Large Binocular Telescope

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The LBT

The Large Binocular Telescope (abbreviated LBT , in German "large binocular telescope") is a telescope for astronomical observations. It stands on the 3,221 meter high Mount Graham in Arizona and is part of the Mount Graham International Observatory . The LBT is currently the largest optical telescope and has two 8.4-meter primary mirrors, which achieve the same light-collecting power as a single 11.8-meter telescope. It also achieves the optical resolution of a 22.8 meter mirror. In test shots, it achieved a Strehl number of 0.6 to 0.8 (a value of 1 would correspond to a perfect image). Further tests gave values ​​from 0.82 to 0.84.

One of the main mirrors of the LBT had its first light on October 12, 2005 , for which the spiral galaxy NGC 891 , which is very similar to our Milky Way, was selected. Finally, at the end of 2007, the second 36-megapixel CCD camera was delivered, so that the first light from the LBT could take place in binocular mode.

Joint project of three countries

The new observatory , which took eight years to build as a joint project between the USA (25 percent University of Arizona , 12.5 percent Research Corporation , 12.5 percent Ohio State University ), Germany (25 percent LBT Beteiligungsgesellschaft = Max Planck Institute for Astronomy , Max Planck Institute for Extraterrestrial Physics , Max Planck Institute for Radio Astronomy , Leibniz Institute for Astrophysics Potsdam , State Observatory Heidelberg ) and Italy (25 percent INAF ) stands on the 3200 meter high Mount Graham. With the 25 percent participation, the German astronomers also secure a quarter of the observation time.

The double telescope reached its full capacity after the necessary test and adjustment work around the spring of 2008. This relates to the two primary focus cameras. All first-generation instruments together should be ready for use from 2011. In terms of its construction, it is the world's largest optical telescope. There are telescopes with larger individual mirrors as well as long-base interferometry , but with other interferometers the mirrors do not have a common mount .

concept

One of the two main mirrors in the direct view

Using two mirrors (each weighing around 16 tons) instead of a single one achieves noticeable advantages:

  • The double telescope collects the same amount of light as an 11.8 meter mirror; it would still be able to individually dissolve the light of two burning candles 100 meters apart up to a distance of 2.5 million km (7 times the lunar distance).
  • The optical resolution of the LBT can be increased to that of a 22.8 meter mirror using interferometry .
  • With the help of interferometry, the light from central stars is also supposed to be blocked out in order to make their possible planets directly visible (“ nulling interferometry ”).

German astrophysicists and cosmologists want to do research in Arizona in the field of star formation.

Cost, control and first measurements

Construction and instruments cost around 100 million euros. The LBT-Beteiligungsgesellschaft (LBTB) is a community of five research institutes in Germany that are participating in the Large Binocular Telescope Project (LBT Project). Five German institutes are developing the associated astronomical instruments:

The primary focus cameras LBC-RED and LBC-BLUE were developed by the Italian Istituto Nazionale di Astrofisica (INAF) . Hardware and software are developed at the University of Arizona. The following instruments were developed for the LBT and integrated one after the other on the telescope:

  • LBT Utility Camera in the Infrared (LUCI)
  • Large Binocular Camera (LBC-Blue & LBC-Red)
  • Multi-Object Double Spectrograph (MODS)
  • LBT Interferometric Camera (Linc-Nirvana)
  • LBT interferometer (LBTI)
  • Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI)
  • ARGOS (Advanced Rayleigh Guided Ground Layer Adaptive Optics System) next-generation artificial guide star ; Three green lasers (532 nm) per eye of the LBT will serve to correct the atmospheric turbulence.

The first of the two twin mirrors was assembled in October 2004, the second followed in autumn 2005, after it had been given its final shape through lengthy polishing in Tucson in 2004/05 . The first recordings were published on October 26, 2005; they show the galaxy NGC 891 and were taken on October 12, 2005. Since the beginning of 2007, the first regular scientific observations have been carried out with the LBT and the LBC-Blue. The first pictures impressively show the performance of the LBT. Since 2017, all three observatory instruments (LBC, LUCI and MODS) have been available in binocular mode.

Instruments

Currently, the LBT has three set-up instruments (LBC, LUCI and MODS) that are available to observers in monucular and homogeneous binocular mode. Heterogeneous observations with LBC on the one hand and LUCI or MODS on the other hand, as of 2019, are being tested.

