A major European report looking at a $1 billion proposal to build a space-based gravitational wave observatory has concluded that the idea is more than just feasible; its development should be accelerated to make the most of this exciting new area of astronomy as soon as possible.
The announcement of the first-ever detection of gravitational waves earlier this year deservedly made headlines around the world. The detection by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States confirmed the existence of gravitational waves, tiny ripples in space-time caused by huge events such as merging black holes.
On the back of this discovery, a report from a group called the Gravitational Observatory Advisory Team (GOAT), an expert panel commissioned by the European Space Agency (ESA), has recommended that ESA pushe ahead with its own plans to launch a more sensitive gravitational wave observatory in 2034 as soon as possible.
“In a single step, gravitational wave astronomy has been placed on a secure observational footing, opening the panorama to the next robust steps in a space-based gravitational wave observatory,” the report stated, commenting on the LIGO discovery.
ESA’s preferred proposal for such an observatory, known as the Evolved Laser Interferometer Space Antenna (eLISA), is to fly three spacecraft in a huge triangle formation in space, each separated by a distance of 1 million kilometers (620,000 miles). Lasers would then be fired between the spacecraft, and by detecting tiny fluctuations in the lasers, gravitational waves could be observed. This is known as laser interferometry, the same technique (albeit on a smaller scale) that was used by LIGO.
The technology for eLISA, which will likely involve a contribution from NASA, is already being tested on the LISA Pathfinder mission, which was launched in December 2015. But the discovery of the first gravitational waves by LIGO has made the mission all the more promising, boosting the opinion in the science community that such an observatory can successfully observe gravitational waves, allowing us to detect phenomena not possible with other forms of astronomy.
In fact, speaking to BBC News, GOAT chairman Dr. Michael Perryman said they were proposing that the project should be accelerated by five years. “After submitting our report, ESA came back to us and asked what we thought might be technically possible, putting aside the money," he said. "We are in the process of finalizing a note on that, which will suggest the third quarter of 2029. So, 13 years from now.”
Merging black holes and binary stars are thought to produce gravitational waves. R. Hurt/Caltech-JPL
The report by GOAT looked at a number of other technologies that could be used on a gravitational wave observatory, including an untested idea to use atom interferometry, essentially detecting fluctuations in an arrangement of atoms fired between two points rather than photons in a laser. But the conclusion was that laser interferometry, as proposed for eLISA, was the most attractive option, being not only proven but also possible with current technologies.
“The Committee has identified no fundamental technical issues which might question or invalidate the measurement of gravitational waves from a laser interferometry based space mission,” the report concluded. “Based on an evaluation of the alternative measurement approaches, laser interferometry remains the preferred option.”
It added: “The technical and scientific knowledge base now residing in Europe argues for the early implementation of a gravitational wave observatory under European leadership.”
The next step is for a detailed proposal for the mission to be put forward, before ESA can consider giving the go-ahead for development of the mission to begin. Given the findings of this report, and the clamor for more gravitational wave-based astronomy, that looks to be a near certainty.