17O tagged posts

Schematic of the internal structure of AGB stars at the interface between the H-burning region and the convective envelope.

Scientists have identified the origin of key stardust grains present in the dust cloud from which the planets in our Solar System formed, a study suggests. Researchers have solved a long-standing puzzle concerning the source of the grains, which formed long before our Solar System and can be recovered from meteorites that fall to Earth. The stars that produced the dust were identified by observing how key reactions shaped the make-up of the grains, scientists say.

During their lifetime, stars around six times larger than the Sun – called Asymptotic Giant Branch or AGB stars – blow off their outer layers, forming an interstellar cloud of gas and dust grains...

Coincidence spectrometer employed in the present work. The HPGe crystal (yellow) is located in close geometry to the target. Both the target and the HPGe detector are surrounded by a 16-segment NaI(Tl) annulus (green). The five-sided plastic scintillators used to reject cosmic-ray muons are not shown.

Stars shine because nuclear reactions in their interiors convert mass to energy at a rate of many million tons/ s. At the same time, these nuclear reactions change the composition of the matter in the stellar interior. Thermonuclear fusion takes place quiescently in stars that are much older than the Sun, and also explosively in novae and supernovae. To explain how stars work, we need to measure the rates of the important nuclear reactions...