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Unformatted text preview: ons different origins!
(more in the
lectures) 33 Stars, Galaxies and the Universe Maruša Bradač Dust in the Milky Way Can we see the dust?
Oh, yeah. 34 Stars, Galaxies and the Universe Gas in the Milky Way The gas is mostly neutral hydrogen
Astronomers call this “HI” (“H one”) HI in the Milky Wa35
y Maruša Bradač Stars, Galaxies and the Universe HI in the Milky Wa36
y Maruša Bradač Stars, Galaxies and the Universe Maruša Bradač Stars, gas, an d dust are
tightly couple d
Stars for m from co ol gas…
Evolving stars release gas an d metals, an d heat the
surroun ding gas.
Gas co ols.
See Step 1. 37 Stars, Galaxies and the Universe Maruša Bradač Gas: Stars for m from the gravitational
collapse of the densest parts of
molecular clou ds.
(Forms a disk because initial
cloud rotates, and angular
momentum is conserved) 38 Stars, Galaxies and the Universe Maruša Bradač Milky Way: Summar y the “pancake” is a disk of stars an d gas on circular orbits, i.e.
rotating. ( Why?)
we are in the disk, 28,000 light-yrs from
the center, orbiting at 2...
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