Extinction
In astronomy, the dimming of starlight as it passes through the interstellar mediumMaterial between the stars, consisting of gas, dust and cosmic rays (high energy charged particles moving at nearly the speed of light). It comprises ~10% of visible matter in the disk of our Galaxy (Milky Way). Until recently it was generally assumed that silicates in the ISM were amorphous, but Click on Term to Read More. Dust scatters some of the light, causing the total intensity of the light to diminish. It is important to take this effect into account when measuring the apparent brightness of stars. The dark bands running across portions of the Milky Way in the sky are due to extinction by copious amounts of dust in the plane of our galaxyConcentration of 10 to 10 stars, dust and gas, that are gravitationally bound. Our galaxy contains ~2 × 10 stars. There are four main types of galaxies: • Elliptical
• Lenticular
• Spiral
• Irregular
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In paleontology and biology, the permanent disappearance of a species after all individuals have died off.
Some or all content above used with permission from J. H. Wittke.
