Illustration: Benito Marcote, JIVE. Image credits: MeerKAT image ©SARAO; EVN map image ©Paul Boven, JIVE (satellite image: Blue Marble Next Generation, courtesy of NASA Visible Earth).
South Africa’s MeerKAT radio telescope has successfully conducted very long baseline interferometry (VLBI) observations with telescopes of the European VLBI Network (EVN)—currently the world’s most sensitive VLBI network. Their synergy sets a new standard for global collaboration and significantly enhances both resolution and sensitivity, opening new avenues for scientific exploration.
The collaboration between MeerKAT and the EVN demonstrated, for the first time, how a highly sensitive, modern radio interferometer telescope in the southern hemisphere can significantly enhance the capabilities of existing VLBI networks at centimetre wavelengths. With MeerKAT contributing to the EVN observations, both sensitivity and resolution were considerably improved, as clearly shown in the images below. This is a mutually beneficial partnership with enormous potential for science.
The significance of this collaboration is far-reaching. It paves the way for future internationalpartnerships that could lead to unique scientific discoveries. MeerKAT is the precursor to the mid-frequency array of the Square Kilometre Array Observatory (SKAO) in South Africa, now under construction, which is designed to deliver high-quality data products with exceptional efficiency. This role makes it a crucial pathfinder for future projects and collaborations. MeerKAT’s partnership with the EVN showcases innovative methods for scientific research with this cutting-edge instrument and lays the groundwork for realising SKA-VLBI in the future.
The South African Radio Astronomy Observatory (SARAO) and the Joint Institute for VLBI ERIC (JIVE) played a central role in achieving these results and producing the images that illustrate them. Based in the Netherlands, JIVE is a European Research Infrastructure Consortium (ERIC) that coordinates the EVN and processes its data.
Commenting on the outcome of this collaboration and its importance, JIVE Director Agnieszka Słowikowska said:
“For radio astronomers, accessing data from next-generation telescopes is key to expanding the frontiers of high angular resolution studies. At JIVE, we are committed to this goal by developing and implementing new methods to achieve what we could call ‘highest precision VLBI’. By fully exploiting the advanced calibration techniques these new instruments allow, we work to enable deeper observations of the Universe, support the study of more sources simultaneously, and provide the most accurate measurements of exotic phenomena.”
The integration of MeerKAT into the EVN has been prepared through various dedicated tests since 2022-2023. This observation, however, marks the first time MeerKAT has participated in a full, regular EVN observation, in the same way as the other EVN telescopes. The initial results of this observation, shown in the accompanying images, confirm MeerKAT’s potential as a powerful VLBI station. This represents a significant milestone for science, given the prominent roles of both MeerKAT and the EVN in global astronomical research.
MeerKAT, built and operated by SARAO, a national facility of South Africa’s National Research Foundation (NRF), was inaugurated in 2018 and has since served as a flagship instrument for astronomical discovery. It consists of 64 dishes, each 13.5 metres in diameter, distributed across an area of up to 8 km. The EVN, meanwhile, is currently the most sensitive VLBI network of radio telescopes in the world, enabling science at milliarcsecond resolution due to its baseline lengths of up to 9,000 km. Both infrastructures are set to benefit enormously from this partnership, each contributing in distinct and complementary ways.
Reflecting on MeerKAT’s enormous capabilities and its joint observations with the EVN, Pontsho Maruping, Managing Director at SARAO, said:
“MeerKAT has been highly successful in its mission to explore the radio sky in unprecedented detail, imaging some of the largest-scale structures in the Universe. At the same time, we place strong emphasis on collaborating with other instruments as we continue to develop MeerKAT’s scientific capabilities before its eventual integration into the SKA-Mid telescope.”
“We’re excited about the collaboration with our JIVE colleagues, using the power and versatility of MeerKAT, alongside other telescopes in the EVN network, harnessing the power of VLBI to target the most compact objects and reveal their finest details”, she continued.
Thanks to the high angular resolution and sensitivity of this new radio interferometric observation, astronomers were able to observe a stream of energetic plasma ejected from the vicinity of a supermassive black hole named J0123+3044. The observation lasted a total of 12 hours, with MeerKAT participating for 4 of those. The resulting images, both with and without MeerKAT data, were produced using methods that maximise sensitivity.
