The Hubble and James Webb space telescopes have obtained images of an unusual section of the Carina Nebula, a vast star-forming region about 7,500 light-years from Earth. Astronomers call this small fragment the "Cat's Head" nebula: from a distance it resembles a cat sitting with its back to the viewer, its head turned to the right, with a bright point glowing in place of an eye.
Although this picture is temporary - over time the material will disperse and the stars will change - it contains a great deal of information. By comparing the Hubble and Webb images, researchers hope to better understand the complex and chaotic process of star birth.
The characteristic shape of the "cat's head" was probably created by powerful ultraviolet radiation and stellar winds - streams of particles - from massive stars in the Carina Nebula. This influence is gradually "blowing away" the surrounding gas and dust, but denser regions inside the pillar resist destruction, at least for now.
Hubble observes in visible light. Its image shows an opaque dark brown pillar of dust. The glowing red "eye" may be a young star still partly embedded in dust. The yellow haze along the right edge probably arises where gas is illuminated and ionized - that is, stripped of electrons - by ultraviolet light from neighboring massive stars. This may trigger photoevaporation, a process in which radiation literally evaporates material.
The different colors in the Hubble image correspond to emission from oxygen, hydrogen and sulfur, as well as starlight scattered by dust. This is how astronomers see the complex mixture of excited gas, dust and stellar illumination.
Webb's infrared images, taken in the near- and mid-infrared, complement the picture. In near-infrared light the pillar becomes more transparent, and details of its surface emerge. To the left of the "cat's head" are ghostly filaments of dust and gas exposed to radiation from massive stars. Webb also shows many stars, some of them still hidden by dust. Even distant background galaxies are visible in the images - through our Milky Way galaxy.
In the mid-infrared, the bright glow of warm dust and carbon-containing molecules excited by starlight outlines the nebula's fine structures. To the right of the pillar is a bright yellow source - probably an infant star in dust. A narrow filament crosses it in the image, but a single image cannot show whether they are physically connected.
These observations help astronomers understand how massive stars affect their surroundings and what conditions lead to the birth of new luminaries. However, for now this is a qualitative description of the process rather than precise measurements.