Coma (Comet Anatomy)
A coma is a significant feature of a comet, which is a celestial body composed of ice, rock, and dust. As a comet approaches the sun, it undergoes sublimation, where solid materials like ice transform directly into gas, forming a surrounding atmosphere of gas and dust known as the coma. The coma can vary in size, sometimes becoming larger than planets, and changes in shape depending on the comet's proximity to the sun. Each comet has two distinct comas: the gas coma, composed of gases released during sublimation, and the dust coma, made up of dust particles expelled alongside the gas. The influence of solar wind and radiation eventually leads to the formation of the comet's tails. Comets have long fascinated humanity, historically viewed as omens before being understood scientifically since the 1600s. Modern research has included missions to study comets more closely, such as the 2014 landing of the European Space Agency's Philae lander on a comet, which provided valuable insights into cometary composition. Scientists are particularly interested in comets because they may carry essential elements for life, and understanding their anatomy could reveal vital information about the origins of water on Earth and potential impacts on life beyond our planet.
Coma (Comet Anatomy)
FIELDS OF STUDY: Astronomy; Observational Astronomy
ABSTRACT: A coma is the cloud of gas and dust around a comet’s nucleus. When it is near the sun, a comet has three parts: a nucleus, a coma, and a tail. The coma is formed by the sublimation of water and other compounds from the nucleus’s surface and creates an atmosphere around the comet. When the comet is very close to the sun, solar winds blow the coma away from the sun, creating the tail. Scientists continue to research comets and their comas because of the significant impact comets could have on Earth.
Coma Formation
A comet is a celestial body made of ice, rock, and dust. When a comet is far away from the sun, it is frozen and solid. However, when its orbit brings it within 2 to 3 astronomical units (AU) of the sun, a comet undergoes a transformation.
As its surface warms, the comet undergoes sublimation. In this process, materials such as ice change directly from a solid to a gas, without going through the intermediate liquid stage. The gas forms the coma, an atmosphere of gas and dust around the comet. A coma grows depending on conditions, and can become extremely large, larger than planets even. The shapes of comas vary. The coma of a particular comet will also change according to how far it is from the sun.
Coma Types
Each comet actually has two comas: the dust coma and the gas coma. The gas coma is made up of the gas that is released when heat from the sun causes the comet to sublimate. Hydrogen molecules also form an invisible gas halo. The dust coma is made up of dust particles that are pulled from the comet when gases are expelled. Solar wind and radiation from the sun eventually push both comas to form the comet’s gas and dust tails.
Humans and Comets
People have always been fascinated by comets, but before the 1600s they perceived them mainly as omens. Since the seventeenth century, people have used science to identify what comets are and how they work. Scientists have tried to learn as much as they can about comets. They have undertaken a number of space missions to try to learn more about comets’ anatomy, including the coma. In 2014, scientists landed the first spacecraft on a comet to study its composition. Although the European Space Agency's lander, Philae, bounced and ended up resting on its side in a shady spot, depriving its instruments of solar power needed to probe the comet, its touchdown provided researchers with information about the soft surface beneath its icy crust.
Potential Impact of Comets
Scientists are interested in comets and their comas because they carry hydrogen, carbon, and other materials that are vital for life. Some scientists believe that much of the water on Earth arrived on comets. Scientists study comets because they could potentially impact life on Earth or elsewhere in the solar system.
PRINCIPAL TERMS
- comet: celestial bodies mostly made up of carbon dust and ice.
- dust coma: the cloud of dust surrounding a comet’s nucleus.
- gas coma: the cloud of gas surrounding a comet’s nucleus.
Bibliography
Amos, Jonathan. "Controllers Now Banking on Philae Wake-Up Call." BBC. BBC, 30 Jan. 2015. Web. 5 Mar. 2015.
"Anatomy of a Comet." Rosetta. Jet Propulsion Laboratory, ESA, n.d. Web. 5 Mar. 2015.
"Comet Facts for Students." Jet Propulsion Laboratory. NASA, 2 Nov. 2010. Web. 5 Mar. 2015.
"Cometary Coma." Cosmos. Swinburne U of Technology, n.d. Web. 5 Mar. 2015.
"Exploring Comets and Asteroids: Time Capsules of the Solar System." NASA. NASA, 13 Nov. 2014. Web. 5 Mar. 2015.
Gibney, Elizabeth. "'Like Froth on a Cappuccino': Spacecraft's Chaotic Landing Reveals Comet's Softness." Nature, 28 Oct. 2020, DOI: 10.1038/d41586-020-03043-4. Accessed 14 June 2022.
"History of Cometary Missions." ESA. ESA, 1 Aug. 2014. Web. 5 Mar. 2015.
"What Is a Comet?" Qualitative Reasoning Group. Northwestern U, n.d. Web. 5 Mar. 2015.