In the middle of the twentieth century, an unusual star was spotted in the constellation of Canes Venatici (Latin for "hunting dogs"). Years later, astronomers determined that this object, dubbed AM Canum Venaticorum (or, AM CVn, for short), was, in fact, two stars. These stars revolve around each other every 18 minutes, and are predicted to generate gravitational waves - ripples in space-time predicted by Einstein.
These images of the planetary nebula Abell 30, (a.k.a. A30), show one of the clearest views ever obtained of a special phase of evolution for these objects. The inset image on the right is a close-up view of A30 showing X-ray data from NASA's Chandra X-ray Observatory in purple and Hubble Space Telescope (HST) data showing optical emission from oxygen ions in orange. On the left is a larger view showing optical and X-ray data from the Kitt Peak National Observatory and ESA's XMM-Newton, respectively. In this image the optical data show emission from oxygen (orange) and hydrogen (green and blue), and X-ray emission is colored purple.
A planetary nebula - so called because it looks like a planet when viewed with a small telescope - is formed in the late stage of the evolution of a sun-like star.
This gallery shows four planetary nebulas from the first systematic survey of such objects in the solar neighborhood made with NASA's Chandra X-ray Observatory. The planetary nebulas shown here are NGC 6543, also known as the Cat's Eye, NGC 7662, NGC 7009 and NGC 6826. In each case, X-ray emission from Chandra is colored purple and optical emission from the Hubble Space Telescope is colored red, green and blue.
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