Thursday September 20, 2012 (The Hertzsprung - Russell Diagram; Nebulae )

The Launch Pad Thursday, 9/20/12 Name two factors that can increase the luminosity of stars. size surface temperature

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Assignment Currently Open Summative or Formative? Date IssuedDate Due Date Into GradeSpeed Final Day Quiz 2S29/7 9/21 Lab – Timeline of the Universe F49/119/13 WS – Star Stages F59/129/13 Quiz 3S39/14 9/28 Lab – Distance and Spacing of the Planets F69/179/18 Lab – Comparing the Terrestrial and Jovian Planets F79/189/19

?? Recent Events in Science Ultra-Distant Galaxy Discovered Amidst Cosmic 'Dark Ages': May Be Oldest Galaxy Ever In the big image at left, the many galaxies of a massive cluster called MACS J dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times. At upper right, a partial zoom-in shows MACS 1149-JD in more detail, and a deeper zoom appears to the lower right. (Credit: NASA/ESA/STScI/JHU) 09/ htm Read all about it!

90% of all stars are in the main-sequence stage. They are varied in their size, color, luminosity, and surface temperature. The Hertzsprung - Russell Diagram Red Giants and Supergiants are very large and very luminous, but have relatively cool surface temperatures. White Dwarfs are relatively dim, mid- temperature stars that are the remains of low- and mid-mass stars.

Nebulae

Interstellar Matter Between stars is the “vacuum of space”, which actually contains varying amounts of “interstellar matter.” A nebula (plural: nebulae) is a large cloud of dust and gases. There are two major types of nebulae: bright nebulae dark nebulae

Bright Nebulae Bright nebulae glow if they are close to a very bright star, or stars. There are two types of bright nebulae: emission nebulae reflection nebulae

Emission Nebulae Emission nebulae are clouds of gases and dust that absorb ionizing ultraviolet radiation from nearby hot stars or star remnants and reemit it as visible light. Crab Nebula

Emission Nebulae The Rosette Nebula is an emission nebula. The Orion Nebula is probably the most well- known emission nebula.

Reflection Nebulae Reflection nebulae are clouds of interstellar dust and gas which reflect the light of a nearby star or stars. The energy from the nearby star or stars is insufficient to ionize the gas of the nebula to create an emission nebula, but is enough to give sufficient scattering to make the dust visible.

Reflection Nebulae The Witch Head reflection nebula, about 900 light years from Earth, is associated with the bright star Rigel in the constellation Orion. The nebula glows primarily by light reflected from Rigel, located just outside the top right corner of the image. Fine dust in the nebula reflects the light. The blue color is caused not only by Rigel's blue color but because the dust grains reflect blue light more efficiently than red.

Reflection Nebulae Reflection Nebula Messier 78

Dark Nebulae A dark nebula is a type of interstellar cloud that is so dense it obscures the light from the background emission or reflection nebula (e.g., the Horsehead Nebula) or that it blocks out background stars (e.g., the Snake Nebula). The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of larger molecular clouds. Dark nebulae are not close to any bright star, therefore they appear dark. Dark nebulae contain the material that forms stars and planets.

Dark Nebulae Van den Bergh 142 Elephant Trunk Nebula

Dark Nebulae Eagle Nebula

Video Segment How the Universe Works: Extreme Stars A Star’s Energy