Ringberg Meeting: Puzzles of Star Formation

July 11-14, 2021

Scope of the meeting

Welcome to this workshop to explore the boundaries and puzzles in the field of star formation. We do not anticipate the classical meeting where everybody presents and summarizes the most recent results, but rather we would like to dig deeper and decipher the real problems in the field that still need to be solved.

Star formation is a topic of active research since the seventies and a lot of progress has certainly been made since then. Nevertheless, there are still many conceptual issues and central puzzles that are not solved yet. These include processes and physics related to the origin of turbulence in the ISM, the formation, evolution and lifetimes of molecular clouds in the turbulent environment of galaxies, the condensation of these clouds into stars, multiple systems and stellar clusters via gravitational collapse and the energetic processes by which these stars affect their gaseous environment and by this self-regulate star formation. With this meeting we want to make an attempt to identify and clarify some of the most pending questions in the field, and to seek paths to solve them, from a theoretical as well as observational point of view.

This requires a new workshop style that is not focused primarily on presentations of most recent insights and successes but, just on the opposite, about what you think is fascinating but not understood, why it is important and (if you have an idea) suggestions of how to solve the puzzle, maybe in a concerted effort. Your task as participant will be to suggest such questions and lead a subsequent discussion.


With an anticipated 32 participants, there is sufficient room for various forms of discussions. Every participant has a 20min slot where an important question or puzzle in the field can be introduced and a discussion be started. In this 20min slot, a maximum of 10min should be devoted to introduce the topic/question and/or show some initial results. The remaining part of the time should be dedicated to discussion. Furthermore, it is possible to "cumulate" slots. Check out the list of participants below. If you want to introduce/discuss a question/puzzle with another participant, two or three slots can be cumulated to 40min or 60min slots. The share of 50% intro/results and 50% discussion should remain.

These 32 individual and/or cumulated discussions will be on the first two days (Mon/Tue). Based on the ideas broad up there, the whole Wednesday morning is open to dive deeper into some of the questions brought up earlier. Please, check out the skeleton program below. Every participant is then invited to suggest ideas for those discussion rounds on Wednesday. These ideas should be sent to the organisers till Tuesday evening to prepare the discussion session on Wednesday morning.

To get the initial program ready, we ask every participant to provide us a title and potential key words for their initial individual or cumulated contributions. Please let us know if you want to combine your presentation with others. Possible keywords (not exhaustive list, more can be added) are provided at the bottom of the page. These keywords are only meant to help sorting topics into the final program. Please, sent us that information latest by Wednesday, July 7, 2021.

We are looking forward to a lively and exciting meeting!


Sunday, July 11, 2021: Afternoon and early evening: Arrival at castle

18:30             Dinner

21:00             Possibility to watch European Championship final

Monday, July 12, 2021

Chair: Andreas Burkert

09:00-09:20 Andreas Burkert & Henrik Beuther: Welcome and Introduction
09:20-10:00 Rolf Kuiper & Henrik Beuther: What are the differences between high- and low-mass star-formation? (pdf-file)
10:00-10:20 Caroline Gieser: Which form first: high- or low-mass stars? (pdf-file)

10:20-10:50 Coffee break

10:50-11:50 Joao Alves, Josefa Grossschedl, Laura Posch: The 3D motion of the local ISM: new window, better puzzles (pdf-file)
11:50-12:10 Sara Rezaei Kh.: How can the 3D shapes of the local molecular clouds help us better understand star formation? (pdf-file)

12:30-14:30 Lunch break & discussion sub-groups

Chair: Joao Alves

14:30-14:50 Mario Tafalla: Can molecular clouds be in free fall? (pdf-file)
14:50-15:10 Jonas Syed: How does the atomic ISM affect molecular cloud formation? (pdf-file)
15:10-15:30 Stefan Heigl: The Puzzle of the Edge Effect - a tale with two ends (pdf-file)
15:30-15:50 Adam Ginsburg: Cluster formation and fragmentation (CMF, IMF) (link)

