Astronomy:Dragonfly Telephoto Array

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Short description: Astronomical telescope built from multiple camera lenses

[ ⚑ ] 32°54′14″N 105°31′44″W / 32.9039°N 105.5289°W / 32.9039; -105.5289

The Dragonfly Telephoto Array is a ground-based optical telescope array developed at the Dunlap Institute for Astronomy & Astrophysics of the University of Toronto in Canada. The array uses a combination of telephoto lenses to observe extragalactic objects.[1] Its main purpose is to take images of ultra-low surface brightness galaxies at visible wavelengths of light. It is well suited for this purpose because its lenses have specially coated optical glass that reduces scattered light.

Design

A Canon EF 400mm f/2.8L IS II USM lens, the model used in the array

The telescope was designed by Roberto Abraham of the University of Toronto and Pieter van Dokkum of Yale University.[2] It was commissioned in 2013[1] and initially had eight commercially available Canon EF 400mm f/2.8L IS II USM camera lenses.[3] This was first increased to ten lenses, and then extended to two clusters of 24 lenses each in 2016.[4][5][6] The array is designed to accommodate the addition of lenses to increase its effective aperture with each additional lens.[3]

With 48 lenses, the instrument has a light gathering power equivalent to a 400 mm f/0.4 lens, or a refracting telescope with an objective lens diameter of 990 mm (39 in). In March 2021 plans were announced to add 120 more lenses.[7]

By using a lens based refractor design rather than a mirror based reflector design the telescope suffers less from issues introduced by diffraction and light scattering.[8] Reflector designs have more light scattering due to interactions with dust and any slight roughness on the mirror.[8] Issues with diffraction occur due to the need to place obstructions in the optical path of reflecting telescopes.[8]

Location

The Dragonfly Telephoto Array is located in the southern part of New Mexico. It is hosted at the Remote Astronomical Society Observatory of New Mexico.[9]

Research

Astronomers used the Dragonfly Telephoto Array to discover Dragonfly 44, a galaxy that is roughly as massive as the Milky Way, with 99.9% of its mass composed of dark matter.[10] At the other end of the scale it was also used to discover NGC 1052-DF2, which measurements with other instruments initially suggested was a galaxy with very little dark matter.[11] Further work indicated that NGC 1052-DF2 was closer to the Earth than previously thought.[12] If this is the case then the galaxy would appear to contain a typical amount of dark matter. Though this distance debate was continued and rebutted by a follow up observation which measured the tip of the red-giant branch distance to NGC 1052-DF2 using Hubble Space Telescope, confirming the earlier surface brightness fluctuation measurements and resolving the ambiguous distance.[13]

References

  1. ↑ 1.0 1.1 "Dragonfly - Dunlap Institute". http://www.dunlap.utoronto.ca/instrumentation/dragonfly/. 
  2. ↑ "A New Kind of Telescope" (in en-US). April 2015. https://magazine.utoronto.ca/research-ideas/technology/a-new-kind-of-telescope-dragonfly-telephoto-array/. 
  3. ↑ 3.0 3.1 Abraham, Roberto G.; van Dokkum, Pieter (January 2014). "Ultra – Low Surface Brightness Imaging with the Dragonfly Telephoto Array". Publications of the Astronomical Society of the Pacific 126 (935): 55. doi:10.1086/674875. Bibcode: 2014PASP..126...55A. 
  4. ↑ "How Do You Make A Galaxy Without Dark Matter?". http://www.dunlap.utoronto.ca/how-do-you-make-a-galaxy-without-dark-matter/. 
  5. ↑ Estes, Adam C. (14 July 2014). "Astronomers Invent New Telescope by Tying Telephoto Lenses Together". https://gizmodo.com/astronomers-invent-new-telescope-by-tying-telephoto-len-1604666784. 
  6. ↑ "Dragonfly - Yale University". http://www.astro.yale.edu/dragonfly/. 
  7. ↑ Lens array captures dim objects missed by giant telescopes, Science, Vol 371 p1301 26 March 2021
  8. ↑ 8.0 8.1 8.2 Jielai Zhang (2018). The Development and Scientific Application of the Dragonfly Telephoto Array (PDF) (PhD). University of Toronto. p. 10.
  9. ↑ "Exo-Dragonfly: Adapting the Dragonfly Telephoto Array to the Observation of Exoplanet Transits". https://iopscience.iop.org/article/10.1088/1538-3873/ade00b. 
  10. ↑ "Meet Dragonfly 44, the galaxy made of 99.9% dark matter". Wired UK (Wired). https://www.wired.co.uk/article/dark-matter-galaxy-dragonfly-44. Retrieved 5 March 2018. 
  11. ↑ Van Dokkum, Pieter; Danieli, Shany; Cohen, Yotam; Merritt, Allison; Romanowsky, Aaron J; Abraham, Roberto; Brodie, Jean; Conroy, Charlie et al. (2018). "A galaxy lacking dark matter". Nature 555 (7698): 629–632. doi:10.1038/nature25767. PMID 29595770. Bibcode: 2018Natur.555..629V. 
  12. ↑ Trujillo, Ignacio (14 March 2019). "A distance of 13 Mpc resolves the claimed anomalies of the galaxy lacking dark matter". Monthly Notices of the Royal Astronomical Society 486 (1): 1192–1219. doi:10.1093/mnras/stz771. Bibcode: 2019MNRAS.486.1192T. https://academic.oup.com/mnras/article-abstract/486/1/1192/5380810?redirectedFrom=fulltext. Retrieved 5 June 2019. 
  13. ↑ Shen, Zili; Danieli, Shany; van Dokkum, Pieter; Abraham, Roberto; Brodie, Jean P.; Conroy, Charlie; Dolphin, Andrew E.; Romanowsky, Aaron J. et al. (2021-06-01). "A Tip of the Red Giant Branch Distance of 22.1 ± 1.2 Mpc to the Dark Matter Deficient Galaxy NGC 1052–DF2 from 40 Orbits of Hubble Space Telescope Imaging". The Astrophysical Journal Letters 914 (1): L12. doi:10.3847/2041-8213/ac0335. ISSN 2041-8205. Bibcode: 2021ApJ...914L..12S. 



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