(ethereal music)
- Since 1996, just one year after the first discovery
of an exoplanet around a normal star,
astronomers have been dreaming.
What might a successor
to the Hubble Space Telescope achieve for exoplanets?
What mysteries might it reveal?
What new discoveries might ensue?
But 26 long years of waiting and wondering are finally over.
The Hubble successor, JWST, has been in space
for almost a year now.
The calibration phase is over, the shakedown is done,
and JWST is finally getting down to business.
Although we are still only a few months
into science operations,
I know that many of you are keen to know what is it
that JWST has discovered already?
Indeed, it was the top rated video topic from our last poll.
So whilst it's still early days,
today we are gonna explore what is it
that exoplanet astronomers have found
using our new 10 billion toy?
Before we get into the science,
we first need to orient ourselves with a timeline of JWST.
The 6.5 meter telescope was launched on December 25th
last year, and has spent six months in commissioning,
which entailed orbital positioning, mirror alignment,
instrument calibration, and performance testing.
Somewhat concerningly, during this time,
at least 19 meteors struck the primary mirror.
Of these, one was particularly large that hit
around May 24th, and it caused noticeable damage
to one of the 18 hexagonal mirrors, although fortunately,
telescope performance appears unaffected.
After six months of commissioning,
NASA was finally ready to share
some of the first images from JWST.
So to this end, the telescope took a short series
of observations really just designed to show off
the telescope for public outreach purposes,
formally known as ERO, the early release observations.
So I bet many of you probably already saw these,
the galaxy cluster SMACS 0723, Stephan's Quintet,
the Carina Nebula, and the Southern Ring Nebula,
magnificent spellbinding images that are gorgeous to behold.
But alongside these taken on the 21st of June,
JWST observed the transiting exoplanet WASP-96b,
a prototypical hot Jupiter type world.
By observing the same transit,
but at multiple different wavelengths
using the nearest instrument on board,
we obtain a spectrum of the atmosphere revealing
the telltale signature of water,
a detection that was announced on July 12th.
Astronomers were definitely very excited to see
those first ERO images.
Like everyone else, our jaws dropped seeing
those gorgeous panoramas for the first time.
But it has to be said that from an astrophysics perspective,
we really didn't learn that much.
For example, we already knew
that WASP-96b had water of vapor in its atmosphere
from Hubble data that was taken years prior.
For us, the really exciting part was actually nerding out
on the engineering data
about the performance of the telescope itself.
On the same day that NASA dropped those first images,
JWST project scientist Jane Rigby
and colleagues published a paper detailing
the performance of the telescope's commissioning phase.
For example, a transit of another exoplanet,
HAT-P-14b clearly shows an example
of what is being dubbed a mirror tilt event.
What's happening here is that one
of JWST's hexagonal mirrors just unexpectedly changed
position, disturbing the time series,
and creating this bump effect.
For astronomers like me that look for exomoons,
this is crucial to know about, because if you didn't account
for this effect, then you might erroneously think
that that little bump up was in fact caused
by an exomoon that was exiting transit ahead of the planet.
That's exactly the kind of signal
that we look for all of the time.
This mirror tilting is currently thought to be triggered
by a buildup of microstresses
within the back plane structure.
Worryingly, these tilt events were happening
several times a day around April 2022,
but appear to have settled down to occurring
just several times per month by June.
So more reassuring news here is that
already there's been a tool developed
that can exploit the phase coherence
of JWST's combined light to precisely identify
when and where these tilt events occur.
Another concern that commissioning has revealed is so-called
a one over F noise, which manifests
as a kind of banded structure in JWST's spectral images.
It appears as though
this noise is actually being spuriously injected
into the pixel detector by the device designed to read
the pixel array known as the SIDECAR ASIC system.
Now, it looks like there might be some ways to correct
for this in part during post-processing using a technique
known as row by row odd even amplify correction,
or ROEBA for short.
Both the tilt and one over F noise are small effects,
and already we are seeing tools developed to mitigate them.
So I'm not too worried about these,
but anyone trying to push JWST
to its limits will certainly need to adopt
analysis techniques to deal with these effects.
With the commissioning and the ERO out of the way,
in the early summer of 2022,
JWST began its first real science operations,
known as the early release science, or ERS.
Boy, do astronomers love their acronyms.
ERS was a DD, which means director discretionary program,
which as the name suggests,
means that the telescope time was allocated
at the director's discretion, Greg Robinson.
This is in contrast to the more conventional format
of a committee of astronomers weighing in known as a TAC,
a time allocation committee.
The goal of ERS was to try and observe
a wide range of phenomena
with all the different instrument modes
to get a sense as to the science performance.
It was largely meant as a community education program,
just get some data out to astronomers as soon
as possible so they can figure out how to process it all.
So ERS was never designed to push the envelope
scientifically, but nevertheless,
the ridiculous precision of JWST means
that some awesome science has already emerged.
In fact, the ERS program has just finished
wrapping up its observations,
and although all of the data has not yet been analyzed,
let's have a look at what has been found so far.
Astronomy can be split into a bunch of different fields,
but today, we're just looking at exoplanets.
I mean, let's face it, they're the most interesting.
Within exoplanets, two ERS programs were approved.
One led by Natalie Batalha focused on transiting exoplanets,
and the other by Sasha Hinkley focused
on direct imaging of exoplanets,
so two very different techniques for studying planets,
and indeed, the types of planets they typically look at.
Let's start with the transit program,
which you can also think of as eclipsing planets,
one of the techniques we here
in the Cool Worlds Lab often make use of.
