Editing Infrared astronomy (section)

== Modern infrared astronomy ==
[[File:New Hubble infrared view of the Tarantula Nebula.jpg|thumb|[[Hubble Space Telescope|Hubble]] infrared view of the [[Tarantula Nebula]].<ref>{{cite news|title=Unravelling the web of a cosmic creeply-crawly|url=http://www.spacetelescope.org/news/heic1402/|access-date=18 January 2014|newspaper=ESA/Hubble Press Release}}</ref> ]]

Infrared radiation with wavelengths just longer than visible light, known as near-infrared, behaves in a very similar way to visible light, and can be detected using similar solid state devices (because of this, many quasars, stars, and galaxies were discovered). For this reason, the near infrared region of the spectrum is commonly incorporated as part of the "optical" spectrum, along with the near ultraviolet. Many [[optical telescope]]s, such as those at [[Keck Observatory]], operate effectively in the near infrared as well as at visible wavelengths. The far-infrared extends to [[Submillimetre astronomy|submillimeter wavelengths]], which are observed by telescopes such as the [[James Clerk Maxwell Telescope]] at [[Mauna Kea Observatory]].

[[File:Artist's impression of the galaxy W2246-0526.jpg|left|thumb|Artist impression of galaxy [[W2246-0526]], a single galaxy glowing in infrared light as intensely as 350 trillion Suns.<ref>{{cite web|title=Artist's impression of the galaxy W2246-0526|url=https://www.eso.org/public/images/eso1602a/ |work=ESO.org|access-date=18 January 2016}}</ref>]]

Like all other forms of [[electromagnetic radiation]], infrared is utilized by astronomers to study the [[universe]]. Indeed, infrared measurements taken by the [[2MASS]] and [[Wide-field Infrared Survey Explorer|WISE]] astronomical surveys have been particularly effective at unveiling previously undiscovered [[star clusters]].<ref name=fr2007>{{Cite journal|bibcode = 2007MNRAS.374..399F|title = A systematic survey for infrared star clusters with &#124;b&#124; <20° using 2MASS|last1 = Froebrich|first1 = D.|last2 = Scholz|first2 = A.|last3 = Raftery|first3 = C. L.|journal = Monthly Notices of the Royal Astronomical Society|year = 2007|volume = 374|issue = 2|page = 399|doi = 10.1111/j.1365-2966.2006.11148.x| doi-access=free |arxiv = astro-ph/0610146|s2cid = 15339002}}</ref><ref name=ma2013>{{Cite journal|url=http://adsabs.harvard.edu/abs/2013Ap%26SS.344..175M|bibcode=2013Ap&SS.344..175M|title=Discovering protostars and their host clusters via WISE|last1=Majaess|first1=D.|journal=Astrophysics and Space Science|year=2013|volume=344|issue=1|page=175|doi=10.1007/s10509-012-1308-y|arxiv=1211.4032|s2cid=118455708}}</ref> Examples of such embedded star clusters are FSR 1424, FSR 1432, Camargo 394, Camargo 399, Majaess 30, and Majaess 99.<ref name=ca2015a>{{Cite journal|url=http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1406.3099|bibcode = 2015NewA...34...84C|title = New Galactic embedded clusters and candidates from a WISE Survey|last1 = Camargo|first1 = Denilso|last2 = Bica|first2 = Eduardo|last3 = Bonatto|first3 = Charles|journal = New Astronomy|year = 2015|volume = 34|pages = 84–97|doi = 10.1016/j.newast.2014.05.007|arxiv = 1406.3099|s2cid = 119002533}}</ref><ref>{{Cite journal |doi=10.1093/mnras/stt703|title=Towards a census of the Galactic anticentre star clusters – III. Tracing the spiral structure in the outer disc|year=2013|last1=Camargo|first1=D.|last2=Bica|first2=E.|last3=Bonatto|first3=C.|journal=Monthly Notices of the Royal Astronomical Society|volume=432|issue=4|pages=3349–3360|doi-access=free|hdl=10183/93387|hdl-access=free}}</ref><ref name=ca2015b>{{Cite journal|url=http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1505.01829|bibcode=2015MNRAS.450.4150C|title=Tracing the Galactic spiral structure with embedded clusters|last1=Camargo|first1=D.|last2=Bonatto|first2=C.|last3=Bica|first3=E.|journal=Monthly Notices of the Royal Astronomical Society|year=2015|volume=450|issue=4|pages=4150–4160|doi=10.1093/mnras/stv840|doi-access=free |arxiv=1505.01829}}</ref> Infrared telescopes, which includes most major optical telescopes as well as a few dedicated infrared telescopes, need to be chilled with [[liquid nitrogen]] and shielded from warm objects. The reason for this is that objects with temperatures of a few hundred [[kelvin]]s emit most of their [[thermal energy]] at infrared wavelengths. If infrared detectors were not kept cooled, the radiation from the detector itself would contribute noise that would dwarf the radiation from any celestial source. This is particularly important in the mid-infrared and far-infrared regions of the spectrum.

