spaceSpace and Physics

Seven Dwarf Galaxies Discovered

1481 Seven Dwarf Galaxies Discovered
This image shows the field of view from the Dragonfly Telephoto Array, centered on M101. Inset images highlight the seven newly discovered galaxies / Yale University

We don't know whether they're happy, dopey, or sneezy, but we do know that these new seven dwarf galaxies are bashful -- they’ve all been hiding in plain sight. Only after astronomers turned a new type of “homemade” telescope toward a nearby galaxy did the seven dwarfs pop into view.

A trio of researchers discovered the celestial surprises while probing a nearby spiral galaxy, called M101, in a small section of sky using a telescope stitched together with telephoto lenses. “These are the same kind of lenses that are used in sporting events like the World Cup,” Yale’s Pieter van Dokkum explains in a news release. “We decided to point them upward instead.”


He and Roberto Abraham from the University of Toronto built the compact, oven-sized telescope in 2012 at New Mexico Skies observatory. They named it the Dragonfly Telephoto Array (pictured) after the insect’s compound eye. 

The septuplet of new galaxies had been previously overlooked because of their diffuse nature. But the Dragonfly’s eight telephoto lenses have a special coating that suppresses internally scattered light -- making the array uniquely adept at detecting very diffuse, low surface brightness.

“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 says. “It’s a new domain. We’re exploring a region of parameter space that had not been explored before.” 

Now the team is trying to figure out if the seven dwarfs orbit around M101 or if they’re located much farther or closer away and just happen to be visible in the same direction as M101. “There are predictions from galaxy formation theory about the need for a population of very diffuse, isolated galaxies in the universe,” Allison Merritt of Yale explains. “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.”


The work was published in the Astrophysical Journal Letters this week. 

Images: Yale University


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