The new images come after NASA unveiled on July 12 five initial scenes captured by the Webb Telescope, the most powerful space observatory yet built. Since launching on Dec. 25, Webb’s 18 hexagonal gold mirrors have been aligned to capture other targets in space, though not all images have been released. Highlights include the Southern Ring Nebula, which looks like a soap bubble expanding from a dead star, and the spectacular Carina Nebula, which consists of swirling dust that looks like jagged rocks. Astronomers have been studying the Cartwheel Galaxy for decades. Initially, it was surveyed by two ground-based observatories in Australia, first the United Kingdom’s Schmidt Telescope and later the Anglo-Australian Telescope. But it is better known than the Hubble Space Telescope, which produced images in the 1990s with more detail of the galaxy’s composition. And just as Webb, in July, revealed the presence of even more distant galaxies hidden from our view, his Cartwheel photos magnified the detailed star formation within the galaxy’s rings and the dozens of other star systems beyond. . The appearance of the Cartwheel comes from a collision of two galaxies that happened hundreds of millions of years ago. “We hypothesize that Cartwheel probably started out looking like our Milky Way, and then this other galaxy came through,” said Marcia Rieke, principal investigator of the Near-Infrared Camera, or NIRCam, one of the Webb telescope’s science instruments. The smaller galaxy, however, instead of getting stuck in the great spiral it entered, continued, pushing the larger one away. It is not visible in the image released by NASA. Galactic collisions are not uncommon in deep space, although they rarely end up in such a perfect shape that it sparks human curiosity. Kirk Borne, who was the principal investigator on the Cartwheel Hubble observation but was not involved with Webb, said the galaxy’s strange shape, formed by coincidence during the merger, had motivated astronomers to study it for decades. Because a smaller galaxy crashed into a larger one—and right through the middle of it—there was less disruption to the shape of each galaxy, and both were relatively able to retain their individuality. “What changed the shape of the Cartwheel was the effect of the gravitational field of this other galaxy changing the orbits of the stars in the original Cartwheel galaxy,” said Dr. Rieke. Dr Bourne, who has studied other galaxy collisions, described the smaller galaxy as a bullet shot through the larger one. After observing the cosmic object in the 1990s, scientists noticed a trail of hydrogen gas it left behind following the smaller galaxy, which Dr. Bourne called the “smoking gun” indicating that he continued to move after the new Cartwheel formation was created. Already 1.5 times the size of the Milky Way, the Cartwheel is still expanding, and new stars are forming both inside its outer ring and at its edge. However, there is no definite answer as to how big the Cartwheel will get, when it will stop growing, or what shape it will take when it does. Cartwheel images were already in hand on July 12, though they weren’t publicly available until this week. They have been filtered to make them more visually accessible, highlighting vibrant blue-toned young stars and red-toned particles from older stars and space dust floating between the rings. While it’s colorful, Joseph DePasquale, senior scientific optics programmer at the Space Telescope Science Institute, which manages the Webb and Hubble spacecraft, pointed out that the stars and dust are actually detected as infrared light rather than colors. The new technology to detect this light in such detail is what distinguishes Webb’s images from those taken by Hubble and the Anglo-Australian Telescope. While Hubble had some ability to capture light in the infrared spectrum, the Webbs are more advanced and produce more vivid images. NIRCam, for example, which was built by about 25 people working with Dr. Rieke for 11 years, has been distinguishing the infrared colors of stars, which are invisible to the human eye, from one another. When Hubble captured the Cartwheel in the 1990s, the galaxy’s “rays” were obscured by gas clouds that scattered light, making it difficult to see the thousands of stars forming inside. Now, because Webb can study mid-infrared and near-infrared wavelengths of light, it is able to filter past space dust. This helps confirm some of the theories of the Cartwheel’s makeup that were created using Hubble’s technology and reveal new information, such as the lack of star formation in some areas between the spokes of the wheel. “I think the combination of the two telescopes, not just making one of them obsolete, actually just enhances the benefits and the power of Hubble because now we can make these comparisons,” Dr. Bourne said.
