Spitzer Images Create 360-Degree View of the Milky Way

360 Degree View of the Milky Way

A new panorama from NASA’s Spitzer Space Telescope shows us our galaxy’s plane all the way around us in infrared light. Image Credit: NASA/JPL-Caltech/University of Wisconsin.

Using more than 2 million infrared snapshots taken over the past 10 years by NASA’s Spitzer Space Telescope, researchers created a new 360-degree mosaic of the Milky Way.

When you look up at the Milky Way on a clear, dark night, you’ll see a band of bright stars arching overhead. This is the plane of our flat spiral galaxy, within which our solar system lies.

A new, zoomable panorama from NASA’s Spitzer Space Telescope shows us our galaxy’s plane all the way around us in infrared light. The 360-degree mosaic comes primarily from the GLIMPSE360 project, which stands for Galactic Legacy Infrared Mid-Plane Survey Extraordinaire. It consists of more than 2 million snapshots taken in infrared light over 10 years, beginning in 2003 when Spitzer launched.

The Milky Way diagrams to the right of the panels show what slice of the galaxy is being seen. The center of the galaxy was the most widely covered and is shown in the second row. The outer regions of our galaxy, away from its bustling center, are in the last three rows.

This infrared view reveals much more of the galaxy than can be seen in visible-light views. Whereas visible light is blocked by dust, infrared light from stars and other objects can travel through dust to reach Spitzer’s detectors. For instance, when looking up at our night skies, we see stars that are an average of 1,000 light-years away; the rest are hidden. In Spitzer’s mosaic, light from stars throughout the galaxy — which stretches 100,000 light-years across — shines through. This picture covers only about three percent of the sky, but includes more than half of the galaxy’s stars and the majority of its star formation activity.

The red color shows dusty areas of star formation. Throughout the galaxy, tendrils, bubbles and sculpted dust structures are apparent. These are the results of massive stars blasting out winds and radiation. Stellar clusters deeply embedded in gas and dust, green jets and other features related to the formation of young stars can also be seen for the first time. Looking toward the galactic center, the blue haze is made up of starlight — the region is too far away for us to pick out individual stars, but they contribute to the glow. Dark filaments that show up in stark contrast to the bright background are areas of thick, cold dust that not even infrared light can penetrate. If you look closely, it’s even possible to spot distant galaxies that lie far beyond the Milky Way.

Scientists are using these images to get to know our galaxy better. They’ve come up with better maps of its central bar of stars and spiral structure, discovered new remote sites of star formation and even come across new mysteries; for example, the dust grains indicate a higher abundance of carbon in the galaxy than expected. The GLIMPSE360 map will guide astronomers for generations, helping them to further chart the unexplored territories of our own Milky Way.

The image combines data from multiple surveys in addition to GLIMPSE360: GLIMPSE, GLIMPSEII, GLIMPSE3D, Vela-Carina, Deep GLIMPSE, CYGX, GALCEN and SMOG. Twelve-micron data from NASA’s Wide-field Infrared Survey Explorer (WISE) was substituted for missing 8-micron data in outer galaxy regions mapped during Spitzer’s post-cryogen mission.

The image, derived primarily from the Galactic Legacy Mid-Plane Survey Extraordinaire project, or GLIMPSE, is online at: http://www.spitzer.caltech.edu/glimpse360.

Spitzer, launched into space in 2003, has spent more than 10 years studying everything from asteroids in our solar system to the most remote galaxies at the edge of the observable universe. In this time, it has spent a total of 4,142 hours (172 days) taking pictures of the disk, or plane, of our Milky Way galaxy in infrared light. This is the first time those images have been stitched together into a single expansive view.

Our 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.

“Spitzer is helping us determine where the edge of the galaxy lies,” said Ed Churchwell, co-leader of the GLIMPSE team at the University of Wisconsin-Madison. “We are mapping the placement of the spiral arms and tracing the shape of the galaxy.”

Using GLIMPSE data, astronomers have created the most accurate map of the large central bar of stars that marks the center of the galaxy, revealing the bar to be slightly larger than previously thought. GLIMPSE images have also shown a galaxy riddled with bubbles. These bubble structures are cavities around massive stars, which blast wind and radiation into their surroundings.

All together, the data allow scientists to build a more global model of stars, and star formation in the galaxy — what some call the “pulse” of the Milky Way. Spitzer can see faint stars in the “backcountry” of our galaxy — the outer, darker regions that went largely unexplored before.

“There are a whole lot more lower-mass stars seen now with Spitzer on a large scale, allowing for a grand study,” said Barbara Whitney of the University of Wisconsin, Madison, co-leader of the GLIMPSE team. “Spitzer is sensitive enough to pick these up and light up the entire ‘countryside’ with star formation.”

The Spitzer team previously released an image compilation showing 130 degrees of our galaxy, focused on its hub. The new 360-degree view will guide NASA’s upcoming James Webb Space Telescope to the most interesting sites of star-formation, where it will make even more detailed infrared observations.

Some sections of the GLIMPSE mosaic include longer-wavelength data from NASA’s Wide-field Infrared Survey Explorer, or WISE, which scanned the whole sky in infrared light.

The GLIMPSE data are also part of a citizen science project, where users can help catalog bubbles and other objects in our Milky Way galaxy.

Source: J.D. Harrington, NASA

Image: NASA/JPL-Caltech/University of Wisconsin

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