15:50-16:20 Coffee break

16:20-16:40 Sümeyye Suri: Filaments and Feedback: the chicken and the egg problem (pdf-file)
16:40-17:00 Nicola Schneider: How stellar feedback impacts the interstellar medium - an observers view (cancelled)
17:00-17:20 Stefanie Walch-Gassner: The role of stellar feedback in star formation (pdf-file)
17:20-17:40 Doris Arzoumanian: Impact of expanding bubbles on the interstellar medium? (pdf-file)

18:30       Dinner

Tuesday, July 13, 2021

Chair: Henrik Beuther
09:00-09:20 Paola Caselli: From prestellar cores to protoplanetary disks (pdf-file)
09:20-09:40 Maria Jose Maureira: What sets the gas/dust temperature at disk scales in embedded low-mass protostars? (pdf-file)
09:40-10:20 Jaime Pineda & Dominique Segura Cox: The role of Streamers on star and disk formation: mirage or reality? (pdf-file)

10:20-10:50 Coffee break

10:50-11:10 Thomas Henning: From star to planet formation (pdf-file)
11:10-12:10 Peter Schilke, Alvaro Sanchez-Monge, Andre Oliva: Revealing the physics of high-mass disks in observations and simulations (pdf-file)

12:30-14:30 Lunch break & discussion sub-groups

Chair: Steffi Walch
14:30-14:50 Ewine van Dishoeck: Chemical puzzles in star formation15:10-15:30 (cancelled)
14:50-15:10 Ralf Klessen: The impact of the local bubble on observed all-sky maps (pdf-file)
15:10-15:50 Daniel Seifried & Juan Soler: And what about magnetic fields? (pdf-file)

15:50-16:20 Coffee break

16:20-16:40 Jonathan Henshaw: Multi-scale gas flows in the interstellar medium and their role in the star formation process (pdf-file)
16:40-17:00 Mattia Sormani: Various puzzles of star formation in galactic centres (pdf-file)
17:00-17:40 Andreas Burkert & Manuel Behrendt: The puzzle of the universal gas depletion timescale (pdf-file)

18:30       Dinner

Collection of ideas for Wednesday discussion rounds. Everybody can suggest during the first 2 days.

Wednesday, July 14, 2021

09:00-10:20  Topical discussions based on input from the first 2 day

- Peter Schilke: Are we being myopic by just staring at accretion along filaments?  What fraction of mass (and angular momentum) is really delivered through steady filaments, and how much in a more random fashion, both in terms of direction and mass flux?
- Stefan Heigl: Can the magnetic field influence streamers?
- Alvaro Sanchez-Monge, Jaime Pineda, Henrik Beuther: What are the best tracers of kinematic accretion flows/streamers on different scales? (pdf-file)
- Daniel Seifried, Ralf Klessen, Steffi Walch: Real Filaments and B-fields in 3D (pdf-file)

10:20-10:50 Coffee break

10:50-12:10 Topical discussions based on input from the first 2 days

- Rolf Kuiper and Andre Oliva: Properties of circumstellar disks forming in a magnetized medium (pdf-file)
- Doris Arzoumanian: Hub-filament paradigm for star formation to consistently  describe the formation of stars from low to high masses (pdf-file)
- Ralf Klessen: Diffuse, dense and very dense gas in the ISM (pdf-file)
- Andi Burkert: Encounter of a gas cloud with the central black hole

12:30-14:00 Lunch

Afterwards: Departure

List of participants

Joao Alves
Doris Arzoumanian
Henrik Beuther
Manuel Behrendt
Andreas Burkert
Paola Caselli
Caroline Gieser
Adam Ginsburg
Josefa Grossschedl
Stefan Heigl
Thomas Henning
Jonathan Henshaw
Ralf Klessen
Rolf Kuiper
Maria Jose Maureira
Andre Oliva
Laura Posch
Jaime Pineda
Sara Rezaei Kh.
Alvaro Sanchez-Mongez
Peter Schilke
(Nicola Schneider)
Dominique Segura-Cox
Daniel Seifried
Juan Soler
Mattia Sormani
Sümeyye Suri
Jonas Syed
Mario Tafalla
(Ewine van Dishoeck)
Steffi Walch