Large Binocular Telescope

Large Binocular Telescope
Organisation LBT Consortium
Location(s) Mount Graham International Observatory, Arizona, United States
Coordinates 32°42′04.71″N 109°53′20.63″W / 32.7013083°N 109.8890639°W / 32.7013083; -109.8890639Coordinates: 32°42′04.71″N 109°53′20.63″W / 32.7013083°N 109.8890639°W / 32.7013083; -109.8890639[1]
Altitude 3,221 m (10,568 ft)[2]
Wavelength visible to near infrared
Built 1996–2004 by Ansaldo
First light October 12, 2005 (1st primary mirror).
September 18, 2006 (2nd primary mirror).
January 11 – January 12, 2008 (1st & 2nd together)[3]
Telescope style Gregorian binocular
Diameter 8.4 m per mirror
Collecting area 111 m2 (1,190 sq ft)
Focal length 9.6 m (f/1.142)
Mounting elevation/azimuth
Enclosure co-rotating building, dual parting slits
Website Large Binocular Telescope

The Large Binocular Telescope (LBT) is an optical telescope for astronomy located on 10,700-foot (3,300 m) Mount Graham, in the Pinaleno Mountains of southeastern Arizona, United States. It is a part of the Mount Graham International Observatory. The LBT is currently one of the world's most advanced optical telescopes; using two 8.4 m (27 ft) wide mirrors, with centres 14.4m apart, it has the same light-gathering ability as an 11.8 m (39 ft) wide single circular telescope and detail of a 22.8 m (75 ft) wide one.[4] Its mirrors individually are the joint second-largest optical telescope in continental North America, behind the Hobby–Eberly Telescope in West Texas; it is also the largest monolithic, or non-segmented mirror, in an optical telescope. Strehl ratios of 60–90% in the infrared H band and 95% in the infrared M band have been achieved by the LBT.[5]

Project

The LBT was originally named the "Columbus Project". It is a joint project of these members: the Italian astronomical community represented by the Istituto Nazionale di Astrofisica, the University of Arizona, University of Minnesota,[6] University of Notre Dame,[6] University of Virginia,[6] the LBT Beteiligungsgesellschaft in Germany (Max Planck Institute for Astronomy in Heidelberg, Landessternwarte in Heidelberg, Leibniz Institute for Astrophysics Potsdam (AIP), Max Planck Institute for Extraterrestrial Physics in Munich and Max Planck Institute for Radio Astronomy in Bonn); The Ohio State University; Research Corporation in Tucson, and the University of Chicago.

The telescope design has two 8.4-meter (28 ft) mirrors mounted on a common base, hence the name "binocular".[4] LBT takes advantage of active and adaptive optics, provided by Arcetri Observatory. The collecting area is two 8.4 meter aperture mirrors, which works out to about 111 m2 combined. This area is equivalent to an 11.8-meter (39 ft) circular aperture, which would be greater than any other single telescope, but it is not comparable in many respects since the light is collected at a lower diffraction limit and is not combined in the same way. Also, an interferometric mode will be available, with a maximum baseline of 22.8 meters (75 ft) for aperture synthesis imaging observations and a baseline of 15 meters (49 ft) for nulling interferometry. This feature is along one axis with the LBTI instrument at wavelengths of 2.9–13 micrometres, which is the near infrared.[7]

The telescope was designed by a group of Italian firms, and assembled by Ansaldo in its Milanese plant.

Mountain controversy

The choice of location sparked considerable local controversy, both from the San Carlos Apache Tribe, who view the mountain as sacred, and from environmentalists who contended that the observatory would cause the demise of an endangered subspecies of the American Red Squirrel, the Mount Graham Red Squirrel. Environmentalists and members of the tribe filed some forty lawsuits—eight of which ended up before a federal appeals court—but the project ultimately prevailed after an act of the United States Congress.

The telescope and mountain observatory survived two major forest fires in eight years, the more recent in the summer of 2004. Likewise the squirrels continue to survive, though experts believe their numbers fluctuate dependent upon nut harvest without regard to the observatory.[8][9]

First light

The telescope was dedicated in October 2004 and saw first light with a single primary mirror on October 12, 2005 which viewed NGC 891.[10][11] The second primary mirror was installed in January 2006 and became fully operational in January 2008.[4]

The first binocular light images show three false-color renditions of the spiral galaxy NGC 2770. The galaxy is 88 million light years from our Milky Way, a relatively close neighbor. The galaxy has a flat disk of stars and glowing gas tipped slightly toward our line of sight.

The first image taken combined ultraviolet and green light, and emphasizes the clumpy regions of newly formed hot stars in the spiral arms. The second image combined two deep red colors to highlight the smoother distribution of older, cooler stars. The third image was a composite of ultraviolet, green and deep red light and shows the detailed structure of hot, moderate and cool stars in the galaxy. The cameras and images were produced by the Large Binocular Camera team, led by Emanuele Giallongo at the Rome Astrophysical Observatory.

In binocular aperture synthesis mode LBT has a light-collecting area of 111 m2, equivalent to a single 11.8-meter (39 ft) surface and will combine light to produce the image sharpness equivalent to a single 22.8-meter (75 ft) telescope. However, this requires a beam combiner that was tested in 2008, but has not been a part of regular operations.[12] It can take images with one side at 8.4 m aperture, or take two images of the same object using different instruments on each side of the telescope.

