A cosmic dragonfly

A galaxy, known as Dragonfly 44, first detected in 2015 using the Dragonfly Telephoto Array in New Mexico by Professor Peter van Dokkum is now claimed to be made of 99.99% dark matter.1 It is a galaxy where very few stars can be seen. It took a two-hour exposure using one of the very biggest telescopes on Earth, one of the Gemini telescopes at the W. M. Keck Observatory in Mauna Kea, Hawaii, to get a picture of this wispy galaxy as shown in Fig. 1 below.


Figure 1: Astronomers photographed the ultradiffuse galaxy Dragonfly 44 using the Gemini Multi-Object Spectrograph (GMOS) on the 8-meter Gemini North telescope in Mauna Kea, Hawaii. Credit: Pieter van Dokkum, Roberto Abraham, Gemini Observatory/AURA

Professor van Dokkum from the Astronomy Department and the Physics Department of Yale University is not only an astrophysicist but also a photographer of insects, particularly dragonflies.It is a strange coincidence, or is it, to find that one of his particular interests in the cosmos are these ultradiffuse, or “fluffy” galaxies. One of them is named Dragonfly 44, which van Dokkum and team determined to be at a distance of 300 million light-years from Earth, in the Coma Cluster.3  That distance is easily close enough for a big telescope to see, which can see galaxies at billions of light-year distances but no one had previously noticed these fluffy galaxies before even though they are ‘so close’.

Dragonfly 44 was like “a dirty smudge on a photo of deep space.”1 And it was one of the largest and brightest galaxies of those they found. From its distance its size was determined and it was concluded that it is as big as our Milky Way galaxy, yet it only emits about 1 percent as much light. So I suppose to van Dokkum the galaxy is reminiscent of the very fragile, lightweight and transparent wings of dragonflies he likes to photograph. Continue reading