her work led to the discovery of the atomic gas reservoir at the edge of the galaxy M83.

She said“We still do not understand why this atomic gas does not efficiently become dense molecular clouds and form stars. As is often the case in astronomy, pursuing answers to one mystery can lead to another. That’s why research in astronomy is exciting.”

This research was presented in a press conference at the 243rd American Astronomical Society (AAS) meeting in New Orleans, Louisiana.

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