To achieve higher [[angular resolution]], some infrared telescopes are combined to form [[astronomical interferometer]]s. The effective resolution of an interferometer is set by the distance between the telescopes, rather than the size of the individual telescopes. When used together with [[adaptive optics]], infrared interferometers, such as two 10 meter telescopes at Keck Observatory or the four 8.2 meter telescopes that make up the [[Very Large Telescope]] Interferometer, can achieve high angular resolution.

[[File:Atmosfaerisk spredning.png|thumb|upright=2.0|Atmospheric windows in the infrared.]]
The principal limitation on infrared sensitivity from ground-based telescopes is the Earth's atmosphere. Water vapor absorbs a significant amount of infrared radiation, and the atmosphere itself emits at infrared wavelengths. For this reason, most infrared telescopes are built in very dry places at high altitude, so that they are above most of the water vapor in the atmosphere. Suitable locations on Earth include [[Mauna Kea Observatory]] at 4205 meters above sea level, the [[Paranal Observatory]] at 2635 meters in [[Chile]] and regions of high altitude ice-desert such as [[Dome C]] in [[Antarctic]]. Even at high altitudes, the transparency of the Earth's atmosphere is limited except in [[infrared window]]s, or wavelengths where the Earth's atmosphere is transparent.<ref name="caltech_windows">{{cite web | url = http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/irwindows.html | title = IR Atmospheric Windwows | access-date = 9 April 2009 | publisher = Cool Cosmos | archive-date = 11 October 2018 | archive-url = https://web.archive.org/web/20181011101051/http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/irwindows.html | url-status = dead }}</ref> The main infrared windows are listed below:

{| class="wikitable" style="width: 90%; margin: 1em auto 1em auto;"
|- valign="top"
!width=13%|Spectrum
!width=13%|Wavelength<br>([[micrometre]]s)
!width=13%|Astronomical<br>bands
!width=61%|Telescopes
|-
|Near Infrared
|0.65 to 1.0
|R and I bands
|All major optical telescopes
|-
|Near Infrared
|1.1 to 1.4
|[[J band (infrared)|J band]]
|Most major optical telescopes and most dedicated infrared telescopes
|-
|Near Infrared
|1.5 to 1.8
|[[H band (infrared)|H band]]
|Most major optical telescopes and most dedicated infrared telescopes
|-
|Near Infrared
|2.0 to 2.4
||[[K band (infrared)|K band]]
|Most major optical telescopes and most dedicated infrared telescopes
|-
|Near Infrared
|3.0 to 4.0
|[[L band (infrared)|L band]]
|Most dedicated infrared telescopes and some optical telescopes
|-
|Near Infrared
|4.6 to 5.0
||[[M band (infrared)|M band]]
|Most dedicated infrared telescopes and some optical telescopes
|-
|Mid Infrared
|7.5 to 14.5
|[[N band]]
|Most dedicated infrared telescopes and some optical telescopes
|-
|Mid Infrared
|17 to 25
|Q band
|Some dedicated infrared telescopes and some optical telescopes
|-
|Far Infrared
|28 to 40
|Z band
|Some dedicated infrared telescopes and some optical telescopes
|-
|Far Infrared
|330 to 370
|
|Some dedicated infrared telescopes and some optical telescopes
|-
|Far Infrared
|450
|[[Submillimetre astronomy|submillimeter]]
|Submillimeter telescopes
|}

As is the case for visible light telescopes, space is the ideal place for infrared telescopes. Telescopes in space can achieve higher resolution, as they do not suffer from [[scintillation (astronomy)|blurring]] caused by the Earth's atmosphere, and are also free from infrared absorption caused by the Earth's atmosphere. Current infrared telescopes in space include the [[Herschel Space Observatory]], the [[Spitzer Space Telescope]], the [[Wide-field Infrared Survey Explorer]] and the [[James Webb Space Telescope]]. Since putting telescopes in orbit is expensive, there are also [[Airborne observatory|airborne observatories]], such as the [[Stratospheric Observatory for Infrared Astronomy]] and the [[Kuiper Airborne Observatory]]. These observatories fly above most, but not all, of the atmosphere, and water vapor in the atmosphere absorbs some of infrared light from space. 
{{Multiple image|direction=horizontal|align=center|width=300|image1=15-044a-SuperNovaRemnant-PlanetFormation-SOFIA-20150319.jpg|image2=15-044b-SuperNovaRemnant-PlanetFormation-SOFIA-20150319.jpg|footer=[[SOFIA]] science — [[supernova remnant]] ejecta producing planet-forming material.}}