James Webb Telescope releases new image of galaxy collision

An impressive cosmic spectacle is taking place 465 million light-years away in the constellation Leo Minor: Two galaxies are merging with each other—a process that began hundreds of millions of years ago and is expected to last hundreds and millions of years. The smaller elliptical galaxy PGC 32628 and the larger spiral galaxy PGC 32620 together form the galaxy pair Arp 107, which has been imaged by Hubble.

Now, NASA has released new images of these so-called interacting galaxies. They come from the James Webb Space Telescope, which targeted Arp 107 with NIRCam (Near Infrared Camera) and MIRI (Mid Infrared Instrument). From the data obtained by these instruments, astronomers pieced together an image that provides a wealth of information about star formation and further reveals how galaxy collisions occur.

The “bridge” between galaxies

The James Webb Telescope has discovered a nearly transparent white “bridge” connecting two galaxies, composed of gas and stars torn from two star clusters. Infrared light also makes visible old stars, which shine brightly in both galaxies. They are shown in white. Red and orange hues show young stars and active star-forming regions in sequence. Overall, NASA writes, Arp 107 “is given a cheerful aura due to its two bright 'eyes' and wide, semicircular 'smile.'”

For comparison: A combined image of Arp 107 with data from the Hubble Telescope, the Victor M. Blanco Telescope, and the Sloan Digital Sky Survey. Image: Wikimedia

The larger of the two components of Arp 107 is a spiral galaxy, one of the so-called Seyfert galaxies. These galaxies are active galactic nuclei (AGN), which radiate large amounts of energy from their centers. The brightest of these active galactic nuclei has a quasar at its center; a supermassive black hole surrounded by a rotating disk of luminous material called an accretion disk. Seyfert galaxies generally emit less radiation than quasar galaxies, making them easier to observe with the James Webb Telescope using low-energy infrared light.

Loss of spiral arm

Arp 107 has some similarities to another galaxy that is also the result of a galaxy collision: the Cartwheel Galaxy (PGC 2248). This so-called ring galaxy is a full 400 million light-years away from Earth, and its shape was formed by the collision of a smaller galaxy with a larger disk galaxy. When a small galaxy passes through the middle of a large galaxy, it releases a huge shock wave that stirs up gas and dust and then creates a region of intense star formation activity.

The Cartwheel Galaxy can be seen in this series of images (Figure 14):

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cosmic butterfly
NGC 6302Also known as the “Beetle Nebula” or “Butterfly Nebula” in English, it is about 4,000 light-years away from Earth. This beautiful structure captured by Hubble is a planetary nebula – they are not related to planets, but are composed of the shell of gas and plasma shed by an ancient star at the end of its evolution.

These Agencies: NASA, ESA, Hubble/William Osterling

However, in the case of Arp 107, the collision occurred differently than in cartwheel galaxies—the smaller galaxy did not hit the spiral galaxy at its center, so it was able to retain much of its structure. Only the characteristic spiral arms have almost completely disappeared. When the two galaxies merge, they will form a larger, irregularly shaped galaxy.

The birth of a new star

The collision of two giant star clusters is a chaotic process. But this can lead to the birth of new stars, as MIRI images in the mid-infrared range clearly show. Shown in blue, these young stars formed in spiral galaxies are surrounded by dust grains and organic molecules typical of star-forming regions.

MIRI image shows the supermassive black hole at the center of the spiral galaxy on the right. It shows the six-beam diffraction peak typical of the Webb telescope. Young stars in the spiral galaxy are highlighted in blue. Image: NASA, ESA, CSA, STScI

Collisions can create new reservoirs of gas in galaxies that are not actively forming new stars, compressing the gas so that it becomes dense enough to form stars. However, not all collisions have this effect; they can also scatter gas, causing galaxies to lose material dense enough to birth new stars. (Human Resources Department)

Galaxy Collision: The Milky Way and the Andromeda Galaxy

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Galaxy Collision: The Milky Way and the Andromeda Galaxy

Current status: The Milky Way (almost vertical belt of stars on the right) and the Andromeda Galaxy (left) are approaching each other at about 110 kilometers per second. (Image source: NASA)

What: NASA

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