Pathways to Discovery in Astronomy and Astrophysics for the 2020s

What are the key scientific challenges for astronomy and astrophysics in the next decade? Pathways to Discovery in Astronomy and Astrophysics for the 2020s, the National Academies' latest decadal survey, identifies the most compelling science goals and presents an ambitious program of ground- and space-based activities for future investment. The report recommends critical near-term actions to support the foundations of the profession as well as the technologies and tools needed to carry out the science.

Key Scientific Challenges for the Next Decade

Worlds and Suns in Context

Priority Area: Pathways to Habitable Worlds

Understanding the connections between stars and the worlds that orbit them, from nascent disks of dust and gas through formation and evolution, is an important scientific goal for the next decade. The effort to identify habitable Earth-like worlds in other planetary systems and search for the biochemical signatures of life will play a critical role in determining whether life exists elsewhere in the universe.


New Messengers and New Physics

Priority Area: New Windows on the Dynamic Universe

Over the next decade, a range of complementary observations—from radio to gamma rays, gravitational waves, neutrinos, and high-energy particles—will enable investigations into the most energetic processes in the universe and address larger questions about the nature of dark matter, dark energy, and cosmological inflation. These growing capabilities will enable closer study of neutron stars, white dwarfs, black hole collisions, stellar explosions, and the birth of our universe.


Cosmic Ecosystems

Priority Area: Unveiling the Drivers of Galaxy Growth

Research in the coming decade will revolutionize our understanding of the origins and evolution of galaxies, from the cosmic webs of gas that feed them to the formation of stars. New observational capabilities across the electromagnetic spectrum along with computation and theory will help resolve the rich workings of galaxies on all scales.


Space and Ground Based Initiatives

The survey’s key recommendations for space- and ground-based initiatives are summarized below. The full report provides detailed guidance on the implementation of major programs and which programs or projects are the most urgent within their category. The report emphasizes that a range of scales and capabilities are necessary for a healthy, balanced, and visionary program.

Implementing the Next Great Observatories

Given the large costs and development timescales for the next generation of space telescopes, the decadal survey recommends that NASA create the Great Observatories Mission and Technology Maturation Program as a new approach for planning and implementing large missions. The program would provide early investment in technology development for multiple mission concepts to lower the risks and costs of projects before they become too complex, large, and costly. The first entrant for the maturation program should be a large Infrared/Optical/Ultraviolet space telescope. The second entrants should be strategic Far-Infrared and X-ray missions.

The decadal survey recommends a large (~6m diameter) Infrared/Optical/Ultraviolet space telescope with high-contrast imaging and spectroscopy as the first mission to enter the Great Observatories Mission and Technology Maturation Program. This is an ambitious mission with the goal of searching for biosignatures from habitable zone exoplanets and providing a powerful new facility for general astrophysics. If mission and technology maturation are successful, as determined by an independent review, implementation should start in the latter part of the decade with a target launch in the first half of the 2040’s.

Sustaining and Balancing the Science

Many of the most exciting opportunities in multi-messenger astrophysics rely on observations of transient astrophysical phenomena discovered via gravitational waves and neutrinos. However, these events also require electromagnetic observations across the spectrum for identification and further study. NASA should establish a time-domain program of small to medium scale missions to sustain the necessary suite of space-based electromagnetic capabilities required to study transient and time-variable phenomena, and to follow-up multi-messenger events.

The large gap in cost and capability between medium-class Explorer missions and the large strategic missions is a significant impediment to achieving the broad set of decadal science priorities. Therefore, NASA should institute a new Probe-class line of missions, with mission proposals competed based on priority areas identified by decadal surveys. The first two priorities for probe-class missions should be a Far-Infrared probe and an X-ray probe to complement the Athena mission. The first probe-class mission should commence within this decade.

NASA’s augmentation of the Explorer program in response to a recommendation from the National Academies’ last decadal survey has resulted in an increased rate of proposal opportunities and launches, yielding a tremendous science output. NASA should maintain Explorer launch rates at the level specified in New Worlds, New Horizons in Astronomy and Astrophysics.

Learn more about these recommendations in Chapter 6 and Chapter 7 of the report

Balancing Operations and Science

NSF’s Major Research Equipment and Facilities Construction (MREFC) program funds the construction of large facilities, but it leaves the sponsoring divisions responsible for lifetime operations and maintenance costs. These operations costs grow with each new facility added and will significantly restrict NSF’s ability to fund research grants and other science programs by mid-decade unless changes are made. NSF should develop a sustainable plan for supporting the operations costs of its astronomical facilities, balanced with funding for scientific research. The addition of new MREFC facilities should be contingent on the implementation of this plan.

