Messier 77 (NIRCam)

This latest Picture of the Month from the NASA/ESA/CSA James Webb Space Telescope features Messier 77 (M77), a barred spiral galaxy famous and appreciated among astronomers for its combination of relative proximity and spectacular features to study. It is located 45 million light-years away in the constellation Cetus (The Whale). This new image, from Webb’s Near-Infrared Camera (NIRCam), highlights its swirling spiral arms, the dust in its disc and its piercingly bright core like never before.

At the heart of M77 is a compact region filled with hot gas that handily outshines the rest of the galaxy put together, even overcoming the light-gathering capacity of Webb’s cameras. This is an active galactic nucleus (AGN), and it’s powered by M77’s central supermassive black hole, which is eight million times as massive as our Sun. Gas in the galaxy’s central regions is pulled by the strong gravity into a tight and rapid orbit around the black hole, where it crashes together and heats up, releasing tremendous amounts of radiation. The starburst pattern radiating from M77’s centre is diffraction spikes that are a feature of the telescope’s optics. They are most often seen from stars, but the bright and compact AGN creates some in this image too.

The bright AGN lies within a larger structure that is uniquely highlighted by Webb’s NIRCam. Since its discovery in 1780, M77 has been variously identified as a nebula (before the concept of separate galaxies beyond our own), a star cluster, and an ordinary spiral galaxy. But near-infrared images reveal a bar spanning from the inner end of one spiral arm to the other, a bar which doesn’t appear in visible-light images of the galaxy. Bars in galaxies channel vast amounts of star-forming material through a dense central region, and indeed M77 is an extremely prolific star-forming galaxy thanks to this bar, spawning tens of Suns worth of new stars every year!

Beyond the bar, M77’s spiral arms spin lazily out into the disc of the galaxy and beyond. The arms are the location of much of this new star birth, with dense clumps of gas collapsing to form tightly-packed clusters of stars. NIRCam pinpoints the light from these stars along the spiral arms, as well as capturing the glow that suffuses the galaxy from the billions of stars in its disc. Particularly along the southern spiral arm, NIRCam also traces infrared emission at slightly longer wavelengths — shown here in red colours — from complex molecules including polycyclic aromatic hydrocarbons (PAHs).

The data used to create this image are from an observing programme (#3707) that surveyed massive, nearby, star-forming galaxies to create a rich dataset useful for many scientific investigations. As can be seen here, the stunning resolution of Webb’s instruments reveals star clusters and rich reservoirs of gas, which can be used to explore the cycle of star formation, life and death in these and other galaxies.

[Image Description: A spiral galaxy shown in near-infrared light. Six long, thin rays of light emit from the centre, which are diffraction spikes created by the telescope’s optics. A glowing bar spans across the centre. A glittering orange ring of stars and dust surrounds the bar; at each side, the ring splits off into a spiral arm that winds outwards, traced by dark red dust and more glowing orange spots. The galaxy’s disc is a pale glow.]

Links

• Messier 77 (MIRI + NIRCam image)
• Messier 77 (MIRI image)
• Space Sparks episode
• Transition video