Exploring Cartwheel
When galaxies collide, interesting things happen. The gravity of two such massive objects colliding (or even passing close to each other) distorts the shape of each galaxy. The shockwaves ripple through the participants, triggering bursts of star formation. In extreme conditions, as seen here, the result is a rare ring-type galaxy. Cartwheel Galaxy can look amazingly weird (and it is). But, it’s also a great example of galactic debris that will eventually be fixed. In a few million years, this scene could look remarkably different. This is one reason why astronomers are so interested in it. It’s not often they see a conflict unfold like this. It’s worth checking out its latest view, just to see the amazing detail JWST provides. There is not only Mr. Cartwheel, but also other galactic companions. (The galaxy plowing master is not in this view.) More on all of them in a minute. Remove all ads on Universe Today Join our Patreon for just $3! Get the ad-free experience of a lifetime The apparent debris from the collision consists of two glowing rings, one inner and one outer. The inner ring hosts a luminous core that harbors a supermassive black hole. It is surrounded by a smaller ring of gas and hot dust. Then there is the outer ring. In fact it has expanded so much after the collision that it is larger than our Milky Way. It spins out of star-forming regions, set off by shock waves from the collision and expansion of the ring in the surrounding regions of gas and dust. Connecting the two main rings is a set of terrifying rays emitting from the core. These are probably the ancient spiral arms from the original galaxy undergoing a reshaping process. They also live with star nurseries. The bluish regions are young stars that formed as a result of the collision.
JWST Senses Dust
Now, there’s a lot to Cartwheel that you don’t see if you look at it in visible light. But, open up an infrared-sensitive telescope and you’ll discover that the Cartwheel is a very dusty place. Clouds of dust obscure the view of some parts of the galaxy. However, all is not lost. Some infrared wavelengths penetrate through dust. Also, the dust emits heat, which is “visible” at infrared wavelengths. That’s where JWST’s Near Infrared Camera (NIRCam) comes in handy. In a sense, he can “see” right through the dust. And, it can also detect clouds of dust scattered throughout the Cartwheel. For example, this is how we can see so many star-forming regions in great detail. Mid-infrared light captured by MIRI reveals chemical details of dusty regions in Cartwheel and the young stars it contains. Young stars, many of which are present in the lower right part of the outer ring, activate the surrounding hydrocarbon dust, causing the orange glow. On the other hand, the well-defined dust between the core and the outer ring forms the “rays” that inspire the galaxy’s name. This dust feeds the supermassive black hole at the center of the galaxy. To really dig into the details of the dust that permeates this galaxy, JWST’s Mid-Infrared Instrument (MIRI) essentially did a little chemical analysis. It turns out that the areas in the rays are rich in hydrocarbons and other compounds, as well as silicon dust. MIRI also produces information about the distances of galaxies in the background. Closer galaxies are blue and more distant galaxies are green and red. The different colors are due to the light emissions from the dust being red-shifted by the expansion of the universe.
Setting the scene at Cartwheel
Cartwheel doesn’t travel alone. It is part of a group of four Cartwheel galaxies located about 500 million light-years away. The companion galaxies are much smaller and are all physically connected to the Ferris Wheel. There is a small, blue Magellanic Cloud-type galaxy called G1. Nearby is a small, yellow compact spiral called G2. These two smaller ones show a lot of star formation. The lower galaxy also shines due to the presence of a supermassive black hole. The fourth member (not seen in the JWST image) is a distant spiral called G3. It has a tidal tail that extends away from it back towards the Cartwheel. It could be the galactic that plowed the Cartwheel and caused all the havoc. When astronomers gather all the imaging data from JWST, they see that this scene is just a snapshot in time. Cartwheel is changing, expanding and reforming. What will happen to it as it changes? The cart-like structure will likely disintegrate as the gas and dust fall back toward the center. If the other companion galaxies don’t interfere, then maybe a few hundred million years from now, the Cartwheel will once again be a beautiful spiral.
Checking Cartwheel before JWST
This isn’t the first time a space observatory has taken a look at the Cartwheel team. The Hubble Space Telescope captured a view of it in 1995, using the newly installed Wide Field Planetary Camera 2 (WFPC2). It was the first time such a high-resolution image of the crash scene had been captured. XMM-Newton also studied this scene, and it has been detected and mapped in radio frequencies by the Paul Wild Observatory at Narrabri in Australia. Cartwheel is part of a group of four galaxies, as seen in this collage of images from ground-based optical and radio telescopes and the Hubble Space Telescope’s Wide Field and Planetary Camera 2. Curt Struck and Philip Appleton (Iowa State University), Kirk Borne (Hughes STX Corporation) and Ray Lucas (Space Telescope Science Institute), Jim Higdon (Australia Telescope National Facility’s Paul Wild Observatory), Victor Blanco (Cerro Tololo) In 2006, NASA unveiled a multi-wavelength image of the Cartwheel cluster. It was created using data from the Hubble Space Telescope, the Galaxy Evolution Explorer (in ultraviolet light), the Spitzer Space Telescope (in infrared) and the Chandra X-ray Observatory. In particular, the Chandra data revealed a number of bright X-ray sources in Cartwheel that possibly indicate the presence of stellar black holes. This is not surprising in a region that is alive with the formation of massive stars that quickly die as supernovae. Cartwheel Galaxy in visible light, X-rays and UV light. Courtesy NASA/ESA/STSci, Chandra Ray Observatory, GALEX. It is likely that Cartwheel will come for more studies with both ground-based and ground-based observatories, specifically JWST. It is a dynamic scene of galaxy evolution that astronomers can use to learn more about the physics and astrophysics of galactic mergers and encounters.
For more information
Cartwheel Galaxy Area The Hubble Wheel Webb records stellar gymnastics in the Cartwheel galaxy
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