NASA Spitzer, Hubble Photos Show Penguin, Egg Galaxy Pair

The force of gravity forces many objects in the universe into spherical shapes, but there is still a plethora of objects — star clusters, nebulae, galaxies and so on — that are not even remotely spherical. Sometimes, the shape of a cosmic object can change as a result of its interaction with another object, due to the tug and pull of gravity between the two.

A NASA image released Thursday shows such a pair of objects — two interacting galaxies collectively called Arp 142, located 23 million light-years away in the southern constellation Hydra.

The two galaxies are poles apart in appearance. The one that appears larger in the image is NGC 2336, and NASA called it the “penguin” galaxy, given its shape as seen in the image. The galaxy was perhaps a normal-looking spiral galaxy at one point in its past, with a flattened disk and symmetric spiral arms, like the Milky Way.

Gravitational interaction with nearby galaxies has changed that, though, and it now looks somewhat like the flightless bird it gets it colloquial name from. The bright glowing orb below it is NGC 2937, the other part of Arp 142, and given its shape, is referred to as the “egg” galaxy, one the penguin seems to be guarding.

The bluish filaments of NGC 2336 are indicative of newly-formed hot stars, while the red filaments are strands of gas mixed with dust. NGC 2937, on the other hand, appears almost entirely featureless, despite the interaction with NGC 2366. Even though there must be some reactions to the presence of another galaxy so close by, NGC 2937 has a uniform distribution of stars that obscures any marked distortions to its shape.

Since there are no red filaments around NGC 2937, that means there is no dust in the galaxy, all of it having been used up long ago in the formation of stars. The stars themselves are much older than the ones in NGC 2336, as evidenced by the greenish glow of the galaxy.

These two galaxies are moving toward each other, and will eventually merge together in the future. Their differently aged populations of stars will intermingle, and the gas and dust from one will infuse into the other. Such mergers were likely common in the universe, especially in the formation of large galaxies like the Milky Way.

The vertical blue streak near the top of the image is another galaxy that has nothing to do with Arp 142, since it is located much farther away in the background.

This image was produced using the visible light capabilities of the Hubble Space Telescope and infrared data from NASA’s Spitzer telescope. Once the space agency launches the James Webb Space Telescope — currently scheduled for spring 2019 — it will be able to see both these wavelengths of light using one instrument.