In the summer of 2013, I attended the Protostars & Planets VI (PPVI) conference, which is held every 6 years.  For the sixth edition, more than 500 astronomers and astrophysicists made it to Heidelberg, Germany, for a week of talks and discussions on the birth of young stars, the primordial disks of gas and dust surrounding them, and the exoplanets that eventually coalesce around them.  It was my first Protostars & Planets conference, and I was seven months into my new position as a young assistant professor at the University of Bern, Switzerland, so there was a sense of anticipation and excitation.  Even before setting foot in Heidelberg, the first thing that struck me about the conference was its format: all of the time was devoted to review talks, which placed early-career researchers at a disadvantage.  The idea was that researchers could form teams and compete for the right to give these review talks.  

As the conference progressed, my frustration started to build up.  There were clearly serious flaws with this format.  Ideally, the most established researchers in each subtopic would provide a balanced, thoughtful review of the state of the art and path the way forward.  It would be a public display of excellent scholarship.  In practice, one got the sense that this was not working as advertised.  After each review talk, members of the audience would march up to the microphone to protest that their work was not being fairly mentioned, or that the speaker held a view that did not reflect the entire landscape of research being performed in that subtopic.  Some of the discussions were contentious, and there was a sense that the opinions of the junior researchers were not being heard.  Considerable energy was devoted to these arguments, rather than the way forward - at least, that is what stuck in my memory.

An even greater source of frustration stemmed from the fact that PPVI was driven by a very specific ideology: start by forming stars, then form the protostellar disks, then the planetesimals, planets, etc.  The implicit assumption was that, if we could not understand the early steps of this process, then the later steps were not worth thinking about.  But exoplanets do exist, even if we do not understand how they formed, what they are made of, or the diversity of atmospheres they harbor.  A related (and deeply flawed) ideology is that we can model these highly complex, non-linear, interacting systems exhaustively in the computer - and if we cannot, we simply buy a larger computer.  A counter-example to this ideology is the carbon dioxide content of the atmosphere of Earth, which is controlled not by planet formation but rather by the carbonate-silicate cycle - a process that we cannot model from first principles, due to complexities such as erosion and plate tectonics.  We should study both the forward and inverse problems - the latter being that one starts from the observations and tries to back out the underlying physics and chemistry.  I was irked that exoplanetary atmospheres was essentially one of the last talks on the last day of the conference - a decision clearly driven by this ideology.  Considering that this is one of the most dynamic and rapidly growing subdisciplines in exoplanet science, it felt like a slap in the face for this community (which I belong to).  This was the last straw for me, and it planted the seeds of a new conference series in my mind.

Over the next few months, I vented my frustration to Didier Queloz, who is one of the co-discoverers of the first exoplanet orbiting a Sun-like star and a Cambridge University professor.  Didier is my Scientific Principal Investigator (PI) for the CHEOPS mission of the European Space Agency (ESA), and I am one of his "whips" (spokesperson for atmospheric characterisation) and Swiss delegates on the mission.  He simply replied, "Let's just do our own."  We agreed that this new conference series would focus solely on exoplanets, with stars, disks, etc, as secondary topics - a radical departure from the usual fare in Europe.  We also agreed that the outlook of the conference series would be international, but its logistical and organisational backbone would be European.  It would complement existing series as such Extreme Solar Systems and Exoclimes, both of which have American-led organisation.

We decided to rope in Thomas Henning of the Max Planck Institute for Astronomy (MPIA).  (Ironically, Thomas was also the organiser of PPVI.)  Together, we decided on the venues of the first three editions: Davos (2016), Cambridge (2018) and Heidelberg (2020).  At Davos, Jason Steffen (of TTV fame) came up to me excitedly and declared his enthusiasm for having Exoplanets IV in Las Vegas.  A year or two later, Ignas Snellen and Nuno Santos expressed their intent for Exoplanets V and VI in Amsterdam and Porto, respectively.  Amazingly, that means we are now booked till 2026!  (I am toying with the idea of having Exoplanets VII in Singapore in 2028.)

