Research with LOFAR is organized into a number of ‘Key Science Projects’ (KSPs) that address particular scientific themes. The LOFAR KSPs are independently organized international research groups which are required to make recognized contributions to the development of LOFAR and its scientific output. Astrophysics groups in Ireland are also part of these international KSPs, a selection of which are listed below.
The sensitivity and extremely large field-of-view of LOFAR make it an ideal instrument for undertaking deep, large area surveys. LOFAR will produce a series of unique surveys of the low-frequency radio sky, which will open a new window on numerous fundamental areas of astrophysics. Notable amongst these are:
- Formation of massive galaxies, clusters and black holes using z ≥ 6 radio galaxies as probes
- Intercluster magnetic ﬁelds using diffuse radio emission in galaxy clusters as probes
- Star formation processes in the early Universe using starburst galaxies as probes
The Surveys KSP will be optimized for obtaining large samples of radio objects in these and other categories, such as the objects in the LOFAR image below. These objects will be studied individually and also collectively for precision statistical analysis. A number of all-sky, multi-frequency surveys are planned over multiple epochs, also enabling variable sources to be recognized.
Our universe can be a violent and rapidly changing place. Exploding stellar giants, accreting supermassive black holes, rapidly rotating superdense neutron stars, can all release enormous energies into their surrounding environments on very short timescales, acting as cosmic thermostats, keeping the environment in an active state, triggering star formation and regulating the growth of galaxies. In nearly all cases, such events and phenomena have associated radio emission, so by observing in the radio band we can understand where and how often such events occur, and gauge their combined impact on the ambient environment. The LOFAR Transients KSP focuses on exploring and understanding the explosive and dynamic universe by observing transient and variable radio sources. Thanks to the enormous field of view and multiple beams of LOFAR, for the first time we are able to monitor a large fraction of the sky on a regular basis, allowing us to make an accurate census of such sources.
Solar Science and Space Weather
Trinity College Dublin, Dublin Institute for Advanced Studies
The Sun is a powerful emitter at radio wavelengths, not only during intense bursts of activity related to phenomena such as solar flares and coronal mass ejections (CMEs), but also during times when it is considered quiet at other wavelengths. Radio emission from energetic and dynamic phenomena such as solar flares and CMEs is of particular interest, as they are major drivers of space weather and can affect the Earth’s space environment. Solar flares and CMEs are also challenging physical phenomena to be understood in their own right. LOFAR opens an unexplored window of the radio spectrum, which is particularly useful for studying particle acceleration and large-scale dynamics. It enables the study of accelerated particles, from very weak to very energetic events, especially when combined with multi-wavelength observations from other terrestrial and space-based observatories. An example of such a study is presented in the image below where an ultraviolet image of the Sun is overlaid with a radio burst observed by LOFAR, produced by energetic electrons travelling at a third of the speed of light. With LOFAR, dynamic processes involved in solar flares and CMEs can be studied from their origins on the Sun as they propagate out through the solar atmosphere. Using radio interplanetary scintillation measurements, CMEs can be tracked, and the solar wind and interplanetary magnetic field conditions analysed, from the outer solar corona to the Earth and other planets. Furthermore, radio observations with LOFAR will provide powerful diagnostics of the Earth’s ionosphere and magnetically-linked regions of its magnetosphere.
Trinity College Dublin, Dublin Institute for Advanced Studies
Researchers at Trinity College Dublin are involved with the LOFAR for Space Weather (LOFAR4SW) project, which is part of the European Union Horizon 2020 INFRADEV-1-2017 Call, ‘Design Studies’. The project will deliver the full conceptual and technical design for creating a new leading-edge European research facility for space weather science. The LOFAR4SW project will engage stakeholders in preparation of the facility which produces unique research data with key impact on advanced predictions of space weather events affecting crucial technological infrastructures of today’s society.
Building on the technology and European coverage of the International LOFAR Telescope (ILT) infrastructure, a fully implemented LOFAR4SW system will enable a wide range of solar and space weather research topics to be tackled. The LOFAR4SW facility is the only way to obtain transformational 3-dimensional tomographic data on velocities and densities that track space weather dynamics throughout space between the Sun and the Earth (the inner heliosphere). This facility will uniquely provide the missing link of measurements of the interplanetary magnetic field on those global scales – a key parameter in forecasting the severity of geomagnetic storms on Earth.
