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10 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Star Formation
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gravitational attraction slowly binds together particles that make up the interstellar medium
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Interstellar Medium
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small particles account for 10% of galaxy's mass.
-this is very cold and emits almost no visible radiation & is very difficult to observe. |
Makeup: 74% hydrogen, 36% Helium, 1% other.
Some of the atoms combine to form molecules-H2, CO, H2O, NH3, H2CO, Carbon, Silica |
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Interstellar Reddening
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recall that blue light has a greater energy; blue is more energetic than red-more energetic particles have larger scattering angles-blue light scatters more easily than red
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This is the reason why our daytime sky is more red when viewed near the horizon.
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Describe trick to locate interstellar medium gas clouds
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Major compounds are H & H2. It's known for every CO (carbon monoxide) there are 10,000 hydrogen molecules.
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CO emits a radio frequency photon wavelength of 2.6mm.
Look for a strong signal near 2.6mm wavelength |
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Jeans Instability
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vast regions of molecular hydrogen that is sufficiently cold & dense-gravity overwhelms kinetic pressure and H2 collapses from inside out. Inner layers fall inward rapidly-increase mass in the central region of the cloud. This forms a PROTOSTAR.
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Protostar
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isn't large enough for nuclear fusion, but it glows (infrared) due to the increase of the kinetic pressure. Matter continues to fall inward towards the core due to gravitational forces; however eventually the kinetic pressure is so great that mass accretion is hallted.
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At this point the protostar becomes a Pre-Main Sequence Star (PMS)
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PMS Star
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PMS star slowly contracts due to forces of gravity; core temp increases-finally reaches 10 mill Kelvin-nuclear fusion begins-outflow of gamma ray photons stops the contraction-
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the star is now a Main Sequence Star
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Distinction between 3 phases
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Protostar to PMS: occurs when mass accretion is halted
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PMS to Main Sequence: occurs when contraction is halted.
a more massive a PMS star is the more quickly it becomes a Main Sequence |
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Brown Dwarf
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basically small PMS stars-gravity wasn't sufficiently strong to elevate core temp to 10 mill Kelvin: remains planet like: these are Jovian planets
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Jovian Planets: Jupiter, Saturn, Uranus, Neptune-Gas Giants.
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Upper limit to star masses
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100 solar masses-PMS to main sequ initial flux of gamma ray photons blasts away large portion of mass.
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