"Penguin & Egg": Interacting Galaxies Arp 142 | James Webb Space Telescope

"Penguin & Egg": Interacting Galaxies Arp 142 | James Webb Space Telescope

This is Arp 142, two interacting galaxies, observed in near- and mid-infrared light. At left is NGC 2937, nicknamed the Egg. Its center is the brighter and whiter. There are six diffraction spikes atop its gauzy blue layers. At right is NGC 2936, nicknamed the Penguin. Its beak-like region points toward and above the Egg. Where the eye would be is a small, opaque yellow spiral. The Penguin’s distorted arms form the bird’s beak, back, and tail. The tail is wide and layered, like a beta fish’s tail. A semi-transparent blue hue traces the Penguin and extends from the galaxy, creating an upside-down U over top of both galaxies. At top right is another galaxy seen from the side, pointing roughly at a 45-degree angle. It is largely light blue. Its length appears approximately as long as the Egg’s height. One foreground star with large, bright blue diffraction spikes appears over top of the galaxy and another near it. The entire black background is filled with tiny, extremely distant galaxies.

The distorted spiral galaxy at center, the Penguin, and the compact elliptical galaxy at left, the Egg, are locked in an active embrace. Their interaction is marked by a faint upside-down U-shaped blue glow.

The pair, known jointly as Arp 142, made their first pass between 25 and 75 million years ago— causing “fireworks,” or new star formation, in the Penguin. In the most extreme cases, mergers can cause galaxies to form thousands of new stars per year, for a few million years. For the Penguin, research has shown that about 100 to 200 stars have formed per year. By comparison, our Milky Way galaxy (which is not interacting with a galaxy of the same size) forms roughly six to seven new stars per year. Arp 142 lies 326 million light-years from Earth in the constellation Hydra.

This gravitational shimmy also remade the Penguin’s appearance. Its coiled spiral arms unwound, and gas and dust were pulled in an array of directions, like it was releasing confetti. It is rare for individual stars to collide when galaxies interact (space is vast), but galaxies’ mingling disrupts stars’ orbits.

Today, the Penguin’s galactic center looks like an eye set within a head, and the galaxy has prominent star trails that take the shape of a beak, backbone, and fanned-out tail. A faint, but prominent dust lane extends from its beak down to its tail.

Despite the Penguin appearing far larger than the Egg, these galaxies have approximately the same mass. This is one reason why the smaller-looking Egg has not yet merged with the Penguin. (If one was less massive, it may have merged earlier.)

The oval Egg is filled with old stars, and little gas and dust. This is why it is not sending out “streamers” or tidal tails of its own and instead has maintained a compact oval shape. If you look closely, the Egg has four prominent diffraction spikes—the galaxy’s stars are so concentrated that it gleams.

Now, find the bright, edge-on galaxy at top right. It is not nearby. Cataloged PGC 1237172, it lies 100 million light-years closer to Earth. It is relatively young and is not overflowing with dust. This is why it practically disappears in Webb’s mid-infrared view.

The background of this image is overflowing with far more distant galaxies. This is a testament to the sensitivity and resolution of Webb’s infrared cameras.

Credits: NASA, ESA, CSA, STScI

Release Date: July 12, 2024

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