For the past decade, astronomers have grappled with the mystery of fast radio bursts, fleeting blasts of intense cosmic energy lasting just a few milliseconds that come from unknown sources billions of light years away.
The hunt for the origins of these perplexing phenomena will soon be aided by a unique experiment unfolding in the remote reaches of the Northern Cape: the MeerLicht, a new optical telescope at the SA Astronomical Observatory near Sutherland, will be coupled with the MeerKat radio array near Carnarvon, roughly 245km away.
Multi-wavelength astronomy is nothing new — for astronomers, the more information from different parts of the electromagnetic spectrum the better — but this will be the first time an optical telescope captures images of exactly the same part of the sky at the same time as a radio telescope.
“This is probably the future for multi-wavelength physics,” says Rob Fender of the University of Oxford. “Colleagues around the world are looking at MeerLicht and thinking: ‘Man, that’s a good idea.’ Colleagues from the Cherenkov array are already proposing a similar facility.”
The Cherenkov telescope array is an international project to build a new-generation ground-based gamma-ray instrument.
Until now, when astronomers detected an interesting event in the radio spectrum, they had to contact colleagues at observatories with optical telescopes and ask them to train their instruments on the object under scrutiny. That “phone a friend” approach worked fine for events that lasted days or weeks, but for transient phenomena that pass in the blink of an eye it was simply too late, says Fender.
He is a principal investigator on ThunderKat, one of the 10 MeerKat large-survey projects that were selected through an international bidding process to probe key areas of scientific interest. MeerKat, which had the last of its 64 dishes completed in March, is the most sensitive radio telescope in the southern hemisphere; it will be incorporated into phase 1 of the Square Kilometre Array in about 2020.
Colleagues around the world are looking at MeerLicht and thinking: ‘Man, that’s a good idea’ – Rob Fender
MeerLicht, which means “more light” in Dutch, is a collaboration between six institutions in the Netherlands, the UK and SA. It dovetails with the department of science & technology’s strategy to promote multi-wavelength astronomy. The €600,000 telescope can see objects a million times fainter than the human eye can detect, over a field of view the width of three full moons.
Though astronomers believe thousands of fast radio bursts happen around the universe every day, only about 30 of them have been detected so far — when telescopes have happened to be pointing in the right direction at the right time.
MeerKat is expected to begin detecting very large numbers of them soon.
That’s where MeerLicht will fit in, taking a picture every minute of a section of the southern sky determined by MeerKat and building an archive of images that can be scrutinised to help identify the location and energy of fast radio bursts.
While fast radio bursts are a particularly hot topic, MeerLicht will also provide optical wavelength data on a whole host of other transient events such as supernova explosions and neutron star collisions.
“As soon as we find interesting things, we will be sending out alerts to the entire astronomy community, telling them they may want to turn their telescopes onto the sources as well,” says the University of Manchester’s Ben Stappers, one of the principal investigators on the MeerKat project Trapum, which is researching pulsars. “We are in an era where there are so many interesting things that it is better to share the information: in fact, astronomy is leading the way in data sharing.”
And should gravitational waves be detected by the US-based Laser Interferometer Gravitational-Wave Observatory and Europe-based Virgo, MeerLicht and MeerKat will scan the southern sky, compare what they capture to their archived images, and hunt for anything new, he says.
WHAT IT MEANS
Thousands of fast radio bursts happen around the universe every day. MeerLicht will be able to capture many of them
Gravitational waves are tiny ripples in the fabric of space-time, and though they were predicted by Albert Einstein more than a century ago, they were only detected for the first time in 2015.
The data may also shed light on the formation of heavy elements such as gold, silver and platinum, which are created when neutron stars collide, says Paul Groot of Radboud University. “All the gold we have on earth was made in this way. But how did it happen, how often, and how does that gold end up here? It is a quest for part of our origins,” he says.
MeerLicht is also the prototype for a Dutch-funded project in Chile called BlackGem, which will have three telescopes continuously scouring the southern sky for optical counterparts to gravitational waves from events such as merging black holes. BlackGem may eventually be expanded to include telescopes in New Zealand and SA, says Patrick Woudt, head of astronomy at the University of Cape Town.
MeerLicht links to all the other optical telescopes at the Sutherland observatory, including the Southern African Large Telescope (Salt), and it fits with the observatory’s strategy of turning the site into a “machine to study the dynamic universe”, says Salt astronomer David Buckley.
“We are building networks to automatically do the science with far less human intervention than in the past, putting in the parameters so computers can talk to each other and do the work when everyone is asleep,” he says.