Stellar Evolution: A Journey with Chandra

Three new images were recently added to the "Chandra X-ray Observatory" set on the Smithsonian Flickr Commons stream. Below, Kim Kowal Arcand, from the Education & Public Outreach group for the Chandra X-ray Observatory, explains the origins of these images. As noted on the Chandra site, the "flight operations, mission planning, data processing and user support for the Chandra mission are carried out by the Chandra X-ray Center at the Smithsonian Astrophysical Observatory (SAO) in Cambridge, Massachusetts." The Chandra X-ray Center is part of a NASA initiative to make its space programs more efficient by encouraging expert teams located outside NASA centers to assume expanded responsibilities.

When the Universe came into existence about 14 billion years ago, the only elements were hydrogen, helium, and traces of lithium, beryllium, and boron. The heavier elements did not yet exist. Heavy elements are produced by nucleosynthesis--the fusion of nuclei deep within the cores of stars. At some point in time, the first stars were formed, and within their cores the fusion process created heavier and heavier elements; the most massive stars produced nuclei as heavy as iron. When the stars used up their nuclear fuel, they started to evolve.

The evolutionary processes of stars depend upon their initial mass. Mid-sized stars eject planetary nebulae, leaving a white dwarf core remnant. More massive stars explode as supernovae, leaving neutron stars or black holes at the centers of the supernovae remnants. The elements that were created within the cores of the first stars were ejected into space where they intermingled with the surrounding interstellar medium. This medium--the gas and dust between the stars--provides the raw material for the formation of new generations of stars. Eventually, these elements became incorporated into large clouds of gas and dust that condensed and formed protostars. And so the cycle of stellar formation (see 30 Doradus) and destruction (see RCW 86 and G350.1+0.3) continues--each new generation further enriching the interstellar medium with heavy elements that become incorporated into the next generation. We are just beginning to understand stellar formation and destruction--and how the Sun, Solar System and life on Earth are connected to this never-ending cycle.

For a more complete picture of this journey, visit the Chandra X-ray Observatory's Field Guide to X-ray Astronomy: Stellar Evolution. 

Discover more Chandra X-ray Observatory images on the Smithsonian Flickr Commons.