July 29, 2018

NGC 6193 and 6188 in Ara (Spring & Summer 2018)


Here is a beautiful region of the constellation Ara in the southern hemisphere.  Near the top is star cluster NGC 6193.  The cluster is dominated by what look like two bright stars.  The lower star is HD 150135, an O-type star that burns very hot and is much larger than our sun.  The upper, brighter star of the two, however, HD 150136, is special.  HD 150136 is a triple system of O-type stars with masses of 62.6 ± 10, 39.5 ± 6.3, and 33 ± 12 solar masses, for a total of 102 ± 16 solar masses.  Source.  That's a big star.  Moreover, the two larger components are in a close orbit of 2.67454 days.  Same source.  That's so close the stars must be almost touching.  It's no wonder they generate fireworks, including X-rays.  The system generates enough UV radiation to light up this cloud, NGC 6188, including the ionization front shown in this image.

Data for this image comes from the 12.5 RCOS system in New South Wales.

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