NSF’s Division of Astronomical Sciences should establish a regular cadence of reviews of its operational portfolio, at a frequency that is sufficient to respond to changes in scientific and strategic priorities in the field. An appropriate target is at least two reviews per decade.

Mid-scale programs (~$4 – 100 million) are vital to astronomy research. NSF should create three new tracks within its Mid-Scale Innovations Program. The first track should be for regularly competed, open calls. The second track should solicit proposals in strategically identified priority areas, with time domain astrophysics as the highest priority. The third track should invite ideas for upgrading and developing new instrumentation on existing facilities.

New Large Facilities

Participation in the U.S. Extremely Large Telescope (ELT) Program is the highest priority recommendation for ground-based astronomy. The ELTs would provide observational capabilities unmatched in space or on the ground and would enable a huge range of new discoveries. NSF should invest in at least one and ideally both ELTs – the Giant Magellan Telescope (sited in Chile) and the Thirty Meter Telescope (sited in either Hawai’i or the Canary Islands). NSF should undertake an external review to evaluate the financial and programmatic viability of both proposed U.S. ELT projects.

Observations of the Cosmic Microwave Background (CMB) have been central to establishing the standard model of cosmology, and these measurements are increasingly important for science ranging from the study of galactic ecosystems to the formation of cosmic structure. NSF and DOE should jointly pursue the design and implementation of the next generation ground-based cosmic microwave background experiment (CMB-S4).

It is of essential importance to astronomy that the Karl Jansky Very Large Array (JVLA) and the Very Long Baseline Array (VLBA) be replaced by an observatory roughly an order of magnitude more sensitive. NSF should proceed with a program to support science design, development, cost studies, and antenna prototyping for the Next Generation Very Large Array (ngVLA). After completion of the studies, NSF should convene a review to assess the project’s readiness and available budget and proceed with construction if possible.

Key Activities in Related Fields

Gravitational wave astrophysics is one of the most exciting frontiers in science. The phased upgrades of current generation facilities such as LIGO and technology development for next-generation observatories promise to answer fundamental questions in physics and astronomy. While this project falls under the purview of NSF’s Physics division, the decadal survey endorses this project as important for meeting its scientific objectives.

The IceCube-Generation 2 neutrino observatory would provide significantly enhanced capabilities for detecting high-energy neutrinos, enabling the study of some of the most energetic phenomena in the universe. While this project falls under the purview of NSF’s Physics division, the decadal survey endorses this project as important for meeting its scientific objectives.

Learn more about these recommendations in Chapter 5 and Chapter 7 of the report

Supporting the Foundations for Astronomy and Astrophysics

The people who make up the profession are the most fundamental component of the astronomy and astrophysics research enterprise. Diversity is a driver of innovation, and the field can be at its most innovative only when it fully utilizes the broadest range of human talent. The decadal survey recommends several programs to support early-career researchers, with a strong emphasis on broadening access, removing barriers to participation, and creating an environment that eschews harassment and discrimination of all kinds.

Diversity, Equity, and Inclusion

NASA, NSF, and DOE should implement a cross-agency working group to establish a consistent format and policy for regularly collecting, evaluating, and publicly reporting demographic data and indicators.

NASA, DOE, and NSF should consider including diversity -- of project teams and participants --in the evaluation of funding awards to individual investigators, project and mission teams, and third-party organizations that manage facilities.

The astronomy community should, through the American Astronomical Society and in partnership with other major professional societies, work with experts from other experienced disciplines (such as archaeology and social sciences) and representatives from local communities to define a Community Astronomy model of engagement that advances scientific research while respecting, empowering, and benefiting local communities.

NASA, NSF, DOE, and professional societies should ensure that their scientific integrity policies address harassment and discrimination by individuals as forms of scientific misconduct.

Racial/ethnic diversity among astronomy faculty remains abysmal. Funding agencies should increase incentives for improving diversity among astronomy and astrophysics faculty, such as increasing the number of awards that invest in the development and retention of early-career faculty and other activities for members of under-represented groups.

Workforce and Training

NASA, NSF, and DOE should reinvest in professional workforce diversity programs at the division/directorate levels. “Bridge” type programs to provide support across academic transitions in the higher-education pipeline and into the professional ranks are especially promising.

NASA, NSF, and DOE should implement undergraduate and graduate “traineeship” funding to incentivize department/institution-level commitment to professional workforce development, and prioritize interdisciplinary training, diversity, and preparation for a variety of career outcomes.

NASA and NSF should continue and increase support for postdoctoral fellowships that provide independence while encouraging the development of scientific leaders who advance diversity and inclusive excellence.

