Archive for inspiral

A Decade of Gravitational Waves

Posted in Biographical, The Universe and Stuff with tags , , , , , , on September 14, 2025 by telescoper

This is just a quick post to mark the fact that it is now ten years to the day since the first detection of gravitational waves by Advanced LIGO. The acronym LIGO stands for Laser Interferometer Gravitational-wave Observatory, by the way. It wasn’t until February 11th 2016 that the result was announced at a press conference (which I blogged about here), but the signal itself arrived on 14th September 2015, exactly a decade ago; the name given to the event was GW150914.

Here are the plots for that first one:

LIGO

That first signal corresponded to the coalescence of two black holes, of masses 29 and 36 times the mass of the Sun and produced a large response in the detectors very soon after Advanced LIGO was switched on. There’s synchronicity for you! The LIGO collaboration have done wondrous things getting their sensitivity down to such a level that they can measure such a tiny effect, but there still has to be an event producing a signal to measure. Collisions of two such massive black holes are probably extremely rare so it’s a bit of good fortune that one happened just at the right time. Actually it was during an engineering test.

There have been many subsequent detections and even more candidates waiting to be confirmed- here’s a full list. The official LIGO site states there are 90 confirmed detections, the 4th observational run (O4) (which is due to end in November 2025) has already found 200 candidates. The latest compilation of gravitational-wave transient sources can be found here.

Most of the detections have been binary black hole mergers, but I particularly remember the excitement in 2017 surrounding the first merger of a neutron star with a black hole. It was fun that rumours started to spread via this blog as people outside the LIGO/transient source community used a comments thread here to share information of what various telescopes were looking at. That was in August 2017, just over 8 years ago.

Anyway, here’s to the next decade. Assuming NSF does not follow Trump’s plan to slash the LIGO budget.

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LIGO: Live Reaction Blog

Posted in The Universe and Stuff with tags , , , , on February 11, 2016 by telescoper

So the eagerly awaited press conference happened this afternoon. It started in unequivocal fashion.

“We detected gravitational waves. We did it!”

As rumoured, the signal corresponds to the coalescence of two black holes, of masses 29 and 36 times the mass of the Sun.

The signal arrived in September 2015, very shortly after Advanced LIGO was switched on. There’s synchronicity for you! The LIGO collaboration have done wondrous things getting their sensitivity down to such a level that they can measure such a tiny effect, but there still has to be an event producing a signal to measure. Collisions of two such massive black holes are probably extremely rare so it’s a bit of good fortune that one happened just at the right time. Actually it was during an engineering test!

Here are the key results:

 

LIGO

 

Excellent signal to noise! I’m convinced! Many congratulations to everyone involved in LIGO! This has been a heroic effort that has taken many years of hard slog. They deserve the highest praise, as do the funding agencies who have been prepared to cover the costs of this experiment over such a long time. Physics of this kind is a slow burner, but it delivers spectacularly in the end!

You can find the paper here, although the server seems to be struggling to cope! One part of the rumour was wrong, however, the result is not in Nature, but in Physical Review Letters. There will no doubt be many more!

And right on cue here is the first batch of science papers!

No prizes for guessing where the 2016 Nobel Prize for Physics is heading, but in a collaboration of over 1000 people across the world which few will receive the award?

So, as usual, I had a day filled with lectures, workshops and other meetings so I was thinking I would miss the press conference entirely, but in the end I couldn’t resist interrupting a meeting with the Head of the Department of Mathematics to watch the live stream…

P.S. A quick shout out the UK teams involved in this work, including many old friends in the Gravitational Physics Group at Cardiff University (see BBC News item here) and Jim Hough and Sheila Rowan from Glasgow. If any of them are reading this, enjoy your trip to Stockholm!

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