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Astronomers Spot Rare Radioactive Molecule In The ‘Guts’ Of A Shredded Star

By Alexandra Lozovschi
Published on: 01:49 PST, Jul 31, 2018

For the first time ever, astronomers have picked up the trace of a rare radioactive molecule that doesn’t exist on Earth, reports Phys.org.

The molecule in question, 26-aluminum monofluoride (26AlF), is a radioactive isotope of aluminum bound with fluorine atoms and was found outside the borders of our solar system, all the way in the Vulpecula constellation (“The Little Fox”) some 2,000 light-years away from our planet.

While scientists have long suspected that this unstable aluminum isotope exists in vast quantities in our galaxy — so abundant, in fact, that it could be quantified to about two times the mass of our sun — this is the first time that a molecule containing 26Al has ever been detected outside our solar system, notes the media outlet, citing the National Radio Astronomy Observatory.

The discovery was made by an international team of astronomers from three continents, who published their findings on July 30 in the journal Nature Astronomy.

In addition to spotting the unique spectral signature of these molecules in space, the scientists, hailing from the United States, Australia, and three European countries, also managed to observe the active source of the radioactive aluminum isotope — another “incredible first,” according to Space.com.

“The first solid detection of this kind of radioactive molecule is an important milestone in our exploration of the cool molecular universe,” said study lead author Tomasz Kami?ski, an astronomer with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

The source of 26Al was traced back to a red nova known as CK Vulpeculae, or CK Vul — the remnant of a stellar explosion caused by the merger of two sun-like stars.

The red nova was first seen from Earth almost 350 years ago, shining brightly over the sky in 17th-century Europe, states the Max Planck Institute for Radio Astronomy.

But it wasn’t until 2013, when astronomers led by Kami?ski studied the stellar remnant with radio telescopes, that they were able to identify the red nova as a source of the radioactive aluminum isotope.

According to Space.com, a red nova is formed when two low-mass stars collide in an explosive merger, producing a burst of cosmic light, and then cool off and start emitting large amounts of molecular gas and dust.

It was in this molecular gas, the debris around CK Vul, that the team picked up the signature of the radioactive molecule 26AlF, more than 300 years after the two stars crashed into one another and shredded each other in a violent explosion.

Commenting on the discovery, Kami?ski chimed in to put a more lyrical spin on the celestial event that allowed his team to make their amazing breakthrough.

“We are observing the guts of a star torn apart three centuries ago by a collision. How cool is that?”

The observations were made possible thanks to the Atacama Pathfinder Experiment telescope (APEX) in the Atacama Desert of Chile and the Northern Extended Millimeter Array (NOEMA) of the Institut de Radio Astronomie Millimetrique (IRAM), Kami?ski mentioned in a Nature Astronomy commentary published alongside the study.

Under normal circumstances, chemical molecules are detected in space after scientists observe their molecular fingerprint in lab experiments and then look for it in the sky with powerful telescopes. However, since 26Al can’t be found on Earth, the team relied on a more stable aluminum isotope, 27Al, and used the fingerprint of 27AlF molecules to glean the needed data for the rare 26AlF molecules.

Aside from finding the radioactive aluminum isotope in the red nova, the astronomers were also able to uncover a few details about the original two stars that merged three centuries ago.

For instance, they found out that one of these low-mass stars was a red giant weighing between 0.8 and 2.5 solar masses. The study also revealed that stellar collisions, such as the studied red nova, can expose even the deepest layers of a star, where heavy elements and radioactive isotopes are forged, and spew them into space.

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

Although his team identified quite a large amount of 26Al in CK Vul, it is not enough to account for all the radioactive isotope molecules believed to exist in the Milky Way. Therefore, the astronomers speculate that there could be other 26Al sources out there in space, waiting to be discovered.

“The observation may be a stepping stone for unambiguous identification of other Galactic sources of 26Al,” the authors wrote in their paper.

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