Free Astronomy Magazine March-April 2016

SPACE CHRONICLES the highest con- centrations of massive, lumi- nous stars in the entire Milky Way — a spectacular family of young, bright, white- blue stars. These stars are rapidly working their way through their vast sup- plies of hydro- gen, and have only a few mil- lion years of life left before they meet a dramatic demise and ex- plode as superno- vae. In the mean- time, despite their youth, these stars aremaking a huge impact on their environment. They are literally making waves! As the stars fling out high-speed particles from their surfaces, strong winds surge out into space. These winds collide with the surrounding material, causing shock waves that heat the gas to millions of degrees and trigger intense bursts of X-rays. These strong stellar winds also carve out cavities in nearby clouds of gas and dust, and kickstart the formation of new stars. T his short sequence zooms in on the open young cluster of stars, Trumpler 14. [ESO, DSS, ESA/Hubble, Risinger (sky- survey.org)] T his colour-compo- site image of the Carina Nebula, made by the MPG/ESO 2.2- metre telescope at La Silla, Chile, reveals ex- quisite details in the stars and dust of the region. The open star cluster Trumpler 14, a collection of very bright, young stars within the Carina Neb- ula, is marked with a red circle. Several more well known astronom- ical objects can be seen in this wide field image: to the bottom left of the image is one of the most im- pressive binary stars in the Universe, Eta Cari- nae, with the famous Keyhole Nebula just adjacent to the star. A second open star cluster, Collinder 228 is also seen in the image, just below Eta Carinae. [ESO] The peculiar arc-shaped cloud visible at the very bottom of the (previous page) image is suspected to be the result of such a wind. That feature is thought to be a bow shock created by the wind flowing from the near- by star Trumpler 14 MJ 218. Astronomers have observed this star to be moving through space at some 350,000 kilometres per hour, sculpt- ing the sur- r o u n d i n g clumps of gas and dust as it does so. Astronomers estimate that around 2000 stars reside within Trum- pler 14, rang- ing in size from less than one tenth to up to several tens of times the mass of the Sun. The most prominent star in Trumpler 14, and the brightest star in the image, is the supergiant HD 93129Aa. It is one of the most bril- liant and hottest stars in our entire galaxy. HD 93129Aa is part of the binary star system HD 93129AaAb consisting of HD 93129Aa and HD 93129Ab. HD 93129Aa is an O-type star that is approximately two and a half million times brighter than the Sun, and has a mass 80 times great- er. It forms a close binary with an- other massive star within the open cluster, meaning that the two orbit around a shared centre of mass. With a surface temperature of over 50,000 degrees, HD 93129Aa is one of the hottest O-type stars in the en- tire Milky Way. n