What can exozodiacal dust, also called exozodi, teach astronomers about identifying Earth-like exoplanets? This is what a recently submitted NASA white paper—which highlights key findings from the annual Architecture Concept Review—hopes to address as a team of researchers discussed how exozodi orbiting within a star’s habitable zone (HZ) could interfere with detecting Earth-like exoplanets.
This study, available on the arXiv preprint server, has the potential to help scientists better understand the observational constraints of observing Earth-like exoplanets and what improvements could be made for future telescopes and instruments to overcome these constraints.
Here, Universe Today discusses this incredible research with Dr. Miles Currie, who is a NASA Postdoctoral Program Fellow at NASA Goddard Space Flight Center, regarding the motivation behind the white paper, significant results, how the field of exozodi could expand in the future, and what exoplanetary systems could be targets for studying exozodi. Therefore, what was the motivation behind this white paper discussing exozodi?
Dr. Currie tells Universe Today, “NASA is currently developing a document synthesizing its strategy for research related to astrobiology over the coming decade, and part of this involves soliciting input from the astrobiology research community on topics that should be investigated in the near term. This white paper on exozodi was a response to that request for information.
“However, more broadly, this was an opportunity for myself and my co-authors to elevate an important issue within the wider community that will likely play a factor in future searches for Earth-like worlds and could ultimately impact our ability to search for signs of habitability and life on these planets.”
For the white paper, the researchers discussed the importance of studying exozodi, how it influences common imaging methods like direct imaging and spectroscopy, and recommendations for enhancing our knowledge of exozodi. As noted, exozodi is a large ring of dust orbiting within a star’s habitable zone that ranges in temperature between approximately 300 Kelvin (27°C/81°F) and approximately 1000 Kelvin (727°C/1,341°F).
The researchers highlight the lack of knowledge regarding exozodi’s origin with several hypotheses from past studies being proposed, including some major event or dust migrating from the colder outer regions of an exoplanetary system.
Regarding the observational constraints that exozodi causes for imaging instruments, the white paper discusses the issue of exozodi causing light-scattering issues, resulting in skewed data. They suggest that future studies could work to remove the exozodi data with the goal of identifying Earth-like exoplanets within the habitable zone. But what are the most significant results from this white paper?
“While this idea of exozodi hampering our ability to detect/characterize exoplanets is not new, few studies have done the work to start quantifying these impacts for next-generation observatories,” Dr. Currie tells Universe Today. “Since this white paper is mostly informational, there are no new results per se, but one nugget of information foreshadows an upcoming paper of mine: Interestingly, exozodi and atmospheric clouds can impact our observations of exoplanets in similar ways.
“It may be difficult to untangle these effects since we don’t know how cloudy the exoplanet may be, or how much exozodiacal dust there is in the system. This can lead to inaccurate measurements of exoplanet atmospheric parameters, like the level of molecular oxygen, a gas that could hint at the possibility of life.”
Dr. Currie mentions how exozodi has been studied for over a decade, with some past studies referenced in their white paper dating as far back as 1998. However, the amount of past research that directly studies exozodi is still limited, with estimates of the dust grain size that comprise exozodi ranging from 1 to 100 micrometers. Several studies postulate that exozodi dust potentially have the same origins as zodiacal dust within our own solar system: leftovers from the solar system formation or debris resulting from the collision of large objects.
Despite this, the NASA Goddard Space Flight Center created a Collisional Exozodi Simulation Catalog in 2013 where users can input a planet’s mass, distance from its star (semi-major axis), along with the size and inclination of the exozodi. The results display exozodi in optical light and scattered light, providing users with multiple ways of how astronomers observe exozodi. But despite the limited number of studies and knowledge, how does Dr. Currie see the field of exozodi expanding in the future?
“Hopefully this white paper fulfills its intention, which is to bring awareness to (and ultimately justify funding for) exozodi research,” Dr. Currie tells Universe Today. “At the end of the white paper, we provided several recommendations for viable near-term research directions, some of which are already being investigated by myself and colleagues. There are also new instruments and observatories coming online soon, both on the ground and in space, that will give us better sensitivity to investigate exozodi more thoroughly.”
Along with the limited number of studies on exozodi, there are a limited number of exoplanetary systems where astronomers have confirmed the existence of exozodi, including 51 Ophiuchi, Fomalhaut, Tau Ceti, and Vega, whose distances from Earth are 410 light-years, 25 light-years, 12 light-years, and 25 light-years, respectively.
51 Ophiuchi is hypothesized to be a young debris disk in the late stages of planetary formation, Fomalhaut was revealed by the James Webb Space Telescope to have multiple rings of debris at varying distances from its star, Tau Ceti was observed to have 10 times the dust as our solar system, and Vega was found to have a debris disk that is approximately 7.5 times the mass of the asteroid belt in our solar system.
Despite not directly naming exoplanetary systems in the white paper, which systems do Dr. Currie think could be prime targets for studying exozodi?
Dr. Currie tells Universe Today, “The reason we didn’t include specific exoplanetary systems is because all systems are expected to have some level of exozodiacal dust, and it can be difficult to predict how much dust there is in a given system until you go searching for it. The HOSTS survey has provided the best constraints on exozodi occurrence rates so far and is only partially complete.
“But there are other instruments and observatories coming online soon that may give us better sensitivity, which we mention in the recommendations section of the white paper. Perhaps another logical place to start would be surveying the HWO Preliminary Input Catalog (HPIC) target stars— eventually these will be the target systems for Earth-like exoplanet surveys.”
For now, the exact origin and exoplanetary system possession of exozodi largely remains a mystery. However, white papers like this can help scientists establish frameworks for conducting further research on exozodi and how it could influence the search for Earth-like exoplanets throughout the universe.
Additionally, since exozodi is currently hypothesized to have the same origins as zodiacal dust within our solar system, better understanding it could also help us gain greater insight into the formation and evolution of our solar system. Scientists have established that the universe is a very dusty place from object collisions and the warming of dust depending on the distance from its star, if it has one.
“Exozodi should not just be thought of as a nuisance for exoplanet observations; it has intrinsic scientific value,” Dr. Currie tells Universe Today. “Dust is a major component of stellar systems, and we still do not fully understand how various populations of dust are connected. Prioritizing exozodi studies therefore helps two fields at once— as the saying goes, ‘one astronomer’s noise is another’s signal.’
“Understanding the system as a whole—the star, the planet, all the way down to the tiniest dust grains—equips us to take on some of the great mysteries of our universe and can help us learn about our place within it to boot.”
More information: Miles H. Currie et al, Exozodiacal dust as a limitation to exoplanet imaging and spectroscopy, arXiv (2025). DOI: 10.48550/arxiv.2503.19932
Journal information: arXiv
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