Sky & Telescope - May 2019 - 69

the signiﬁcance of the current new focus on the low surface
brightness universe cannot be understated. It's not simply
that a new type of galaxy was discovered, but that these
previously hidden galaxies are now turning up all over the
place and in great numbers. As is typical in science, one new
answer generates even more interesting follow-up questions.
Some 20% to 30% of these newly discovered galaxies have
enormous populations of very luminous globular clusters as
well. Is there a relationship between globular cluster abundance and dark matter? Follow-up spectroscopic observations
on ultra-diffuse galaxies using the Keck telescopes on Mauna
Kea show this to be the case.
The best example of a large ultra-diffuse galaxy with enormous amounts of dark mat ter but hardly any stars is Dragonﬂy 44 in the Coma Cluster, which is 99.9% dark matter. On
the other hand, Keck observations reveal that another newly
discovered galaxy near NGC 1052. In spite of having a huge
population of ultra-luminous globular clusters, NGC 1052DF2 contains almost no dark matter at all. It is becoming
increasingly clear that galaxies in the ultra-diffuse domain
have as much diversity as the more readily visible galaxies
we've been detecting since the advent of astrophotography.
They are also challenging our current assumptions and raising new questions about galaxy formation.
While astronomers can use existing instrumentation
to detect all of these things, Dragonﬂy simply makes it far
easier. The array is producing groundbreaking discoveries and
observational conﬁrmations very early in its career. How long
would we have had to wait to ﬁnd ultra-diffuse galaxies in
the Subaru data had it not been for the pioneering work by
the Dragonﬂy array pointing the way?
q TEAM PLAYERS Dragonfly Telephoto Array team members and
graduate students seen from left to right: Roberto Abraham, Pieter van
Dokkum, Jielai Zhang, Shany Danieli, Lamiya Mowla, Deborah Lokhorst,
and Allison Merritt.

p COMING SOON A 6-element "Son of Dragonfly" array will utilize
full-aperture narrowband filters in front of each lens to search for faint
hydrogen emissions predicted to connect galaxies.

It's clear from this example alone that Dragonﬂy's parallelprocessing approach to astronomical research can supplement
and enhance the work of the world's largest instruments.
Dragonﬂy seems to make ﬁnding otherwise challenging
objects incredibly easy, acting in some cases as a kind of ﬁnderscope for larger telescopes, which then know where to look.
Think of Dragonﬂy as a bloodhound for ultra-dim targets.

What's Next?
Dragonﬂy has garnered a lot of attention in the astronomical
community, inspiring similar projects. In development are the
Huntsman Telephoto Array at Siding Spring Observatory in
Australia, as well as smaller experimental arrays that both the
University of Alabama and York University are assembling.
As for Dragonﬂy itself, there are several new and exciting
projects that go well beyond the team's original vision. The
Naiad Array in development will effectively be the "Son of
Dragonﬂy." This 6-lens array will have full-aperture, 6-inch
narrowband ﬁlters. Astronomers will use the array to look
for weak luminescence from hydrogen gas trapped by dark
matter ﬁlaments in the cosmic web, a predicted (but not yet
observed) connection between all galaxies in the universe. In
the meantime, researchers are using the main array to undertake a wide-area survey in a search for very nearby ultradiffuse galaxies and are producing exciting new results in a
range of other areas. This includes looking for light echoes
from past supernovae, which would reveal the type of supernova responsible for the explosion long after it happened.
There's no question that results from Dragonﬂy are changing our understanding of the universe, revealing fascinating
new details on the structure and origin of galaxies, and will
continue to do so for years to come. Is this a new paradigm
for small, powerful, low-cost astronomical observatories?
Probably, and it will be exciting to see how Dragonﬂy and
other projects inspired by it evolve in the coming years. You
can follow their progress at dragonﬂytelescope.org.

¢ RICHARD S. WRIGHT, JR. is a senior software engineer for
Software Bisque. Follow his Sky & Telescope astrophotography
blog at https://is.gd/imaging.
s k y a n d t e l e s c o p e . c o m * M AY 2 0 1 9

http://www.dragonflytelescope.org https://www.is.gd/imaging http://www.skyandtelescope.com

Sky & Telescope - May 2019

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