This image of the ring galaxy NGC 660, captured with the Gemini Multi-Object Spectrograph on the Fredrick C. Gillett Gemini North telescope on Mauna Kea in Hawaii, was obtained in August 2012. Color composite produced by Travis Rector, University of Alaska Anchorage. (Special to West Hawaii Today/Gemini Observatory/AURA)
A Gemini Legacy image showing two galaxies colliding to create a polar ring galaxy is poetry in motion, telescope staff say.
“What you see in this new Gemini Legacy image, then, is not a single dynamic body but either the ‘bloody’ aftermath of one galaxy piercing the heart of another or the remains of a furious tidal struggle between two galaxies that shattered one galaxy’s ‘lamp,’ scattered its dust and gas, and formed a colorful, 40,000-light-year-long ring of visual glory,” wrote Gemini spokesman Peter Michaud in his description of the image.
The Legacy images are photographs of formations in space Gemini officials hope will inspire the public, Michaud said Friday.
When two galaxies collide, the result is a ring of activity. What’s different about the image released this week, of polar ring galaxy NGC 660, is the edge-on view of the action. The galaxy is 40 million light years away.
“It shows the star formation areas very well-resolved, with lots of detail,” Michaud said. “The galaxy in the middle has a lot more star formation than is typical.”
Although the Legacy images are created more to showcase beauty than specific scientific goals, the images can be the basis of new scientific insights, Michaud said. Polar ring galaxies in particular can provide “a bit of foreshadowing for us,” he added, because the Milky Way is expected to collide with the Andromeda galaxy in about 5 billion years.
Michaud said astronomers have only located a handful of polar ring galaxies, and don’t yet know much about their origins. Most polar ring galaxies have what he described as an “early type spiral system,” also called a lenticular galaxy, in the center. NGC 660 is the only one known with what is known as a late-type lenticular galaxy as its host, he added.
He said he has always been struck by the X-shape of the galaxy, although that shape is less pronounced in Gemini’s latest image of the formation than in other images.
Brian Svoboda of the University of Arizona, who recently studied the chemical and temperature environment of NGC 660, said he believes a “unique morphology arises from a previous interaction with a gas-rich galaxy.”
NGC 660 contains more gas, and associated star formation, than its host, which strongly suggests a violent formation, Svoboda said. The ring may be about 1 billion years old, he added.
Scientists also believe the galaxy may contain dark matter. Scientists look for dark matter by determining how fast the polar ring rotates at different distances from the center of the system, telescope officials said.
“Radio observations have shown that while the ring’s velocity close to NGC 660’s core is normal, the velocity in the ring’s outer parts remains consistent; theoretically the rotational velocity should have dropped off significantly due to the region’s gas-poor environment,” officials said. “This finding points to the existence of huge amounts of dark matter in NGC 660.”