Far infrared astronomy
Encyclopedia
Far-infrared astronomy is the branch of astronomy
and astrophysics
that deals with objects visible in far-infrared radiation (extending from 30 µm towards submillimeter wavelengths around 450 µm).
In the far-infrared, stars are not especially bright, but we can see emission from very cold matter (140 Kelvins or less) that is not seen at shorter wavelengths.
Huge, cold clouds of gas and dust in our own galaxy
, as well as in nearby galaxies
, glow in far-infrared light. This is due to thermal radiation
of interstellar dust contained in molecular clouds.
In some of these clouds, new stars are just beginning to form. Far-infrared observations can detect these protostar
s long before they "turn on" visibly by sensing the heat they radiate as they contract.
The center of our galaxy also shines brightly in the far-infrared: These emissions are from dust in circumstellar shells around numerous old red giant
stars. These stars heat up the dust and cause it to glow brightly in the infrared
. The Bolocam Galactic Plane Survey
mapped the galaxy for the first time in the far-infrared.
Except for the plane of our own galaxy
, the brightest far-infrared object in the sky is central region of a galaxy
called Messier 82
. The nucleus of M82 radiates as much energy in the far-infrared as all of the stars in our galaxy combined. This far-infrared energy comes from dust heated by a source that is hidden from view. The central regions of most galaxies shine very brightly in the far-infrared. Many galaxies ("active galaxies") have active nuclei hidden in dense regions of dust. Others, called starburst galaxies
, have an extremely high number of newly forming stars heating interstellar dust clouds
. These galaxies, far outshine all others galaxies in the far-infrared.
The Earth's atmosphere is opaque over most of the far-infrared, so that ground-based observations are limited to submillimetre wavelengths using high-altitude telescopes such as the James Clerk Maxwell Telescope
, the Caltech Submillimeter Observatory
, and the Submillimeter Array
. Most far-infrared astronomy is performed by satellites such as the Herschel Space Observatory
, Spitzer
, IRAS
, and ISO
. Future missions will include ASTRO-F
and the airborne SOFIA
telescope.
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
and astrophysics
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
that deals with objects visible in far-infrared radiation (extending from 30 µm towards submillimeter wavelengths around 450 µm).
In the far-infrared, stars are not especially bright, but we can see emission from very cold matter (140 Kelvins or less) that is not seen at shorter wavelengths.
Huge, cold clouds of gas and dust in our own galaxy
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
, as well as in nearby galaxies
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
, glow in far-infrared light. This is due to thermal radiation
Thermal radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation....
of interstellar dust contained in molecular clouds.
In some of these clouds, new stars are just beginning to form. Far-infrared observations can detect these protostar
Protostar
A protostar is a large mass that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. The protostellar phase is an early stage in the process of star formation. For a one solar-mass star it lasts about 100,000 years...
s long before they "turn on" visibly by sensing the heat they radiate as they contract.
The center of our galaxy also shines brightly in the far-infrared: These emissions are from dust in circumstellar shells around numerous old red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
stars. These stars heat up the dust and cause it to glow brightly in the infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
. The Bolocam Galactic Plane Survey
Bolocam Galactic Plane Survey (BGPS)
Observations for the Bolocam Galactic Plane Survey took place from June 2005 until September 2007 and covers 170 square degrees of the galactic plane visible from the northern hemisphere. The survey detected 8400 sources to a limiting non-uniform 1-sigma noise level in the range 30 to 60 mJy/beam...
mapped the galaxy for the first time in the far-infrared.
Except for the plane of our own galaxy
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
, the brightest far-infrared object in the sky is central region of a galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
called Messier 82
Messier 82
Messier 82 is the prototype nearby starburst galaxy about 12 million light-years away in the constellation Ursa Major...
. The nucleus of M82 radiates as much energy in the far-infrared as all of the stars in our galaxy combined. This far-infrared energy comes from dust heated by a source that is hidden from view. The central regions of most galaxies shine very brightly in the far-infrared. Many galaxies ("active galaxies") have active nuclei hidden in dense regions of dust. Others, called starburst galaxies
Starburst galaxy
A starburst galaxy is a galaxy in the process of an exceptionally high rate of star formation, compared to the usual star formation rate seen in most galaxies. Galaxies are often observed to have a burst of star formation after a collision or close encounter between two galaxies...
, have an extremely high number of newly forming stars heating interstellar dust clouds
Interstellar cloud
Interstellar cloud is the generic name given to an accumulation of gas, plasma and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium. Depending on the density, size and temperature of a given cloud, the hydrogen in it...
. These galaxies, far outshine all others galaxies in the far-infrared.
The Earth's atmosphere is opaque over most of the far-infrared, so that ground-based observations are limited to submillimetre wavelengths using high-altitude telescopes such as the James Clerk Maxwell Telescope
James Clerk Maxwell Telescope
The James Clerk Maxwell Telescope is a submillimetre-wavelength telescope at Mauna Kea Observatory in Hawaii. Its primary mirror is 15 metres across: it is the largest astronomical telescope that operates in submillimetre wavelengths of the electromagnetic spectrum...
, the Caltech Submillimeter Observatory
Caltech Submillimeter Observatory
The Caltech Submillimeter Observatory is a diameter submillimeter wavelength telescope situated alongside the James Clerk Maxwell Telescope at Mauna Kea Observatory. It is engaged in submillimeter astronomy, of the terahertz radiation band.The CSO and JCMT were combined to form the first...
, and the Submillimeter Array
Submillimeter Array
The Submillimeter Array consists of eight diameter radio telescopes arranged as an interferometer for submillimeter wavelength observations. It is the first purpose-built submillimeter interferometer, constructed after successful interferometry experiments using the pre-existing James Clerk...
. Most far-infrared astronomy is performed by satellites such as the Herschel Space Observatory
Herschel Space Observatory
The Herschel Space Observatory is a European Space Agency space observatory sensitive to the far infrared and submillimetre wavebands. It is the largest space telescope ever launched, carrying a single mirror of in diameter....
, Spitzer
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
, IRAS
IRAS
The Infrared Astronomical Satellite was the first-ever space-based observatory to perform a survey of the entire sky at infrared wavelengths....
, and ISO
Infrared Space Observatory
The Infrared Space Observatory was a space telescope for infrared light designed and operated by the European Space Agency , in cooperation with ISAS and NASA...
. Future missions will include ASTRO-F
ASTRO-F
Akari is an infrared astronomy satellite developed by Japan Aerospace Exploration Agency, in cooperation with institutes of Europe and Korea. It was launched on 21 February 2006 at 21:28 UTC by M-V rocket into Earth sun-synchronous orbit...
and the airborne SOFIA
Stratospheric Observatory for Infrared Astronomy
The Stratospheric Observatory for Infrared Astronomy is a joint project of NASA and the German Aerospace Center to construct and maintain an airborne observatory. NASA awarded the contract for the development of the aircraft, operation of the observatory and management of the American part of the...
telescope.