A famous Hubble Space Telescope image of a portion of the Eagle Nebula, Messier object 16.
From: http://www.ast.cam.ac.uk/HST/press/m16.html
half-life (abbreviated t 1/2) - This is the time needed for half the amount of a radioactive parent nuclide to decay to a radiogenic daughter nuclide.
molecular cloud - This is a relatively cold and dense portion of the interstellar medium that consists mainly of gas molecules. The solar nebula is thought to have formed from a protosolar molecular cloud that collapsed. Molecular clouds appear as dark blobs in images such as the one below.
A famous Hubble Space Telescope image of a portion
of the Eagle Nebula, Messier object 16.
From: http://www.ast.cam.ac.uk/HST/press/m16.html
epsilon units - This is a unit for isotope ratios that is measured in parts per ten-thousand. It is analogous to del units and percent units except the latter are based on parts per thousand and parts per hundred, respectively.
parsec (abbreviated 'pc') - This is a unit of distance used by astronomers. 1 pc = 3.258 light years. Contrary to what Hans Solo implies in the first (and best) Star Wars movie, it is not a speed.
supernova - This is what happens to a massive star after it uses up its nuclear fuel and it explodes. The end comes as the star tries to fuse Fe into something more massive, and discovers that this process absorbs energy. No longer able to keep itself inflated by the thermal energy released by fusion reactions, the star collapses under its own weight, with its center compressing into an ultradense object (neutron star or black hole), and its exterior bouncing off the dense core and being ejected into space to form an expanding shell. Along the way, the star has done r-process and other types of nucleosynthesis.
Eta Carinae, an impressive double-lobed supernova
remnant.
From: http://www.st-edmunds.cam.ac.uk/cis/polkinghorne/images/supernova.jpg
AGB (asymptotic giant branch) star - A type of Red Giant star that has fused He into heavier nuclides such as C and O, to form a core of heavier elements. Red Giant stars are huge, with diameters that would encompass much of our present inner solar system. Our sun will eventually turn into a red giant.
Our fate: Jupiter and the
Red Giant star that has expanded
throughout the inner solar system,
swallowing Earth and the other
terrestrial planets.
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Evolutionary track of a low-mass (e.g., solar-mass
or smaller) star into a
Red Giant Branch and AGB star, portrayed on an H-R
diagram of luminosity
vs. temperature.
From: http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit2/lowmass.html
Final evolutionary track of a low-mass star into a
white dwarf, portrayed on
an H-R diagram of luminosity vs. temperature.
From: http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit2/lowmass.html
Wolf-Rayet star - This is a very hot, very luminous star. It is probably an old star that has lost its H-envelope during a red giant phase, corresponding to the "bare core" shown on the previous H-R diagram.