We’d like to thank Henson Shaving for supporting PBS.
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?
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” (NGST).
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 realized
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 administrator for most the
60's - 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 the 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 of cosmic time.
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 by looking at 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 get back to work on the next step - the phase 2 proposal.
The first step was the phase 1 proposal, 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.
Do not 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 ever 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, typically you 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.
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 space 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.
In fact it's already done one.
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.
Those white blobby things are massive elliptical galaxies of the cluster, several 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 galaxy.
Those pointy things are diffraction spikes, caused by interactions of incoming light with
the hexagonal aperture of the scope.
And 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.
We’d like to thank Henson Shaving for supporting PBS.
Henson Shaving is the maker of the Al13 razor and even though I do have a beard, I do need
a good shave from time to time.
Created by a family run aerospace machine shop that’s built parts the Mars Rover and
the International Space Station, that expertise allows them to prevent the blade from flexing,
which results in a safe and smooth shave.
And by using standard double edged razor blades, you’ll be able to use it without having
to buy proprietary blades.
To learn more, just checkout https://hensonshaving.com/PBS
Today we’re doing comments for the two recent episodes - the one about the strong force
and quantum chromodynamics, and then the one about how the Higgs boson could tell us what
dark matter really is.
Let’s start with the strong force.
Lassi Tiihonen and John Rizzo raise an excellent point: our strong force video didn’t really
explain how atomic nuclei stick together.
Our explanation focused on how the strong force causes quarks stick together to form
hadrons like protons and neutrons.
We didn’t address how those protons and neutrons - those nucleons - then stick together
to form multi-nucleon nuclei.
This probably deserves its own episode because the process is pretty weird.
The force-carrying gluons don’t extend directly between nucleons.
Instead, nucleons continuously spit out virtual pi and rho mesons - quark, anti-quark pairs
- which are then absorbed by neighboring nucleons.
This constant exchange process keeps the nucleons bound together, analogously to how the atoms
in molecules are bound by the exchange of electrons.
Robin Saunders reminds us that there’s a relationship between gluon flux tubes and
string theory.
That string theory actually began as an attempt to understand QCD, before being abandoned
because it predicted a particle which behaves like a graviton.
And asks whether the methods of string theory are being brought back to understanding gluons
again?
The answer is yes, and thanks for bringing that up.
The core mechanics of string theory were developed to describe the very stringy one-dimensional
gluon bonds between quarks, particularly in mesons.
They could be modeled as elastic threads with various vibrational modes.
The model worked, but only because they look a bit like elastic threads.
The approach was useful for prediction, but not very explanatory.
Quantum chromodynamics actually started to explain was going on, so it suplanted hadronic
string theory.
But as Robin notes, one of the vibrational modes of these strings looked like the graviton,
so the entire theory was shrunk in size by about 20 orders of magnitude and developed
into a theory of quantum gravity.
We explain everything in our string theory episodes.
But now, decades later, with string theory still failing to produce a slam-dunk testable
prediciton, people are starting to take the prodigious math developed for the theory and
apply it to other places - including back to where it all started - gluon behavior.
A couple of you also commented on the recent finding that the proton seems to contain the
influence of the charm quark, not just the up and down quarks as previously thought.
Indeed - and what a fascinating result.
That was published after we filmed this episode, so we’re going to have to do a new episode
on the finding.
Stand by.
OK, on to our episode on how the Higgs boson could be the key to discovering the dark matter
particle.
mrwho995 points out that we forgot to mention one of the important Higgs experiments - it’s
not just ATLAS at the Large Hadron Collider that’s producing Higgs bosons, there’s
also the Compact Muon Solenoid or CMS at the LHC.
And it seems mrwho is part of that team.
One of the clearest signatures of a Higgs boson decay is into four muons.
CMS is optimized for muon detection, so is also a major workhorse for studying the Higgs.
It’s really hard to keep up with all the amazing work that’s happening in physics,
so, mrwho995, thanks for helping us cover the bases.
nyrdybyrd points out that the info from this Higgs episode is an influential argument for
a badass new particle collider.
This is a good point.
I’ve heard it argued that it’s silly to build new particle colliders in the hope of
discovering particles that we don’t know exist.
But that’s not the only, or even best reasons to improve our particle collider capacities.
For example, the discovery of the Higgs boson was only the beginning - now that we know
it exists, there’s so much we can learn from it if we can produce them more efficiently.
That said, there are various plans to build so-called Higgs factories that don’t involve
just building bigger and bigger colliders.
I’m not saying we shouldn’t do that, but we should also think about how to most cleverly
spend our science money.
Namishki901 feels as though digging smaller has always returned more benefit than looking
bigger.
Sure, quantum theorists of various colours can tell themselves that they’re hunting
for the fundamental substrate of the universe, so far chasing their tails in the process.
Meanwhile we astrophysicists just get on with business and discover the big bang, dark matter
and dark energy, and figure out how the universe is going to end.
Did that sounds snarky?
Sorry.
In reality we physicists are all just playing around with the small, special-case questions
about “physical” reality.
Just ask a mathematician.