Time for the Southern Hemisphere Gravitational Wave Observatory

What applies to optical astronomy also applies to gravitational wave astronomy: the more observatories you have, the better your view of the sky. This is why the list of active gravitational-wave observatories is growing. But so far they are all in the northern hemisphere. As a recent article on arXiv As he points out, this means we’re missing out on quite a few gravitational events.

It is calculated that the science of gravitational wave astronomy is still in its infancy. In the early days of large optical telescopes, there was also a north bias for their locations. Part of this was based on the technical challenges of building telescopes in the Global South, but there was also a cultural bias that is still with us today. It is useful to keep this bias in mind and try to correct it.

But this latest work shows that building a gravitational-wave observatory in the Southern Hemisphere will not only be an act of expanding global participation, but will provide us with significantly more observational data. This is especially true given that our galaxy’s dense central region is in the southern sky.

As a base case, the authors are considering adding an observatory similar to LIGO in Australia. There are currently two LIGO detectors in the United States and a Virgo detector in Italy. Together they discover about 3 events per year, although this number is rising as technologies improve. Adding an Australian detector would double that number to more than 6 events. With three source detections, we can triangulate the action in the sky, allowing optical telescopes to collect data for multi-messenger astronomy.

The sensitivity of the current cosmic explorer and observatories. Credit: Evan D. Hall

Of course, by the time an observatory can be built in the Global South, gravitational-wave detectors will be vastly improved. So the authors look at a more realistic case of building an advanced third-generation detector in Australia. This can work in conjunction with the American Cosmic Explorer and the European Einstein Telescope. Where LIGO uses 4 km detector arms, these new detectors will use 20 km arms or even 40 km arms. They will be able to detect sources of gravity that we can currently only dream of seeing.

In this case, adding an Australian reagent would not significantly increase the number of observed events, raising the number from an estimated 40 per year to 44 per year. But as you can imagine, these new observatories will be so advanced that outages will be inevitable. In this case, the Australian Observatory will give us a great advantage. With just Einstein and the Cosmic Explorer, if one of them goes down for maintenance, the discovery rate drops to a few years. But with two observatories still active, the rate remains around 40 per year.

As we advance in gravitational-wave astronomy, eventually there will be detectors all over the world, and even in space. Gravitational wave astronomy will come to the Global South. But as this study shows, the time is sooner rather than later.

reference: Gardner, James W, and others. “Multiple Messenger Astronomy with the Southern Hemisphere Gravitational Wave Observatory.arXiv Advance edition arXiv:2308.13103 (2023).

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