Galactic Hook

Credit: NASA and ESA

The Uni­verse seems to mar­vel in the weird. A hook, like a cos­mic ques­tion mark, makes NGC 4696 stand out from its more shape­less ellip­ti­cal galax­ies in this image from NASA’s Hub­ble Space Telescope.

Explore NGC 4696 start­ing with the unusual hook, or ques­tion mark shaped thread of dust. Astronomers see dust lanes in spi­ral galax­ies. Ellip­ti­cal galax­ies, how­ever, are usu­ally globs of aging stars look­ing like bright halos. Ellip­ti­cal galax­ies likely form from the merg­ing of spi­ral galax­ies. The com­press­ing and stretch­ing of gas and dust causes a brief burst of star for­ma­tion. The gas and dust run out quickly though and with no new mate­r­ial, ellip­ti­cal galax­ies grow older and more faint.

What makes NGC 4696 so dif­fer­ent is the huge dust lane, stretch­ing 30,000 light-years across the galaxy’s bright core. At cer­tain wave­lengths of light, thin fil­a­ments of hydro­gen gas give the galaxy a mar­bled effect. Stranger still is what we can­not see in this Hub­ble image. Using NASA’s orbit­ing Chan­dra X-ray Obser­va­tory, astronomers see jets of mate­r­ial blast­ing away from the core of the galaxy at nearly the speed of light indi­cat­ing a super­mas­sive black hole lurks in the cen­ter of this odd galaxy.

As we explore far­ther from the cen­ter of NGC 4699, beyond the haze of its dis­tant stars, we see a myr­iad of back­ground galax­ies. Those dis­tant galax­ies, of all shapes and sizes, offer astronomers a his­tory les­son in how galax­ies are made.

NGC 4699 is the largest galaxy in the Cen­tau­rus Clus­ter, a huge group of galax­ies about 150 mil­lion light-years away.