Lighting the Way in the Search for Distant Exoplanets

Is it possible there’s another Earth-like planet in the universe that could support life? Research being carried out by Pieter de Visser at the Netherlands Institute for Space Research (SRON) on the search for planets outside our solar system, called exoplanets, could hold the answer. SRON has a worldwide reputation as a pioneering space research institute. “We know that there are about 5,000 exoplanets around other stars. And in the coming decades, the main questions will be – what do these planets look like, what do they consist of, what’s on their surface and in their atmosphere?” he says.

Pieter is an Instrument Scientist in the Technology programme at SRON. He’s well known for his innovative work with microwave kinetic inductance detectors or MKIDs. These detectors are extremely sensitive to small amounts of light, and they need to be to detect distant exoplanets. Even the closest exoplanet to Earth, Proxima Centauri b, is approximately four light-years or 38 trillion kilometres away. “The detectors are made from superconducting materials. If you cool them down far enough, close to absolute zero [-273°C], they become superconducting,” he explains. This cooling increases the sensitivity of the detectors which allows them to detect single particles of light called photons.

Another advantage of MKIDs is their ability to measure light across a wide range of wavelengths simultaneously. “Normally, you take a colour picture by filtering, so in your cell phone, for instance, you have a blue, green and red filter, which together compose a picture, but our detectors can detect the colour of each individual photon all at once,” Pieter says. He and his team recently had a breakthrough in optimising this colour-resolving power. This is important because different chemical molecules absorb and emit light at different wavelengths. By measuring the spectrum of an exoplanet’s light, they can determine the chemical composition of its atmosphere. This will yield vital clues as to whether it could sustain life.

SRON provides the type of high-level technical support that Pieter needs for his experimental research, something that would not be available in a university setting. There’s a cleanroom with a dedicated staff of highly skilled engineers who can fabricate the MKIDs and create the specialised setup needed for these detectors. Not only do the detectors need a cryogenic environment, but they also have to be shielded from magnetic fields and external light so they can reach their true sensitivity. “In addition, the detectors need electronics for their readout and to process the data that comes from that. We have a group of people who write the firmware for the processors on these devices and write the software to communicate with them and analyse that data,” he says. This kind of dedicated support enables him to carry out quality-driven work and participate in international projects.

Forging alliances is essential for Pieter’s research. He has strong collaborations with an experimental astronomy group at Delft University of Technology (TU Delft) where he supervises three PhD students. The students are also closely affiliated with SRON for their PhD research. He enjoys supervising Master’s and PhD students and seeing how everyone can work together to develop cutting-edge technology and solve important questions. He also supervises a PhD student at the Leiden Observatory as part of his collaboration with Leiden University. Together they plan to work on building an instrument for a new telescope in Chile, called the Extremely Large Telescope, which will be used to study exoplanets upon its completion in a few years’ time. In addition, Pieter has strong connections with a group in Finland and NASA. These interdisciplinary collaborations bring together scientists from different fields to advance the research further.

Pieter did a joint PhD at SRON and TU Delft, and after a brief stint away doing a postdoc on more fundamental physics, in 2016, he was invited to return to continue his work on superconducting detectors. He enjoys the fact that at SRON, he has the opportunity to work on both fundamental and applied research. One big advantage of working at a research institute like SRON over profit-driven industry is that it is willing to invest in the type of long-term projects needed for space instrumentation development. Pieter also values the security that comes with working at SRON. He says, “They support you as a researcher and your ideas. It shows that they actually believe in you and want to do this together.”