Scientists use Keck to study densest galaxy found to date

Astronomers using W.M. Keck Observatory on Mauna Kea have identified a galaxy in the nearby universe that has a density of stars 15,000 times greater than that of Earth’s neighborhood in the Milky Way.

The M60-UCD1 galaxy has about half of its stars within an 80 light-year radius. For comparison, Keck Observing Support Manager Bob Goodrich noted the closest star to Earth, aside from the sun, is Proxima Centauri, about four light-years away.

Goodrich and the astronomers who worked on the M60-UCD1 discovery pointed out that even the relatively close distances in that galaxy are beyond current abilities to travel from one location to another quickly.

“Our technology is pretty unequal” to the task of traveling distances measured in light-years, Goodrich said.

“Traveling from one star to another would be a lot easier in M60-UCD1 than it is in our galaxy,” Jay Strader of Michigan State University said. “But it would still take hundreds of years using present technology.”

Strader was the first author on a paper on the subject.

The paper was published in the Sept. 20 issue of The Astrophysical Journal Letters.

Scientists described M60-UCD1 as a type of “ultra-compact dwarf galaxy.”

Images from NASA’s Hubble Space Telescope first showed the galaxy; scientists used NASA’s Chandra X-ray Observatory, Keck and other ground-based optical telescopes for follow-up observations.

Goodrich said the discovery and subsequent study showed how “using different instruments on large telescopes can be very fruitful.”

Observations by the 6.5-meter Multiple Mirror Telescope in Arizona showed the amount of elements heavier than hydrogen and helium were similar to our sun.

“The abundance of heavy elements in this galaxy makes it a fertile environment for planets and, potentially, life to form,” co-author Anil Seth of the University of Utah said.

A particularly interesting element of the discovery, Goodrich added, has scientists trying to determine if the galaxy is a “jam-packed” star cluster or a smaller galaxy that has had stars ripped away from its outer reaches.

The latter happens when two galaxies approach each other, and the larger galaxy’s gravitational force pulls stars from the smaller galaxy into itself.

M60-UCD1 could be the remainder of such a small galaxy, with its outer stars gone, leaving only the densely clustered inner stars, he said.

“Discoveries like this start to fill in that gap (in knowledge about star clusters and stripped galaxies),” he added.

If M60-UCD1 is a stripped galaxy, it could have been 50 to 200 times bigger than it is now.

Researchers said the galaxy is about 10 billion years old.