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LOFAR
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up and operational in various European countries including Germany, France, the UK, and
Sweden (“LOFAR”). Not only is LOFAR one of the most extensive radio telescopes ever built, the
multiple stations set up throughout Europe provide a larger coverage of the sky and can gather
a larger amount of data than a conventional telescope.
With its successful completion and operational status, LOFAR is currently one of the
largest radio telescopes in the world, and it uses a network of omnidirectional and dipole
antennas to observe within low frequency ranges of 10 MHz to 250 MHz (“The LOFAR
Telescope”). These low-cost antennas are the main application basis for LOFAR with two types:
the Low Band Antenna (LBA) which covers frequencies between 10 MHz and 90 MHz and the
High Band Antenna (HBA) which covers frequencies of 110 MHz and 250 MHz. The main
stations based in the Netherlands range in baseline distances of 50 to 1500 kilometers (“About
LOFAR”). In addition, the Netherlands stations are spread out over an area of about 1000 km in
diameter (“LOFAR"). With a telescope that covers such a wide area, as a whole LOFAR contains
thousands of antennas which ultimately increases the power and sensitivity to which it can
observe its low frequency ranges with the LBAs and the HBAs.
LOFAR’s Key Science Projects
With the impressive technology that LOFAR offers, the projects and topics (referred to
as Key Science Projects (KSP) by ASTRON) that it is being used for since its inception are listed as
follows:
Epoch of Reionization
Noted as the most exciting application that LOFAR is utilized for is the search for an
emission line that comes from what is known as the Epoch of Reionization. LOFAR is on
the lookout for a 21-cm emission line that will aid in the study of reionization of matter
that occurred around a redshift value of z=20 in the so-called ‘Dark Ages’ of the universe
– a deemed recombination period where the neutrality to ionization of matter within
the universe occurred. Alternative data suggests that multiple phases of reionization
may have occurred between redshift values of z~6 to z~15-20, and LOFAR is being used
at a range of z=11.4 (115 MHz) to z=6 (180 MHz) to probe this range to search for the
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emission line in order to obtain a better understanding of what processes were going on
throughout this period of evolution in the universe (“Key Science Projects”).
Deep extragalactic surveys
One of the most important tasks of LOFAR is conducting large-sky surveys. The
astrophysical contributions of these sky-surveys include researching the formation of
massive galaxies, clusters and black holes, focusing on inter-cluster magnetic fields using
different radio emissions from galaxies and clusters, the star formation processes in the
early universe, and exploration of new parameters of the universe to potentially
uncover new phenomena. Examples of the data that has been found include
observations of diffuse emissions from a magnetized galaxy cluster which shows the
distribution of the emission from hot gas (see Figure 1) and simulations of combined
observations of distant galaxy formation in respect to the relationship of redshift and
right ascension data (see Figure 2) (“The Science Drivers”).
Transient sources
Among observing many objects and phenomena in space, LOFAR is also being used to
focus on how studying transient sources will further the understanding of the energies
that emit from explosive objects, accretions of black holes, and rapidly rotating neutron
stars. Using LOFAR to study the radio emissions from these objects/phenomena helps in
determining and understanding where and/or how often they occur and how they
impact their surrounding environment (“The Science Drivers”).
Ultra-high energy cosmic rays
In the areas of particle and astrophysical particle physics, LOFAR is being used to study
the origins of high-energy cosmic rays (HECRs) at energies between 1015
and 1020.5
eV.
Scientists are already using LOFAR to study galaxies, gamma-ray bursts, etc., and the
cosmic rays that emit a pulse throughout the universe are detectable provided there are
air showers occurring from the interaction of cosmic rays with the Earth’s atmosphere
(“Key Science Projects”).
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Solar science and space weather
The focus on solar science and space weather uses LOFAR to study solar activity such as
flares and coronal mass ejections (CMEs). Solar radiation is within the ideal frequency
for LOFAR detection making it a prime source for studying CMEs that travel into space
and the probability of CMEs hitting the Earth (“Key Science Projects”). These
phenomena influence the environment of the Earth and directly relate to the field of
space weather. Solar science information obtained by LOFAR will further the
understanding of space weather and can be used to predict the effects of solar
radiation/emissions on Earth (“The Science Drivers”).
Cosmic magnetism
Magnetic fields are evident everywhere throughout the universe; information on
magnetic energy relates to large-scale evolutions found inside galaxies, galaxy clusters,
and interstellar/inter-cluster medium. Magnetic fields also provide information for the
pressure found within interstellar gas and star formation (“The Science Drivers”). Using
LOFAR to study this cosmic magnetism is helping to answer the questions in
astrophysics about objects such as dwarf galaxies, galactic halos, and intergalactic
material (“Key Science Projects”).
