Hot Binary Star System AB7 in Nearby Small Magellanic Cloud Galaxy | ESO

Hot Binary Star System AB7 in Nearby Small Magellanic Cloud Galaxy | ESO

AB7, also known as SMC WR7, is a binary star in the Small Magellanic Cloud, a satellite galaxy of the Milky Way. A Wolf–Rayet star and a supergiant companion of spectral type O orbit in a period of 19.56 days. The system is surrounded by a ring-shaped nebula known as a bubble nebula.

Distance from Earth: ~180,000 light years

AB7 is a binary star, consisting of one WR-star—highly evolved massive star-and a mid-age massive companion of spectral type O. These exceptional stars have very strong stellar winds: they continuously eject energetic particles—like the "solar wind" from the Sun—around 10 to 1,000 million times more intensely than our star. These powerful winds exert an enormous pressure on the surrounding interstellar material and forcefully shape those clouds into "bubbles", well visible in the photos by their blue color. AB7 is particularly remarkable: the associated huge nebula and HeII region indicate that this star is one of the, if not the, hottest WR-star known so far, with a surface temperature in excess of 120,000 degrees! Just outside this nebula, a small network of green filaments is visible—they are the remains of another supernova explosion.

Credit: European Southern Observatory (ESO)
Release Date: April 9, 2003

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