Credit: CTIO/NOIRLab/SOAR/NSF/AURA Image processing: T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab) & D. de Martin (NSF NOIRLab)

Orbiting around the Milky Way about 210,000 light-years away is the Small Magellanic Cloud (SMC). This satellite galaxy is a dwarf galaxy, about a twentieth the size of our own galaxy. Sitting among its hundred million stars is a 'bauble' of hydrogen gas, captured here with the 4.1-meter Southern Astrophysical Research (SOAR) Telescope, one of the telescopes at Cerro Tololo Inter-American Observatory (CTIO), operated by NSF NOIRLab. This HII (pronounced H two) region is a cloud ripe with star formation. Young, hot, blue stars formed from the material in the molecular cloud, and now emit highly energetic ultraviolet radiation. The photons of the radiation field bombard the remaining hydrogen gas with energy that ionizes the atoms, or, in other words, excites them to a higher energy level. Astronomers use the term HII to refer to this ionized state of the hydrogen. Ionized hydrogen emits light at a specific wavelength called H-alpha. For researchers down on Earth, this wavelength is a unique identity marker for ionized hydrogen, and is responsible for the characteristic red color of HII regions.

Provider: NOIRLab

Image Source: https://noirlab.edu/public/images/iotw2350a/

Curator: NSF's NOIRLab, Tucson, AZ, USA

Image Use Policy: Creative Commons Attribution 4.0 International License