New Developments in Gravitational Wave Astronomy

It's been less than a decade since the first detection of gravitational waves and already astronomers are looking at new ways to improve their detection of what might be natures most hidden and subtle vibrations. 

In The Guardian, Philip Ball looks at what astronomers have planned in the future. It's rather mind boggling. Consider an array of satellites millions of kilometres apart that can detect changes in their distance less than the width of an atom. Or an array of radio telescopes that can detect changes in the rotation of pulsars as gravitational waves pass through them. 

Lisa will send laser beams from one spacecraft to bounce off a mirror freely floating inside another craft. With three spacecraft you can make an L-shaped double-armed structure like Ligo. But the arms don’t have to be at right angles: instead, Lisa will position its three spacecraft several million miles apart at the corners of a triangle, so that each corner becomes one of three detectors. The whole array will follow the Earth’s orbit, trailing our planet by about 30m miles.

To test the feasibility of doing laser interferometry in space, in 2015 Esa launched a pilot project called Lisa Pathfinder – a spacecraft that demonstrated the technology on a tiny scale. The mission, completed in 2017, “blew us away”, says Esa’s Paul McNamara, who was the project scientist managing the mission. “It met our requirements on day one, with no tweaking, no nothing.” It showed that a mirror floating inside a spacecraft could be kept incredibly still, wobbling by no more than a thousandth of the size of a single atom. To keep it that steady, the spacecraft uses tiny thrusters to push back against the force produced by the light coming from the sun.

In other words, says McNamara, “our spacecraft was way more stable than the size of the coronavirus”. Which is just as well, because Lisa will need to detect a change in arm length, due to a GW, of about a tenth the width of an atom over a million miles.

If this doesn't trigger your sensawunda (an SFnal term for sense of wonder or awe), nothing will.