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Observations using ALMA found the radioactive aluminum isotope-26 from the CK residue Vulpeculae
Astronomers using ALMA and NOEMA made the first definitive detection of a radioactive molecule in the world. interstellar space. The radioactive part of the molecule is an isotope of aluminum. The observations reveal that the isotope was dispersed in space after the collision of two stars, which left a remainder known as CK Vulpeculae. This is the first time that a direct observation has been made of this element from a known source. Previous identifications of this isotope were from gamma ray detection, but their precise origin was unknown.
Composite image of CK Vulpeculae, the remains of a double-star collision. This impact launched radioactive molecules into the space, as can be seen in the orange structure with two lobes in the center. This is an ALMA image of 27 aluminum monofluoride, but the rare isotropic version of the AIF resides in the same region. The red and diffuse image is an ALMA image of the wider dust in the area. Blue is an optical datum of the Gemini Observatory. Credit: ALMA (ESO / NAOJ / NRAO), T. Kamiński; Gemini, NOAO / AURA / NSF; NRAO / AUI / NSF, B. Saxton
The team, led by Tomasz Kamiński (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA), used Atacama's large submillimeter network. (ALMA) and NOrthern Extended Millimeter Array (NOEMA) to detect a source of the aluminum-26 radioactive isotope. The source, known as CK Vulpeculae, was first seen in 1670 and, at the time, appeared to observers as a bright, red "new star". Although initially visible to the naked eye, it quickly faded away and now requires powerful telescopes to see the remains of this fusion, a dark central star surrounded by a halo of matter glowing that escapes from it.
348 years after the initial event observed, the remains of this explosive stellar melting led to the clear and convincing signature of a radioactive version of aluminum, known as the ; aluminum-26. It is the first unstable radioactive molecule definitely detected outside the solar system. Unstable isotopes have an excess of nuclear energy and eventually disintegrate into a stable form.
"This first observation of this isotope in a star-shaped object is also important in the broader context of galactic chemical evolution," notes Kamiński. "This is the first time that an active producer of the radioactive nuclide aluminum-26 has been directly identified."
Kamiński and his team have detected the unique spectral signature of molecules composed of aluminum-26 and fluorine (26AlF) in the debris surrounding CK Vulpeculae, which is about 2000 light-years from Earth. As these molecules rotate and tumble in space, they emit a distinct fingerprint of light at millimeter wavelength, a process known as the rotational transition. Astronomers consider this to be the "gold standard" for detecting molecules [1]
Artist impression of the collision of two stars, such as those that formed CK Vulpeculae The inset illustrates the internal structure of a red giant before the merger. A thin layer of 26-aluminum (brown) surrounds a helium nucleus. An extended convective wrap (not to the scale), which forms the outermost layer of the star, can mix matter from the inside of the star to the surface, but it never reach enough depth to dredge aluminum up to the surface. Only a collision with another star can disperse aluminum 26. Credit: NRAO / AUI / NSF; S. Dagnello
The observation of this particular isotope provides new insights into the fusion process that created CK Vulpeculae. It also demonstrates that the deep, dense inner layers of a star, where heavy elements and radioactive isotopes are forged, can be flipped and sunk in space by stellar collisions.
"We observe the intestines of a torn star" Astronomers also determined that the two stars that merged were of relatively low mass, one being a red giant star with a mass between 0, 8 and 2.5 times that of our Sun.
Being radioactive, aluminum 26 will disintegrate to become more stable and, in this process, one of the protons of the nucleus decays into a neutron. During this process, the excited nucleus emits a very high energy photon, which we observe as a gamma ray [2].
Previously, gamma ray emission detections showed that about two solar masses of aluminum-26 are present in the Milky Way, but the process that created the radioactive atoms was unknown. Moreover, due to the detection of gamma rays, their precise origin was also largely unknown. With these new measurements, astronomers have definitely detected for the first time an unstable radioisotope in a molecule outside our solar system.
At the same time, the team concluded that the production of aluminum-26 by objects similar to It is unlikely that CK Vulpeculae is the main source of aluminum-26 in the way Milky. The mass of aluminum-26 in the CK Vulpeculae corresponds to about one-fourth of the Pluto mass, and since these events are so rare, it is highly unlikely that they are the only producers of the Isotope in the Milky Way. This leaves the door open to further studies on these radioactive molecules
Notes
[1] Characteristic molecular fingerprints are usually derived from laboratory experiments. In the case of 26AlF, this method is not applicable because aluminum 26 is not present on Earth. Laboratory astrophysicists at the University of Kassel / Germany therefore used fingerprint data from stable and abundant 27AlF molecules to obtain accurate data on the rare 26AlF molecule.
[2] The aluminum-26 contains 13 protons and 13 neutrons in its nucleus (one less neutron than the stable isotope, aluminum-27). When it breaks down, aluminum-26 becomes magnesium-26, a completely different element.
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