Quizlet Flashcards
Apparent brightness =
Luminosity / distance^2
Larger magnitudes are?
Dimmer
Radiation from stars is:
Blackbody radiation
Stellar spectra are much more informative than the black body curves
True
Spectral class from highest to lowest
(Hottest) O, B, A, F, G, K, M (coolest)
Blackbody spectrum:
Radiation emitted by an object depending only on its temperature
Wiens law:
Peak wavelength is inversely proportional to temperature
Total energy (per area and time) emitted is proportional to the 4th power of:
Temperature F (energy per area per unit time) = sigmaT^4
Spectroscopic parallax:
Nothing to do with parallax but does use spectroscopy in finding the distance to a star
Spectroscopic parallax
- Measure the stars apparent magnitude and spectral class
- Use spectral class to estimate luminosity
- Apply inverse square law to find distance
Stellar luminosity classes
Ia: bright super giants
Ib: supergiants
II: bright giants
III: giants
IV: Subgiants
V: Main-sequence stars and dwarfs
Binary stars are:
Two stars orbiting a common center of mass
Which star in a binary star is the primary star and which is the secondary star (A and B)
The brighter star is the primary and the dimmer is the secondary
Wide binaries:
Are stars that have orbits that keel them spread apart from one another
Close binaries:
Evolve nearby and transfer mass from one to the other
The primaries sometimes consume the material from companion or the whole star
Binary systems provide:
The best means for scientists to determine the mass of the star
As the pair of binary stars pull on eachother astronomers can calculate size and from there determine what:
Temperature and radius
Distance to nearest stars can be measured by:
Parallax
Apparent brightness is as observed from earth
Depends on distance and absolute luminosity
Spectral classes corespondent to:
Different surface temperatures
Stellar size is related to luminosity and temperature
True
Mass determines:
Where a star lies on the main sequence
Star formation happens when a part of a dust cloud begins to contract under its own gravitational force:
As it collapses the center becomes hotter and hotter until nuclear fusion begins at the core
Stars can be as big or as small as:
.075 solar masses and 150 solar masses
Dark dust clouds are dark because:
Starlight from behind the cloud does not penetrate the cloud
Interstellar gas composed of:
90% hydrogen 9% helium
Star formation begins with:
Fragmenting collapsing cloud of dust and gas
Brown dwarves never become stars
True :(
During its stay on the main sequence a star is in:
Equilibrium
Helium fusion occurs when the core temperature reaches:
1000,000,000 K
Red giants never become hot enough for fusion past carbon to take place
True
