ASTR 1346 1st Edition Lecture 9 Outline of Last Lecture I Parallax A Distance B Baselines C Parsec Outline of Current Lecture I Star Formation II Electromagnetic Spectrum III Interstellar Matter A Interstellar Medium B Obscuration C Extinction D Reddening IV Gas V Dust VI Giant Molecular Clouds Current Lecture l Stars form from dust and gas and are still forming today Massive stars don t shine longer The birth of a star goes from protostar pre main sequence main sequence ll Einstein showed that the energy of a photon decreases with its wavelength and is calculated by photon energy speed of light wavelength The ozone layer absorbs UV light X Rays and Gamma Rays Water vapor and carbon dioxide block our infrared light and water vapor and oxygen block microwaves Infrared and radio observations show us that the space between stars is not empty Infrared and radio waves can pass through dust grains lll Interstellar matter is gas and dust that fills the universe It blocks light from stars and is not uniformly distributed At some places it s very rare and in others very dense These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute A Interstellar Medium is the matter between stars This contains at least 10 of all known mass in our galaxy and is made up of dust and gas B Obscuration is caused by dust particles dust grains and makes the universe look redder C Extinction is the general dimming of starlight by interstellar matter D Reddening is when the blue part of the light from different stars is obscured and scattered more than the red so the universe appears redder lV Gas is the vast majority of the universe Gas is very cold and made up of individual atoms and small molecules 90 hydrogen 9 helium and 1 heavier elements Particles are spherical and invisible V While most of the universe is gas there is a tiny bit of dust in there which helped make the planets Dust consists of clumps of atoms and molecules that have a coating of ice on them This helped them stick together to form bigger and bigger particles Particles are elongated but the large scale structure is more complex Vl Giant Molecular Clouds are very dark and huge and is where stars form They have a very low temperature a lot of matter and stability with just a little bit of instability About 6 000 GMC s are estimated to exist in our galaxy Part of the Orion Nebula is in a GMC