ESASky - user friendly portal to access astronomical data from many data sources worldwide

Abstract

Introduction: The rapid growth in the volume, diversity, and complexity of astronomical data requires efficient mechanisms for discovery, access, and scientific exploitation. Astronomical archives and Virtual Observatory services are essential components of modern research infrastructures, providing access to extensive science-ready datasets. Within this context, valueadded services that simplify access and enhance usability play an increasingly important role. ESASky is a web-based astronomical portal developed by ESA’s European Space Astronomy Centre. It offers a user-friendly interface to access multi-wavelength and multi-messenger data from a wide range of missions, surveys, and observatories, streamlining the interaction between the scientific community and decades of accumulated astronomical data. Summary: ESASky offers a unified and visually oriented environment to explore and access heterogeneous astronomical datasets. It integrates data from multiple ESA missions, including Euclid, Gaia, James Webb and Hubble Space Telescopes and XMM-Newton, as well as numerous external archives connected through Virtual Observatory protocols. This enables seamless exploration of the sky across wavelengths and supports scientific investigations based on the combination of data from multiple facilities. A central aspect of ESASky is its focus on scienceready data products and intuitive visualisation. Users can explore the sky, visualise hierarchical multiresolution (HiPS) image mosaics, and access catalogues and spectra without requiring detailed knowledge of individual mission archives. By abstracting the complexity of underlying data infrastructures, ESASky adds value by transforming distributed datasets into a coherent and accessible environment for scientific discovery. Recent developments have further enhanced the capabilities of the portal. These include the interactive visualisation of time series data; sending ESASky sessions to an ESA Datalabs Jupyter notebook; and the provision of a JavaScript API that allows ESASky to be embedded within external applications, including ESA science archives. Additional features include extended access to Virtual Observatory data holdings, integration of multimessenger alert streams such as gravitational wave and neutrino events, and the development of pyESASky, enabling integration within JupyterLab environments. ESASky also plays an increasing role as a component within broader data ecosystems. It is integrated as a visualisation interface in several ESA science archives, enabling users to transition seamlessly from data discovery to detailed analysis workflows. By improving discoverability and accessibility of archival observations, the portal facilitates the re-use of existing datasets, thereby maximising the long-term scientific return of ESA and partner missions. Conclusion: ESASky demonstrates how user-oriented, value-added services enhance the accessibility and scientific exploitation of astronomical data. By providing a unified interface to explore multi-mission and multi-wavelength datasets, it facilitates efficient data discovery and re-use while supporting a wide range of scientific workflows. Its continued development, including expanded data integration and interoperability, ensures its role as a key component in maximising the long-term value of astronomical archives. Acknowledgments: This work builds on a longterm collaborative effort to develop and operate ESASky, with contributions from ESA mission teams, archive specialists, and data providers. It also benefits from the support of the Centre de Données astronomiques de Strasbourg and the standards and frameworks developed by the International Virtual Observatory Alliance, which enable interoperability across the astronomical data ecosystem.