Lecture-10 - Lecture # 10: Birth of Stars Facts about stars...

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10/30/11 Physics 20 Lecture # 11 1 Lecture # 10: Birth of Stars Facts about stars Formation of proto-stars Interstellar matter and dust Why and where do stars form ? Stages of star birth Mass of the stars Hertzprung-Russell Diagram The lowest and highest mass stars
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10/30/11 Physics 20 Lecture # 11 2 Facts about Stars and their Life All stars are born in clouds of interstellar gas Stars shine with energies produced by nuclear fusion in their core Stars die when they exhaust all sources of fuel to fusion We can measure mass, temperature and age of stars There are different types of stars Stars in our galaxy are formed at the rate of 2 or 3 per year
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10/30/11 Physics 20 Lecture # 11 3 Star Forming Regions A star forming region Newborn stars produce white patches where starlight illuminates gas The clouds look dark where dust particles block the light
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10/30/11 Physics 20 Lecture # 11 4 Interstellar Medium The gas and dust which fill the space between stars within a galaxy are referred to as interstellar medium The gas between the stars is composed of 98% H and He and 2% heavier elements We use spectroscopy to measure abundance of interstellar clouds by studying their absorption lines The interstellar medium in our galaxy contains gas with different temperatures and densities
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10/30/11 Physics 20 Lecture # 11 5 Radio emission from Carbon monoxide molecules between the stars in our Galaxy
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10/30/11 Physics 20 Lecture # 11 6 Where Stars Form ? Stars are born in the interstellar clouds, called molecular clouds The temperature of molecular clouds is 10-30 K Molecular H is hard to detect because it has too cool a temperature to produce emission lines About half the atoms of elements heavier than He are found in solid grains of interstellar dust. Interstellar dust constitutes about 1% of the a molecular clouds mass
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10/30/11 Physics 20 Lecture # 11 7 Interstellar Dust Interstellar dust absorbs shorter wavelengths. This is the reason there are “dark” regions in some star forming regions Stars in the interstellar clouds look redder compared to those outside. This is because the shorter wavelengths (blue) are absorbed by dust while the longer wavelengths (red) are not absorbed. This is called interstellar reddening .
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10/30/11 Physics 20 Lecture # 11 8 Visible light image vs. Infrared light image of the same cloud. Most of the light is absorbed in visible but not infrared
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10/30/11 Physics 20 Lecture # 11 9 A Newborn star is obscured from the optical image (left) but is visible in the infrared wavelengths (right)=> dust absorption
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10/30/11 Physics 20 Lecture # 11 10 Trifd Nebula M20 Charles Messier (1730-1817) was named “The Comet Ferret” by Louis XV for his skill at ±nding comets.
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This note was uploaded on 11/17/2011 for the course PHYSICS 20 taught by Professor Mubarek during the Spring '11 term at UC Riverside.

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Lecture-10 - Lecture # 10: Birth of Stars Facts about stars...

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