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Monday January 7 Wed Jan 9 Astro 1p02.docx
Monday January 7 Wed Jan 9 Astro 1p02.docx

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School
Brock University
Department
Political Science
Course
POLI 1F90
Professor
Bozidar Mitrovic
Semester
Winter

Description
Monday January 7, 2013 Astro 1p02: Star formation: - to find out about the process of star formation one should look at the young stars - mass luminosity relation for main sequence stars is L(luminosity)= M*3.5 (mass of a star) - lifetime of a star = amount of fuel/energy output - M/L = M/M*3.5 = 1/M*2.5 - The youngest stars are located at the top left corner of the main sequence - they appear as bluish (high surface temp.) and they have very high luminosities - The observations show that such stars are surrounded by gas and dust of interstellar material (ISM) - Gas: 74% by mass is hydrogen (H) 24% by mass is helium (He) 2% by mass is all the other elements - dust: consists of core and mantle, 10-100nm across (1nm=10*-9 meters) o core – silicate material o ices of water, ammonia and methane Wednesday January 9 , 2013 - When the clouds of interstellar material are observed in the visible part of the spectrum (wave lengths: 400 nm – 700 nm), they are called nebulae - There are several types of nebulae: o Dark nebula  Starlight is absorbed by the dust particles in the nebula o Reflection nebula (Bluish in colour)  They are bluish for the same reason that the sky appears to be blue on a clear sunny day  Molecules (and dust) in the air scatter blue light more efficiently than the longer wave lengths  Red wave lengths can pass through the molecules where as the blue wave lengths get scattered by the molecules  The stars appears as reddish but the nebula itself is bluish in colour o Emission Nebula (Reddish in colour)  A hot (o-or b-type) star  UV-radiation is intense from a hot star  This process (of electron, UV photon to emitted photon) where a photon of one wavelength is absorbed by an atom and then the atom emits a photon of a different wavelength is called Fluorescence - The stars are formed in a particular type of dark nebula – the Giant Molecular Cloud (example: Eagle Nebula or M16) - Giant – because the
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