This image shows the field of view from the Dragonfly Telephoto Array,
centered on M101.
Inset images highlight the seven newly discovered
galaxies.
Meet the seven new dwarf galaxies
Yale University astronomers,
using a new type of telescope made by stitching together telephoto
lenses, recently discovered seven celestial surprises while probing a
nearby spiral galaxy. The previously unseen galaxies may yield important
insights into dark matter and galaxy evolution, while possibly
signaling the discovery of a new class of objects in space.
For
now, scientists know they have found a septuplet of new galaxies that
were previously overlooked because of their diffuse nature: The ghostly
galaxies emerged from the night sky as the team obtained the first
observations from the “homemade” telescope.
The discovery came
quickly, in a relatively small section of sky. “We got an exciting
result in our first images,” said Allison Merritt, a Yale graduate
student and lead author of a paper about the discovery in The
Astrophysical Journal Letters. “It was very exciting. It speaks to the
quality of the telescope.”
Pieter van Dokkum, chair of Yale’s
astronomy department, designed the robotic telescope with University of
Toronto astronomer Roberto Abraham. Their Dragonfly Telephoto Array uses
eight telephoto lenses with special coatings that suppress internally
scattered light. This makes the telescope uniquely adept at detecting
the very diffuse, low surface brightness of the newly discovered
galaxies.
These are the same kind of lenses that are used in sporting events
like the World Cup. We decided to point them upward instead,” van Dokkum
said. He and Abraham built the compact, oven-sized telescope in 2012 at
New Mexico Skies, an observatory in Mayhill, N.M. The telescope was
named Dragonfly because the lenses resemble the compound eye of an
insect.
“We knew there was a whole set of science questions that
could be answered if we could see diffuse objects in the sky,” van
Dokkum said. In addition to discovering new galaxies, the team is
looking for debris from long-ago galaxy collisions.
“It’s a new domain. We’re exploring a region of parameter space that had not been explored before,” van Dokkum said.
The
Yale scientists will tackle a key question next: Are these seven newly
found objects dwarf galaxies orbiting around the M101 spiral galaxy, or
are they located much closer or farther away, and just by chance are
visible in the same direction as M101?
If it’s the latter, Merritt
said, these objects represent something entirely different. “There are
predictions from galaxy formation theory about the need for a population
of very diffuse, isolated galaxies in the universe,” Merritt said. “It
may be that these seven galaxies are the tip of the iceberg, and there
are thousands of them in the sky that we haven’t detected yet.”
Merritt
stressed that until they collect more data and
determine the distances
to the objects, researchers won’t know their true nature. But the
possibilities are intriguing enough that the team has been granted the
opportunity to use the Hubble Space Telescope for further study.
“I’m
confident that some of them will turn out to be a new class of
objects,” van Dokkum said. “I’d be surprised if all seven of them are
satellites of M101.”
Meanwhile, there is also more work to be done
with the new telescope. “We are collecting new data with the Dragonfly
telescope every clear night. We’re all curious to see what other
surprises the night sky has in store for us,” Merritt said.
