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Submillimetre astronomy or submillimeter astronomy (see spelling differences) is the branch of observational astronomy
Observational astronomy

Observational astronomy is a division of the astronomy science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the measurable implications of physical model s....
 that is conducted at submillimetre wavelengths
Terahertz radiation

In physics, terahertz radiation refers to electromagnetic waves sent at frequency in the Hertz#SI_prefixed_forms_of_hertz range. It is also referred to as submillimeter radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz....
 of the electromagnetic spectrum
Electromagnetic spectrum

The electromagnetic spectrum is the range of all possible electromagnetic radiation frequencies. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation from that particular object....
. Astronomers place the submillimetre waveband between the far-infrared and microwave
Microwave

Microwaves are electromagnetic radiation with wavelengths ranging from 1 mm to 1 m, or frequency between 0.3 hertz and 300 GHz....
 wavebands, typically taken to be between a few hundred micrometre
Micrometre

A micrometre or micron is one Micro- of a metre, or equivalently one thousandth of a millimetre. It is also commonly known as a micron....
s and a millimetre
Millimetre

The millimetre is a Units of measurement of length in the metric system, equal to one thousandth of a metre, which is the current International System of Units SI base unit of length....
. It is still common in submillimetre astronomy to quote wavelengths in 'microns', the old name for micrometre.

Using submillimetre observations, astronomers examine molecular clouds
Molecular cloud

A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen ....
 and dark cloud cores with a goal of clarifying the process of star formation
Star formation

Star formation is the process by which dense parts of molecular clouds collapse into a ball of Plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young stellar objects and planet formation as its i...
 from earliest collapse
Gravitational collapse

Gravitational collapse in astronomy is the inward fall of a massive body under the influence of the force of gravity. It occurs when all other forces fail to supply a sufficiently high pressure to counterbalance gravity and keep the massive body in hydrostatic equilibrium....
 to stellar birth.






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Submillimetre astronomy or submillimeter astronomy (see spelling differences) is the branch of observational astronomy
Observational astronomy

Observational astronomy is a division of the astronomy science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the measurable implications of physical model s....
 that is conducted at submillimetre wavelengths
Terahertz radiation

In physics, terahertz radiation refers to electromagnetic waves sent at frequency in the Hertz#SI_prefixed_forms_of_hertz range. It is also referred to as submillimeter radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz....
 of the electromagnetic spectrum
Electromagnetic spectrum

The electromagnetic spectrum is the range of all possible electromagnetic radiation frequencies. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation from that particular object....
. Astronomers place the submillimetre waveband between the far-infrared and microwave
Microwave

Microwaves are electromagnetic radiation with wavelengths ranging from 1 mm to 1 m, or frequency between 0.3 hertz and 300 GHz....
 wavebands, typically taken to be between a few hundred micrometre
Micrometre

A micrometre or micron is one Micro- of a metre, or equivalently one thousandth of a millimetre. It is also commonly known as a micron....
s and a millimetre
Millimetre

The millimetre is a Units of measurement of length in the metric system, equal to one thousandth of a metre, which is the current International System of Units SI base unit of length....
. It is still common in submillimetre astronomy to quote wavelengths in 'microns', the old name for micrometre.

Using submillimetre observations, astronomers examine molecular clouds
Molecular cloud

A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen ....
 and dark cloud cores with a goal of clarifying the process of star formation
Star formation

Star formation is the process by which dense parts of molecular clouds collapse into a ball of Plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young stellar objects and planet formation as its i...
 from earliest collapse
Gravitational collapse

Gravitational collapse in astronomy is the inward fall of a massive body under the influence of the force of gravity. It occurs when all other forces fail to supply a sufficiently high pressure to counterbalance gravity and keep the massive body in hydrostatic equilibrium....
 to stellar birth. Space-based observations of these dark clouds will attempt to determine chemical abundances and cooling mechanisms for the molecules which comprise them. In addition, submillimetre observations will attempt to determine the mechanisms for the formation and evolution of galaxies
Galaxy

A galaxy is a massive, gravitation system that consists of stars and stellar remnants, an interstellar medium of gas and cosmic dust, and an important but poorly-understood component tentatively dubbed dark matter....
.