Auroral Detection for Exoplanetary Research
The multitude of projects that LOFAR is being used for paves the way for other areas of
research that it could possibly be used for one day, such as in-depth auroral research to
discover exoplanets. Detecting exoplanets that are far away from their host star is a harrowing
process; scientists now theorize that using radio emissions from auroral activity could lead to
the discovery of other planetary bodies outside the solar system that also exhibit auroras.
According to Dr. Jonathan Nichols, a researcher at the University of Leicester, evident data from
studying auroral processes on Jupiter may account for the radio emissions observed from
certain objects that ultimately suggests that auroras do indeed occur on bodies outside the
solar system. The notion is that auroral activity occurs elsewhere, and the radio emissions are
powerful enough, possibly even one thousand times brighter than those of Jupiter, to be
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detectable on Earth from great distances (“New Evidence”). Looking at the cosmic magnetism
and radio emission research that LOFAR is being used for includes the process of studying the
magnetic fields of objects by observing the radio emissions that are detected (“Key Science
Projects”). Auroras themselves are a natural occurrence within our solar system because they
occur when charged particles in an object’s magnetosphere collide with the atoms in the upper
atmosphere, thus, causing the beautiful glowing bands of light. A key thing to note, however, is
that before these particles hit the atmosphere, they emit radio waves into space (“New
Evidence”). To date, scientists only know of auroras occurring within the confines of the solar
system and none have been detected beyond the orbit of Neptune. However, LOFAR data on
the auroral activity of Jupiter sheds light on how the auroral activity that occurs within the solar
system could aid in the discovery of exoplanets outside it. Data on the location and motion of
Jupiter’s auroral emissions reveals that high-sensitivity observations of radio emissions will
shed light on planetary data as well as attempt to detect exoplanetary radio emissions (“LOFAR
Transients”). Scientists also predict that these exoplanetary emissions could reach energies that
are 103
to 105
times those of Jupiter’s which suggests that they could be detectable within a
range of tens of parsecs (Zarka). Referring to Figure 3 shows the information obtained by
applying scaling laws to predictions of radio flux and spectral ranges compared to LOFAR
sensitivities for possible exoplanets. Essentially, LOFAR data on Jupiter’s auroral activity and
radio emissions strongly suggests that exoplanetary radio emitters should exist (“LOFAR
Transients”). With the help of scientists using LOFAR to study Jupiter’s auroras and the radio
emissions that stem from its auroral regions, the observational data provides a high probability
to allowing researchers to start focusing on distances beyond Neptune for any auroras and
possible exoplanets.
Given the capabilities that LOFAR has to study auroral activity, the idea to utilize and
focus this instrument outside the solar system would be greatly beneficial to planetary science.
The information that could be gathered from a telescope of this power and frequency ranges
would not only provide a new method of exoplanetary detection but studying the radio
emissions could even provide information on the exoplanet’s period, magnetic field, any
orbiting moons around the planet, and the host star-planet relationship (“New Evidence”). The
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telescope is already ground-based, and there would be no need to move and/or put any
part/addition of the instrument into space. Also, as mention previously, the antennas that are
used at each station are cheap which makes the issue of cost not exponentially significant. If
scientists start focusing LOFAR at distances past the orbit of Neptune, there is a great
probability for collecting new data to support this theory on exoplanetary detection based off
of auroral activity. A new method would increase the importance of detecting auroras outside
the solar system, and if new exoplanets could be found based on radio emission detection, it
may even provide new candidates for hosting life.
Conclusion
The amount of research that LOFAR is currently providing is impressive in many areas.
Given the capabilities that LOFAR has, the evidence supporting the use of LOFAR to search for
auroral activity outside the solar system in order to uncover new exoplanets is extremely
promising. The key science projects that LOFAR is focusing on reveals the power and sensitivity
of the array that is ideal in radio astronomy and for auroral detection within the solar system
and beyond it. If LOFAR has the capabilities and the sensitivity to detect radio emissions that
are similar to those that are produced by the auroras in the solar system, the opportunities to
develop a new method for exoplanetary research based on auroral activity will provide new
information to find these exoplanets and information on auroral behavior outside the solar
system. If scientists decide to start focusing LOFAR outside the solar system, the probability for
this new type of research is almost certainly possible. Not only is LOFAR a highly useful radio
telescope for the current work it is being used for, but it is also an extremely ideal instrument
that could easily be used to start focusing on auroral activity beyond Neptune’s orbit and
finding these new potential planets.
