In a groundbreaking development for astronomical observation, four powerful lasers have been activated at the European Southern Observatory’s (ESO) Paranal site in Chile. These lasers are part of the GRAVITY+ project, which aims to enhance the observational capabilities of the Very Large Telescope Interferometer (VLTI) by creating artificial stars to correct atmospheric distortion.
The GRAVITY+ project, spearheaded by the Max Planck Institute for Extraterrestrial Physics (MPE), combines the four 8-meter ESO Very Large Telescopes into a single, giant virtual telescope through a technique known as interferometry. This upgrade significantly boosts the performance of the VLTI, allowing for more precise measurements of black hole masses and facilitating studies of the Galactic Center and early Universe quasars.
Enhancing Observational Power
The installation of these lasers marks a significant milestone in the GRAVITY+ project. By enabling precise atmospheric corrections anywhere in the southern sky, the VLTI’s observational range has been expanded considerably. This advancement allows astronomers to overcome previous limitations that relied on bright natural reference stars, which were not always available near the target of interest.
According to Frank Eisenhauer, GRAVITY+ principal investigator and director at MPE,
“The VLTI with GRAVITY has already enabled so many unpredicted discoveries, we are excited to see how GRAVITY+ will push the boundaries even further.”
Technological Breakthroughs
MPE played a crucial role in the development of GRAVITY+, leading the overall design and installing four new, state-of-the-art wavefront sensors. These sensors observe the artificial stars created by the laser guide stars, providing advanced adaptive optics correction for the VLTI. This technique compensates for the blurring effects caused by Earth’s atmosphere, enhancing the VLTI’s capabilities with cutting-edge sensors, lasers, and deformable mirrors.
Before the laser installation, atmospheric correction at the VLTI depended on bright natural stars. Now, with the ability to create artificial stars, the VLTI can observe anywhere in the sky. The laser light excites a small spot in a layer of atmospheric sodium atoms, approximately 90 kilometers above Earth, creating a laser guide star and significantly expanding the VLTI’s reach.
Exploring the Galactic Center and Beyond
The MPE Infrared Group plans to utilize the new adaptive-optics systems for pioneering studies in two major research areas: the Galactic Center and early Universe quasars. The improved sharpness and sensitivity will allow researchers to detect and track faint stars orbiting the supermassive black hole at the Milky Way’s center, potentially enabling a direct measurement of the black hole’s spin.
Moreover, these enhancements will allow spatial resolution of the gas swirling around supermassive black holes in distant galaxies, leading to direct measurements of black hole masses across cosmic time. MPE astronomer Taro Shimizu noted,
“These upgrades open up the instrument to observations of objects in the early distant Universe, less than a few hundred million years after the Big Bang. We will be able to measure black hole masses more precisely than ever before.”
First Observations and Future Potential
The first laser target for the GRAVITY+ and ESO teams at Paranal was a cluster of massive stars at the center of the Tarantula Nebula. Initial observations revealed that a bright object in the nebula, previously thought to be the most massive single star known, is actually a binary of two stars. This discovery highlights the stunning resolving power and scientific potential of the upgraded VLTI.
This improvement is more than just an update; it was first envisioned decades ago. The laser system was proposed as early as 1986, before the VLT and VLTI even existed. The final report of the “Very Large Telescope Project,” co-authored by MPE director and Nobel laureate Reinhard Genzel, stated,
“If it could work in practice, it would be a breakthrough.”
Now, this breakthrough is a reality.
Consortium and Collaboration
The GRAVITY+ consortium includes several prestigious partners, highlighting the collaborative nature of this project:
- Max Planck Institute for Extraterrestrial Physics (MPE); Max Planck Institute for Astronomy; University of Cologne (Germany)
- Institut National des Sciences de l’Univers, French National Centre for Scientific Research; Institut de Planétologie et d’Astrophysique de Grenoble; Laboratoire d’instrumentation et de recherche en astrophysique (LIRA); Lagrange Laboratory; Centre de Recherche Astrophysique de Lyon (France)
- Instituto Superior Técnico’s Centre for Astrophysics and Gravitation (CENTRA); University of Lisbon; University of Porto (Portugal)
- University of Southampton (UK)
- Katholieke Universiteit Leuven (Belgium)
- University College Dublin (Ireland)
- Instituto de Astronomia – Universidad Nacional Autónoma de México (Mexico)
- European Southern Observatory
The GRAVITY+ project represents a significant leap forward in astronomical research, promising to unlock new insights into the universe’s most enigmatic phenomena. As the project progresses, the scientific community eagerly anticipates the groundbreaking discoveries that will undoubtedly follow.
