Pan: NGC 5643

Today’s NASA/ESA Hubble Space Telescope Picture of the Week features the glorious spiral galaxy NGC 5643, which is located roughly 40 million light-years away in the constellation Lupus. NGC 5643 is what’s known as a grand design spiral, referring to how the galaxy’s two large, winding spiral arms are clear to see. The spiral arms are defined by bright blue stars, lacy reddish-brown dust clouds and pink star-forming regions.

As fascinating as the galaxy appears at visible wavelengths, some of NGC 5643’s most interesting features are invisible to the human eye. Ultraviolet and X-ray images and spectra of NGC 5643 show that the galaxy hosts an active galactic nucleus: an especially bright galactic core powered by a feasting supermassive black hole. When a supermassive black hole ensnares gas from its surroundings, the gas collects in a disc that heats up to hundreds of thousands of degrees. The superheated gas shines brightly across the electromagnetic spectrum, but especially at X-ray wavelengths.

NGC 5643’s active galactic nucleus isn’t the brightest source of X-rays in the galaxy, though. Researchers using ESA’s XMM-Newton discovered an even brighter X-ray-emitting object, called NGC 5643 X-1, on the galaxy’s outskirts. What could be a more powerful source of X-rays than a supermassive black hole? Surprisingly, the answer appears to be a much smaller black hole! While the exact identity of NGC 5643 X-1 is not yet known, evidence points to a black hole that is about 30 times more massive than the Sun. Locked in an orbital dance with a companion star, the black hole ensnares gas from its stellar companion, creating a superheated disc that outshines the galactic centre.

NGC 5643 was also the subject of a previous Picture of the Week. The new image incorporates additional wavelengths of light, including the red color that is characteristic of gas heated by massive young stars.