An accretion disk is a structure, which is an amalgamation of gas, plasma or particles around
the black hole. It is attracted by the gravitational pull and orbits the black
hole while it slowly spirals into it, so it is a phenomenon that describes the
way how a big celestial body amasses matter like black holes.
Detailed Definition:
One can not observe black holes or
their event horizon, but since black holes have accretion disks, which are a type of structure and accumulations of gas, plasma or particles that were attracted by the huge
gravitational pull of black holes. Humans are able to see those accretion disks,
because the spinning matter is so fast, which in turn generates heat and emits
x-rays and gamma rays. The high amount of angular momentum makes it impossible
for the matter to simply fall into the black hole like it would on earth or one
would think. Angular momentum decreases despite there being no friction in
space, because of turbulence, which is caused by the fact that rotation
increases the effect of magnetic fields. Temperatures in the accretion disks
tend to vary quite a bit, which is determined by the composition of the
accretion disk and its source. Temperatures can go from a few thousand to a few
million Kelvin.
Etymology:
Accretion from
Latin ad+ crescere-->accrescere--->accretionem
Disk from Latin discus
Sample Sentence(s):
The accretion disk is the natural consequence of
how gravitational pull attracts matter and makes it impossible to simply fall
into the black hole.
Many people think they saw a picture of a black
hole, but in reality they only saw a picture of its accretion disk.
