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(Sub)mm-Wavelength Observations of Pre-Planetary Nebulae and Young Planetary Nebulae

WORKPLANS: Workshop on Planetary Nebula Observations

Instituto de Física e Química, Universidade Federal de Itajubá, Av. BPS 1303, Pinheirinho, Itajubá 37500-903, Brazil
ACRI-ST, 260 Route du Pin Montard, 06904 Sophia-Antipolis, France
Center for Imaging Science, School of Physics and Astronomy, and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623, USA
Department of Physics & Astronomy, University of Denver, 2112 E. Wesley Ave., Denver, CO 80208, USA
Departamento de Física Teórica, Universidad Autóonoma de Madrid, 28049 Madrid, Spain
Author to whom correspondence should be addressed.
Workshop scientific organizers. These authors contributed equally to this work.
Galaxies 2020, 8(1), 23;
Received: 27 February 2020 / Accepted: 5 March 2020 / Published: 16 March 2020
(This article belongs to the Special Issue Workplans II: Workshop for Planetary Nebula Observations)


This workshop is the second of the WORKPLANS series, which we started in 2016. The main goal of WORKPLANS is to build up a network of planetary nebulae (PNe) experts to address the main open questions in the field of PNe research. The specific aims of the WORKPLANS workshop series are (i) to discuss and prioritize the most important topics to be investigated by the PN community in the following years; (ii) to establish a network of excellent researchers with complementary expertise; (iii) to formulate ambitious observing proposals for the most advanced telescopes and instrumentation presently available (ALMA, SOFIA, VLT, GTC, HST, etc.), addressing those topics; and (iv) to develop strategies for major proposals to future observatories (JWST, ELT, SPICA, Athena, etc.). To achieve these goals, WORKPLANS II brought together experts in all key sub-areas of the PNe research field, namely: analysis and interpretation of PNe observational data; theoretical modeling of gas and dust emission; evolution from Asymptotic Giant Branch stars (PNe progenitors) to PNe; and the instrumentation and technical characteristics of the relevant observatories.
Keywords: planetary nebulae; stars: evolution; stars: late type; stars: mass-loss; stars: winds and outflows; stars: abundances; plasmas; dust; extinction; astrochemistry planetary nebulae; stars: evolution; stars: late type; stars: mass-loss; stars: winds and outflows; stars: abundances; plasmas; dust; extinction; astrochemistry

