What we as a race seem to know and don’t casts serious doubt on whether we’ll survive – or whether we deserve to. And we don’t mean the big questions, the fundamental quest for existence, we’re talking about things we already technically know and how many people actually know them. For example: far more people know the cast list for this season’s Dancing With The Stars than the fact the Milky Way itself has mini-galaxies orbiting it. That’s terrifying.
Yes, the entire Milky Way has mini-moon-a-likes, tiny galaxies like the Magellanic Clouds and the Ursa Majors. There’s even the Fornax Dwarf. Which sounds like it should have a hundred hitpoints and a 3d6 attack. All told there are almost a dozen dwarf galaxies orbiting our own, collections of stars whose centers of gravity describe paths around the Milky Way core, and now some scientists say there’s one more.
Researchers at the University of California computer-modeled perturbations to the gases at the edges of our solar system, accounting for known effects, and found that one more mass is needed to explain their observations – like working out the moon exists by examining the tides. This strategy is well known; it’s how early astronomers found out where to look for Neptune, examining wobbles in the orbits of other planets.
But it’s not a perfect system. The missing satellite would need to be 1% the size of our home galaxy, and ten billion stars is a pretty hard thing to miss. It’s important to match mathematical predictions against observable evidence, and even then you can go wrong. Similar orbital “perturbations” to those that located Neptune were used to predict Pluto’s location, and were later found to be mistakes. For years we had a rather small rock that happened to be in the right (or rather wrong) place classified as a planet.
The satellite’s immense invisibility could be because of it’s location in the plane of the galaxy: instead of conveniently swinging far “above” or “below” the galactic discs as the other satellites are considerate enough to do, the missing mass is predicted to be on the other side of the Milky Way. Meaning we have the entirety of almost every local star in the sky between us and it, and if it’s made up of old or burned-out stars it won’t emit enough light for detection until it orbits round to our side again. Which’ll be a job for our great-great-great-greatest-to-the-nth-degree descendants to detect.
The result? Another awesome idea which requires more evidence – but when your day job is detecting hidden galaxies, you’ll never sit at your desk cursing TPS reports.
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