The Dragonfly Telephoto Array is a ground-based

optical telescope An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electr ...

array developed at the Dunlap Institute for Astronomy & Astrophysics of the

University of Toronto The University of Toronto (UToronto or U of T) is a public research university in Toronto, Ontario, Canada, located on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institu ...

in Canada. The array uses a combination of

telephoto lens A telephoto lens, in photography and cinematography, is a specific type of a long-focus lens in which the physical length of the lens is shorter than the focal length. This is achieved by incorporating a special lens group known as a ''telephoto ...

es to observe

extragalactic Extragalactic astronomy is the branch of astronomy concerned with objects outside the Milky Way galaxy. In other words, it is the study of all astronomical objects which are not covered by galactic astronomy. The closest objects in extragalactic ...

objects. 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

The telescope was designed by Roberto Abraham of the University of Toronto and

Pieter van Dokkum Pieter is a male given name, the Dutch form of Peter. The name has been one of the most common names in the Netherlands for centuries, but since the mid-twentieth century its popularity has dropped steadily, from almost 3000 per year in 1947 ...

Yale University Yale University is a Private university, private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the List of Colonial Colleges, third-oldest institution of higher education in the United Sta ...

. It was commissioned in 2013 and initially had eight commercially available Canon EF 400mm f/2.8L IS II USM camera lenses. This was first increased to ten lenses, and was extended to two clusters of 24 lenses each in 2016. The array is designed to accommodate the addition of lenses to increase its effective aperture with each additional lens. With 48 lenses, the instrument has a light gathering power equivalent to a 400mm lens, or a refracting telescope with an objective lens diameter of . In March 2021 plans were announced to add 120 more lenses. By using a lens based refactor design rather than a mirror based reflector design the telescope suffers less from issues introduced by diffraction and light scattering. Reflector designs have more light scattering due to interactions with dust and any slight roughness on the mirror. Issues with diffraction occur due to the need to place obstructions in the optical path of reflecting telescopes.

Research

Astronomers used the Dragonfly Telephoto Array to discover

Dragonfly 44 Dragonfly 44 is an ultra diffuse galaxy in the Coma Cluster. This galaxy is well-known because observations of the velocity dispersion in 2016 suggested a mass of about one trillion solar masses, about the same as the Milky Way. This mass was co ...

, a galaxy that is roughly as massive as the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked ey ...

, with 99.9% of its mass composed of

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...

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

References

External links

* {{Official website, https://www.dragonflytelescope.org/ Optical telescopes