jwst cycle 2, and n+1 time’s charm for vlti

in which i press my luck proposing for telescope time 

more than a year ago, i wrote about the incredible luck of batting above 500 during my first semester proposing for observing time on research-grade telescopes. since then, i’ve submitted many more proposals for both ground and space based telescopes, especially “cycle 2,” the second year of the James Webb Space Telescope (JWST) operations. i wanted to write something briefly about my experience with submitting for JWST, re-submitting a rejected ground-based proposal, and essentially reusing that re-submitted proposal for a third proposal.

2nd time’s a charm

after batting 500 in late 2021, in march 2022 i submitted a more ambitious proposal to the european southern observatory, to use a telescope camera called GRAVITY to measure the properties of a faint, cold exoplanet. i put together a solid proposal, but there were a few weaknesses. a single line within the feasibility argument gave the impression that the proposed observations were especially risky, or difficult to acquire. i meant to stress instead that the observations had failed before because they require good weather – with ESO you can justify having specific weather requirements, and they will wait until the sky is sufficiently clear, or the atmosphere is stable, before beginning the observations. that, plus a few more organizational decisions gave the reviewers enough pause, and the telescope was so oversubscribed, that the proposal was rejected

about half a year later, the proposals for the same telescope reopened, and with very minor edits i resubmitted. with a sentence reworded and a few paragraphs rearranged, and maybe more importantly, a new, randomly selected committee of reviewers reading my work, and the proposal was accepted! it was a big deal, since the proposal asks for observations spead out over the course of 2 years, which the observatory tends to be even more selective about. the experience also taught me that just because something is rejected the first time, it isn’t because the idea or even necessarily the execution is bad. it might need just a little bit of hindsight, or a different committee to get accepted.

3rd time’s a charm

then, in early 2023, a new planet was discovered that was similar, but different to the planet i had been awarded telescope time to study. since the original planet was interesting because it was so cold, i was excited to have another planet to be able to compare it to, and i wanted to compare using observations from the same telescope at ESO.

so i took the bones of the old proposal, changed around the names, wrote about half a new page of text, made a new figure, and submitted in march 2023 (while i was in les houches, france, for a conference). a few weeks ago, i got the exciting news that the proposal was accepted! so im flush with interesting projects for my ph.d thesis.

JWST cycle 2

the real beast was the dreaded “cycle 2.” proposals for jwst cycle 1, which have produced wonderful and exiting results all year, were actually submitted while i was still in high school, before the telescope’s launch was inevitably delayed. so, about half a year of successful operations, and the next call for proposals was announced by the space telescope science institute. (hey, that’s where i work!)

we have some idea about how good the telescope is based on observations completed last summer, but there are a lot of open questions remaining, and a lot more science to do. i research taking pictures of planets in other solar systems, right? we can do that with JWST, and in particular we can image colder exoplanets with JWST than we can with other telescopes, because JWST observes in mid-infrared wavelengths of light that are blocked by the earth’s atmosphere, where cold-ish things appear brightest. the wavelength of light you emit the most of, as a 300K object, is around 10 micrometers, right where JWST observes.

the difficulty is that JWST is (to me) a smaller telescope, only about 6.5m in diameter (compared to the largest ground based telescopes that are 8-10m), and to take pictures of exoplanets you need very high resolution (since they are, comparably, so close to their host stars). to resolve a planet with JWST, we need it to either be close by, or on a long, widely separated orbit.

we also need to be able to gather enough light from the planet to see it (we’re limited by the brightest of the star compared to the planet). these two selection effects mean that the planets we can currently take pictures of are hot planets on wide orbits, and planets only source of heat is from their formation, when they first are smashed together from hundreds of smaller asteroids and planetesimals (and for gas giants, when they hoover up a ton of superheated gas from around their parent star). so, if we can only take pictures of hot planets, we can only take pictures of young planets.

to recap, jwst is good at observing cold things since it observes in the infrared and in space, but most planets are too close in for jwst to resolve. most, but not all. so for “cycle 2” proposals i went looking for the coldest know planets that have been detected using indirect methods, like radial velocities, and compared them to simulations of how close in and how cold of a planet jwst can observe. it turns out, there are two cold, old jupiter like planets in solar systems relatively near to ours that could potentially be observable with jwst. one of these was already scheduled for observations in cycle 1, but the other hadn’t been considered.

so my colleague Daniella and I wrote a very targeted, small proposal to use only 7 hours of jwst time to take an image of this planet. Daniella had previously studied this planetary system, 14 Herculis, with those indirect radial velocities i mentioned, and had determined how massive the planet is and approximately how widely separated it is. i could then use my simulations to prove it would be observable with the telescope, and we used the fact that the planet is so uniquely cold to justify why our observations would be impactful. it turns out, colder gas giant planets should have interest clouds made of water and ice (like our own clouds on Earth), but we’ve never been able to measure and understand those clouds, since we haven’t yet observed a very cold planet directly. maybe i’ll be able to make that measurement for the first time?

for cycle 2, it seems like these specific, targeted proposals performed well, and ours was accepted! it was really something special, waiting for the results in the cafeteria at the space telescope science institute with my colleagues, and then exclaiming in surprise when the email hit my inbox and getting a round of cheers. jwst and hst proposals are a bigger deal to american astronomers than ground based telescope proposals, because NASA funds successful space telescope proposals with grant money. so daniella and i might end up paying for a year of our own salaries by getting this proposal accepted.

the observations are scheduled for next march, around my 25th birthday. maybe, if the universe is kind, when im just a little older, ill be the first person to see light from the planet 14 Herculis c. until then, clear skies.






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