Photos Looking Down
Simply put, the smaller the black hole, the more regularly it gets backed up with hot, X-ray-emitting gases. So by measuring the "quasi-periodic oscillations" (QPOs) of black hole X-rays, they can work out the size of the disk, and therefore the size of the black hole. The researchers used archived X-ray data of QPOs to test their method on 15 known black holes. The method worked like a charm, and gave their current mini-hole measurement a lot of weight. "I was especially intrigued when I heard their result," said black hole researcher Vicky Kalogera from Northwestern University. Past attempts to find the smallest black holes had large error bars, which made them hard to trust. The QPO method appears to be far more precise, she said. Kalogera hopes the new method will turn up more small black holes and solve another puzzle: why theory predicts many small black holes while observations have turned up very few. "I would be very interested to see what else we see in coming years and how the sample size changes as a result of this method," said Kalogera. Related Links: Larry O'Hanlon's blog: Earth Impacts |
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