Støvskive

Støvskive, or a dust disk, is a disk-shaped assemblage of dust and gas that surrounds a star or stellar remnant. In young stellar objects it is often called a protoplanetary disk and serves as the site of planet formation. Around older stars, debris disks consist mainly of dust produced by collisions.

The disk composition includes silicate and carbonaceous dust grains, ices, and trace amounts of gas such as hydrogen and carbon monoxide. It is typically flattened and extends from a few astronomical units to several hundred AU. The temperature decreases with distance from the star, yielding warm inner regions and cool outer regions. Dust grains settle toward the midplane, and rings, gaps, or spirals can indicate the presence of forming planets or disk-stirring processes.

Støvskive are detected through infrared excess emission, scattered light, and submillimeter radiation. Modern telescopes such as ALMA and high-contrast imaging systems on large telescopes resolve disks directly and reveal ring-like structures. Spectroscopic observations constrain gas content and dynamics.

Formation and evolution: a støvskive forms from the residual material of star formation; over time, gas dissipates, planets accumulate, and the disk becomes a debris disk dominated by dust produced in collisions. Transitional disks show inner holes, suggesting ongoing planet formation or photoevaporation.

Significance lies in understanding planet formation, disk evolution, and solar system history. Typical lifetimes for gas-rich protoplanetary disks are a few million years; debris disks can persist for hundreds of millions of years. Notable examples include the Beta Pictoris, TW Hya, and HL Tau disks.