A galaxy 45 million light years away is so bright at its center that it overwhelms the cameras designed to capture it. The James Webb Space Telescope, operated by NASA, ESA and CSA, recently aimed its Mid-Infrared Instrument at Messier 77 in the constellation Cetus, and the core of this spiral galaxy simply outshone everything else. The light from the galaxy's heart was so intense and concentrated that it created optical artifacts in the image, a rare occurrence for an entire galaxy.
A black hole eight million times the mass of the Sun
At the center of Messier 77 sits an active galactic nucleus, or AGN. This is a compact region of hot gas powered by a supermassive black hole with a mass eight million times that of our Sun. The black hole's gravity pulls gas from the surrounding galaxy into a tight, fast orbit. As that gas crashes together and heats up, it releases enormous amounts of radiation. The result is a core that outshines the rest of the galaxy combined, pushing past the light gathering capacity of Webb's own instruments.
Diffraction spikes from a galaxy, not a star
The bright orange lines radiating from the center of the image are not real features of the galaxy. They are diffraction spikes, distortions created when intense light bends at the edges of Webb's hexagonal mirror panels and around the strut holding its secondary mirror. This six plus two pointed pattern is common in images of stars, but it rarely appears for galaxies. Messier 77 is one of the few galaxies whose nucleus is bright and compact enough to produce this effect.
A starburst ring 6,000 light years across
Messier 77 is also known as a prolific star forming galaxy. Webb's near infrared image reveals a bar of stars stretching across the central region, invisible in visible light images. That bar is enclosed by a bright ring called a starburst ring, formed by the inner ends of the galaxy's two spiral arms. The ring spans more than 6,000 light years and contains densely concentrated orange bubbles, each marking regions of extremely high star formation rates. Because Messier 77 is relatively close to Earth, this ring is one of the most well studied examples of its kind.
The galaxy's disc is filled with gas and dust, both a product of past stars and fuel for future ones. Webb's MIRI instrument captured the glow of interstellar dust grains at longer wavelengths, shown in blue, forming a halo around the galaxy. The image offers a rare look at a galaxy where the center is so active it distorts its own portrait, while the outer regions continue to churn out new stars at a furious pace.
