Free Astronomy Magazine November-December 2024

23 NOVEMBER-DECEMBER 2024 ence Foundation Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF NOIRLab. Located in the constellation Monoc- eros (the Unicorn), the Rosette Neb- ula spans 1.3 degrees of sky, roughly the width of an index finger held out at arm’s length. For comparison, the well-known Orion Nebula, lo- cated in the constellation Orion just below the hunter’s belt, spans one degree of sky. Although the Rosette Nebula has a diameter of 130 light- years — more than five times as large as the Orion Nebula — their apparent sizes are similar because the former is four times as distant. As prominent as the nebula’s ‘petals’ is the conspicuous absence of gas at its center. The culprits responsible for excavating this hollow core are the most massive stars of NGC 2244 — the open star cluster nurtured by the nebula. This cluster was born around two million years ago after the nebula’s gasses coalesced into clumps brought together by their mutual gravity. Eventually, some clumps grew to be massive stars that produce stellar winds powerful enough to bore a hole in the neb- ula’s heart. NGC 2244’s massive stars also emit ultraviolet radiation, which ionizes the surrounding hydrogen gas and lights up the nebula in an array of brilliant colors. The billowing red clouds are regions of H-alpha emis- sion, resulting from highly ener- gized hydrogen atoms emitting red light. Along the walls of the central cavity, closer to the mas- sive central stars, the radiation is energetic enough to ionize a heavier atom like oxygen, which glows in shades of gold and yel- low. Finally, along the edges of the flower’s petals are wispy tendrils of deep pink glowing from the light emitted by ion- ized silicon. T he Rosette Nebula, as seen by DECam, presented as a video. [CTIO/NOIRLab/DOE/ NSF/AURA/N. Bartmann/T. Slovinský − Image Processing: T.A. Rector (University of Alaska Anchorage/NSF NOIR- Lab), D. de Martin & M. Za- mani (NSF NOIRLab) − Music: Stellardrone - Airglow] ASTRO PUBLISHING