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LIGO Spots Another Gravitational Wave Soon After Powering Back On (newscientist.com)
New submitter nichogenius writes: The latest observation run of LIGO and VIRGO only started April 1st, but has already observed another black hole merger. The LIGO detectors have been offline since the 25th of August, 2017 for a series of upgrades. The latest observational run is the first run where gravitational wave events are being publicly announced as they happen rather than being announced weeks or months later. Few details of the merger are available at this time, but there is some information available on LIGO's twitter and raw details can be obtained from LIGO's event database page.
Gravitational detection events are being publicly broadcast using NASA's VOEvent system. If you know a bit of python, you can setup your own VOEvent client using the pygcn module with example code available in this tutorial.
Gravitational detection events are being publicly broadcast using NASA's VOEvent system. If you know a bit of python, you can setup your own VOEvent client using the pygcn module with example code available in this tutorial.
it is nice to see that machine back on and working. I would have liked a bit more background, what actually has changed during the upgrade. It seems that this contained only in a ``premium article" in the new scientist. Fortunately there are other sources where on can look things up: 40 percent more sensitive machine leading to twice the volume of space to be observable. Some main mirrors were replaced, the laser power increased and a technique called ``squeezing" introduced which counteracts the now stronger distortion of the beam. Also new is that detections of events are publicly announced as soon as they are available. Here is the source: https://news.stanford.edu/2019...
Really. That is what I read Slashdot comments for. Much appreciated.
overenthUsiastic
Because stars tend not to merge with each other, and thus they don't send out strong gravitational waves. As long as they radiate strongly, they would rather repulse each other than merge.
https://en.wikipedia.org/wiki/...
As a matter of fact, the very same LIGO let us see two neutron stars doing that exactly back in 2017.
On the other hand, as far as I'm aware, there are no conclusive observation of black holes, which makes for a much more spectacular headline.
And then there is another reason: You want events that send out gravitational waves with a frequency between 100 Hz and 3000 Hz, because that's where LIGO is sensitive. Thus you are confined in the mass of the objects whose gravitational events you can monitor. For other frequencies you either need much larger instruments (e.g. of the length of the Earth's diameter or even larger), or much higher resolutions for the measurements.
Neutron stars don't have a large radiation pressure. They are inactive stars. Yes, they accelerate stuff from their accredition disc, and thus they send out huge amounts of particles and synchrotron radiation, but only on their poles. But around their equator, they don't have any radiation pressure at all.
The physics of a collision of 30x stellar mass stars would be very different than for black holes, if only because stars have a (comparatively) large spatial extent, while the black holes are much more compact and, as a result, can get their masses much closer together before they merge. Compact masses getting close together creates 1) very strong gravitational disturbances and 2) very fast orbital speeds. Large stars can't get their masses close enough, and could not orbit each other fast enough, to be detectable by LIGO.
On the other hand, as far as I'm aware, there are no conclusive observation of black holes, which makes for a much more spectacular headline.
And by the way, as of an hour ago, that's not true anymore
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