chapter 15 Flashcards
- 90% hydrogen
- 10% helium
composition & density of the interstellar medium
- small particles of grains of matter, particularly carbon and silicates, distributed throughout interstellar space
- effective at absorbing & diverting light
interstellar dust
the dimming of visible and UV light by the interstellar dust
interstellar extinction
removing blue light which causes an object to appear redder
reddening
dust with a temp of 100K shines most strongly at a wavelength of 29nm, whereas cooler dust (10k) shines at a longer wavelength
wien’s law
- warm
- high-density region of the interstellar medium made up mostly of atomic/molecular hydrogen & dust
interstellar clouds (2)
- cool
- low-density region of the interstellar medium that fills the space between interstellar clouds
intercloud gas
to strip the electron away from the atom, leaving only a positively charged nucleus
ionize
less dense gas that composes 99% of the matter in the medium
interstellar gas
a region of interstellar gas that has been ionized by UV radiation from nearby hot, massive stars
H II region
- an interstellar cloud composed of mostly molecular hydrogen
- giant clouds have a mass of 100-1,000 of solar mass
molecular cloud (2)
the gravitational attraction between all the parts of a cloud, which holds the cloud together and can sometimes make it collapse
self-gravity
a dense clump within a molecular cloud that forms as the cloud collapses and fragments
molecular-cloud cores
- protostar eventually switches from convection to radiation, which slows down the nuclear reactions
- infalling material adds to the mass & self-gravity of the protostar
- self-gravity is always matched by pressure
- star has to reach 10 million K in order to fuse hydrogen
evolving protostar (4)
the path a star follows across the H-R diagram it evolves through its lifetime
evolutionary track
- the path that a protostar follows on the H-R diagram as it contracts toward the main sequence
- explains the relationship between surface temp of a star and the temp deep in its interior
Hayashi track (2)
an atom/molecule that lost or gained one or more electrons
ion
material streaming away in opposite directions from both sides of the accretion disk of a young star
bipolar outflow
a glowing, rapidly moving knot of gas & dust that is excited by bipolar outflows in young stars
herbig-haro objects
a young stellar object that has dispersed enough of the material surrounding it to be seen in visible light
T Tauri stars
- a group of stars that all formed at the same time in the same general location
- can take up to 10-100 million years to reach its main star sequence
star cluster (2)
