For those who want a bit more details in a fairly accessible format there was a recent and IMHO interesting talk[1] at Perimeter Institute about these results from one of the founders of NANOGrav.
The NANOGrav collaboration behind these results was using the Arecibo telescope as one of their primary data sources. Due to the extremely low frequencies involved, they relied on data over many years to reduce noise. Here's what they said before it fell apart[2]:
Many of these pulsars can be timed only with Arecibo thanks to its incredible sensitivity. NANOGrav’s most recent analyses show that a detection of gravitational waves is likely imminent. Any gap longer than several months in our 16 years of data will impede our ability to characterize the low-frequency gravitational-wave universe and carry out the associated multi-messenger science. It will also likely add systematics to our datasets that will make them more difficult to model. If Arecibo wasn’t repaired, its loss would be a disaster for both US gravitational-wave and radio astronomy.
They made a follow-up statement after the loss[3], so it's not a fatal blow but definitely a tough loss:
While our future sensitivity to gravitational waves will decrease without Arecibo, legacy Arecibo observations will anchor combined future datasets which will be integral to opening this new window on the universe at low frequency gravitational waves and to gleaning insights into how galaxies form and evolve.
Although the article reads as sensational, it is actually based on three recently accepted papers in Physical Review Letters. It also gives some insight into several research groups wanting to claim being the first having seen evidence for new physics, be it from sparse observational data.
"Last September, the collaboration posted a paper on the preprint server arXiv.org, which hosts scientific articles that have yet to go through peer review, showing that its monitored pulsars all displayed similar blips. (The paper has since been peer-reviewed and published.)"
Yeah. One would thought they would lead with the peer-reviewed publications rather than preprints.
I believe you misinterpret the article. Physicists on earth are using small timing fluctuations in the radiation arriving from multiple far-flung pulsars to try and detect gravitational waves. This is what is meant by a galaxy-sized gravitational wave detector.
People aren't on Hacker News for the jokes, and a significant fraction don't like seeing threads hijacked by silliness. We've all seen Reddit, and are choosing not to be there for a reason.
That's not to say that you can't get away with jokes here. But the bar for them to work is very high.
The detector could just be the entire galaxy, it doesn't have to be an artificial construct.
To your question, you have already seen it, hiding in plain sight.
Space is awfully big though - the actual structure presumably would be detectable with hindsight but these galaxies are an unbelievably long way away and a detector would presumably be thin on that scale.
The NANOGrav collaboration behind these results was using the Arecibo telescope as one of their primary data sources. Due to the extremely low frequencies involved, they relied on data over many years to reduce noise. Here's what they said before it fell apart[2]:
Many of these pulsars can be timed only with Arecibo thanks to its incredible sensitivity. NANOGrav’s most recent analyses show that a detection of gravitational waves is likely imminent. Any gap longer than several months in our 16 years of data will impede our ability to characterize the low-frequency gravitational-wave universe and carry out the associated multi-messenger science. It will also likely add systematics to our datasets that will make them more difficult to model. If Arecibo wasn’t repaired, its loss would be a disaster for both US gravitational-wave and radio astronomy.
They made a follow-up statement after the loss[3], so it's not a fatal blow but definitely a tough loss:
While our future sensitivity to gravitational waves will decrease without Arecibo, legacy Arecibo observations will anchor combined future datasets which will be integral to opening this new window on the universe at low frequency gravitational waves and to gleaning insights into how galaxies form and evolve.
[1]: http://pirsa.org/20100068
[2]: http://nanograv.org/announcement,/press/2020/08/19/Arecibo.h...
[3]: http://nanograv.org/announcement,/press/2020/12/02/Arecibo.h...