Added 1 new A* page:Just a few days after I wrote about a huge upcoming radio telescope in China, and some background on A*'s discovery through radio waves, there's more radio telescope news! I needed two different articles to get the picture, but basically, last year a 64m radio telescope in Australia, using new software that analyzed readings in real time specifically for this purpose, detected and identified a fast radio burst, or "FRB": a strong radio pulse, lasting just milliseconds, with a dispersed signal—just the sort of signal that scientists would expect a radio wave traveling through vast stretches of intergalactic space to have, because electrons out there interfere with the lower end of the signal, making it arrive just a bit after the higher frequency part of the signal.
This same telescope in Australia, the Parkes telescope, detected an FRB in 2001 that initiated a search for such signals; the problem was, they would not be noticed until analyzing the telescope's record, long after the burst had been received (that 2001 burst wasn't noticed until analysis in 2007!), making it hard if not impossible to triangulate the source of the burst by comparing its arrival times at other telescopes around the globe. But this past year, with special software lying in wait to catch an FRB signal instantly, other radio telescopes around the globe were alerted, and able to scan for the burst's afterglow—which lasted for six days—within hours. Comparing the difference in arrival times of the burst at different points on the globe allowed the source of the burst to be triangulated, and when checked with an optical telescope, a distant galaxy was found along that vector—and its redshift could be measured, giving its distance: 6 billion light years away.
Knowing the distance, and the dispersion of the signal, scientists could then calculate the density of electrons (and presumably, matter they're attached to) lying between our galaxy and the source galaxy—and this matter density measured up to the 4-5% ordinary matter density (the rest theorized to be unknown stuff dubbed "dark matter" and "dark energy") predicated by prevailing cosmological theory—which is a nice confirmation for proponents of those theories to have, because up until now, only about half of that matter had been visible to our telescopes. People were probably worried it wasn't going to show up! But thanks to swift thinking and action by radio telescope researchers, it's been found!
And fast radio burst science just got a big kick in the pants: there's now a new thing these radio telescopes can find in the sky! This burst is thought to have resulted from a collision of neutron stars (this theory is supported in part to the mere millisecond length of the burst, and because the elliptical source galaxy appears to be old, meaning you would have more stars in their final stages, like neutron stars (or black holes?)) rather than a supernova or something, but radio wave bursts probably come from all sorts of heavy events—maybe even 10,000 per day coming in from every direction. So that's quite a bit of heavy astronomy to see—not to mention all that previously unseen intergalactic material to map!—and we may see a fresh wave (no pun intended) of radio telescope science coming our way, even beyond the one that's already been shaping up with worldwide arrays aiming to analyze Sgr A*!
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