In astronomy, the dimming of starlight as it passes through the Material 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. 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 Concentration of 106 to 1012 stars, dust and gas, that are gravitationally bound. Our galaxy contains ~2 × 1011 stars. There are four main types of galaxies: • Elliptical
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.