Chapter 16 Flashcards
(23 cards)
Interstellar medium
The gas between the stars
Stars form in
dark clouds of dusty
gas in interstellar space.
We can determine the composition of interstellar gas from
its absorption lines in the spectra of stars.
Molecular Clouds
a dense, cold, and vast region of space composed primarily of hydrogen molecules and dust
Interstellar Dust
Tiny solid particles of block
our view of stars on the
other side of a cloud.
Particles are
<1 micrometer in size and
made of elements like C,
O, Si, and Fe.
Interstellar Reddening
Stars viewed through the edges
of the cloud look redder because
dust blocks (shorter-wavelength)
blue light more effectively than
(longer-wavelength) red light.
What kind of light passes through a cloud more easily than visible light.
Long-wavelength infrared light
Infrared light reveals
Stars on the other side of the cloud.
Interstellar Mediums Consist
70% hydrogen
28% helium
2% heavier elements
( Can be diff. depending on temp/density)
~1% of Molecular Clouds
interstellar dust
If thermal energy remains in the interstellar cloud?
It would raise the cloud’s temp and thermal pressure
Gravity follows an?
Inverse Sq. Law
Close Binary
A binary star system in which who stars are very close together
Life Track
Drawn on a HR diagram to rep. the changes in a star’s surface temp. and luminosity during its life
“evolutionary track”
Stages in the Life Track
Stage 1: Formation
Stage 2: Convective Contraction
Stage 3: Radiative Contraction
Stage 4: Self-Sustaining Fusion
Stage 1 (Star Birth Stages)
Formation
- Forms w/in collapsing cloud fragments
- Concealed by dusty molecular gas
- Energy moves mainly in the surface
Stage 2 (Star Birth Stages)
Convective Contraction
- surface temp remains at 3000 K
- Grav. contraction leads to a decrease in luminosity
- Life track drops straight down on the HR diagram
Stage 3 (Star Birth Stages)
Radiative Contraction
- Surface temp begins to rise, slight increase luminosity
- Life track bends towards higher surface temp
- Core temp and rate of fusion increase gradually
Stage 4 (Star Birth Stages)
Self Sustaining Fusion
- fusion rate becomes high enough to balance the rate at which the energy escapes the surface
Degeneracy Pressure
Type of pressure unrelated to an object’s temp, which crises when electrons/neutrons are packed tightly that the exclusion principles come to play.
Brown Dwarf
Degeneracy pressure stops the construction of a proto-star before the release of fusion energy can balance the energy radiated from the proto-star’s surface.
Radiative Pressure
Pressure exerted by photons of light
