Milky Way Galaxy is a flat spiral disk; our Solar System sits in the outer one-third of the Milky Way, in one of its spiral arms.
When we look toward the center of our Galaxy, we see a crowded, dusty region jam-packed with stars.
Visible-light telescopes cannot look as far into this region because the amount of dust increases with distance, blocking visible starlight. Infrared light, however, travels through the dust and allows Spitzer to view past the Galaxy’s center.
“For the first time, we can actually measure the large-scale structure of the Galaxy using stars rather than gas. We have established beyond the shadow of a doubt that our Galaxy has a large bar structure that extends halfway out to the Sun’s orbit. We know more about where the Milky Way’s spiral arms are,” said team member Prof Edward Churchwell from the University of Wisconsin-Madison.
In addition to providing new revelations about galactic structure, Spitzer and the images processed by Prof Churchwell and his colleagues have made possible the addition of more than 200 million new objects to the catalog of the Milky Way.
“This gives us some idea about the general distribution of stars in our Galaxy, and stars, of course, make up a major component of the baryonic mass of the Milky Way. That’s where the ballgame is.”
The star-studded panorama of Milky Way Galaxy named GLIMPSE360 is available online at http://www.spitzer.caltech.edu/glimpse360
It is interactive and zoomable, giving users the ability to look through the plane of the Galaxy and zero in on a variety of objects, including nebulae, bubbles, jets, bow shocks, the center of the Galaxy and other exotic phenomena.
The survey conducted by the astronomers has also helped them understand the distribution of the Milky Way’s stellar nurseries, regions where massive stars and proto-stars are churned out.
“We can see every star-forming region in the plane of the Galaxy,” said team member Prof Robert Benjamin from the University of Wisconsin-Whitewater.
“This gives us some idea of the metabolic rate of our Galaxy. It tells us how many stars are forming each year,” explained team member Dr Barb Whitney from the University of Wisconsin-Madison.
While Spitzer is helping astronomers resolve some of the mysteries of the Milky Way, it is adding new cosmological puzzles for them to ponder. For example, the infrared data gathered by the team has revealed that interstellar space is filled with diffuse polycyclic aromatic hydrocarbon gas.
“These are hydrocarbons – very complicated, very heavy molecules with fifty or more carbon atoms,” Prof Churchwell said.
“They are brightest around regions of star formation but detectable throughout the disk of the Milky Way. They’re floating out in the middle of interstellar space where they have no business being. It raises the question of how they were formed. It also tells us carbon may be more abundant than we thought.”