The Exoplanets II conference in Cambridge, England, caught us by surprise in many ways.  For Exoplanets I, we made preparations for 300 participants, but did not manage to fill all of the slots.  For Exoplanets II, all 300 available slots were filled by the early-bird registration deadline for students!  This completely unexpected development meant that some of the senior researchers were prevented from even registering.  A waiting list of 150 quickly built up; not long after, even the waiting list was shut down due to over-capacity.

Valuable community lessons were also learnt from Exoplanets II.  Despite the Scientific Organising Committee (SOC) consisting of 7 women out of 13 members in total, gender balance among the speakers did not attain parity.  This is due to a set of inter-related - and sometimes complex - reasons.  At some level, it reflects the fact that full professorships in exoplanet science in Europe are rarely filled by women - part of this may be due to topical inertia, as Europe is in the midst of pivoting its resources towards this topic.  Some other part of it is almost certainly due to archaic hiring practices.  

There was also plenty of debate regarding the role of the session chair.  Were the chairs biased towards picking more established folks to ask questions?  (When I chaired the opening session of Exoplanets II, I had a hard time getting people to ask questions, so I know this was not the whole story.)  Furthermore, having the ability to ask a concise, decisive, understandable question at a 300-person conference is a skill, one that took me years to hone.  There was also some discontent about individuals giving comments instead of asking questions during the Q&A sessions.  I personally think the dividing line is not so clear-cut - not all comments are useless, and not all questions are meaningful or thoughtful.  It depends on the intention behind the comment or question.

When a senior person is giving a review talk, it is her or his responsibility to practise inclusive, balanced, thoughtful yet critical scholarship, which means teaching the younger people in the room the state of the art of the subdiscipline in question, even if she or he disagrees with some of the published results.  Not all published results have equal importance - establishing scientific veracity was not, is not and never will be a democratic process - but it is important to elucidate why.  A shining example at Exoplanets II was Josh Winn's review talk on exoplanet detection - Josh has the rare gift of being able to surgically deliver fine scholarship with the timing of a stand-up comedian.  A firm, critical grasp of the published literature is a crucial component of a researcher's toolkit.  When a review-talk speaker cherry-picks the literature in a misleading way, it is the responsibility of other senior researchers in the room to stand up and point it out, otherwise the junior researchers will walk away with misconceptions that will echo for months or even years.  I have personally benefited from thoughtful, even deep, comments given by established figures in exoplanet science.  What is not constructive are comments made for the purpose of grandstanding - no one needs to know how smart you are, especially if you are veering off-topic.

Indeed, what is the role of the session chair?  In my mind, it is to make the session as compact and educational as possible.  The session chair is not just a mindless time-keeper - there are times when going slightly overtime is warranted, either because the speaker is doing such a dazzling job or the discussion is particularly important for most of the people in the room.  In these situations, the session chair needs to show a softer side.  At other times, when the speaker or audience member asking questions veers towards being long-winded, it is the job of the session chair to remind them to be concise.  In some situations, the session chair should exercise her or his authority to cut someone off - even if the speaker is just wasting one minute of time, it is really N minutes of wasted time since there are N members in the audience.  The session chair should be ruthless and not bow to authority - professors and students should receive equal treatment based on their actions, and not their rank.  The session chair may need to make decisions that are unpopular.

As the Exoplanets conferences expand towards having 500 or more participants, it becomes clear that the same practices and structures used to manage 200-person conferences no longer scale and break down.  How do we manage this expansion in an inclusive manner?  The usual practice is to create splinter or break-out sessions, where part of the conference is devoted to parallel sessions.  I would argue that this reduces inclusivity, as the original intention was to keep everyone on the same stage.  Here, Thomas Henning has a great idea: to create focused, curated poster sessions based on coherent themes.  A curator would spend 5 to 10 minutes on stage introducing each poster session, and further select several participants to deliver 1-minute "elevator pitches" of their posters.  Each session could be held over an extended, 3-hour lunch break, allowing ample time for discussion.  The theme of each poster session would change each day, thus allowing 100-200 people some voice in the conference discussions.

We will not get everything right immediately.  But the long-term outlook of the Exoplanets conference series allows us to continue to actively collect and implement constructive feedback, and forge ahead towards better ways of coming together as an exoplanet community.