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Another Large Black Hole In 'Our' Galaxy

3 months 1 week ago
RockDoctor (Slashdot reader #15,477) writes: A recent paper on ArXiv reports a novel idea about the central regions of "our" galaxy. Remember the hoopla a few years ago about radio-astronomical observations producing an "image" of our central black hole — or rather, an image of the accretion disc around the black hole — long designated by astronomers as "Sagittarius A*" (or SGR-A*)? If you remember the image published then, one thing should be striking — it's not very symmetrical. If you think about viewing a spinning object, then you'd expect to see something with a "mirror" symmetry plane where we would see the rotation axis (if someone had marked it). If anything, that published image has three bright spots on a fainter ring. And the spots are not even approximately the same brightness. This paper suggests that the image we see is the result of the light (radio waves) from SGR-A* being "lensed" by another black hole, near (but not quite on) the line of sight between SGR-A* and us. By various modelling approaches, they then refine this idea to a "best-fit" of a black hole with mass around 1000 times the Sun, orbiting between the distance of the closest-observed star to SGR-A* ("S2" — most imaginative name, ever!), and around 10 times that distance. That's far enough to make a strong interaction with "S2" unlikely within the lifetime of S2 before it's accretion onto SGR-A*.) The region around SGR-A* is crowded. Within 25 parsecs (~80 light years, the distance to Regulus [in the constellation Leo] or Merak [in the Great Bear]) there is around 4 times more mass in several millions of "normal" stars than in the SGR-A* black hole. Finding a large (not "super massive") black hole in such a concentration of matter shouldn't surprise anyone. This proposed black hole is larger than anything which has been detected by gravitational waves (yet) ; but not immensely larger — only a factor of 15 or so. (The authors also anticipate the "what about these big black holes spiralling together?" question : quote "and the amplitude of gravitational waves generated by the binary black holes is negligible.") Being so close to SGR-A*, the proposed black hole is likely to be moving rapidly across our line of sight. At the distance of "S2" it's orbital period would be around 26 years (but the "new" black hole is probably further out than than that). Which might be an explanation for some of the variability and "flickering" reported for SGR-A* ever since it's discovery. As always, more observations are needed. Which, for SGR-A* are frequently being taken, so improving (or ruling out) this explanation should happen fairly quickly. But it's a very interesting, and fun, idea.

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EditorDavid

Representative Line: The Rounding Error

3 months 1 week ago

At one point, someone noticed that some financial transactions weren't summing up correctly in the C# application Nancy supported. It didn't require Superman or a Peter Gibbons to figure out why: someone was using floating points for handling dollar amounts.

That kicked off a big refactoring project to replace the usage of double types with decimal types. Everything seemed to go well, at least until there was a network hiccup and the application couldn't connect to the database. Let's see if you can figure out what happened:

MessageBox.Show("Please decimal check the connection details. Also check firewall settings (port 1433) and network connectivity.");

What a clbuttic mistake.

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Remy Porter

'Fish Doorbell' Enters Fifth Year with Millions of Fans

3 months 1 week ago
Long-time Slashdot reader invisik reminds us that the "fish doorbell" is still going strong, according to the Associated Press. "Now in its fifth year, the site has attracted millions of viewers from around the world with its quirky mix of slow TV and ecological activism." The central Dutch city of Utrecht installed a "fish doorbell" on a river lock that lets viewers of an online livestream alert authorities to fish being held up as they make their springtime migration to shallow spawning grounds. The idea is simple: An underwater camera at Utrecht's Weerdsluis lock sends live footage to a website. When somebody watching the site sees a fish, they can click a button that sends a screenshot to organizers. When they see enough fish, they alert a water worker who opens the lock to let the fish swim through. "Much of the time, the screen is just a murky green with occasional bubbles, but sometimes a fish swims past. As the water warms up, more fish show up..."

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EditorDavid