26 November 2013

Birth of black hole witnessed, marking watershed moment for astronomy

The virtual impossibility of observational astronomy has never been clearer. With astronomers having recorded so many events, now that they’ve used so many different instruments to wring all possible insight from what little information somehow makes it all the way to Earth, simply pointing telescopes at stars is providing diminishing returns. To keep moving forward we need to make use of the universe’s most unusual and, in many cases, violent events so we can see some truly novel data. It’s not just a matter of patience, since the the space industry can’t possibly set up enough telescopes to look everywhere at once. With so much depth through which to zoom, it would seem a lost cause to try to capture unexpected, short-lived events.

And yet, this week a momentous event occurred somewhere in the universe, now dubbed GRB 130427A, and an “armada of instruments” from all over the world saw it produce a gamma ray burst more powerful than what many researchers believed theoretically possible. Now thought to be the collapse of a giant star and the birth of a black hole, the event has been described as a “Rosetta stone moment” for astronomy. It has sent out information astronomers will be studying for many years to come, and while it’s too soon to draw any real conclusions, there is already widespread excitement about the sheer newness of it.

And yet, GRB 130427A only lasted about 80 seconds at observable intensities; with so much empty space to trawl, how did astronomers manage to notice the event at all, let alone document it so thoroughly? The answer lies in New Mexico, at the Los Alamos National Laboratories, in the form of six robotic cameras collectively referred to as RAPTOR, or RAPid Telescopes for Optical Response. The RAPTOR telescopes are networked together and all obey a central computer brain; between their dedicated computing hardware and robotic swivel-mounts, they can turn to view any point in the sky in less than three seconds.

As the world’s fastest “optical response” devices, RAPTOR’s telescopes have a great duty: to make sure we don’t miss the big stuff when it happens, because in astronomy there are no second chances. This gamma ray burst is thought to be the brightest in decades, perhaps in a century, and if astronomers had missed it, it’s likely that nobody working today would have gotten the chance to capture one again.

They accomplish their goal by performing extremely diffuse, wide-angle sweeps of the sky to pick up hints at about where and when a major event is taking place. When one of the telescopes sees a hint of something good, it and the others quickly reorient and zoom to capture it in full detail. The telescopes have different specializations — for instance RAPTOR-T, which views all events through four aligned lenses with four different color filters. By looking at the differences in color distribution in the sample, RAPTOR-T can provide info about the distance to an event or about some elements of its environment.

However, the event was also seen by a number of other instruments, gamma ray detectors and x-ray telescopes that are much more sluggish than RAPTOR. NASA’s Fermi, NuSTAR, and Swift satellites managed to see some portion of the event as it unfolded, but most telescopes joined in to view the event’s so-called afterglow. This was an incredibly violent happening, and it threw out debris and damage over a wide radius; for several hours, that radius glowed and astronomers watched as it faded.

The intensity of high-energy gamma rays in that afterglow faded in tandem with its conventional light emissions. That’s the first such link astronomers have found between gamma rays and optical phenomena. That’s just one way it could be astronomy’s latest Rosetta Stone observation. Look forward to a slew of exciting updates over the next several months, as astronomers sort through the implications of having witnessed the birth of an unprecedented singularity.

Now read: Sleeping Supermassive Black Holes Can Have Periods Of Intense Flare-Ups


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