NASA Hubble Space Telescope Traces Halo of Stars in a Distant Galaxy

The NASA Hubble Space Telescope has probed the extreme outskirts of a stunning elliptical galaxy. The new findings reveal new details about the most remote portion of an elliptical galaxy ever to have been explored.

The elliptical galaxy is called Centaurus A. Like other elliptical galaxies, it has a bright center and swirling, spiral arms. Beyond these features, the galaxy also has a dim halo of stars sprawling into space.

It's this halo that has intrigued researchers. Scientists have found that not only does the halo of stars extend much further from the galaxy's center than expected, but that the stars within this halo are surprisingly rich in heavy elements.

"Tracing this much of a galaxy's halo gives us surprising insights into a galaxy's formation, evolution, and composition," said Marina Rejkuba of the European Southern Observatory, in a news release. "We found more stars scattered in one direction than the other, giving the halo a lopsided shape-which we hand't expected!"

The scientists mapped a region about 450,000 light-years across. They found that in addition to the stars' uneven distribution, they showed surprising properties relating to the proportion of elements heavier than hydrogen and helium. Stars within haloes of other spirals normally are low in these heavy elements.

That said, scientists plant to continue to research Centaurus A. While this new study reveals a bit more about the galaxy, there's still much more to investigate.

"Even at these extreme distances, we still haven't reached the edge of Centaurus A's halo, nor have we detected the very oldest generation of stars," said Laura Greggio, co-author of the new study. "This aged generation is very important. The larger stars from it are responsible for manufacturing the heavy elements now found in the bulk of the galaxy's stars. And even though the large stars are long dead, the smaller stars of the generation still live on and could tell us a great deal."

By examining elliptical galaxies like these, astronomers can learn a bit more about galaxy evolution. Not only that, but researchers can find out more about the way galaxies form in general.

The findings are published in the Astrophysical Journal.