1. Introduction

Planetary nebulae (PNe) are formed by the ejection of the outer layers of evolved low and intermediate mass stars (∼1–8 M ). These objects have important roles in stellar evolution, in the enrichment of the interstellar medium (ISM) and in the evolution of galaxies. PNe are unique astrophysical laboratories in which we can investigate a wide variety of physical conditions from highly-ionized plasma to low-temperature dusty molecular regions in a spatially resolved manner. The findings from PNe research are applicable not only within the field, but also to a broad range of astrophysical objects with similar characteristics. Solving the open issues in the field of PN would therefore have a great impact not only for the PN research community, but also for the astronomical community as a whole.
The IAU PN Working Group discusses several open problems in the field of PN in the white paper entitled “The present and future of planetary nebula research” [1]. According to the paper, the main problems to be investigated by the community are:
  • uncover PNe that cannot be identified in the optical spectral range
  • improve central star evolutionary models
  • improve our knowledge of the atmospheres and winds of central stars
  • investigate the role of binary central stars in the evolution/formation of PNe
  • understand the history and mechanisms of mass-loss and structure formation in the circumstellar nebulae
  • improve techniques to derive chemical abundances
  • understand the abundance discrepancies measured from collisional and recombination lines
  • understand the formation mechanisms and survival of dust and molecules in PNe
The IAU PN working group white paper [1] also makes clear the need of further multi-wavelength observations in the PN research field and serves as a motivation for this workshop series. As in any topic in Astronomy, research on PNe is strongly driven by observations. New facilities built in the last few decades have improved the instruments and opened new spectral windows. Other new and forthcoming facilities, like ALMA and future telescopes such as JWST, will play a key role on the state-of-art astronomy research in the next years. Multiwavelength studies have become possible and, since different wavelength ranges probe different realms of chemistry and physics, the multiwavelength approach has already greatly improved our understanding of a wide range of astronomical objects, including PNe. This provides strong motivation for bringing together researchers with expertise in different wavelength ranges but with a common goal, namely, to understand the formation and evolution of PNe.
To fully explore the possibilities of the current and future instruments for the study of PNe, it is essential to aggregate different expertise—and the formation of an international network of scientists is then a natural step. Such a network provides a framework for the more efficient use of astronomical data and helps the PN community compete for time on the main telescopes, where a strong worldwide presence is an important factor.
The aim of the WORKPLANS series of workshops is to build a network of PN observers whose expertise in observations or theoretical analysis is spread across different sub-fields and spectral domains. The participants are organized in groups to formulate and draft proposal concepts for future observations maximizing the scientific output. During the workshop, we overview the key questions in the field, review the capabilities of observational facilities for (current and future) PN research, discuss which observations are best suited to solving the open problems in the field, and discuss the corresponding necessary analysis (in terms of tools and expertise).
Workshops with similar purposes have been organized with great success by the Asymptotic Giant Branch stars (AGB) research community, which has regular meetings strategically scheduled before each ALMA observing cycle. These meetings generated successful proposals that were granted observing time by this highly competitive observatory. The PNe community is relatively small, with a history of successful collaborations, as exemplified by the ChanPlaNS and HerPlaNS collaborations, both of which have produced significant results (e.g., [2,3,4,5,6,7,8]). These surveys were conceived during the Planetary Nebulae Workshop held in Rochester, NY, USA, in 2009 [9], with follow up at the Planetary Nebulae Workshop in Miraflores de la Sierra, Madrid, Spain in 2013; both meetings were organized with goals similar to those of WORKPLANS.


In the first WORKPLANS (25–29 January 2016), 51 researchers gathered in the Lorentz Center1, Leiden, Netherlands, for what was a very fruitful week. We started the meeting with a broad review of potential relevant topics to be investigated in the next years in the PNe field (with talks mainly on Monday). From Tuesday to Thursday, we focused on the scientific and technical aspects of specific wavelength ranges. In the mornings, we reviewed the capabilities of the main telescopes and instruments from each spectral range. The afternoons of these three days were dedicated to group discussions, networking and drafting observing proposals. Brief summaries of those discussion and proposal were given at the end of the day. On Friday, a summary was given by the group leaders, together with the current status of the draft. At least eight proposals were drafted and submitted soon after the workshop.


The format and goals of WORKPLANS II were similar to its previous edition. The main change was to reduce the time for the “X-ray observations” session, based on experience from WORKPLANS I and the increasing limitations of current facilities. The “X-rays” session was merged into the optical/ultraviolet session, which was made independent from the “infrared observations” session. These changes better balanced the current interests of the PN community and the facilities presently available and under construction. We also made small changes to the program in comparison to WORKPLANS I to add a little more time for plenary discussions. The workshop program is compiled in Table 1.
We organized the workshop to occur with ample time before deadlines for submission of observing proposals for various major facilities (in particular the JWST Cycle 1 proposal deadline), while attempting to avoid periods with classes in universities, to maximize attendance. The workshop was held during the week of 16–20 December 2019, in the Lorentz Center, the Netherlands.
WORKPLANS II had short-term and long-term practical goals. In the short term, we intended to reinforce the previously formed network, inviting at least some of the discussion leaders who emerged during the last workshop while expanding the network by inviting new participants. During the workshop, we formed task forces to address the topics previously mentioned. The task forces focused on a specific spectral realm to strategize proposals designed to use the current forefront facilities that can complement extant data. We invited experts in observations to cover the whole radiative spectrum, from X-rays to radio. Teams were assembled that also included specialists with deep knowledge of the fundamental physics of PNe and hence were prepared to analyze and model the observed objects. We also discussed preparations for the use of future instruments, in particular JWST, to be launched in 2022. This represents one of our key long-term goals. Another long-term goal is to keep WORKPLANS as a regular and productive tradition in the PNe community.
Fifty-five participants from all around the world, covering a wide range of expertise, gathered for WORKPLANS II. To maximize the workshop science output, in addition to having a wide range of expertise, in the preparation of our participants list and the program, we also considered the balance of gender, career stage, and geographical representation. The list of participants is compiled in Table 2, and the group picture appears in Figure 1.
A good measure of the success of WORKPLANS II was that, by the end of the workshop, the participants were already talking about a third installment.

