Coma (cometary)

The coma is the nebulous envelope around the nucleus of a comet. It is formed when the comet passes close to the Sun on its highly elliptical orbit; as the comet warms, parts of it sublimate. This gives a comet a "fuzzy" appearance when viewed in telescopes and distinguishes it from stars. The word coma comes from the Greek "kome" (κόμη), which means "hair" and is the origin of the word comet itself.

The coma is generally made of ice and comet dust. Water dominates up to 90% of the volatiles that outflow from the nucleus when the comet is within 3-4 AU of the Sun. The H₂O parent molecule is destroyed primarily through photodissociation and to a much smaller extent photoionization. The solar wind plays a minor role in the destruction of water compared to photochemistry. Larger dust particles are left along the comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by light pressure.

On 11 August 2014, astronomers released studies, using the Atacama Large Millimeter/Submillimeter Array (ALMA) for the first time, that detailed the distribution of HCN, HNC, H₂CO, and dust inside the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON). On 2 June 2015, NASA reported that the ALICE spectrograph on the Rosetta space probe studying comet 67P/Churyumov–Gerasimenko determined that electrons (within 1 km (0.62 mi) above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma.

Coma (optics)

In optics (especially telescopes), the coma, or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration.

Coma is an inherent property of telescopes using parabolic mirrors. Unlike a spherical mirror, a bundle of parallel rays parallel to the optical axis will be perfectly focused to a point (the mirror is free of spherical aberration), no matter where they strike the mirror. However, this is only true if the rays are parallel to the axis of the parabola. When the incoming rays strike the mirror at an angle, individual rays are not reflected to the same point. When looking at a point that is not perfectly aligned with the optical axis, some of the incoming light from that point will strike the mirror at an angle. This results in an image that is not in the center of the field looking wedge-shaped. The further off-axis (or the greater the angle subtended by the point with the optical axis), the worse this effect is. This causes stars to appear to have a cometary coma, hence the name.

Coma (Pendulum song)

"Coma" is the third single by Australian ambient house band Pendulum. The single was released in July 1997 and peaked at #46 on the ARIA Singles Chart spending just 2 weeks on the Chart. It was later included on the album 3 Knocks and Triple J Hottest 100, 1997, where it ranked #32. It was the final single release from the band as they split in early 1998.

References

Asshole (album)

Asshole is the second solo album release by Kiss member, Gene Simmons. It was released in 2004 on Sanctuary Records. Due to its controversial title, the album's title does not appear on the front cover of the album. On the side of the CD case the title reads "***hole".

The album contains songs Simmons wrote based on work by Bob Dylan and Frank Zappa, among other musicians, specifically Dave Navarro who plays guitar on the The Prodigy cover "Firestarter".

Track listing

Personnel

Hole (surname)

Hole is a surname. Notable people with the surname include:

My December

My December is the third studio album by American pop rock recording artist Kelly Clarkson. The album was released on June 22, 2007 throughout most of Europe (such as Germany, Ireland, Italy and the Netherlands), on June 23, 2007 in Australia, on June 25, 2007 in the United Kingdom, Hong Kong, Poland and Mexico, and on June 26, 2007 in North America. Clarkson confirmed the name of the album in her journal on her fanclub website on February 27, 2007.

Since its release, My December has shipped one million copies in the U.S. and has been certified Platinum. It has also been certified Platinum in other countries, including Canada and Australia. The album was voted as the fifth best album of 2007 by the readers of Billboard. It ranked at number 53 on the Australian Year End Chart. The album was heavily reviewed by critics, who noted the album's stronger rock influence when compared with Clarkson's previous album Breakaway.

Background

Release date

My December was released on June 26, 2007 in North America. In numerous interviews and press releases, the release date for My December had been stated as July 24, 2007.

Sugar

Sugar is the generalized name for sweet, short-chain, soluble carbohydrates, many of which are used in food. They are carbohydrates, composed of carbon, hydrogen, and oxygen. There are various types of sugar derived from different sources. Simple sugars are called monosaccharides and include glucose (also known as dextrose), fructose and galactose. The table or granulated sugar most customarily used as food is sucrose, a disaccharide. (In the body, sucrose hydrolyses into fructose and glucose.) Other disaccharides include maltose and lactose. Longer chains of sugars are called oligosaccharides. Chemically-different substances may also have a sweet taste, but are not classified as sugars. Some are used as lower-calorie food substitutes for sugar described as artificial sweeteners.

Sugars are found in the tissues of most plants, but are present in sufficient concentrations for efficient extraction only in sugarcane and sugar beet. Sugarcane refers to any of several species of giant grass in the genus Saccharum that have been cultivated in tropical climates in South Asia and Southeast Asia since ancient times. A great expansion in its production took place in the 18th century with the establishment of sugar plantations in the West Indies and Americas. This was the first time that sugar became available to the common people, who had previously had to rely on honey to sweeten foods. Sugar beet, a cultivated variety of Beta vulgaris, is grown as a root crop in cooler climates and became a major source of sugar in the 19th century when methods for extracting the sugar became available. Sugar production and trade have changed the course of human history in many ways, influencing the formation of colonies, the perpetuation of slavery, the transition to indentured labour, the migration of peoples, wars between sugar-trade–controlling nations in the 19th century, and the ethnic composition and political structure of the New World.