LBC

The two LBC cameras are mounted in the primary focus (F / 1.14) of the twin mirrors. As the only LBT instrument, they are not two identical versions of the same instrument. The LBC-Blue camera is optimized for a wavelength range between 350 nm and 650 nm and is located on the left telescope (SX). LBC-Red is optimized for a wavelength range between 550 nm and 1000 nm and is located on the right telescope (DX). The detectors each consist of four individual CCD chips with 2048 × 4608 pixels each . The arrangement of the CCD chips, three vertically and one horizontally, results in an incomplete viewing angle of 25 × 23 minutes of arc .

LUCI

LUCI (formerly LUCIFER) forms the near-infrared instrument of the observatory and allows both imaging and spectroscopic observations. The two almost identical instruments are in a bent Gregorian focus (F / 15) between the two telescope mirrors. They allow observations in a wavelength range between 0.89 μm (LUCI1) or 0.95 μm (LUCI2) and 2.44 μm. They are each equipped with a Teledyne HAWAII-2RG (H2RG) HgCdTe detector and 3 camera systems. The N3.75 camera is mainly used for imaging observations in the [Seeing | seeing] limited mode. The advantage here is the comparatively large viewing angle of 4 × 4 arc minutes. The N1.8 camera is used for spectroscopic observations. Compared to the N3.75, this provides a viewing angle of 4 × 2.8 arc minutes that is reduced in height. For observations with adaptive optics the N30 camera is used, which enables a diffraction-limited image scale of 0.015 arc seconds per pixel. The viewing angle in this mode is 30 × 30 arc seconds.

MODS

The two MODS instruments are in direct Gregorian focus (F / 15) below the two primary mirrors of the LBT. They are used for imaging and spectroscopic observations in the optical spectral range (320 nm – 1100 nm). A dichroic beam splitter splits the light beam into two beams and deflects them onto two rectangular CCDs with 3072 × 8196 pixels, which are each optimized for the blue and red wavelength range. The full size of the CCDs is usually only used for spectroscopic recordings. In the imaging mode, the reading of the detectors is limited to the central 2900 × 2900 pixels (6 × 6 minutes of arc).

Scientific results

By the end of 2018, 371 scientific publications had been published in recognized specialist journals based on observations made by the LBT. This includes:

  • The first detection of potassium in the atmosphere of a Jupiter-like exoplanet ( HD189733b and HD209458b ).
  • The first image of magnetic fields on the surface of another star.
  • The detailed observation of the 200 km large lava lake Loki Patera on Jupiter's moon Io .

Protests against the project

Apaches and environmentalists protested against the project, which delayed construction several times. The mountain is said to be sacred to the Apaches. The conservationists fear that a special ecosystem with five climate zones would be damaged.

See also

Web links

Commons : Large Binocular Telescope  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c Overview - Large Binocular Telescope Observatory. Retrieved September 1, 2019 .
  2. ^ Sharper than Hubble: Large Binocular Telescope achieves major breakthrough. Retrieved October 15, 2012 .
  3. ^ First Light. Retrieved September 1, 2019 .
  4. ↑ Large Binocular Telescope: First Light with Both Eyes. Retrieved October 15, 2012 .
  5. ^ The Large Binocular Telescope (LBT). Retrieved October 15, 2012 .
  6. ↑ http://medusa.as.arizona.edu/lbto/LBT%20Website%20General%20Public/LBT%20Interferometer.htm  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / medusa.as.arizona.edu  
  7. ^ Rothberg, B. et al .: Current status of the facility instruments at the Large Binocular Telescope Observatory . In: Proceedings of the SPIE . tape 10702 , 2018, p. 1070205 , doi : 10.1117 / 12.2314005 , bibcode : 2018SPIE10702E..05R .
  8. ↑ LBC Overview. Retrieved October 5, 2019 .
  9. ↑ LUCI Overview. Retrieved October 5, 2019 .
  10. ↑ LUCI Detector. Retrieved October 5, 2019 .
  11. ↑ LUCI Camera. Retrieved October 5, 2019 .
  12. ↑ MODS Overview. Retrieved October 5, 2019 .
  13. ↑ MODS Detector. Retrieved October 5, 2019 .
  14. ↑ LBTO Publications. Retrieved October 6, 2019 .
  15. ↑ Chemical element potassium detected in atmosphere of exoplanet. Retrieved October 6, 2019 .
  16. ↑ Mapping Stars with PEPSI. Retrieved October 6, 2019 .
  17. ↑ Giant telescope takes a close look at a lava lake on Jupiter's moon Io. Retrieved October 6, 2019 .
  18. ^ Court Decision Is Called Threat To Building of Biggest Telescope . In: The New York Times . August 28, 1994, ISSN  0362-4331 ( nytimes.com [accessed May 17, 2015]).

Coordinates: 32 ° 42'5 "  N , 109 ° 53'22"  W.