4. Honoring Prof. Stuart Pottasch

The workshop paid tribute to the life and research of Stuart R. Pottasch and his extensive contribution to Planetary Nebulae research. Stuart was born in 1932 in New York city, and passed away on 4 April 2018 in Groningen. He married Anne Maria de Groot in Leiden with whom he had three children. After she passed away, he then married Greet Mientjes. Besides his passion for Planetary Nebulae, he was also well known for having a large collection of cactuses and parrots. He became one of the youngest professors (if not the youngest) at Groningen University, when he was appointed professor at the Kapteyn Astronomical Institute in 1963 by Adriaan Blaauw. His research legacy includes over 400 papers, of which 93 are first author (43 on PNe), and over 20 Ph.D. students, with his first student being Harm Habing.
While he is known for his research in PNe, Stuart’s research is very vast and diverse and includes bright rims, nova outbursts, solar corona, ISM, H II regions, and more. In fact, his two most cited papers are on the interpretation of the Solar UV emission line spectrum. His focus on PNe started with the launch of the Astronomical Netherlands Satellite (ANS) in 1974, and he went on to exploit facilities such as the IUE, IRAS, ISO, Spitzer, and later Herschel to better understand this fascinating stage of stellar evolution. His research in PNe is equally vast, and encompasses nearly all areas of PN research: studies of the central star, nucleosynthesis, nebular physical conditions and chemical composition, dust, PN distances and distribution, and PNe in the galactic context. In 1984, he published a fascinating and very comprehensive book on the subject “Planetary Nebulae: A study of late stages of stellar evolution”. During the last two decades, he became very interested in the use of IR lines to derive the nebular chemical composition and their enrichment to the ISM.
While gone, Stuart’s research will have a long lasting impact in the study of PNe for many years to come, and a current and new generation of PN scientist will keep benefitting from his tremendous and productive career.

Author Contributions

All authors contributed equally to the workshop and this paper conceptualization, methodology, resources, writing—original draft preparation, writing—review and editing, visualization, and funding acquisition. Project administration and supervision by I.A. All authors have read and agreed to the published version of the manuscript.


I.A. acknowledges the support of Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—Finance Code 001. This research is supported by Space Telescope Science Institute grant HST-GO-15953.001-A to RIT (J.K.). T.U. was supported by NASA under grant NNX15AF24G issued through the Science Mission Directorate. E.V. acknowledges support from the “On the rocks II project” funded by the Spanish Ministerio de Ciencia, Innovación y Universidades under grant PGC2018-101950-B-I00. The Workshop was organized with the financial support of the Lorentz Center, which was provided by the Netherlands Organization for Scientific Research (NWO) and the Leiden University.


We are very thankful to the Lorentz Center for the organizational support of WORKPLANS I and II.

Conflicts of Interest

The authors declare no conflict of interest.


