Infrared astronomy
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Infrared astronomy is a sub-discipline of
Infrared astronomy began in the 1830s, a few decades after the discovery of infrared light by William Herschel in 1800. Early progress was limited, and it was not until the early 20th century that conclusive detections of astronomical objects other than the Sun and Moon were made in infrared light. After a number of discoveries were made in the 1950s and 1960s in radio astronomy, astronomers realized the information available outside the visible wavelength range, and modern infrared astronomy was established.
Infrared and
History
The discovery of infrared radiation is attributed to William Herschel, who performed an experiment in 1800 where he placed a thermometer in sunlight of different colors after it passed through a prism. He noticed that the temperature increase induced by sunlight was highest outside the visible spectrum, just beyond the red color. That the temperature increase was highest at infrared wavelengths was due to the spectral response of the prism rather than properties of the Sun, but the fact that there was any temperature increase at all prompted Herschel to deduce that there was invisible radiation from the Sun. He dubbed this radiation "calorific rays", and went on to show that it could be reflected, transmitted, and absorbed just like visible light.[1]
Efforts were made starting in the 1830s and continuing through the 19th century to detect infrared radiation from other astronomical sources. Radiation from the Moon was first detected in 1856 by
The field of infrared astronomy continued to develop slowly in the early 20th century, as Seth Barnes Nicholson and Edison Pettit developed thermopile detectors capable of accurate infrared photometry and sensitive to a few hundreds of stars. The field was mostly neglected by traditional astronomers until the 1960s, with most scientists who practiced infrared astronomy having actually been trained physicists. The success of radio astronomy during the 1950s and 1960s, combined with the improvement of infrared detector technology, prompted more astronomers to take notice, and infrared astronomy became well established as a subfield of astronomy.[3][4]
Infrared space telescopes entered service. In 1983, IRAS made an all-sky survey. In 1995, the European Space Agency created the Infrared Space Observatory. Before this satellite ran out of liquid helium in 1998, it discovered protostars and water in our universe (even on Saturn and Uranus).[5]
On 25 August 2003, NASA launched the
During May 2008, a group of international infrared astronomers proved that intergalactic dust greatly dims the light of distant galaxies. In actuality, galaxies are almost twice as bright as they look. The dust absorbs much of the visible light and re-emits it as infrared light.
Modern infrared astronomy
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
Like all other forms of
To achieve higher angular resolution, some infrared telescopes are combined to form astronomical interferometers. 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.
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
Spectrum | Wavelength (micrometres) |
Astronomical bands |
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 | Most major optical telescopes and most dedicated infrared telescopes |
Near Infrared | 1.5 to 1.8 | H band | Most major optical telescopes and most dedicated infrared telescopes |
Near Infrared | 2.0 to 2.4 | K band | Most major optical telescopes and most dedicated infrared telescopes |
Near Infrared | 3.0 to 4.0 | L band | Most dedicated infrared telescopes and some optical telescopes |
Near Infrared | 4.6 to 5.0 | 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 | 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
Infrared technology
One of the most common infrared detector arrays used at research telescopes is
Special requirements for infrared astronomy include: very low dark currents to allow long integration times, associated low noise readout circuits and sometimes very high pixel counts.
Low temperature is often achieved by a coolant, which can run out.
Observatories
Space observatories
Many space telescopes detect electromagnetic radiation in a wavelength range that overlaps at least to some degree with the infrared wavelength range. Therefore it is difficult to define which space telescopes are infrared telescopes. Here the definition of "infrared space telescope" is taken to be a space telescope whose main mission is detecting infrared light.
Eight infrared space telescopes have been operated in space. They are:
- Infrared Astronomical Satellite (IRAS), operated 1983 (10 months). A joint mission of US (NASA), UK and the Netherlands.
- ESAmission.
- Midcourse Space Experiment (MSX), operated 1996-1997, BMDO mission.
- Spitzer Space Telescope, operated 2003-2020, NASA mission.
- Akari, operated 2006-2011, JAXA mission.
- ESAmission.
- Wide-field Infrared Survey Explorer (WISE), operated 2009-, NASA mission.
- James Webb Space Telescope (JWST), operated 2022-, NASA mission.[15]
- ESAmission.
In addition, SPHEREx is a telescope scheduled for launch in 2025.[16] NASA is also planning to launch the Nancy Grace Roman Space Telescope (NGRST), originally known as the Wide Field InfraRed Space Telescope (WFIRST), in 2027.[17]
Many other smaller space-missions and space-based detectors of infrared radiation have been operated in space. These include the Infrared Telescope (IRT) that flew with the Space Shuttle.
The Submillimeter Wave Astronomy Satellite (SWAS) is sometimes mentioned as an infrared satellite, although it is a submillimeter satellite.
Infrared instruments on space telescopes
For many space telescopes, only some of the instruments are capable of infrared observation. Below are listed some of the most notable of these space observatories and instruments:
- Cosmic Background Explorer (COBE) satellite (1989-1993) Diffuse Infrared Background Experiment (DIRBE) instrument
- Hubble Space Telescope (1990-) Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument (1997-1999, 2002-2008)
- Hubble Space Telescope Wide Field Camera 3 (WFC3) camera (2009-) observes infrared.
Airborne Observatories
Three airplane-based observatories have been used (other aircraft have also been used occasionally to host infrared space studies) to study the sky in infrared. They are:
- Galileo Observatory, a NASA mission. Was active 1965-1973.
- Kuiper Airborne Observatory, a NASA mission. Was active 1974-1995.
- mission. Was active 2010-2022.
Ground-based observatories
Many ground-based infrared telescopes exist around the world. The largest are:
See also
References
- ^ "Herschel Discovers Infrared Light". Cool Cosmos. Archived from the original on 25 February 2012. Retrieved 9 April 2010.
- ^ "First Results from the ESO Ultra HD Expedition". ESO Announcement. Retrieved 10 May 2014.
- ^ S2CID 121996857.
- ISBN 0-521-63311-7.
- ^ "Science in Context - Document". link.galegroup.com. Retrieved 25 September 2017.
- ^ "Unravelling the web of a cosmic creeply-crawly". ESA/Hubble Press Release. Retrieved 18 January 2014.
- ^ "Artist's impression of the galaxy W2246-0526". ESO.org. Retrieved 18 January 2016.
- S2CID 15339002.
- S2CID 118455708.
- S2CID 119002533.
- hdl:10183/93387.
- .
- ^ "IR Atmospheric Windwows". Cool Cosmos. Archived from the original on 11 October 2018. Retrieved 9 April 2009.
- ^ Space News. Archived from the originalon 9 December 2012. Retrieved 14 January 2014.
- ^ Strickland, Ashley (11 July 2022). "President Biden reveals the James Webb Space Telescope's stunning first image". CNN. Archived from the original on 12 July 2022. Retrieved 12 July 2022.
- ^ Interrante, Abbey (3 August 2022). "PUNCH Announces Rideshare with SPHEREx and New Launch Date". NASA. Retrieved 3 August 2022.
- ^ "NASA Awards Launch Services Contract for Roman Space Telescope". NASA (Press release). 19 July 2022. Retrieved 19 July 2022.