[ad_1]
Astronomers using ALMA and NOEMA made the first definitive detection of a radioactive molecule in 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.
The team, led by Tomasz Kaminski (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA), used the large millimeter of Atacama. / Arra submillimeter and the extended millimeter NWrthern matrix to detect a source of the radioactive aluminum isotope – 26. 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 observed event, 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 Kaminski. "This is the first time that an active producer of the radioactive nuclide aluminum-26 has been directly identified."
Kaminski and his team detected the unique spectral signature of molecules composed of 26 aluminum 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 regard this as the "gold standard" for detecting molecules [1].
The observation of this particular isotope provides new information on 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 entrails of a torn star" Astronomers also determined that the two stars that merged were of relatively low mass, one being a giant red 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 will disintegrate 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, however, 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 milky way. 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 for 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 disintegrates, the 26 aluminum becomes a 26 mg, a completely different element.
Reference: "Astronomical detection of a radioactive molecule 26AlF in a remnant of an ancient explosion", T. Kaminski et al., 2018 July 30, Nature Astronomy [http://dx.doi.org/10.1038/s41550-018-0541-x, preprint: http://arxiv.org/abs/1807.10647, preprint (PDF): http://www.eso.org/public/archives/releases/sciencepapers/eso1826/eso1826a.pdf].
The team is composed of Tomasz Kaminski (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA), Romuald Tylenda (N. Copernicus Astronomical Center, Warsaw, Poland), Karl M. Menten ( Max Amanda Karakas (Monash Center for Astrophysics, Melbourne, Australia), Jan Martin Winters (IRAM, Grenoble, France), Alexander A. Breier (Laboratory Astrophysics, Kassel University, Germany), Ka Tat Wong (Monash Center for Astrophysics, Melbourne, Australia), Thomas F. Giesen (Laborastrophysik, University of Kassel, Germany) and Nimesh A. Patel (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA.) [19659017] SpaceRef on Twitter and Like us on Facebook
[ad_2]
Source link
