After a decade when other astronomical targets got more attention, the Milky Way has come back into vogue as a hot research subject in the new millennium, leading to a whole new picture of how the galaxy formed, how unimaginably huge it is, and what it looks like from afar.

"There's been a renaissance in studying the Milky Way," says Steven Majewski, an astronomer at the University of Virginia who specializes in the structure of the galaxy.

As a result of the newfound interest, astronomers are rapidly unraveling the Milky Way's mysteries.

What they're learning is that the mighty Milky Way attained some of its girth by gravitationally dominating many merger transactions, otherwise known as galaxy gobbling. And surprisingly, our home galaxy was recently found to be surrounded by an invisible sphere that appears to influence space for well more than 100,000 light-years in all directions.

Cosmic archeology  

Majewski says the new interest stems in large part from an incredible finding in the 1994, when astronomers spotted a nearby galaxy they'd never seen before.

The Sagittarius dwarf galaxy turned out to be the closest neighbor to our own, just 75,000 light-years from Earth. Researchers began to suspect the galaxy was being absorbed by the Milky Way, an idea that got further support in a study released two weeks ago.

Other evidence of mergers has shown up in the past couple of years in the form of stellar entrails, small streams of stars that travel in packs throughout the Milky Way but on paths unrelated to the movement of the rest of the galaxy's stars.

"We're leaning that with a lot of the events that occurred in the Milky Way's past, there is still fossilized evidence left behind that we can use to find out what happened," Majewski said in a telephone interview last week.

The swirl of stars that make up our cosmic neighborhood is rapidly becoming less like uncharted waters and more like an archeological site, a place where objects are mapped out but still need some of the dust brushed away for a better look. This dust is not actually brushed away, but rather astronomers are seeing through it with new space observatories and powerful ground-based telescopes with huge apertures.

Bird's-eye view

Earth is located on the outskirts of the main disk of the Milky Way, on one of its spiral arms, some 27,000 light-years from the galactic center. From this vantage point, it has always been impossible to see the whole galaxy. Astronomers have never had a good view of anything on the far side of the main disk, because the density of dust and stars clouds the view.

Enough knowledge has been gleaned, however, to assume that the Milky Way looks something like other spiral galaxies, relatively flat pinwheel-like structures with spherical central bulges where high concentrations of stars are gathered around a supermassive central black hole.

Now a truly representative bird's-eye view of our galaxy has been created by selecting a portion of stars from the Two Micron All Sky Survey (2MASS).

The new picture maps out 30,000 so-called carbon stars, as seen in the infrared, the wavelength employed by night-vision goggles to sense heat. Unlike visible light, infrared penetrates dust. While carbon stars represent only a fraction of the 500 million stars detected in the 2MASS survey, they tend to all shine equally bright. This allows researchers to more accurately determine the distance to each one based on how thermally bright it appears from Earth, making it possible to generate a 3-D map.

Equally important, says Michael Skrutskie, a University of Virginia research who worked with Majewski and others create the new map, is the fact that carbon stars are rather run-of-the-mill: not to young, not to old, nor too light or heavy.

"On the whole, carbon stars are representative of the broader galactic population," Skrutskie says.

The map, released in January, reveals for the first time the galaxy's entire outer boundary of stars.

Next Page: The invisible sphere of influence