Atechnetium star, or more properly aTc-rich star, is astar whosestellar spectrum contains absorption lines of theradioactivemetaltechnetium. The most stableisotope of technetium is⁹⁷Tc with ahalf-life of 4.21 million years: too short a time to last for the age of theEarth (about 4.5 billion years). Therefore, the detection in 1952 of technetium in stellar spectra, was unambiguous proof ofnucleosynthesis in stars,^[1] one of the more extreme cases beingR Geminorum.^[1]

Stars containing technetium belong to the class ofasymptotic giant branch stars (AGB)—stars that are likered giants, but with a slightly higherluminosity, and which burnhydrogen in an inner shell. Members of this class of stars switch tohelium shell burning with an interval of some 100,000 years, in "dredge-ups". Technetium stars belong to the classesM, MS,S, SC andC-N. They are most oftenvariable stars of thelong period variable types.

Current research indicates that the presence of technetium in AGB stars occurs after some evolution and that a significant number of these stars do not exhibit the metal in their spectra.^[2] The presence of technetium seems to be related to the "thirddredge-up" in the history of the stars. In between thethermal pulses of these RGB stars, heavy elements are formed in the region between the hydrogen and helium fusing shells via the slow neutron capture process; thes-process. The materials are then brought to the surface via deep convection events.^[3]99Tc, an isotope with a half-life of only 200,000 years, is produced in AGB stars and brought to the surface duringthermal pulses. Its presence is taken as a reliable indicator that athird dredge-up has taken place.^[4]

• Barium star – Spectral class G to K giants, whose spectra indicate an overabundance of s-process elements
• Carbon star – Star whose atmosphere contains more carbon than oxygen
• Mercury-manganese star – Type of star with a prominent spectral line due to absorption from ionized mercury
• S-type star – Cool giant star with approximately equal quantities of carbon and oxygen in its atmosphere

• David Darling."technetium star". www.daviddarling.info.

• Star types
• Technetium

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