3 questions: Lisa Barsotti on the new and improved LIGO



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The search for infinitely weak undulations in space-time is back to full steam. Today, LIGO, the Gravitational Wave Observatory with Laser Interferometer, operated jointly by Caltech and MIT, resumes its quest for gravitational waves and the immense cosmic phenomena from which they emanate.

Over the past few months, LIGO's twin detectors in Washington and Louisiana have been disconnected, upgraded from their lasers, mirrors and other components, allowing detectors to hear gravitational waves in a much larger range. 550 million light-years away – about 190 million light years farther than before.

When the LIGO detectors come back, they will be joined by Virgo, the European company based in Italy, which also connects today after undergoing updates that have doubled its sensitivity. With LIGO and Virgo back online, scientists anticipate that detections of gravitational waves from the farthest reaches of the universe can be a regular occurrence.

MIT News He spoke to Lisa Barsotti, a member of LIGO, the lead researcher at MIT's Kavli Institute of Astrophysics and Space Research, on possible discoveries to come.

Q: Give us an idea of ​​the new capabilities that LIGO detectors have now. What kind of updates have been made?

AN: Both LIGO detectors are coming back online more sensitive than ever, thanks to a wide range of improvements. In particular, we have more than doubled laser power on interferometers to reduce one of LIGO's fundamental sources of noise – the "shooting noise", caused by the uncertainty of the arrival time of the photons in the main photodetector. , "squeezed" light, which uses quantum optics to further reduce the firing noise.

Combined with other updates to mitigate technical noise (eg noise introduced by the control scheme or diffuse light) we improved the sensitivity to binary neutron stars by 40% in each detector, compared to the previous observation run.

Q: What do these new features mean to you, as a researcher who will examine the data from these updated detectors?

AN: Personally, I'm very excited to see the LIGO detectors operating in tight light! This new technology was developed here at MIT after many years of research to make it compatible with the rigorous requirements of LIGO, and our graduate students have led the commissioning of this new system at the observatories. It is particularly gratifying to see that we have made LIGO better.

In addition, high-power laser operation was enabled by another upgrade developed and built here at MIT – an "acoustic-mode shock absorber" glued to LIGO's main optics that mitigates instabilities that originated with high laser power. We look forward to seeing many years of work in our labs that make up for in this observation race!

Q: What new phenomena do you expect to detect and how quickly could you detect them with these new features?

AN: We expect to detect more stellar binary neutron systems (so far only one has been detected) and, thanks to the better sensitivity of the LIGO, we must be able to observe them with high signal-to-noise ratio. And more black holes, obviously! The more sources we detect, the more we learn about how these systems form and evolve.

If we are very lucky, we may observe something new, like a neutron star black hole system, or maybe something totally unexpected. LIGO detectors are not only better than before – the Virgin's detector in Italy has more than doubled its sensitivity over the last observation run, and this will improve our ability to locate sources in the sky, making it easier to follow multi-length telescopes of wave. So if the last observation race, "O2", is remembered as the one that started multimedia astronomy, I hope the next one, "O3", is one in which multimedia astronomy becomes the new normal!

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