The following abbreviations are used in this manuscript:
AGBAsymptotic Giant Branch
ALMAAtacama Large Millimeter/submillimeter Array
ChanPlaNSChandra Planetary Nebula Survey
CSICConsejo Superior de Investigaciones Científicas
ELTExtremely Large Telescope
ESOEuropean Southern Observatory
GTCGran Telescopio Canarias
HerPlaNSHerschel Planetary Nebula Survey
HSTHubble Space Telescope
IAAInstituto Astrofísica Andalucía
IACInstituto de Astrofísica de Canarias
IAUInternational Astronomical Union
IFFInstituto de Física Fundamental
INAOEInstituto Nacional de Astrofísica, Óptica y Electrónica
IPAGInstitut de Planétologie et d’Astrophysique de Grenoble
ISMInterstellar Medium
JPLJet Propulsion Laboratory
JWSTJames Webb Space Telescope
NASANational Aeronautics and Space Administration
NSFNational Science Foundation
NUINational University of Ireland
OANObservatorio Astronómico Nacional
OIR LabNational Optical-Infrared Astronomy Research Laboratory
PNPlanetary Nebula
RITRochester Institute of Technology
SETISearch for Extraterrestrial Intelligence
SOFIAStratospheric Observatory for Infrared Astronomy
SPICASpace Infrared Telescope for Cosmology and Astrophysics
UCLUniversity College London
UNAMUniversidad Nacional Autónoma de Mexico
VLTVery Large Telescope
WORKPLANSWorkshop on Planetary Nebula Observations


