Colliding stars eject radioactive molecules

A collision between two stars has led to the first ever direct detection of a radioactive molecule in interstellar space

Composite image of CK Vul, the remains of a double-star collision. This impact launched radioactive molecules into space, as seen in the orange double-lobe structure at the center. This is an ALMA image of 27-aluminum monofluoride, but the rare isotopic version of AlF resides in the same region. The red, diffuse image is an ALMA image of the more extended dust in the region. The blue is optical hydrogen emission as seen by the Gemini observatory.

An image of CK Vul, the remnant of a collision between two stars. The event launched radioactive molecules into space, as seen in the orange structure at the centrer. Credit: ALMA (ESO/NAOJ/NRAO), T. Kamiński & M. Hajduk; Gemini, NOAO/AURA/NSF; NRAO/AUI/NSF, B. Saxton

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The first definitive detection of a radioactive molecule in interstellar space has been made by astronomers observing the remnant of a stellar collision.

The molecule is a form of aluminium monofluoride, or 26AlF, and is thought to have been ejected into space during a collision between two stars.

This stellar collision was witnessed over Earth in 1670, reportedly appearing like a new star in the sky.

A sharp burst of light associated with the collision has since faded, and it is now only visible using powerful telescopes.

“The first solid detection of this kind of radioactive molecule is an important milestone in our exploration of the cool molecular universe,” says Tomasz Kamiński of Harvard-Smithsonian Center for Astrophysics and lead author of the study.

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The remnant of the collision is a central star surrounded by a glowing halo of material named CK Vul, and this is where the spectral signature of the molecules was found.

The observations give an insight into the chemistry behind the merger that created CK Vul.

The study also shows that the inner layers of a star can be thrown out into space during a collision.

“This first direct observation of this isotope in a stellar-like object is also important in the broader context of galactic chemical evolution,” says Kamiński.

“This is the first time an active producer of the radioactive nuclide 26Al has been directly observationally identified.”


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