Dublin City University
Although we know that magnetic fields fill interstellar and intracluster space, their presence on both small and large scales is an often over-looked topic in astrophysics. The full Stokes polarization response and low frequency coverage of LOFAR make it uniquely suited for changing this situation and investigating the magnetic cosmic web in detail. The presence of magnetic fields in astrophysical objects is mainly inferred in one of two ways:
- Firstly, through detecting synchrotron emission, a radiation mechanism which is a direct consequence of magnetic structure
- Secondly, using the rotation of the intrinsic polarization of background sources as their own radiation passes through foreground magnetized media.
Both mechanisms are ideally observed at the low frequencies measured by LOFAR as they are not only intrinsically faint, but their amplitude is also inversely proportional to frequency. The Magnetism KSP will not only examine the Faraday structure of individual objects such as nearby galaxies (see image below), magnetized galaxy cluster haloes, and the interstellar Galactic plane where magnetic fields play vital roles from the onset of star formation to the growth of galaxies; but will also investigate the primordial generation, structure and evolution of magnetic fields on cosmological scales.
Armagh Observatory and Planetarium, Dublin Institute for Advanced Studies
There are many different types of stars in the Universe. One particular type, called M dwarfs, are known to produce massive explosions on their surface. These explosions of energy, known as flares, can be detected across the electromagnetic spectrum from ultraviolet and x-ray to optical and radio waves. M dwarfs are much smaller and fainter than most stars, and LOFAR, as the largest radio telescope operating at low frequencies, is ideally suited to detect these faint radio sources in the sky. Radio observations allow us to understand the processes which drive these flares. Studying and understanding flares on other stars is very important for exoplanet research. Many exoplanets (planets orbiting other stars) have been detected around M dwarfs, and they are known to orbit much closer to their star than the Earth around the Sun. This means that any possible atmosphere of these exoplanets may be affected by large flares from the star. Observing these stars with LOFAR can provide information on the type of emission from stellar flares, and whether they can damage exoplanet atmospheres, potentially redefining the habitable zone around these stars. Better understanding these flares also allows us to compare other stars to our Sun, to better understand the potential for large solar flares.
Dublin Institute for Advanced Studies
The Earth’s atmosphere frequently generates some of the most powerful electrical events in nature. This happens in the form of lightning during intense thunderstorms, when the atmosphere can produce megavolt electric fields and lightning can release up to a gigajoule of energy. This energy release causes the air around the lightning to get hotter than the surface of the Sun, exciting electrons which generate strong radio signals ranging from kHz – MHz, which we can detect with telescopes like LOFAR.
These extreme weather patterns are not unique to the Earth. Although the atmospheres may differ, powerful lightning strikes have been observed on other solar system bodies like Jupiter, Saturn, and Uranus. LOFAR has the frequency range and sensitivity required to detect these solar-system lightning storms from space. Regular monitoring of the most likely candidates to produce storms in our solar system at radio frequencies can help us understand the processes and formation of these space-storms and their powerful lightning events. This research could allow us to extend ground-based radio lightning observations to nearby exoplanets that are expected to have extended turbulent atmospheres. Observations like these could possibly place excellent constraints on the atmospheric variables for such a planet.
NUI Galway, Dublin Institute for Advanced Studies, Trinity College Dublin
Pulsars are some of the most extreme objects in our cosmic backyard, forming from dying stars that have collapsed to form neutron stars that can fit within any county in Ireland. This multiple orders-of-magnitude change in scale results in the same effect as an ice skater bringing their arms in, resulting in them spinning in an extremely stable manner, often at significant fractions of the speed of light. At the moment, the fastest known pulsar can perform a rotation in under 2ms, while the slowest rotates only once every 23 seconds. With such extreme masses, rotation velocities and companion stars often sharing their star system, they are the perfect laboratories for some of our most extreme theories, such as general relativity or gravitational waves.
Given they only emit light in the direction of Earth for a fraction of their rotation, I-LOFAR sees pulsars as sudden flashes of light, at an extremely regular cadence. As a result of their incredibly stable nature, combining information on the arrival time of each flash of light can allow us to get extremely precise measurements of the properties of a pulsar. For example, pulsar J1738+0333 has a rotation period known to within two attoseconds (that’s 0.000000000000000002 seconds!).
I-LOFAR is also surveying a subclass of pulsars known as rotating radio transients (RRATs). Unlike most pulsars, these sources are more akin to a lighthouse that needs a bulb replaced, as they may only spark to life once or twice an hour, or at even rarer cadences in some cases. Though since the neutron star itself is still spinning, there is still a wealth of information that can be collected on these sources from the rare occasion that they are visible in the sky.