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Figure 1. Participants of WORKPLANS II.
Figure 1. Participants of WORKPLANS II.
Galaxies 08 00023 g001
Table 1. WORKPLANS II program.
Table 1. WORKPLANS II program.
Monday 16 December
09:30–10:00Arrival, office assignment, coffee and tea
10:00–10:10WelcomeLorentz Center Staff
10:10–10:20Goals and Structure of the MeetingIsabel Aleman
10:20–10:40Talk In Honour to Prof. S. PottaschJeronimo Bernard-Salas
Session 1: Open Problems and Possible Solutions IChair: Letizia Stanghellini
10:40–11:05Uncertainties in AbundancesMonica Rodriguez
11:05–11:30The Abundance Discrepancy ProblemRoger Wesson
11:30–12:00Plenary Discussions
12:00–13:30Lunch and Informal Discussions
Session 2: Open Problems and Possible Solutions IIChair: Jorge Garcia-Rojas
13:30–13:55S-Process Elements in PNeNick Sterling
13:55–14:20PAHs in PNeEls Peeters
14:20–14:45Dust budget in galaxiesMikako Matsuura
14:45–15:10Challenges of multi-wavelength PN surveysQuentin Parker
15:10–15:40Plenary Discussions
15:40–16:00Coffee and Tea Break
Session 3: Open Problems and Possible Solutions IIIChair: Eva Villaver
16:00–16:25Shaping of Planetary NebulaeNoam Soker
16:25–16:50Binaries in Planetary NebulaDavid Jones
16:50–17:30Plenary Discussions
17:30–18:00Posters–flash presentations
18:00Wine and Cheese welcoming party with poster session
Tuesday 17 December
Session 4: Infrared IChair: Jan Cami
09:00–09:30IR ObservatoriesEric Lagadec
09:30–09:50Observations of Planetary Nebulae with Herschel and AKARIToshiya Ueta
09:50–10:10Observations of Planetary Nebulae with JWSTRaghvendra Sahai
10:10–10:30Observations of PNe/Evolved StarsElvire De Beck
with SPICA/Origins Space Telescope
10:30–11:00Coffee and tea break
11:00–12:00Plenary Discussions–Which infrared data do we need
to solve the open questions?
12:00–13:30Lunch and Informal Discussions
Session 5: Infrared IIChair: Griet Van de Steene
13:30–14:30Defining Strategic Plan–Defining Projects and Groups
14:30–18:00Hands-on Sessions–Groups discuss and draft proposals
Wednesday 18 December
Session 4: Optical, UV, X-Rays IChair: Denise Gonçalves
09:00–09:30Optical/UV Observatories IRomano Corradi
09:30–09:50Optical/UV Observatories IIHenri Boffin
09:50–10:10What MUSE can do for PNeJeremy Walsh
10:10–10:30X-Rays Observatories and the Observation of PNeMartin Guerrero
10:30–11:00Coffee and tea break
11:00–12:00Plenary Discussions–Which Optical/UV/X-rays data
do we need to solve the open questions?
12:00–13:30Lunch and Informal Discussions
Session 5: Optical, UV, X-Rays IIChair: Joel Kastner
13:30–14:30Defining Strategic Plan–Defining Projects and Groups
14:30–18:00Hands-on Sessions–Groups discuss and draft proposals
Thursday 19 December
Session 6: Radio to Submillimetre IChair: Valentin Bujarrabal
09:00–09:30Radio IWouter Vlemmings
09:30–10:00Radio IICarmen Sanches-Contreras
10:00–10:30Polarization and Magnetic Fields in PNeLaurence Sabin
10:30–11:00Coffee and tea break
11:00–12:00Plenary Discussions–Which radio/Sub/mm data
do we need to solve the open questions?
12:00–13:30Lunch and Informal Discussions
Session 7: Radio to Submillimetre IIChair: Albert Zijlstra
13:30–14:30Defining Strategic Plan–Defining Projects and Groups
14:30–18:00Hands-on Sessions–Groups discuss and draft proposals
Friday 20 December
Session 10: Wrap UpChair: Quentin Parker
09:00–09:30Workshop SummaryQuentin Parker
09:30–11:20Summary of the prepared proposalsGroup Leaders
11:20–12:00Closing RemarksOrganizers
Table 2. WORKPLANS II participants list.
Table 2. WORKPLANS II participants list.
Isabel AlemanUniversidade Federal de ItajubáBrazil
Jeronimo Bernard-SalasACRI-STFrance
Joel KastnerRITUSA
Toshiya UetaUniversity of DenverUSA
Eva VillaverUniversidad Autónoma de MadridSpain
Lecturers and Participants
Stavros AkrasUniversity of Rio GrandeBrazil
Karla Ziboney Arellano-CórdovaIACSpain
Mike BarlowUCLUK
Henri BoffinESOGermany
Panos BoumisNational Observatory of AthensGreece
Jesse BublitzRIT & IPAGUSA, France
Valentin BujarrabalOANSpain
Jan CamiUniversity of Western OntarioCanada
SETI InstituteUSA
Alessandra CandianUniversity of AmsterdamNetherlands
Alexandros ChiotellisNational Observatory of AthensGreece
Romano CorradiGTC - IACSpain
Elvire De BeckChalmers University of Technology,Sweden
Onsala Space Observatory
Jorge Garcia-RojasIACSpain
Veronica Gomez-LlanosUNAMMexico
Denise GonçalvesValongo ObservatoryBrazil
Martin GuerreroIAA-CSICSpain
Harm HabingLeiden UniversityNetherlands
David JonesIACSpain
Eric LagadecNice ObservatoryFrance
Foteini (Claire) LykouThe University of Hong KongChina
Arturo ManchadoIACSpain
M. Belén MariValongo ObservatoryBrazil
Mikako MatsuuraCardiff UniversityUK
Rodolfo MontezHarvard-Smithsonian Center for AstrophysicsUSA
Masaaki OtsukaKyoto UniversityJapan
Quentin ParkerThe University of Hong KongHong Kong, China
Els PeetersUniversity of Western OntarioCanada
SETI InstituteUSA
Andrés Felipe Perez-SanchezLeiden UniversityNetherlands
Guillermo Quintana-lacaciIFF-CSICSpain
Matthew RedmanNUI GalwayIreland
Nicole ReindlUniversity of PotsdamGermany
Andreas RitterThe University of Hong KongHong Kong, China
Mónica RodríguezINAOEMexico
Laurence SabinUniversity of GuadalajaraMexico
Raghvendra SahaiNASA/JPLUSA
Carmen Sanches-ContrerasCSICSpain
Noam SokerTechnionIsrael
Letizia StanghelliniNSF’s OIR LabUSA
Nicholas SterlingUniversity of West GeorgiaUSA
Jesus ToaláUNAMMexico
Griet Van de SteeneRoyal ObservatoryBelgium
Wouter VlemmingsOnsala Space ObservatorySweden
Jeremy WalshESOGermany
Roger WessonUCLUK
Albert ZijlstraThe University of ManchesterUK
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