That was for sure a month dominated by extreme astrophysical events: A black hole was photographed and the gravitational waves of no less than five collisions among black holes and neutron stars were recorded. (Also, black hole expert Kip Thorne comes here to Athens
in a few days, which only adds to the feeling.)
LIGO/Virgo - again
I’d bet you heard a hundred times already about the black hole photo, and we’ll come to this in a minute, but not about the LIGO/Virgo experiments’ detection of gravitational waves from five new “mergers”. There is a point to make here and to put it in context let me stress that five such events detected over the course of two years
were worth a Nobel prize. The fact that now five events recorded within a single month
don’t make headlines speaks volumes about the wild progress in the field.
One century ago waves of gravity were a dream that noone had dreamt; four years ago they crashed our reality with a bang; and today? they are mainstream. Sometimes it’s hard to believe all this was achieved by the same animal species that executes its own because of whom they choose to have sex with, but there you have it.
Not seeing is believing
So, esteemed reader, you might already know that the Event Horizon Telescope which took photos of a black hole in another galaxy was made up from eight telescopes spanning the globe, looking at the same patch of sky for a week two years ago and then painstakingly combining their data. Their combination resulted in a virtual telescope the size of earth; this is what it takes to start seeing that which is not there (and, also, which appears forty million times smaller than the moon).
But what do the famous first pictures of a black hole actually show?
The bright glow comes from material attracted by the hole, gathering and moving around it, its image appearing warped because of the hole’s gravity. The brighter-looking bottom half is swirling in our direction with speeds close to that of light.
The central dark part is neither the hole itself nor its “event horizon”, the infamous area from which nothing escapes. Instead, the dark part is the hole’s shadow, formed as its attraction bends the light from the glowing gas and it never comes our way.
Two points of note are that this shadow was indeed the expected result proving the hole’s presence (given that the Telescope was only capable of blurry vision so far), and that seeing the shadow depended on the angle that the hole would happen to rotate at with respect to earth.
The 'Scope has more in store. Data analysis is going on as we speak for its next promise, the image of Sagittarius A*, “our own” black hole sitting at the center of the Milky Way ...I think I can already hear the slow clap starting.
Let's turn to nuclear physics for a change
Fusion, the holy grail of nuclear power, the kind of reaction that could deliver boundless energy with no radioactive byproblems – fusion, as I was saying, was just given a small promising kick forward by a lab studying the insides of stars. In University of Washington folks found how to swirl plasma so that it stays stable for long enough for meaningfully long-lasting fusion to take place.
But what do stars' interiors have to do with this? They are made of plasma and this is where fusion happens. Now, plasma, it is matter where electrons swim freely among atoms instead of being tied up to individual ones. Even though exotic, it is routinely made in labs studying stellar interiors for some decades now.
Also, it is known that our precious fusion does
spark inside lab plasma, but there is always a problem: plasma is too difficult to stabilize and handle. To put it in context, now the swirling method kept it around for 16 millionths of a second, considered a phenomenal time length.
Incidentally, the field of fusion research has been plagued by exaggeration and fake claims over the decades, so this small piece of news might turn out to be long-awaited actual juice. Let's just wait and see if we get our personal fusion-fueled tabletop designer coffee makers in a few years :p