September '19: The latest in ph-word
So, in this rather uneventful month, a few astrophysical happenings shared the (dim) limelight. Probably the most interesting one was the detection of a comet coming from outside the solar system. This is only the second ever object from outside our 'hood that gets observed (after asteroid Oumuamua two years ago). And this time is even better, because "Borisov" is still in the beginning of its entry into the solar system. So there will be the opportunity to observe it for several months as it curves around the sun and to get up close and personal with the chemical composition of other stellar systems.
Moving further out, there are not only stellar systems but now we also have stellar threads. Some hundreds groups of stars, i.e. large numbers of stars moving together, were found to be spread in long strings across the Milky Way. This is probably because of each group having being created from the same shred of hydrogen cloud. Funnily, the younger threads seem to follow the spiral arms of the Milky Way, but they are also perpendicular to them. The older threads seem to be aligned too ... but not following anything. This could simply mean that the spiral arms used to have a different orientation, and looking more closely at the older starry stringlights could tell us a thing or two about our galaxy's past.
And moving even further out, it was found that within a few months six galaxies turned into quasars, i.e. the black holes at their centres became tremendously active, spewing their notorious colossal spinning jets that can be seen billions of light-years away. Six is an impressive number given that so far astronomers had observed no galaxies turning into quasars so abruptly and they thought that it takes a long long time. But all this probably just attests to the capabilities of the involved Zwicky Transient Facility, an observation plan at Palomar observatory that started two years ago and is targeted at cosmic objects that undergo rapid changes.