The James Webb Space Telescope (JWST) has zoomed in to the heart of the Cigar Galaxy, a region of space that is ablaze with an explosive bout of star-birth.
This starburst galaxy, also known as Messier 82 (M82), has a compact but turbulent environment at its core that could give scientists a clearer picture of how stars are born en masse, and how extreme environments shape the galaxies around them.
Located around 12 million light-years away in the constellation of Ursa Major, M82 is forming stars 10 times faster than our own relatively quiet galaxy, the Milky Way. The team imaged the core of this starburst galaxy with the JWST’s Near-Infrared Camera (NIRCam) to investigate what conditions are driving the formation of infant stars.
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“M82 has garnered a variety of observations over the years because it can be considered as the prototypical starburst galaxy,” Alberto Bolatto, team leader and University of Maryland researcher, said in a statement. “Both Spitzer and Hubble space telescopes have observed this target.
“With the JWST’s size and resolution, we can look at this star-forming galaxy and see all of this beautiful new detail.”
sHow the JWST sees right through starbursts
Star formation is common across the cosmos, but has been able to maintain an air of mystery because gas and dust that forms the raw material necessary for star formation also effectively shrouds the process.
While gas and dust are very efficient at absorbing visible light, however, infrared light is able to slip through this material. That means, with its powerful and sensitive infrared view of the cosmos, the JWST is the perfect instrument to get right to the heart of star birth.
The NIRCam images collected by Bolatto and colleagues also benefited from a special mode that prevented the bright infant stars at the heart of M82 from overwhelming the instrument.
The JWST M82 shortwave infrared light image shows dark, reddish-brown tendrils of dust weaving their way through the white, cigar smoke, glowing core of M82. Small green specks in the image represent regions of iron that remain from supernova explosions of now-dead massive stars. Red-looking patches show areas where molecular hydrogen is being heated by radiation from young stars.
“This image shows the power of the JWST,” team member and University of Arizona scientist Rebecca Levy said in the statement. “Every single white dot in this image is either a star or a star cluster. We can start to distinguish all of these tiny point sources, which enables us to acquire an accurate count of all the star clusters in this galaxy.”
A smoking cigar’s galactic winds
When the JWST’s NIRCam imaged M82’s core in infrared light, the star-forming region took on a strikingly fresh visage. Suddenly, gaseous streams of galactic winds appeared, stretching further from the galaxy’s main starburst core then previously noticed, almost like a network of blood vessels extending from a biological heart rather than a galactic one.
This galactic wind is powered by star formation and supernova deaths of older stars. Like lifeblood pumped through blood vessels in the human body, the galactic wind moves elements around that facilitate galactic growth through further star formation, thus strongly influencing the body around it.
NIRCam was able to trace the structure of these galactic winds as they emit sooty chemical molecules known as polycyclic aromatic hydrocarbons (PAHs). Because PAHs are small dust grains that survive in cool regions but are destroyed by hotter temperatures, this revealed how cold and hot components interact within the wind.
The fine structure of galactic winds in M82 was something the team was not expecting to uncover — nor were they anticipating any similarities in the shape of PAH emission and structure of hot, ionized gas tendrils.
“It was unexpected to see the PAH emission resemble ionized gas,” Bolatto explained. “PAHs are not supposed to live very long when exposed to such a strong radiation field, so perhaps they are being replenished all the time. It challenges our theories and shows us that further investigation is required.”
The team hopes that further JWST observations of M82 and other starburst galaxies could help answer some lingering questions about star birth. The scientists will also combine these new images with complementary large-scale images of the Cigar Galaxy and its galactic winds.
Light spectra from this galaxy should help astronomers determine the accurate ages of the star clusters in M82. This could, in turn, reveal how long each phase of star formation lasts in starburst galactic environments.
“With these amazing JWST images and our upcoming spectra, we can study how exactly the strong winds and shock fronts from young stars and supernovas can remove the very gas and dust from which new stars are forming,” team member and European Space Agency (ESA) scientist Torsten Böker said in the statement. “A detailed understanding of this ‘feedback’ cycle is important for theories of how the early universe evolved because compact starbursts such as the one in M82 were very common at high redshift.”
The team’s research has been accepted for publication in The Astrophysical Journal.