A famous Hubble Space Telescope image of a portion of the Eagle Nebula, Messier object 16. Evaporation can be seen on the surfaces of the clouds.
From: http://www.ast.cam.ac.uk/HST/press/m16.html
YSO - young stellar object. Includes newly-forming (not yet fusing H) and newly-formed (fusing H) stars that still contain disks.
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. Evaporation can be seen on the
surfaces of the clouds.
From: http://www.ast.cam.ac.uk/HST/press/m16.html
proplyd - Abbreviation for "protoplanetary disk", a disk of dust + gas that surrounds newly-forming stars (YSOs), out of which planetary systems form. The solar nebula was our system's proplyd. They were first imaged in the Orion Nebula by the Hubble Space Telescope.
Hubble Space Telescope images of proplyds in the central
part of the Orion Nebula. AU = astronomical unit, where 1 AU = the average
distance between the Earth and the sun. For comparison, Pluto orbits the
sun on average at about 39 AU. In images 1, 2, 3, and 4, the shapes of
the proplyds are streamlined because of strong stellar winds from nearby
stars. The proplyd in image 5 is encased in a large bubble (blue-green).
From: http://messier.seds.org/more/m042_hst3.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.
decay constant (abbreviated lambda) - This is related to half life by: lambda = ln2 / t1/2
supernova - this is the explosion of a dying star, which sends all the products of its interior into the interstellar medium. The star explodes because it runs out of nuclear fuel for fusion reactions. When these reactions stop, the star can no longer be inflated against the weight of the overlying gas, and it collapses. The overlying material of the star bounces off a dense core and rapidly sends the material into space.
Hubble Space Telescope image of a supernova with a
double-lobe structure.
del notation - This is a unit for isotope ratios that is measured in parts per thousand. It is analogous to percent units except the latter are based on parts per hundred.
blackbody - An idealized physical body that emits radiation in a manner determined by temperature alone. A colder object emits most of its radiation at long wavelengths; a hotter object emits mostly at shorter wavelengths. In Fig. 3 of Dauphas and Chaussidon (2011), the presence of dust around YSOs causes differences in light emission (mostly at infrared or IR wavelengths) compared to that expected for a blackbody alone. "IR excesses" can be used to study the properties of disks around YSOs. The more warm dust, the greater the IR excess, with the wavelength of peak emission related to temperature as described above.
main sequence star - a star that burns (fuses) H into He in its core.
RGB and AGB stars - red giant
branch (RGB) and asymptotic giant branch (AGB) stars are red giant stars.
This phase of stellar evolution follows the main sequence and involves
a great inflating of the star, caused by the exhaustion of nuclear fuel
(first H, then He) in the core, even as H or He continue to burn in a shell
around the core. This shell structure of energy production causes
the star to expand. When our sun passes into a Red Giant phase, the entire
inner solar system will lie inside the "cool, extended envelope" of the
star.
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Cross-section of a RGB (left) and AGB star (right).
RGB stars evolve into AGB stars.
From: http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit2/lowmass.html