The Very Large Telescope’s GRAVITY instrument is online and already gathering data from the extreme environment surrounding our galaxy’s supermassive black hole, Sagittarius A S2’s orbit is the epitome of extreme. In 2018, the star will reach the closest part of its 16-year journey around Sagittarius A*, coming as close as 17 light-hours of the black hole’s event horizon. At this point, the star will be traveling 30 million kilometers per hour, that’s 2.5 percent the speed of light. This makes S2 the perfect tracer for astronomers using GRAVITY to measure its position to extreme precision to check whether its

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