Dark Sky and Environmental Protection

Mega satellite constellations will more significantly affect work in astronomy and astrophysics in the future. The NSF should work with the appropriate federal regulatory agencies to develop and implement a regulatory framework to control the impacts of satellite constellations on astronomy.

To ensure that the skies remain open to radio astronomy, NSF, in partnership with other agencies as appropriate, should support and fund a multi-faceted approach to the avoidance and mitigation of radio-frequency interference.

Human-induced climate change will be one of the greatest challenges of this century. The astronomy community can minimize its impact on climate by reducing travel-related carbon emissions. Examples include remote observing, hybrid conferences, and virtual conferences.

Learn more about these recommendations in Chapter 3

Supporting the scientific foundations of astronomy and astrophysics is essential for maintaining a balanced program. These investments include support for processing, archiving, and interpreting data; theoretical modeling and simulations; and laboratory and computational analyses.

Investigator Grants and Programmatic Balance

Over the last decade, there has been a growing imbalance between funding for facility operations and maintenance, and supporting the work of scientists. To support science performed by individual investigators, NSF should increase funding for Astronomy and Astrophysics Research Grants by 30 percent over five years. This will have the effect of restoring proposal success rates to a healthy competitive level.

Low funding rates at both NASA and the NSF have affected the ability to carry out theoretical investigations, which are crucial for interpreting essentially all signals received from space. NASA’s Astrophysics Theory Program should resume an annual cadence, and receive a 30 percent funding augmentation over 5 years.

Laboratory experiments are crucial for measuring the parameters needed to interpret data from distant astrophysical objects, such as characterizing exoplanet atmospheres. NASA and NSF should convene a panel of experts to identify what laboratory data is needed to support next generation observatories; identify the resources that can be brought to bear to satisfy those needs; and consider new approaches for building the requisite databases.

Proposal success rates are an important indicator of program balance, particularly when aiming to give first-time early-career proposers a realistic chance of success. NSF, NASA, and DOE should release data on proposal success rates on an annual basis, and they should track metrics that allow them to statistically analyze what is being supported.

Data Analysis and Data Archiving

Researchers observing through NSF ground-based facilities must apply for separate funding to support data analysis. This is inefficient and causes delays, hampering the scientific output of the most powerful facilities. NSF should establish a mechanism for funding data analysis and production of high-level data products for large principal investigator-led programs on MREFC-scale astronomical facilities.

Astrophysical questions increasingly transcend traditional wavelength, division, and agency boundaries, and there is a growing need for data use across multiple archives. NASA and NSF should explore mechanisms to improve coordination among U.S. archive centers and to create a centralized nexus for interacting with the international archive communities.

Although community-based projects have done much to fill the needs for up-to-date data pipelines and software for ground-based telescopes, NSF could help to provide foundational support for these efforts. The NSF and stakeholders should develop a plan to address how to design, build, deploy, and sustain pipelines for producing science-ready data across all general-purpose ground-based observatories.

Learn more about these recommendations in Chapter 4 of the report.

Observational capabilities for astronomy would stagnate without new technologies and instrumentation. Early and significant investments in technology for large strategic missions and large NSF facilities would help refine budget and risk projections prior to construction and reduce the likelihood of cost and schedule overruns.

Recommendations for Technology and Instrumentation Development

NASA should increase funding levels for the Detector Development and Supporting Technology components of the Astrophysics Research and Analysis Program. Current funding levels are too small to advance technologies to acceptable levels for incorporation in future Explorer, suborbital, and SmallSat missions.

NASA should continue funding for the Strategic Astrophysics Technology Program, and should expand proposal calls to include intermediate level technology maturation targeted in strategic areas identified for the competed Probe class missions.

Looking to the coming decade, the need to support advanced technologies is even greater than it was a decade ago. NSF should restore the Advanced Technologies and Instrumentation Program to $14 million a year (FY20)—the same level of support it had in 2010—and further increase it to a target level of $20 million a year (FY20) by 2028.

Pathways to improving the balloon program include increasing the number of flights, achieving higher float altitudes, making the program accessible to more PIs, and exploring methods for supporting new PIs. NASA should undertake an external review of the balloon program to establish a framework for accomplishing these goals.

Learn more about these recommendations in Chapter 6 of the report.

Achievements from the Past Decade

The past decade has been one of extraordinary discoveries in astronomy and astrophysics, including:

About the Study

The decadal survey identifies the most compelling science challenges and frontiers in astronomy and astrophysics and presents a comprehensive research strategy to advance astronomy and astrophysics in the next decade and beyond. This is the seventh decadal survey for astronomy and astrophysics conducted over the history of the National Academies, and like its predecessors, it will serve as a guide for scientists, policy makers, and agencies invested in the astronomical sciences.

