Dragonfly Telephoto Array

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.

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 was extended to two clusters of 24 lenses 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 the light gathering power equivalent to a 99 cm diameter refractor, with a focal length of 40 cm.

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.[7] 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.[8] Further work indicated that NGC 1052-DF2 was closer to the earth than previous thought.[9] If this is the case then the galaxy appears to contain a typical amount of dark matter.[9]

References
  1. "Dragonfly - Dunlap Institute". Dunlap Institute for Astronomy and Astrophysics. Retrieved 5 March 2018.
  2. "A New Kind of Telescope". University of Toronto Magazine. Retrieved 29 May 2020.
  3. 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. arXiv:1401.5473. Bibcode:2014PASP..126...55A. doi:10.1086/674875. S2CID 119197160.
  4. "How Do You Make A Galaxy Without Dark Matter?". Dunlap Institute for Astronomy and Astrophysics. Retrieved 15 Apr 2019.
  5. Estes, Adam C. "Astronomers Invent New Telescope by Tying Telephoto Lenses Together". Gizmodo. Retrieved 5 March 2018.
  6. "Dragonfly - Yale University". Retrieved 5 March 2018.
  7. "Meet Dragonfly 44, the galaxy made of 99.9% dark matter". Wired. Retrieved 5 March 2018.
  8. Van Dokkum, Pieter; Danieli, Shany; Cohen, Yotam; Merritt, Allison; Romanowsky, Aaron J; Abraham, Roberto; Brodie, Jean; Conroy, Charlie; Lokhorst, Deborah; Mowla, Lamiya; o'Sullivan, Ewan; Zhang, Jielai (2018). "A galaxy lacking dark matter". Nature. 555 (7698): 629–632. arXiv:1803.10237. Bibcode:2018Natur.555..629V. doi:10.1038/nature25767. PMID 29595770. S2CID 4460376.
  9. 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. arXiv:1806.10141. Bibcode:2019MNRAS.486.1192T. doi:10.1093/mnras/stz771. S2CID 118889598. Retrieved 5 June 2019.
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