This NASA/ESA Hubble Space Telescope image of a vibrant spiral galaxy called NGC 5042 resides about 48 million light-years from Earth in the constellation Hydra (the water snake). The galaxy nicely fills the frame of this Hubble image, while a single, foreground star from the Milky Way shines with cross-shaped diffraction spikes near the galaxy’s edge toward the top, center of the image.
Hubble observed NGC 5042 in six wavelength bands from the ultraviolet to infrared to create this multicolored portrait. The galaxy’s cream-colored center is packed with ancient stars, and the galaxy’s spiral arms are decorated with patches of young, blue stars. The elongated yellow-orange objects scattered around the image are background galaxies far more distant than NGC 5042.
Perhaps NGC 5042’s most striking feature is its collection of brilliant pink gas clouds studded throughout its spiral arms. These flashy clouds are H II (pronounced “H-two” or hydrogen-two) regions, and they get their distinctive color from hydrogen atoms that were ionized by ultraviolet light. If you look closely at this image, you’ll see that many of these reddish clouds are associated with clumps of blue stars, often appearing to form a shell around the stars.
H II regions arise in expansive clouds of hydrogen gas, and only hot and massive stars produce enough high-energy, ultraviolet light to create a H II region. Because the stars capable of creating H II regions only live for a few million years — just a blink of an eye in galactic terms — this image represents a fleeting snapshot of this galaxy.