Adaptive optics

In the summer of 2010, the "First Light Adaptive Optics" (FLAO) – an adaptive optics system with a deformable secondary mirror rather than correcting atmospheric distortion further downstream in the optics – was inaugurated.[5][13] Using one 8.4 m side, it surpassed Hubble sharpness (at certain light wavelengths), achieving a Strehl ratio of 60–80% rather than the 20–30% of older adaptive optic systems, or the 1% typically achieved without adaptive optics for telescopes of this size.[13][14] Adaptive optics at a telescope's secondary (M2) was previously tested at MMT Observatory by the Arcetri Observatory and University of Arizona team.[15]

In the media

The telescope has also made appearances on an episode of the Discovery Channel TV show Really Big Things, National Geographic Channel Big, Bigger, Biggest,[16] and the BBC program The Sky At Night. The BBC Radio 4 radio documentary "The New Galileos" covered the LBT and the JWST.[17]

Controversy

Some fringe reporting has incorrectly conflated the shared geographic location of the Vatican Advanced Technology Telescope (VATT) with the LBT's LUCIFER acronym. This has led to some erroneous reporting of hidden agendas being held by the Vatican.[18]

Discoveries

LBT, with the XMM-Newton was used to discover the galaxy cluster 2XMM J083026+524133 in 2008, over 7 billion light years away from Earth.[19] In 2007 the LBT detected a 26th magnitude afterglow from the gamma ray burst GRB 070125.[20]

Instruments

Some current or planned LBT telescope instruments:[4]

LUCI

LUCI (originally LUCIFER: Large Binocular Telescope Near-infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research) is the near-infrared instrument for the LBT.[22][23] The name of the instrument was changed to LUCI in 2012. LUCI operates in the 0.9 - 2.5 µm spectral range using a 2048 x 2048 element Hawaii II detector array from Rockwell and provides imaging and spectroscopic capabilities in seeing- and diffraction limited modes. In its focal plane area, long-slit and multi-slit masks can be installed for single-object and multi-object spectroscopy. A fixed collimator produces an image of the entrance aperture in which either a mirror (for imaging) or a grating can be positioned. Three camera optics with numerical apertures of 1.8, 3.75 and 30 provide image scales of 0.25, 0.12, and 0.015 arcsec/detector element for wide field, seeing-limited and diffraction-limited observations. LUCI is operated at cryogenic temperatures, and is therefore enclosed in a cryostat of 1.6 m diameter and 1.6 m height, and cooled down to about -200 C by two closed cycle coolers.[22]

LBTO collaboration

Comparison of nominal sizes of primary mirrors of the Large Binocular Telescope and some notable optical telescopes

Partners in the LBT project [24]

Additional photos

Other MGIO facilities

See also

References

  1. ↑ "LBTO Science and Operations Homepage". arizona.edu.
  2. ↑ LBT 2010 Brochure
  3. ↑ "Large Binocular Telescope Achieves First Binocular Light" (Press release). Large Binocular Telescope Corporation. 2008-02-28.
  4. 1 2 3 4 "Giant telescope opens both eyes". news.bbc.co.uk. 2008-03-06. Retrieved 2008-03-06.
  5. 1 2 "Sharper than Hubble: Large Binocular Telescope achieves major breakthrough". physorg.com.
  6. 1 2 3 "First science from the Large Binocular Telescope". Nd.edu. 2007-04-13. Retrieved 2009-08-09.
  7. ↑ "LBTI Instruments". Retrieved 24 June 2015.
  8. ↑ "The Mount Graham Red Squirrel". Medusa.as.arizona.edu. 2000-05-24. Retrieved 2010-04-25.
  9. ↑ "News Media". Azgfd.gov. 2006-05-03. Retrieved 2010-04-25.
  10. ↑ "medusa.as.arizona.edu". medusa.as.arizona.edu. 2005-10-12. Retrieved 2010-04-25.
  11. ↑ "spaceref.com". spaceref.com. Retrieved 2010-04-25.
  12. ↑ "LBTI Project".
  13. 1 2 "Sharper than Hubble: Large Binocular Telescope achieves major breakthrough". Max Planck Society. Retrieved 18 June 2010.
  14. ↑ "Max-Planck-Institut für Astronomie". mpia.de.
  15. ↑ "Laird Close, et al. – Adaptive Optics at the MMT and First Science Results". Retrieved 24 June 2015.
  16. ↑ Big, Bigger, Biggest
  17. ↑ Luck-Bake, Andrew. "The New Galileos". BBC. Retrieved 2009-05-14.
  18. ↑
  19. ↑ ""XMM discovers monster galaxy cluster", DR EMILY BALDWIN, ASTRONOMY NOW, August 27, 2008". Astronomynow.com. 2008-08-27. Retrieved 2010-04-25.
  20. ↑ "First science from the Large Binocular Telescope".
  21. ↑ "Advanced Rayleigh guided Ground layer adaptive Optics System". Retrieved 24 June 2015.
  22. 1 2 "LUCI - A Near-Infrared Camera & Spectrograph for the LBT". Max Planck Institute for Extraterrestrial Physics. Retrieved 5 July 2016.
  23. ↑
  24. ↑ "Project partners". Retrieved 20 Jan 2016.
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