Webb explores largest star-forming cloud in our galaxy

Sagittarius B2 is the Milky Way galaxy’s most massive and active star forming cloud, producing half of the stars created in the galactic centre region despite having only 10 percent of the area’s star-making material. Now, Webb has revealed stunning new views of the region, using both its near-infrared and mid-infrared instruments, to capture its colourful stars as well as gaseous stellar nurseries in unprecedented detail. 

Sagittarius B2 is located only a few hundred light-years from the supermassive black hole at the heart of our galaxy called Sagittarius A*, a region densely packed with stars, star-forming clouds, and complex magnetic fields. The infrared light that Webb detects is able to pass through some of the area’s thick clouds to reveal young stars and the warm dust surrounding them. Astronomers think that analysis of Webb’s data will help unravel enduring mysteries of the star formation process, and why Sagittarius B2 is forming so many more stars than the rest of the galactic centre.

However, one of the most notable aspects of Webb’s images of Sagittarius B2 are the portions that remain dark. These ironically empty-looking areas of space are actually so densely filled with gas and dust that even Webb cannot see through them. These thick clouds are the raw material of future stars and a cocoon for those still too young to shine.

The high resolution and mid-infrared sensitivity of Webb’s MIRI (Mid-Infrared Instrument) revealed this region in unprecedented detail, including glowing cosmic dust heated by very young massive stars. The reddest area, known as Sagittarius B2 North, (note: north is to the right in these Webb images) is one of the most molecularly rich regions known, but astronomers have never seen it with such clarity.

The difference longer wavelengths of light make, even within the infrared spectrum, are stark when comparing the images from Webb’s MIRI and NIRCam (Near-Infrared Camera) instruments. Glowing gas and dust appear dramatically in mid-infrared light, while all but the brightest stars disappear from view.

In contrast to MIRI, colourful stars steal the show in Webb’s NIRCam image, punctuated occasionally by bright clouds of gas and dust. Further research into these stars will reveal details of their masses and ages, which will help astronomers better understand the process of star formation in this dense, active galactic centre region. Has it been going on for millions of years? Or has some unknown process triggered it only recently?

Astronomers hope Webb will shed light on why star formation in the galactic centre is so disproportionate. Though the region is stocked with plenty of gaseous raw material, on the whole it is not nearly as productive as Sagittarius B2. While Sagittarius B2 has only 10 percent of the galactic centre’s gas, it produces 50 percent of its stars.

More information
Webb is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope’s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.

Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

Release on esawebb.org

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