NASA’s James Webb Space Telescope specializes in capturing infrared light, which our eyes can’t see. It shows these galaxies, called Arp 142, in a slow cosmic dance. Webb’s observations, using near- and mid-infrared light from the NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument), show them joined by a blue haze of stars and gas, a result of their mingling.
Their interaction began 25 to 75 million years ago when the Penguin (NGC 2936) and the Egg (NGC 2937) completed their first pass. They will continue to move together, completing several more loops before merging into a single galaxy hundreds of millions of years from now.
Before their first approach, the Penguin had a spiral shape. Today, its galactic center shines like an eye, with its unwound arms forming a beak, head, backbone, and fanned-out tail.
Like all spiral galaxies, the Penguin is rich in gas and dust. The galaxies’ gravitational “dance” pulled on the Penguin’s thinner areas of gas and dust, causing waves and star formation. Look for these areas in two places: what looks like a fish in its “beak” and the “feathers” in its “tail.”
Surrounding these newer stars is smoke-like material that includes carbon-containing molecules, known as polycyclic aromatic hydrocarbons, which Webb is great at detecting. Dust, seen as fainter, deeper orange arcs, also swoops from its beak to tail feathers.
In contrast, the Egg’s compact shape remains mostly unchanged. As an elliptical galaxy, it is filled with aging stars and has much less gas and dust to form new stars. If both were spiral galaxies, each would end the first “twist” with new star formation and twirling curls, known as tidal tails.
Another reason for the Egg’s undisturbed appearance: These galaxies have about the same mass, which is why the smaller-looking elliptical wasn’t consumed or distorted by the Penguin.
It is estimated that the Penguin and the Egg are about 100,000 light-years apart — quite close in astronomical terms. For context, the Milky Way galaxy and our nearest neighbor, the Andromeda Galaxy, are about 2.5 million light-years apart. They too will interact, but not for about 4 billion years.
Now, look to the top right to spot a galaxy that is not at this party. This edge-on galaxy, cataloged PGC 1237172, is 100 million light-years closer to Earth. It’s also quite young, full of new, blue stars.
Check out the images below which show the same galaxy as captured by Hubble (left) and Webb (right).
