The hunt for gravitational waves from space has just had its first breakthrough. ESA's LISA Pathfinder has successfully demonstrated the crucial technology that will allow scientists to have a gravitational wave observatory in orbit in the next few decades.
On March 1, two masses were released inside the space laboratory, set up to achieve perfect free fall under the influence of gravity alone. Today, scientists revealed the results from the experiment, explaining that the system minimized all other external forces and reached five times the precision that was expected.
"With LISA Pathfinder we have created the quietest place known to humankind. Its performance is spectacular and exceeds all our expectations by far,” said Professor Karsten Danzmann, co-principal investigator of the LISA Technology Package, in a statement. “Only by reducing and eliminating all other sources of disturbance we could observe the most perfect free fall ever created. And this has shown us that we can build LISA, a space-based gravitational-wave observatory."
The LISA experiment is expected to fly in 2034, and it will be composed of three spacecraft millions of kilometers apart. Lasers will be shot from each spacecraft, and changes in the light will allow the detection of gravitational waves.
To guarantee they are truly observing gravitational waves, the detectors always need to be precisely aligned. This also means the scientists need to make sure the craft can shield the detectors from every external force.
To test this, LISA Pathfinder released two 2-kilogram (4.4-pound) gold-platinum cubes that were 38 centimeters (15 inches) apart. A laser interferometer was placed between them to measure their position relative to each other and the craft.
"The measurements done by this first laser interferometer in space are by far better than we had expected," added Apl. Professor Gerhard Heinzel, leader of the research group Interferometry in Space at the Albert Einstein Institute and Leibniz Universität Hannover. "We can determine the distance of the two free-falling test masses to less than the diameter of a single atom."
LIGO’s discovery of gravitational waves earlier this year has opened the door to a whole new branch of observational astrophysics. LISA will be able to look at events that are too subtle for LIGO to observe, such as binary stars, supermassive black holes orbiting each other, and signals from the first instants after the Big Bang. LISA may also be able to see stuff we don’t even yet know exists.
Presenting the mission results online, Fabio Favata, ESA Coordinator for Astronomy and Fundamental Physics missions, said: "LISA Pathfinder is to LISA for gravitational waves as Gemini was to Apollo for going to the Moon. A necessary first step."
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