Submillimetre astronomy from the ground


The most significant limitation to the detection of astronomical emission at submillimetre wavelengths with ground based observatories is atmospheric emission, noise and attenuation. Like the infrared, the submillimetre atmosphere is dominated by numerous water vapour absorption bands and it is only through "windows" between these bands that observations are possible. The ideal submillimetre observing site is dry, cool, has stable weather conditions and is away from urban population centres. There are only a handful of such sites identified, they include Mauna Kea
Mauna Kea Observatory

The Observatories at Mauna Kea, , are an independent collection of astronomical research facilities located on the summit of Mauna Kea on the Hawaii , United States....
 (Hawaii
Hawaii

File:Pahoehoe and Aa flows at Hawaii.jpgThe State of Hawaii is a U.S. state in the United States, located on an archipelago in the central Pacific Ocean southwest of the continental United States, southeast of Japan, and northeast of Australia....
, USA), the Llano de Chajnantor Observatory
Llano de Chajnantor Observatory

Llano de Chajnantor Observatory is an astronomical observatory located at 5104 m altitude in the Chilean Atacama desert, 50 kilometers to the east of San Pedro de Atacama....
 on the Atacama Plateau (Chile
Chile

Chile, officially the Republic of Chile , is a country in South America occupying a long and narrow coastal strip wedged between the Andes mountains and the Pacific Ocean....
), the South Pole
South Pole

The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's rotation intersects the surface....
, and Hanla (India
India

India, officially the Republic of India , is a country in South Asia. It is the List of countries and outlying territories by total area country by geographical area, the List of countries by population country, and the most populous liberal democracy in the world....
). Comparisons show that all four sites are excellent for submillimetre astronomy, and of these sites Mauna Kea is the most established and arguably the most accessible. The Llano de Chajnantor Observatory
Llano de Chajnantor Observatory

Llano de Chajnantor Observatory is an astronomical observatory located at 5104 m altitude in the Chilean Atacama desert, 50 kilometers to the east of San Pedro de Atacama....
 site will soon host the world's largest groundbased astronomy project, the Atacama Large Millimeter Array
Atacama Large Millimeter Array

The Atacama Large Millimeter/submillimeter Array is an international astronomy project that consists of an astronomical interferometer formed from an array of radio telescopes, located at Llano de Chajnantor Observatory in the Atacama desert in northern Chile....
 for millimetre and submillimetre astronomy. The Submillimeter Array
Submillimeter Array

The Submillimeter Array consists of eight 6 m diameter radio telescopes arranged as an interferometer for submillimetre astronomy wavelength observations....
 (SMA) located at Mauna Kea consists of eight 6-metre diameter radio telescopes arranged as an interferometer
Interferometry

Interferometry is the technique of diagnosing the properties of two or more waves by studying the pattern of interference created by their Superposition principle....
 for submillimetre wavelength observations. The largest existing submillimetre telescope, the James Clerk Maxwell Telescope
James Clerk Maxwell Telescope

The James Clerk Maxwell Telescope is a 15-metre Terahertz radiation telescope at Mauna Kea Observatory in Hawaii. It is the largest astronomical telescope in the world designed specifically to operate in the submillimetre astronomy regime ....
, is also located on Mauna Kea.

Submillimetre astronomy from near-space


With high-altitude balloons and aircraft, one can get above even more of the atmosphere. The BLAST
BLAST (telescope)

The Balloon-borne Large Aperture Submillimeter Telescope was a Submillimetre astronomy telescope that hung from a high altitude balloon. It had a 2 meter primary mirror that directs light into bolometer arrays operating at 250, 350, and 500 micrometre....
 experiment and SOFIA
Sofia

Sofia , is the Capital and largest city of the Bulgaria, with 2,5 million people living in the Capital Municipality. It is located in western Bulgaria, at the foot of the mountain massif Vitosha, and is the administrative, cultural, economic, and educational centre of the country....
 are two examples, respectively.

