April 2026 update

This page provides an overview of the Habitable Worlds Observatory (HWO) Science Case Development Documents (SCDDs), which were developed in 2024-25 under the HWO Community Science Working Groups.  Such science cases are central for shaping top-level science objectives, instrument needs, and overall observatory architecture which will yield a transformative mission that addresses the priorities of the scientific community and the Astro2020 US Decadal Survey. 

In May–August 2025, this webpage supported the public release of ~70 science cases, and the solicitation of comments and endorsements from the worldwide astronomy research community.  A Google table linked below provided access to draft versions of the science cases, as well as links to papers that were subsequently posted on arXiv. The NASA HWO Community Science and Instrument Team, appointed in June 2025, is analyzing these science cases to help inform recommendations for mission requirements.

The majority of these documents were published in February 2026 in the Astronomical Society of the Pacific Conference Proceedings Series as HWO25 Proceedings Part I: Community Science Case Development Documents, edited by J. C. Lee, J. Noviello, S. LaMassa, and M. Postman.

The full published volume can be accessed:


Learn more about HWO:

HWO SCDD Curators

Stephanie LaMassa (STScI) & Jessica Noviello (UMBC/NASA GSFC)

HWO Community Science Working Groups (2024-25)

Evolution of the Elements 

Co-Chairs: Janice Lee (STScI) & Paul Scowen (NASA GSFC)

    • Trace the rise of the periodic table via studies of the formation, distribution, and evolution of stars, and their deaths.
    • Science themes: Stars & Stellar Populations, Star Formation, ISM, Cosmic Explosions

Galaxy Growth

Co-Chairs: Marc Postman (STScI) & Swara Ravindanath (Catholic University/NASA GSFC)

    • Study how galaxies, constituents, and their environments evolve over the history of the HWO-observable universe.
    • Science themes: Intergalactic Medium & Intracluster Medium, AGN, Ionizing Photons, Dark Sector

Living Worlds

Co-Chairs: Giada Arney (NASA GSFC) & Niki Parenteau (NASA Ames)

    • Exploring finding & characterizing potentially habitable exoplanets and search them for the possibility of life with HWO.
    • Science themes: Biosignature Possibilities, Biosignature Interpretation, Target Stars & Systems

Solar System in Context

Co-Chairs: Evgenya Shkolnik (Arizona State University) & Tyler Robinson (University of Arizona)

    • Explore UVOIR imaging and spectroscopy of Solar System Objects at all scales, along with exoplanet observations to understand the full range of planet possibilities and histories.
    • Science themes: Characterizing Exoplanets, Solar System Observations, Demographics & Architecture, Birth & Evolution

From the May-August 2025 public release and endorsement period

This portal hosts all ~60 current SCDDs, with documents being added through May 30. A subset of the authors are inviting feedback, while all welcome endorsement from members of the broader community. This open, transparent process ensures shared ownership of HWO’s scientific direction and supports future planning by the HWO Technology Maturation Project Office and the forthcoming Community Science and Instrument Team (CSIT).

The HWO SCDDs will be published through two venues: on arXiv and in the proceedings of the HWO25 Meeting. To support this, there are two deadlines:

  • Endorsers who sign on by June 22 will be acknowledged in the arXiv post (planned for the week of June 30), as well as the HWO25 proceedings.
  • A second deadline, August 15, allows additional time for community engagement and incorporation of feedback from the HWO25 Meeting; endorsers who sign on by then will be acknowledged in the HWO25 proceedings.
  • Update: while endorsements for submitted SCDDs are closed, there are new SCDDs that are still open to feedback and endorsement. All SCDDs will be re-opened for endorsement and feedback on July 11 until the August 15 deadline.

Notes:

  • These SCDDs are products of the community and do not reflect a commitment by the HWO Project to implement these ideas in the mission design or architecture.

  • The inclusion, form, and timing of acknowledgments, as well as participation in publication activities, are at the discretion of the authors (not all SCDDs may participate in every step uniformly

Please find the table of SCDDs at this link 

Each SCDD has a form in the table linked above where community members can choose to endorse a science case and/or provide comments for the principal authors to consider.

Guidelines

  • Comments will be addressed at the discretion of the SCDD's principal authors.
  • Be respectful and constructive in your comments.

Co-authorship types include:

Authorship type guidelines follow standard practice for scientific publication, e.g., nature.com.

  • Corresponding author
  • Principal Co-Authors: Authors responsible for drafting and coordinating the document.
  • Contributing Authors: Authors who made significant intellectual contributions.
  • Endorsers: Endorsement signals support for the scientific goals of the case and HWO’s proposed role for achieving them — not authorship or responsibility for its content.



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