New telescope to detect gravitational wave events

A new telescope, made up of two identical arrays on either side of the planet, will detect sources of gravitational waves.

The Gravitational-wave Optical Transient Observer (GOTO), led by the University of Warwick, ushers in a new era of gravitational wave science. Deployed in two antipodal sites to completely cover the sky, GOTO will scour the sky for optical clues about the violent cosmic events that are creating ripples in the fabric of space itself.

GOTO began when the British University of Warwick and Australia’s Monash University bridged the gap between gravitational wave detectors and electromagnetic signals† Now the international cooperation has 10 partners, six of which are in the UK. GOTO has received £3.2 million in funding from the Science and Technology Facilities Council (STFC) to deploy the entire facility.

“This is really encouraging from an international collaborative perspective that the UK is willing to support this project, with new telescopes to be built in Australia,” said Associate Professor Duncan Galloway of the Monash University School of Physics and Astronomy.

“The new site gives us a huge improvement in our chances of observing the gravitational wave detection counterparts. Detecting the optical counterparts quickly is a key factor in how much we can learn from gravitational wave detections. The first such event, GW170817, was identified in 11 hours ; but our GOTO network can be up and running in minutes and autonomously observing the field.”

Long hypothesis as a by-product of the collision and fusion of cosmic behemoths such as neutron stars and black holes, gravitational waves were finally directly detected by the Advanced LIGO (Laser Interferometry Gravitational-Wave Observatory) in 2015.

Since 2015, there have been many successive detections, but since observatories like LIGO can only measure the effects of the gravitational wave as it passes through our local slice of spacetime, it can be difficult to pinpoint the source’s point of origin.

GOTO was designed to fill this perception gap by searching for optical signals in the electromagnetic spectrum that could indicate the source of the GW — quickly locating the source and using that information to target a fleet of telescopes, satellites and instruments.

Since most GW signals involve the fusion of massive objects, these ‘visual’ signals are extremely volatile and need to be located as quickly as possible, which is where GOTO comes in handy. The idea is that GOTO will act as a sort of intermediary between people like LIGO, who detect the presence of a gravitational wave event, and more directional multi-wavelength observatories that can study the event’s optical source.

Professor Danny Steeghs from the University of Warwick, principal investigator of GOTO, said: “Fleets of telescopes around the world are available to look at the sky when gravitational waves are detected, to learn more about the source. But because the gravitational wave detectors can’t determine where the ripples are coming from, these telescopes don’t know where to look.”

After the successful testing of a prototype system in La Palma, in the Spanish Canary Islands, a much more extensive second-generation instrument is being deployed in the project.

Two telescope mount systems, each consisting of eight separate 40 cm (16 in) telescopes, are now operational on La Palma. Together, these 16 telescopes cover a very large field of view with 800 million pixels across their digital sensors, allowing the array to cover the visible sky every few nights.

These robotic systems will operate autonomously, continuously patrolling the sky, as well as focusing on particular events or areas in the sky in response to warnings of possible gravitational wave events.

Professor Steeghs continued: “The award of £3.2 million in STFC funding was critical to enabling us to build GOTO, as it had always been envisioned; arrays of wide-angle optical telescopes in at least two locations so that they could patrol and search the optical sky regularly and quickly.

“This will enable GOTO to provide that much-needed link, to give the targets for larger telescopes to point to.”

At the same time, the team is preparing a site at the Siding Spring Observatory in Australia, which will contain the same dual, 16-telescope system as the installation on La Palma.

The plan is to have both sites operational this year to be ready for the next LIGO/Virgo observation run gravitational wave detectors in 2023.

The optical search for gravitational wave events is the next step in the evolution of gravitational wave astronomy. It has been accomplished once before, but with the help of GOTO it should become much easier.

If astronomers can find convincing counterparts to gravitational wave signals, it will be possible to measure distances, characterize the sources, study their evolution and determine the environments in which they are formed.

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