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Cliff Lau University of Toronto
AST201 Lecture 9 (February 10, 2011)
Temperature colour/strength of spectral lines
Distance parallax
Luminosity distance + apparent brightness
Spectral type colour/temperature/pattern of spectral lines
Luminosity class shape of spectral lines
We can organize much of what we know about them using the H-R diagram
Stars do not live forever; they are born and they die
Most distant stars we can see are blue because although these stars are rare,
they are extremely luminous
But these stars dont live long, so they mostly die where they were born;
therefore, to find the sties of star formation, look for blue stars
Taking pictures in multiple parts of the electromagnetic spectrum is essential
to understand star formation
Dust absorbs visible light, heats up, and reemits that light in the infrared
From a molecular cloud fragment to a spinning disk of dust and gas orbiting a
protostar to a protostar surrounded by a disk and a pair of bipolar jets
Protostellar jets are one of the few phenomena in the universe that change
fast enough that we can watch them doing it
In the end, we wind up with many red dwarf stars and very few blue giants
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