APOD: May 9, 1999 - Fractal Interstellar Dust Up Close (original) (raw)

Astronomy Picture of the Day

Discover the cosmos!Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

May 9, 1999

Explanation: Our universe is a very dusty place. Dustusually shows its presence by blocking out light emitted from stars or nebulae behind it, sometimes creating the illusion of ahorse's heador a sombrero hat. But nobody really knows what a typical interstellar dust grain looks like. By studying how dustabsorbs, emits, and reflects light, astronomers do know that interstellar dust is much different than the cell and lint based dust found around a typical house.Interstellar dust grains are composed mostly of carbon, silicon, and oxygenand are usually less than about 1/1000 of a millimeter across. Recent work indicates that most dust grains are not spherical. The above picture shows the result of a fractal adhesion modelfor dust grains involving random conglomerates of spherical compounds of different properties, here artificially highlighted by different colors.