Science of the James Webb Telescope Explained! (Script) (Patreon)

You’ve probably heard about the James Webb Space Telescope and seen some cool pictures. But why should astronomers have all the fun? How do we get to use this new toy ourselves?

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The James Webb Space Telescope has now been in full operational science mode for several weeks now, and has seen some pretty amazing stuff, from colliding galaxies to planets and exoplanet atmospheres to the earliest, most distant galaxies ever observed.

You can check out its amazing accomplishments in lots of places - like the official NASA and Goddard Flight Center websites, and all over YouTube - but special shoutout to Anton Petrov for the best “best of JWST” that I’ve seen.

Many of you asked whether we were going to do a JWST episode, and at first I thought it wasn’t needed due to the massive coverage. But then I realized there’s something missing. Rather than tell you about what the telescope has done, or will do, I want to talk about the process of actually using a telescope like this. What it takes to get time on the JWST, and how you can use it yourself.

The fact is, anyone CAN use JWST. It was built by NASA with significant contributions from the Canadian and European Space Agencies, but it was built for everyone.

You don’t have to be employed by NASA, or a US citizen, or even a professional astronomer. But before we get to using JWST, let’s talk about the telescope itself. After all, if you’re going to use it you better know what it’s useful for. The James Webb Space Telescope, JWST, or “the Webb” has been in the works for decades. Really, from right after the launch of the Hubble Space Telescope in 1990.

The planning picked up over the 90s, and pretty quickly core properties started to crystalize for what was then the “Next Generation Space Telescope”. It was to be a much bigger scope that Hubble - because with telescopes size matters. The size of the aperture determines how sensitive it is to very faint objects.

Hubble has a 2.4 meter diameter mirror - the NGST had to be much bigger -  8m diameter to make it a worthy upgrade, which would give it 6 times the collecting area of Hubble.

To get an 8m mirror into space under the incredible stresses of space launch, it was realised early on that a foldable mirror was the way to go. Another early decision that persisted was the focus on the infrared light - and I’ll come back to why. The history of the development of this telescope is a rocky one. The mission encountered many setbacks, from technological to the fiscal to the political. Its cost grew to consume 25% of NASA’s entire budget, before being axed by the US Congress, then reinstated, and then streamlined, and finally launched, just a decade or so after the original launch goal.

The NGST became the James Webb Space Telescope after NASA’s second administrator - a controversial choice all on its own that I’ll leave you to Google. After decades of planning and billions of dollars spent, everyone was relieved to say the least that the telescope deployment proceded perfectly. JWST now sits at the Earth’s second Lagrange point, its mirrors fully unfolded and its infrared instruments humming along nicely.

JWST wasn’t planned just to be a bigger, better Hubble. In fact it’s not that at all. The telescope is focused on the infrared - that light on the longer-wavelength side of visible light. Hubble, on the other hand, did visible light into ultraviolet. The choice of long wavelength light specializes JWST for a number of particular science goals. A big one is to study the early universe.

The very first galaxies shone with intense ultraviolet light as the dense, young gas of the early universe collapsed into the first stars. But that UV light has now been traveling to us for most of cosmic history, and the expanding universe has stretched the light by more than a factor of 10. Energetic ultraviolet photons reach us as infrared, stretched and worn out by their journey. JWST is designed to catch that light and has already observed galaxies much closer to the Big Bang than ever before.

JWST is also great at exploring galaxies of any epoch. It’s IR sensitivity allows it to see the cool dust and gas that lives between the stars, as well as peer through that dust which normally blocks shorter wavelength light. Combined with its sensitivity sensitified to the earliest galaxies this let’s us complete our map of galaxy evolution over cosmic history.

Another key science area is planets. IR sensitivity lets us peer into the dusty whirlpools around new stars and watch the formation of planets in action. It also let’s us see the atmospheres of planets in other solar systems, which is an important step towards finding other life out there in the universe.

JWST runs four separate instruments that allow it to take images as well as break light up into spectra, with sensitivities from visible red light through the slightly longer wavelengths of near-infrared all the way to the much longer wavelength mid-infrared. It has various other tricks, like the ability to take spectra of many objects at once; or using a coronagraph to block the bright light of a star to better see its planets, to name just a couple.

