The term "accretion disc" is commonly used in astrophysics to describe a rotating disc of gas and dust that surrounds a celestial object such as a black hole or a protostar. The word "accretion" is spelled /əˈkriːʃ(ə)n/, with the stress placed on the second syllable, and is derived from the Latin verb "accretio", meaning growth. The word "disc" is spelled /dɪsk/ in IPA, and refers to a flat, round object or shape. The spelling of "accretion disc" reflects its origin and meaning in the field of astrophysics.
An accretion disc is a term commonly used in astronomy to describe a relatively flat, rotating structure composed mainly of gas, dust, and other celestial debris that orbits a massive central object, such as a star, a black hole, or a white dwarf. The term "accretion" refers to the process of matter accumulating or being gathered by gravitational forces. Consequently, an accretion disc serves as a vital component in the formation and evolution of celestial bodies.
Within an accretion disc, gravity causes the material to spiral inward towards the central object, resulting in increased density as it nears the center. Due to conservation of angular momentum, the material cannot fall directly onto the central object, but loses energy and angular momentum over time. This energy loss typically manifests in the form of radiation, leading to the creation of luminous rings or disks around the central object.
Accretion discs play a significant role in various astronomical phenomena, including the formation of stars and planetary systems. Additionally, accretion discs around black holes and neutron stars are responsible for emitting tremendous amounts of energy in the form of X-rays and other high-energy radiation, called accretion-powered sources.
With their complex and dynamic nature, accretion discs offer valuable insights into the cosmos. Their study enables astronomers to unravel the mechanisms behind celestial body formation, energy generation, and the behavior of matter under extreme gravitational forces, contributing to our understanding of the universe.
The word "accretion disc" is derived from combining two terms: "accretion" and "disc".
1. Accretion: This term comes from the Latin word "accretio", meaning growth or increase. In astrophysics, accretion refers to the process by which matter, such as gas and dust, accumulates and forms into larger objects under the influence of gravity, such as a star or a black hole.
2. Disc: The word "disc" originated from the Latin word "discus", which referred to a circular object or a round plate-like shape. In the context of astronomy, a disc is a flat and disk-shaped structure that often revolves around a central object.