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Hubble Images a Grand Spiral

This NASA/ESA Hubble Space Telescope image features the spiral galaxy NGC 5643.

ESA/Hubble & NASA, A. Riess, D. Thilker, D. De Martin (ESA/Hubble), M. Zamani (ESA/Hubble)

This NASA/ESA Hubble Space Telescope image features the glorious spiral galaxy NGC 5643, which is located roughly 40 million light-years away in the constellation Lupus, the Wolf. NGC 5643 is a grand design spiral, which refers to the galaxy’s symmetrical form with two large, winding spiral arms that are clearly visible. Bright-blue stars define the galaxy’s spiral arms, along with 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 disk 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 unknown, 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 disk that outshines the NGC 5643’s galactic core.

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