This study’s key objective was to map the national and international scientific landscape and to chart a path for investment, identifying programs with transformational scientific potential and new observational capabilities. The recommendations in this report are meant to support the people who drive innovation and discovery, and to promote the technologies and tools needed to carry out the science. The report also recommends sustaining activities on a broad range of cost and timescales, as well as activities that enable future visionary projects by maturing them scientifically and technically.

The National Academies selected committee members in a process independent of sponsoring agencies after casting a wide net for participant recommendations. Members of the 20-person steering committee were selected to cover as fully as possible the scientific scope of the survey, the range of observational (ground, space, and particle/gravitational astrophysics) and theoretical disciplines, as well as technical and managerial background in space and/or ground-based facilities, and to comprise as representative a group of experts as possible in terms of individual, institutional, and geographical demographics. National Academies policies governing potential conflicts of interest by steering committee and panel members were strictly enforced. In particular, broad and open-minded thinkers were sought out as opposed to advocates for individual missions or subfields.

The information gathering and deliberative phases of the decadal survey were carefully coordinated. Members of the astronomical community were invited to submit whitepapers to the survey, and these papers formed the foundation and starting point for all of the panel deliberations. The survey received 573 science whitepapers in early 2019, contributed by more than 4500 authors from the astronomical community. A second call for APC (Activity, Project, and State of Profession Consideration) whitepapers in July 2019 elicited 294 responses. Every whitepaper was assigned to and read by one or more of the decadal panels.

The decadal survey appointed 13 panels as listed below.  All in all, these panels included 127 members.  Each panel drafted its own report with suggestions for the steering committee to consider as it held its own deliberations to reach its recommendations for the main report. To underscore the importance of the panel reports, they have been published together with the main report as appendices.

Science Panels

  • Panel on Compact Objects and Energetic Phenomena
  • Panel on Cosmology
  • Panel on Galaxies
  • Panel on Exoplanets, Astrobiology, and the Solar System
  • Panel on the Interstellar Medium and Star and Planet Formation
  • Panel on Stars, the Sun, and Stellar Populations

Program Panels

  • Panel on An Enabling Foundation for Research
  • Panel on Electromagnetic Observations from Space 1
  • Panel on Electromagnetic Observations from Space 2
  • Panel on Optical and Infrared Observations from the Ground
  • Panel on Particle Astrophysics and Gravitation
  • Panel on Radio, Millimeter and Submillimeter Observations from the Ground

State of the Profession Panel

  • Panel on State of the Profession and Societal Impacts

For the first time, the decadal survey included a panel specifically focused on the state of the profession and societal impacts. The panel’s report, published as an appendix to the decadal survey, provided critical input for the steering committee’s recommendations related to workforce and demographic issues in the field as well as areas of concern and importance to the community.

Sponsoring agencies briefed the committee on plausible budget scenarios but also asked that the committee be aspirational when setting scientific goals. The report recommends and ranks highest priority research activities and provides decision rules, where appropriate, to account for deviations in the projected budget or other unanticipated discoveries.

The field of astronomy and astrophysics is poised to tackle some questions that are so grand that the facilities and instruments needed to address them require commitment and timelines beyond the decade. Addressing these challenges requires re-imagining how large missions are developed and implemented. In particular, the most ambitious strategic missions demand more significant early investments in maturing mission concepts and technologies prior to adoption, with checks and course corrections along the way.

This decadal survey was sponsored by the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), the Department of Energy (DOE) Office of High Energy Physics, and the Air Force Office of Space Research (AFOSR). These federal agencies all participate in different aspects of the U.S. space- and ground-based astronomy and astrophysics program.

This study was organized by the National Academies’ Space Studies Board and Board on Physics and Astronomy. Learn more about our work by signing up for email updates.

Download the Report and Report Resources

Report Cover Images: NASA/ESA; NSF/LIGO/Sonoma State University/A. Simonnet; Illustris Collaboration; NASA Goddard; NASA/JPL-Caltech; NASA/Ames/JPL-Caltech • Science Theme Images: ESA/Hubble, M. Kornmesser; Event Horizon Telescope collaboration; NASA, ESA, STScI/AURA • Space and Ground Based Initiatives: ESA/Hubble & NASARubin Observatory/NSF/Aura • Foundations Images: iStockIllustris Collaboration; NASA Goddard • Achievements Images: R. Hurt/Caltech-JPL; NASA/W. Stenzel; Event Horizon Telescope Collaboration; ESO/L. Calçada/; Northrop Grumman; NAOJ