Technological University of the Shannon: Midlands, Dublin Institute for Advanced Studies, Trinity College Dublin
The solar atmosphere regularly releases huge amounts of magnetic energy, resulting in the acceleration of particles and the ejection of billions of tonnes of material into the solar system. These particles and eruptions can cause a threat to a variety of Earth-based technologies, such as damage to satellites and interruptions to electricity grids, as well as cause radiation hazards for astronauts or the crew of flights close to the Earth’s poles. Hence there is a need to understand the origin of this eruptive activity so that forecasts can be made of any resulting ‘space weather’. The energetic particles that accompany this activity are powerful sources of radio emission known as solar radio bursts (SRBs). The automatic detection of SRBs can allow us to study the statistics of solar eruptions, providing insight into the origin of such activity. However automatically detecting and classifying SRBs is a major challenge made more complex in recent years with new technology such as the Low Frequency Array (LOFAR). Each individual LOFAR station produces high-volume data streams (up to 3 Gigabits per second), hence processing and classifying SRBs in this data stream with accuracy is a significant computational challenge.
As the world of computing accelerates the digitalisation of everything, the world has a wonderful opportunity to solve ‘big global problems’. With that in mind, one specific aspect of a global problem is the effect the sun will have on our earth’s future. Artificial Intelligence (AI), can now help solve some of those problems. AI has made significant advancements in autonomous driving, robotics, voice recognition, and the recent landing of the “perseverance” probe on Mars. AI technology is now an everyday enabler in how we run our daily lives, the speed of how we can solve problems, and make decisions.
A recent example is how we managed to create an artificially intelligent algorithm known as YOLO (You only look once) that not only identifies SRBs but does it at high speed as well. What YOLO does is take hundreds of thousands of examples of SRBs and trains itself to identify different features of SRBs such as shape, colour, and intensity. YOLO is then presented with an observation made by LOFAR and scans the observation for SRBs. If YOLO identifies an SRB it then highlights it as an area of interest with what is called a bounding box as seen in the image.
Planetary Radio Emissions
Dublin Institute for Advanced Studies
The planet Jupiter has a strong magnetic field and radio emissions across a range of wavelengths. Jovian decametric observations allow us to follow the auroral radio activity of Jupiter, whose waves are produced above the magnetic poles by energetic electrons. These waves give us many insights into the activity of the magnetized and ionized environment of the planet (the magnetosphere).
Very high resolution observations reveal the fine structures of the Jovian radio emissions, in particular the millisecond bursts of the emissions produced by interaction between Jupiter and its volcanic moon Io. Their analysis allows us to follow the motion of the radio sources along the auroral magnetic field lines, to measure the electric potential jumps encountered by the electrons that generate these emissions or to test the saturation of the mechanism of radio emission generation, called “Maser-Cyclotron instability”.
Dublin Institute for Advanced Studies
Scientific and Technological Excellence by Leveraging LOFAR Advancements in Radio astronomy (STELLAR) is a collaboration between Institute of Astronomy and National Astronomical Observatory (IANAO) in Bulgaria, Netherlands Institute for Radio Astronomy (ASTRON), the Dublin Institute for Advanced Studies (DIAS), and the Technical University of Sofia (TUS), which is funded by EU’s Horizon 2020 Twinning program. STELLAR is a transformative project for training the next generation of Bulgarian radio astronomers, and will significantly increase the LOFAR technical and scientific expertise at TUS and IANAO.
STELLAR will achieve its objectives through carefully planned trainings for IANAO and TUS staff at ASTRON and DIAS, including lectures, workshops, summer schools, and research staff exchanges. The project will allow IANAO and TUS to develop and strengthen collaborations with ASTRON and DIAS.
The STELLAR project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 952439. Learn more at https://lofar.bg/stellar
Birr Kids Space Ireland
Birr Scientific & Heritage Foundation
Joe Hogan (Openet)
Birr Lions Club
Birr Chamber of Commerce
Science Foundation Ireland
Dept. of Jobs, Enterprise, and Innovation
Offaly County Council
Dept. of Arts, Heritage, Regional, Rural, and Gaeltacht
Dept. for Communities
Armagh Observatory and Planetarium
Birr Castle Gardens & Science Centre
Rosse Row, Birr,