New telescope to be the ‘GOTO’ for gravitational wave events

GOTO at the Roque de los Muchachos Observatory at La Palma. Behind the observatories, the sun is setting.

A new telescope, made up of two identical arrays on opposite sides of the planet, will track down sources of gravitational waves.

The Gravitational-wave Optical Transient Observer (GOTO), led by the University of Warwick, will help shepherd in a new era of gravitational wave (GW) science.

Deployed across two antipodal locations to fully cover the sky, GOTO will scour the skies for optical clues about the violent cosmic events that create ripples in the fabric of space itself.

GOTO began when the UK’s University of Warwick and Australia’s Monash University wanted to address the gap between GW detectors and electromagnetic signals. Now the international collaboration has 10 partners, six of which are in the UK.

GOTO has received £3.2 million of funding from the Science and Technology Facilities Council (STFC) to deploy the full-scale facility.

Ripples in space-time

GWs had long been hypothesised as a by-product of the collision and merger of cosmic behemoths such as neutron stars and black holes. In 2015, they were finally detected directly by the Laser Interferometry Gravitational-Wave Observatory (LIGO).

Since 2015, there have been many subsequent detections. However, observatories like LIGO can only measure the effects of the GW as it passes through our local patch of space time. Therefore, it can be difficult to track down the source’s point of origin.

It would be like knowing that a truck has passed by feeling the rumble in a road’s surface and trying to work out where it came from based on that alone.

Needle in a haystack

GOTO is designed to fill this observational gap by searching for optical signals in the electromagnetic spectrum that might indicate the source of the GW. GOTO quickly locates the source and uses that information to direct a fleet of telescopes, satellites and instruments at it.

As most GW signals involve the merger of massive objects, these ‘visual’ cues are extremely fleeting as they must be located as quickly as possible, which is where GOTO comes in.

The idea is that GOTO will act as a sort of intermediary between:

  • LIGO, which detects the presence of a gravitational wave event
  • more targetable multi-wavelength observatories that can study the event’s optical source.

All the wavelengths

Professor Danny Steeghs of University of Warwick, GOTO’s principle investigator, said:

There are fleets of telescopes all over the world available to look towards the skies when GW are detected, in order to find out more about the source. But as the GW detectors are not able to pinpoint where the ripples come from, these telescopes do not know where to look.

If the GW observatories are the ears, picking up the sounds of the events, and the telescopes are the eyes, ready to view the event in all the wavelengths, then GOTO is the bit in the middle, telling the eyes where to look.

Two hemispheres, no waiting

Following the successful testing of a prototype system in La Palma, in Spain’s Canary Islands, the project is deploying a much expanded, second generation instrument.

Two telescope mount systems, each made up of eight individual 40 centimetres (16 inch) telescopes, are now operational in La Palma. Combined, these 16 telescopes cover a very large field of view with 800 million pixels across their digital sensors, enabling the array to sweep the visible sky every few nights.

These robotic systems will operate autonomously, patrolling the sky continuously but also focusing on particular events or regions of sky in response to alerts of potential GW events.

Patrolling and searching

Professor Steeghs continued:

The award of £3.2 million of STFC funding was critical in allowing us to build GOTO, as it was always envisaged to be; arrays of wide-field optical telescopes in at least two sites so that these could patrol and search the optical sky regularly and rapidly.

This will allow GOTO to provide that much-needed link, to give the targets for bigger telescopes to point towards.

The future of GW science

In parallel, the team is preparing a site at Australia’s Siding Spring Observatory, which will contain the same two-mount, 16 telescope system as the La Palma installation.

The plan is to have both sites operational this year to be ready for the next observing run of the LIGO and Virgo GW detectors in 2023.

The optical search for GW events is the next step in the evolution of GW. It has been achieved once before, but with GOTO’s help it should become much easier.

Dynamic and exciting time

Professor Steeghs added:

The hope is to catch the event quickly, then follow it as it fades, and also to trigger an alert to other, bigger telescopes so they can all collect more information, and we can build a really detailed picture of these astronomical phenomena.

It is a really dynamic and exciting time. In astronomy we are used to studying events, which are millions of years old and aren’t going anywhere. This is a fast-paced, very different way of working where every minute counts.

Further information

The GOTO collaboration includes:

  • Armagh Observatory and Planetarium
  • Instituto de Astrofísica de Canarias
  • Monash University
  • National Astronomical Research Institute of Thailand
  • University of Leicester
  • The University of Manchester
  • University of Portsmouth
  • The University of Sheffield
  • University of Turku, Finland
  • The University of Warwick.

Top image:  GOTO at the Roque de los Muchachos Observatory, La Palma. Credit STFC

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