More than three centuries after the discovery of a massive collision between two stars, an international team of astronomers found the rest of the event, a bright Nova surrounded by an extremely rare radioactive molecule.
The material, known as 26-aluminum monofluoride or 26AIF, carries unstable radioisotope of aluminum (26AI) and is the first of its kind that can be observed directly in space.
"The first proof of this kind of radioactive molecule is an important milestone in our exploration of the cool molecular universe," said Tomasz Kamiński, senior researcher behind the discovery.
Scientists have long known about the presence of this molecule in the universe. Previous studies had postulated that our Milky Way itself hosts three solar masses worth 26AI, but there was no direct evidence of its presence until international group Atacama Large Millimeter / Submillimeter Array and the Northern Extended Millimeter Array used to study the remnants of this fusion. [1
First discovered in 1670, the fusion appeared as a bright, red nova about 2,300 light-years from Earth. It was naked for a few years, but eventually disappeared in the darkness of the cosmos. Today, only sophisticated telescopes can see the rest of the stellar collision, now called CK Vulpeculae or CK Vul.
CK Vul, as the researchers have described, looks like a dark central star shrouded in a halo of free-flowing material. These debris host a number of molecules, including the radioactive ones discovered by the team.
Scientists have known for years that molecules in space can be detected by the unique spectral signature of the millimeter-wavelength light they emit. In this case, the team determined the characteristic fingerprint of 26AIF molecules and used this information to identify the radioactive material around CK Vul.
The discovery provided critical insight into stellar fusion and helped the team claim that the two colliding stars did not do so too severely. One, as they said, is probably a red giant weighing 1 to 2.5 suns.
More importantly, the work also shows the deep inner layers of a sun-like star, in which radioactive isotopes are suspected to be burst into space by the stellar collisions seen in outer space.
"We observe the bowels of a star that was torn apart by a collision three centuries ago," added Kamiński. "How cool is that?"
That is, it's worth noting that the team believes that star collisions like these are not the only source of three solar masses worth 26AI in the Milky Way. These events are extremely rare and the amount of radioactive molecules recorded in CK Vul – nearly a quarter of the mass of Pluto – clearly indicates that there are more that are waiting to be discovered. However, since the telescopes involved in this work can detect only 26Al with fluorine, they also emphasized the possibility that the amount of radioactive version of aluminum could be much larger than previously thought.
The study entitled "Astronomical Detection of Radioactive Molecule 26AlF in the Rest of an Ancient Explosion" was published July 30 in the journal Nature Astronomy.