Submillimetre astronomy from space


Space-based observations at the submillimetre wavelengths remove the ground-based limitations of atmospheric absorption. The Submillimeter Wave Astronomy Satellite (SWAS) was launched into low Earth orbit on December 5, 1998 as one of NASA
NASA

The National Aeronautics and Space Administration is an agency of the Federal government of the United States, responsible for the nation's public list of space agencies....
's Small Explorer Program (SMEX) missions. The mission of the spacecraft is to make targeted observations of giant molecular clouds and dark cloud cores. The focus of SWAS is five spectral lines: water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
 (H2O), isotopic water (H218O), isotopic carbon monoxide
Carbon monoxide

Carbon monoxide, with the chemical formula CO, is a colorless and odorless, tasteless, yet highly toxic gas. Its molecules consist of one carbon atom covalent bond to one oxygen atom....
 (13CO), molecular oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 (O2), and neutral carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 (C I).

The SWAS satellite was repurposed in June, 2005 to provide support for the NASA Deep Impact
Deep Impact (space mission)

Deep Impact is an ongoing NASA space probe launched on 12 January 2005 that was designed to study the composition of the interior of the comet 9P/Tempel by colliding a section of the spacecraft into the comet....
 mission. SWAS provided water production data on the comet until the end of August 2005.

The European Space Agency
European Space Agency

The European Space Agency , established in 1975, is an intergovernmentalism organisation dedicated to the Space exploration, currently with 18 member states....
 plans a space-based mission known as the Herschel Space Observatory
Herschel Space Observatory

The Herschel Space Observatory is a European Space Agency mission originally proposed in 1982 by a consortium of European scientists that included Thijs de Graauw , Gisbert Winnewisser , Michael Rowan-Robinson , Glenn White , and Malcolm Longair ....
 (formerly called Far Infrared and Sub-millimetre Telescope or FIRST) for 2009. Herschel will deploy the largest mirror ever launched into space and study radiation in the far infrared and submillimetre wavebands. Rather than an Earth orbit, Herschel will enter into a Lissajous orbit
Lissajous orbit

In orbital mechanics, a Lissajous orbit is a quasi-periodic orbital trajectory that an object can follow around a collinear libration point of a three-body system without requiring any propulsion....
 around L2, the second Lagrangian point
Lagrangian point

The Lagrangian points , are the five positions in an orbital configuration where a small object affected only by gravity can theoretically be stationary relative to two larger objects ....
 of the Earth-Sun system. L2 is located approximately 1.5 million km from Earth and the placement of Herschel there will lessen the interference by infrared and visible radiation from the Earth and Sun. Herschel's mission will focus primarily on the origins of galaxies and galactic formation.

See also


  • Far infrared astronomy
    Far infrared astronomy

    Far infrared astronomy is the branch of astronomy and astrophysics which deals with objects visible in far-infrared radiation .In the far-infrared, stars are not especially bright, but we can see emission from very cold matter which is not seen at shorter wavelengths....
  • SOFIA
    Sofia

    Sofia , is the Capital and largest city of the Bulgaria, with 2,5 million people living in the Capital Municipality. It is located in western Bulgaria, at the foot of the mountain massif Vitosha, and is the administrative, cultural, economic, and educational centre of the country....
  • Radio window
    Radio window

    The radio window is the range of frequencies of electromagnetic radiation that the earth's atmosphere lets through. The wavelengths in the radio window run from about one centimeter to about eleven-meter waves....
  • Atmospheric window
    Atmospheric window

    The atmospheric window refers to those parts of the electromagnetic spectrum that are, with the earth's atmosphere in its natural state, not absorbed at all....
  • Astronomical window
  • Optical window
    Optical window

    The meaning of this term depends on the context:* In astronomy, the optical window is the optical portion of the electromagnetic spectrum that passes through the Earth's atmosphere all the way to the ground....
    Category:Submillimetre telescopes


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