Most cosmic dust particles are between a few molecules to 0.1 µm in size.
Cosmic dust can be further distinguished by its astronomical location: intergalactic dust, interstellar dust, interplanetary dust (such as in the zodiacal cloud) and circumplanetary dust (such as in a planetary ring).
In the Solar System, interplanetary dust causes the zodiacal light.
Solar System dust includes comet dust, asteroidal dust, dust from the Kuiper belt, and interstellar dust passing through the Solar System.
Thousands of tons of cosmic dust are estimated to reach the Earth's surface every year, A smaller fraction of dust in space is "stardust" consisting of larger refractory minerals that condensed as matter left by stars.
Interstellar dust particles were collected by the Stardust spacecraft and samples were returned to Earth in 2006.
Cosmic dust was once solely an annoyance to astronomers, as it obscures objects they wish to observe.
When infrared astronomy began, the dust particles were observed to be significant and vital components of astrophysical processes.
Their analysis can reveal information about phenomena like the formation of the Solar System.
For example, cosmic dust can drive the mass loss when a star is nearing the end of its life, play a part in the early stages of star formation, and form planets.
In the Solar System, dust plays a major role in the zodiacal light, Saturn's B Ring spokes, the outer diffuse planetary rings at Jupiter, Saturn, Uranus and Neptune, and comets.
The interdisciplinary study of dust brings together different scientific fields: physics (solid-state, electromagnetic theory, surface physics, statistical physics, thermal physics), fractal mathematics, surface chemistry on dust grains) meteoritics, as well as every branch of astronomy and astrophysics.