Images of the supermassive black hole ejecting jets of energetic particles, visible at radio wavelengths, obtained with the EVN array without (left) and with (right) the inclusion of MeerKAT. The combination of the two telescopes enables us to decipher the jet structure with great resolution and sensitivity. Image credits: JIVE, SARAO.
In these EVN measurements, MeerKAT and the Hartebeesthoek 26-meter telescope in South Africa provided the longest north–south baselines—the distances between pairs of telescopes that determine the angular resolution of the interferometric array. MeerKAT’s exceptional sensitivity played the dominant role in shaping the resolution of the deepest images.
Marcel Gouws, Senior Systems Analyst at SARAO, offered a brief overview of the technological work that made this achievement possible:
“To reach this milestone, we needed to overcome significant technical challenges, including precise beamforming phase corrections and the development of specialised data products. The dedication and coordinated efforts of both the EVN and MeerKAT teams were pivotal to this success, enabling the next steps in future collaborations.”
This development marks a major step in South Africa’s 50-year history of Very Long Baseline Interferometry, which began when the Hartebeesthoek Radio Astronomy Observatory, currently part of the NRF-SARAO, joined the EVN. With MeerKAT now capable of initial VLBI observations, South African stations greatly enhance the resolving power of current VLBI arrays. This milestone underscores the country’s continued dedication to astronomical breakthroughs through international collaboration.
Jessica Dempsey, Director of ASTRON and JIVE Council Chair, applauded the achievement, saying:
“This is a great achievement by the SARAO team, enabling MeerKAT to observe together with the EVN. It marks an important milestone in the expansion of the global VLBI network—where arrays such as the EVN, MeerKAT, and soon the SKAO will work in synergy. This collaboration not only showcases the power of international partnerships in radio astronomy but also paves the way for transformative scientific discoveries through cutting-edge technological innovation.”
Together, MeerKAT and the EVN are forging a new path in radio astronomy, promising deeper insights into the cosmos and its mysteries.
EVN stations
Effelsberg (Germany), e-MERLIN (Lovell, Jodrell Bank Mark II, Pickmere, Darnhall, Knockin, Defford, Cambridge; United Kingdom), Hartebeesthoek (South Africa), Irbene (Latvia), Kunming, Medicina (Italy), Metsähovi (Finland), Noto (Italy), Onsala (Sweden), PyeongChang (South Korea), Sardinia (Italy), Tamna (South Korea), Tianma (China), Toruń (Poland), Ulsan (South Korea), Ürümqi (China), Westerbork (Netherlands), Wettzell (Germany), Yebes (Spain), Yonsei (South Korea)
Contact
Fernando Camilo, SARAO Chief Scientist. Email: fernando@sarao.ac.za
Ioanna Kazakou, JIVE Communications Officer. Email: kazakou@jive.eu
Additional information on SARAO
The South African Radio Astronomy Observatory (SARAO), a facility of the National Research Foundation (NRF), is responsible for managing all radio astronomy initiatives and facilities in South Africa, including the MeerKAT radio telescope in the Karoo, as well as the Geodesy and VLBI activities at the HartRAO facility. SARAO also coordinates the African Very Long Baseline Interferometry Network (AVN) for the eight SKA partner countries in Africa, along with South Africa’s contribution to the infrastructure and engineering planning for the Square Kilometre Array radio telescope. To maximise the return on South Africa’s investment in radio astronomy, SARAO is managing programmes to create capacity in radio astronomy science and engineering research, as well as the technical capacity required to support site operations.
Additional information on JIVE
For over 30 years, the Joint Institute for VLBI ERIC (JIVE) has been leading the development and use of Very Long Baseline Interferometry (VLBI) and other radio astronomy techniques. Using VLBI, JIVE combines data from multiple radio dishes to create an image of a celestial radio source as if it were observed by a telescope the size of the Earth.
In 2014, JIVE became the first European Research Infrastructure (ERIC) dedicated to astronomy. It coordinates the radio telescopes of the European VLBI Network (EVN), correlates their data, and supports astronomers using the EVN throughout their research, from proposal ideas to data reduction.
JIVE's full members are the Netherlands (NWO, ASTRON), France (CNRS), Italy (INAF), Latvia (Ministry of Education and Science of the Republic of Latvia), Spain (IGN), Sweden (VR), and the United Kingdom (STFC). The MPIfR in Germany, the NRF-SARAO in South Africa, and the NAOC/SHAO in China are JIVE's participating research institutes and members of the JIVE Council as well. For an overview, click here.