OK, so that’s a glimpse at what JWST can do. So now that humanity has this new toy, how do we actually use it? Let’s start with how most working astrophysicists hope to use JWST. Most of what the telescope will look at over its hopefully long life will be through the General Observer or GO program. Through this program, anyone who has a good idea can ask nicely to borrow the multi-billion dollar facility for a bit. And by ask nicely I mean develop a proposal that lays out in excruciating detail the science goals, the targets, the types of observation, and why of all the telescopes in or out of the world only JWST has a hope of doing this and why these observations are going to advance our understanding of the universe in really important ways and why YOU are definitely going to be able to pull off the project if you get the data. No big deal.

If you’re one of the lucky few to pass these hurdles, then you get a very happy email notifying you of your success. You celebrate for a few days, and then get to the next step - the phase 2 proposal. The first was the phase 1, by the way. Phase 2 is when you lay out the exact observing plan in even more meticulous detail. You give the precise locations on the sky of everything you want to look at, what instruments will be used, the exact settings for those instruments, the exposure times, etc. etc. Don’t mess this part up, because if you spend an hour looking at the wrong spot or with the wrong settings, you probably won’t be allowed to play with the telescope again.

And the final thing you need to do is wait for your data. NASA queues up all the successful programs and executes them over the following year. One day you’ll get another email with a download link to your data, at which point the real work can begin: analyzing the data and trying to bring to fruition that genius idea you had, like, 18 months ago.

Once you have your data, you typically have a 12 month grace period in which only you and your team get to access it. After that, the data becomes available to anyone in the world - I’ll come back to that. Make good use of your headstart. If your project was compelling enough to get accepted, you can bet that there are astrophysicists out there who want the data too. You’ll use that 12 months to try to publish your findings before you get scooped.

So, that’s how the typical scientist goes about using JWST directly, and it’s how many of the world’s major observatories work. It all sounds like a lot of work, and believe me it is. I’ve been through this process many times myself, though not yet with JWST. But there’s another way to get all of this juicy data without these annoying hoops. Basically, you let someone else do the hard work with the designing observations, proposing, sweating through the review process, etc. You just wait for the data to become available and then download it.

These days, essentially all major observatories keep modern, searchable databases of most of what they look at. JWST data is accessed through the Mikulski Archive for Space Telescopes, or MAST, which also includes the data from Hubble, Gaia, Kepler, and many other missions. The sheer quantity and richness of data in MAST and other archives is enough to support many astrophysicists without them ever having to write a single observing proposal.

One of the reasons is that a lot of the data taken by these telescopes - and certainly JWST - is actually meant for the entire scientific community, not for individual researchers. So-called legacy programs are all about maximizing the value of data for as many scientists and science questions as possible. A classic example is the Hubble Ultra Deep Field, which is a million second exposure that Hubble took of one apparently empty spot on the sky, but which reveals 10,000 galaxies back into the early universe. Many astronomers did a lot of science with this one image. JWST will also do deep fields.

Here’s one already. This is the SMACS 0723 cluster. JWST pointed at it for 12 and a half hours across different filters to produce the deepest infrared image of any spot on the sky ever taken. For comparison, this is the Hubble image of the same cluster. The white blobby things are massive elliptical galaxies of the cluster, some … billion light years away. These arcs are much more distant galaxies whose light is warped by the gravitational field of the cluster. Some of these things are shining at us from out of the very early universe - maybe when it was 7% its current age. And this bright star is, well, a star - in the milky Way. Those pointy things are diffraction spikes, caused by interactions of incoming light with the hexagonal aperture of the scope.

There’ll be legacy programs to study everything else that JWST is good for. These surveys often focus on areas of the sky that have been studied extensively by other telescopes, which might seem redundant, but JWST sees the universe very differently, so studying the same objects in this new light really deepens our knowledge. Oh, and a proper legacy program doesn’t have a proprietary period, which means the data is available to anyone after it’s taken, including you if you want it.

OK, so that’s a primer on what JWST can do and how astronomers use it. Let’s wrap up by getting a bit more practical. How could YOU get started doing something with this telescope? It’s actually pretty straightforward. We don’t have time to do a full tutorial right now, so I’m going to link some resources below. But here’s an example from YouTube channel galactic hunter, who shows you how to download several images of the Carina nebula in different infrared filters, and uses these to build the sort of beautiful color image that we usually get from NASA. If anyone sends us their there own processing of JWST data we’ll try to show who it in a future episode.

We’ve waited a long, long time for JWST, and its time to reap the rewards for our patience and the hard work of many brilliant and dedicated people. I hope you enjoy the steady stream of amazing images and even more amazing science that’s sure to flow in from Earth’s Lagrange 2 point over the next years as the James Webb Space Telescope shows us things never before seen, and some never imagined, from the furthest reaches of space time.