Sky's Up July-September 2017 - Page 8

Looks can be deceiving 8 PrECisiON MOtiON CONtrOller T he Final Frontier, Looking as Star Trek fans christened the realms For ET beyond Earth, appears as a vast, quiescent, landscape. Sure, solar system bodies –the frequent targets of amateur astronomers – slide around the sky. But only slowly. You can watch the moons of Jupiter orbit their gassy master, but it takes an hour or more by Seth The slow-motion to see much change Shostak gait of the heavens in position. And yes, during a solar eclipse led our ancestors or a stellar occultation, it’s possible to assume that to witness in real time the relentless of the moon around our planet. the universe was parade But again, it’s poky. unchanging, an idea The slow-motion gait of the heavens that was probably led our ancestors to assume that the universe was unchanging, an idea that bolstered by the was probably bolstered by the fact that fact that the night the night sky is silent. We instinctively that if there’s no noise, there’s no sky is silent. We sense action. instinctively sense But it’s all an illusion, of course. The that if there’s no universe is no more static than the continents. Everyone who’s ever taken noise, there’s no an astronomy course knows there’s action. But it’s all an plenty of systematic change, as space expands and galaxies appear to recede. illusion, of course. Important, but slow. However, in the limited confines of stellar systems, sudden and violent dramas can occur. And occasionally do. In October 1604, a new star (or nova) appeared in the constellation Ophiuchus. This was the topic of polite dinner conversation in Europe for weeks, as no one had either expectation of, nor explanation for, this strange light in the sky. It was as wondrous as a new comet. However, even a nova – a star that dramatically brightens – takes many hours to do its thing. Today, we know there is far faster action above our heads. For example, black holes not only form, but occasionally collide. Such exotic 8 head-ons seem to be the cause of the several gravitational wave events detected by the Laser Interferometer Gravitational-Wave Observatory. The time it takes black-hole pairs to merge is no more than an eye blink – a few tenths of a second. The impact ripples space, and eventually, after billions of years, shakes the mirrors of LIGO. An entirely new type of transient object, Fast Radio Bursters (FRBs), was found by radio astronomers only a decade ago. They belch powerful radio blasts into space and last less than a second. While no one knows for sure what causes these brief eruptions, they too could be manifestations of colliding neutron stars or black holes. We are often surprised by such celestial “bumps in the night.” This is probably because we don’t expect anything that’s big – and much of the stuff in the cosmos is big – to change very quickly. It’s also true that historically, a lot of observational astronomy has had to deal with the faintness of stars and nebulae by means of time exposures. If your camera shutt