a glowing cloud of hot interstellar gas inside of which stars are being formed is called a(n) protoplanetary disk.
a glowing cloud of hot interstellar gas inside of which stars are being formed is called a(n) protoplanetary disk.
a glowing cloud of hot interstellar gas inside of which stars are being formed is called a(n)?
protoplanetary disk
Na
Na
for scientific studies of the identities and the initial abundances of short-lived radioactive nuclei that remained alive at differing concentrations within the interstellar gas cloud that formed the solar system, but which are now extinct in the solar system, clayton's factor (k+1) has grown in importance owing to experimental discoveries of many such nuclei within the meteorites. these are called the "extinct radioactivities" because none remain on earth today but which did leave clear evidence of their prior existence in meteorites. solution for a model history for the origin of our solar system that simultaneously fits their residual abundances became the guiding principle for a new discipline that focuses on local "extra" nucleosynthesis near the solar interstellar cloud during the billion years preceding solar birth. in 1983, at a time when astrophysicists relied for simplicity on a well mixed interstellar gas, clayton introduced a new related aspect of the interstellar medium that has proven to be essential for understanding the abundances of the extinct radioactivities; namely the time required for isotopic mixing between freshly synthesized atoms ejected from supernovae with distinct physical phases of interstellar gas. he showed that because those time delays allowed more interstellar decay of radioactive nuclei, each phase of interstellar gas contains a distinctly different concentration of each of the extinct radioactive nuclides, whereas the early solar system radioactivities measure only those abundances present in the dense molecular-cloud phase in which the solar system was born. in the 21st century many researchers have begun to present their own calculations of the effect of interstellar inter-phase mixing, often unaware of clayton's (1983) paper owing to the intervening decades. aspects of interstellar-phase mixing are sure to remain important for decades to come while astronomers probe the circumstances of solar birth using accurate meteoritic data revealing the abundances of the extinct radioactive nuclei. clayton therefore gave emphasis to "extinct radioactivity" in the glossary of his 2003 book on isotopes in the cosmos. chapters 16 and 17 of "catch a falling star".
donald d. clayton