Ground-based interferometry on Earth has proven to be a successful method for conducting science by combining light from several telescopes into acting like a single large telescope. But how can a ultraviolet (UV)/optical interferometer telescope on the Moon deliver enhanced science, and can the Artemis missions help make this a reality? This is what a recently submitted study to the SPIE Astronomical Telescopes + Instrumentation 2024 conference hopes to address as a team of researchers propose the Artemis-enabled Stellar Imager (AeSI) that, as its name implies, could potentially be delivered to the lunar surface via NASA’s upcoming Artemis missions. This proposal was recently accepted as a Phase 1 study through NASA’s Innovative Advanced Concepts (NIAC) program and holds the potential to develop revolutionary extremely high-angular resolution way of conducting science on other planetary bodies while contributing to other missions, as well.
Here, Universe Today discusses this incredible research with Dr. Gioia Rau, who is an Astrophysicist at NASA’s Goddard Space Flight Center and Program Director at NSF, regarding the motivation behind this study, significant takeaways from this work, next steps should this proceed past Phase 1, long-term goals regarding lunar surface locations, and how AeSI can advance our understanding of exoplanet habitability. Therefore, what was the motivation behind this study?
Dr. Rau tells Universe Today, “The motivation behind this study is to assess whether we can build and operate, in collaboration with the human Artemis Program, a large, sparse aperture observatory (interferometer) on the lunar surface and determine whether it is competitive with a previously developed free-flyer option. The end goal is to enable the study of our Universe at Ultra High Definition at ultraviolet and optical wavelengths with ~200x the angular resolution of HST! Ultraviolet observations are unobtainable from the Earth’s surface due to the overlying atmosphere and even in the visible the Earth’s atmosphere limits the ultimate resolution obtainable with ground-based interferometers.”
For the study, the researchers build off longstanding proposals for putting UV/optical interferometers in space, but due to the lack of infrastructure on the lunar surface, scientists have preferred using satellites and orbiters, which the researchers refer to as “free-flyers”. For AeSI, the researchers propose constructing a lunar interferometer using infrastructure being brought to the Moon via NASA’s Artemis Program with the goal of delivering advanced science regarding exoplanetary systems, including the surfaces of stars, their interiors, magnetic fields, space weather, and exoplanet habitability.
Artist’s rendition of six interferometers on the lunar surface being combined to simulate one, giant interferometers. (Credit: Figure 3/Rua et al. (2024))
To accomplish this, AeSI will be comprised of a 1-kilometer baseline UV/optical imaging interferometer near the lunar south pole, which is the landing region for the Artemis Program, specifically Artemis III. Along with the enhanced science, the team also promotes the project’s scalability, noting it can potentially be as large as 30 or more elements to serve as a single interferometer. Additionally, the team addresses several issues that could arise during this endeavor, including lunar dust, seismic activity, and the use of robotic aides as auxiliary support for construction. Therefore, what are the most significant takeaways from this study?
Dr. Rau tells Universe Today, “The most significant takeaways from this study are that the project is feasible, demonstrating that the visionary idea of our PI, Dr. Kenneth Carpenter (NASA/Goddard Space Flight Center), can be realistically developed. The study provides important recommendations for further research and technology development, which will be crucial for advancing the project and addressing any technical challenges and further technology development needed.”
As noted, AeSI has been approved for a Phase 1 study (less than 4% success rate!) through NASA’s Innovative Advanced Concepts (NIAC) program, with NIAC having successfully helped advance technology within the aerospace industry since 1998, with its original name being NASA Institute for Advanced Concepts until it was closed in 2007. Only two years later, Congress requested the National Academy of Sciences to review why it was closed, which made recommendations going forward, resulting in the current NIAC program in 2011.
Since then, NIAC has contributed technological advancements in nanosatellites, planetary exploration, exoplanet spectroscopy, astrophysics, cosmology, solar science, human space exploration, and many others. These proposals go through three phases, with each phase enabling increased funding and time for the project. Therefore, given AeSI is a Phase 1 study, what are the next steps if it should be approved for advancement?
Dr. Rau tells Universe Today, “The next steps would involve seeking Phase 2 support from NIAC as well as exploring additional funding and resources. Phase 2 would focus on further developing and refining the initial 9-month study we are doing in Phase 1. We believe our visionary concept has the potential to revolutionize scientific research and provide a significant opportunity for technology demonstration on the lunar surface, therefore we truly hope we will obtain further support by NIAC and/or other supporting sources!”
Regarding long-term goals for AeSI, Dr. Rau tells Universe Today, “There are multiple constraints on locating interferometers on the lunar surface, in particular optical and UV ones! We describe this more in detail in the NIAC Phase 1 study final report, which will be public, and published early next year. Our project is currently planned to start with a stage 1 made of 15 rovers in an elliptical array configuration with a 1 km major axis. The observatory will evolve in later stages to an array of ~30 rovers with an enhanced hub to combine the beams from the larger number of rovers (mirror stations) and will provide extremely high angular resolution of celestial objects such as distant sun-like stars, Active Galactic Nuclei (AGN), exoplanets, cool evolved stars, and more!”
As noted, along with the enhanced science being conducted on stars, one of the science goals of AeSI will also be to ascertain the habitability of exoplanets, which comes as NASA has confirmed the existence of more than 5,700 exoplanets within our Milky Way Galaxy. Of these, almost 70 are currently designated to be in the ‘habitable zone’ of their parent star, with 29 of them potentially being terrestrial (rocky) worlds and the remaining 41 potentially being “water worlds” or mini-Neptunes. These potentially habitable worlds have been found to orbit within and outside the habitable zone, with some whose orbits take them both inside and outside the habitable zone during one orbit. Therefore, how could AeSI advance our understanding of exoplanet habitability?
Dr. Rau tells Universe Today, “AeSI will provide a deeper insight into the characteristics of the parent stars in distant exoplanetary systems. By analyzing these stars more thoroughly, we can gain a better understanding of the conditions that influence the habitability of their orbiting planets. This includes examining the interactions between planets and their stars, which can significantly impact the potential for life on these exoplanets.”
As NASA prepares to send humans back to the Moon for the first time since 1972 with the Artemis Program, it’s important to note the incredible science that can be accomplished with the infrastructure established by Artemis. Therefore, with ground-based interferometry from the Earth being a long established and successful scientific field having contributed to better understanding radio astronomy, solar physics, nebulas, galaxies, and exoplanets, AeSI provides a unique opportunity to conduct revolutionary science, images of distant stars with the highest angular resolution ever, on other planetary bodies while testing new technologies, as well.
Dr. Rau concludes by telling Universe Today, “AeSI will provide the very first ultra-high angular resolution views of the Universe in the ultraviolet (UV). This is a huge leap for so many aspects of astrophysics, from understanding magnetic activity in stars and its impact on surrounding planets, to detailed studies of exoplanets, space weather, AGN, stellar astrophysics and more! AeSI’s high-angular resolution ultraviolet and optical observations will open new frontiers in astrophysics, offering a richer and more detailed picture of the universe’s most energetic and enigmatic components.”
How will AeSI help enhance UV/optical interferometry in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
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