Cartwheels in the sky

Credit: ESA/Hub­ble & NASA

Vio­lent col­li­sions cause this galaxy to do a cart­wheel in this image from the NASA/ESA Hub­ble Space Telescope.

Explore this image of the Cart­wheel Galaxy on the right. What other shapes and sto­ries do you see in this Hub­ble image? Leave a note below.

Astronomers believe that in the past, the Cart­wheel Galaxy was a large spi­ral galaxy just like the Milky Way. A smaller galaxy, per­haps one of the two galax­ies seen in the image, passed right through the larger Cart­wheel Galaxy. Shock­waves sent rip­ples through­out the galaxy sweep­ing up dust and gas. This grav­i­ta­tional tug-of-war causes a burst of star birth. As you start in the cen­ter of the Cart­wheel Galaxy, notice the older, yellow-colored stars. Thick lay­ers of dust make the stars red­der in this region. As you move out to the large outer ring, fol­low the faint spokes. Arriv­ing in the outer ring, the stars turn to blue, indi­cat­ing they are young. The out­er­most ring is more than 1.5 times the size of our Milky Way Galaxy. Astronomers call this a ring galaxy.

Although galax­ies do merge and inter­act, no stars col­lide in the process. The dis­tances between stars is great. Clouds of gas and dust do push into each other cre­at­ing new stars. And the immense grav­ity of galax­ies can fling spi­ral arms into long tails.

One of the smaller galax­ies shows a burst of new star for­ma­tion too but sci­en­tists can­not tell whether this is the galaxy that dis­rupted the Cartwheel.

The Cart­wheel Galaxy lies about 500 mil­lion light-years from Earth toward the small south­ern con­stel­la­tion Sculp­tor. Sculp­tor is a “new” con­stel­la­tion. It was orig­i­nally charted by French astronomer Nico­las Louis de Lacaille in 1751–52. The Inter­na­tional Astro­nom­i­cal Union later adopted it as one of the 88 mod­ern con­stel­la­tions.