In total, four different instruments were used here
to study three different exoplanets,
WASP-18b, WASP-39b, and WASP-43b.
As with WASP-96b from the ERO program,
these are classic hot Jupiter exoplanets,
essentially, the easiest type of planet
that an exoplanet astronomer could possibly hope for.
JWST will eventually push the envelope, trust me,
but that is not the point of the ERS program.
The spectra obtained for these are gorgeous,
and WASP-39b stole the show in August this year
when just a portion of the spectrum was published,
revealing the unambiguous signal of carbon dioxide,
shown here by the increased absorption of 4.3 microns.
Now, whilst there has been hints of this molecule
and other explanatory spectrum in the past,
this is the first real slam dunk detection of this molecule.
The significance is a staggering 26 sigma for goodness sake.
Yet more, we are hearing that in those yet unseen
and unpublished portions of the spectrum,
there are even more surprises, so stay tuned.
In fact, as we were editing this video, what do you know?
The team released the other portions, showing the detection
of carbon oxide in the other bands, but also found
carbon monoxide, water vapor, and sulfur dioxide.
Sulfur dioxide is particularly neat,
predicted years ago by Kevin Zana and colleagues,
and is thought to form through a series
of photochemical reactions of hydrogen sulfide
in the upper atmosphere.
Looking at the transit light curves,
well, they appear almost noiseless.
Such is the quality of the JWST data.
Now, as beautiful as those transits might look
to an astronomer's eye, I can appreciate
that they're not quite as visually captivating as say,
the deep field image that was dropped during the ERO.
So let's now switch from exoplanet transits
to exoplanet imaging, because at least here,
we have some real photos to look at.
The ERS imaging program picked
on two previously discovered exoplanets.
Those were HIP 65426b and VHS 1256b,
and it observed a third star
that had a known protoplanetary disc around it.
That was HD 141569.
Let's focus on HIP 65426b, a planet discovered
fairly recently in 2017 using the very large telescope.
The host star is 385 light years from Earth,
and has clear evidence for an exoplanet around it
on a distant orbit, roughly 90 times wider
than Earth's orbit around the sun.
Now, you can see in this image
that the planet is pretty bright.
It's luminous, and that means that it must be
a young planet that has only recently formed.
Using JWST'S coronagraph,
light from the host star is heavily suppressed to tease out
the relatively dim light from the planet by itself.
The team were able to observe the planet
in multiple different modes corresponding
to different colors of light,
and they recover the planet easily in every case.
Let me just emphasize,
these are the first JWST images of an exoplanet.
What's amazing is it the longest wavelengths used here are
11 and 15 microns, making this the first detection
of an imaged exoplanet beyond five microns.
Going a step further,
and comparing the brightness of the planet
as a function of wavelengths to theoretical models,
the mass of the planet can be inferred,
and is pinned down here to be around seven Jupiter masses.
The ERS program has now finished.
All the data's in the cab,
but only a fraction of it has been analyzed so far.
But even as we speak, JWST is moving
into its cycle one observing mode, which means
that it's following the more conventional TAC process
of assigning telescope times.
So that means that astronomers like myself write proposals
as to what JWST should look at,
and then a committee of astronomers come together,
argue about which proposals are the most exciting,
and those should be given telescope time.
Now, this is in contrast to how Kepler,
TESS, or Gaia operate.
Those are survey missions using
standardized pre-programmed observing plans
spanning multiple years.
But this isn't as easy as it sounds.
For cycle one, the number of requested hours exceeded
the available hours by a factor of 4.1,
so the majority of proposals were rejected.
Cycle one will definitely push the envelope a bit more
than ERS, but I think it's cycle two, which of course,
follows cycle one, where the gloves will come off,
and JWST can finally start getting into the kind
of ambitious science that we've long dreamed of.
And my team, that's really what we're looking forward to.
The call for cycle two proposals has just been announced,
and indeed, we are planning some exciting programs
to look for exomoons.
In fact, based off the early data that we have already,
we are able to say that JWST is the first telescope
ever built by humanity that is capable
of detecting exomoons analogous to the moons that we have
in our solar system, moons like Ganymede,
Titan, and the moon.
We know that these things are common in our backyard,
so it's incredibly exciting that we might finally have
a telescope that could reveal such worlds
from many light years away, and on top of exomoons,
there's many other exciting targets, of course.
One of my personal favorites is
the seven planet TRAPPIST-1 system,
which has already been approved for cycle one observations.
Unfortunately for exomoons, cycle two won't start
until late 2023, and will finish a year later,
so it's gonna be a while before we actually get
that data in hand, even if the TAC agrees with us
the exomoons are interesting to go after.
The exoplanet transit community has been largely
prioritizing studying atmospheres these days,
so we know it's gonna be tough to persuade them
that exomoons are worth JWST's time as well,
but I have never been more optimistic about the future.
With JWST, we can finally answer questions
that have simply been impossible to tackle until now.
So let me know what kind
of JWST exoplanet science are you most excited about?
Planet imaging, atmosphere retrievals, exomoons,
or maybe something else altogether.
And of course, that is just exoplanets, just a fraction
of the exciting agenda that JWST has in store for us,
so look out for an exciting future
of new astronomical discoveries, everyone.
And until next time, stay thoughtful, and stay curious.
(bright music)
Thank you so much watching, everybody.
I hope you enjoyed this video.
If you did, be sure to like, share, subscribe,
and if you really wanna help us out,
you can become a donor to my research team,
the Cool Worlds Lab at Columbia University.
This week, I wanna thank Methot Fortson,
our longtime supporter who has just reupped his commitment,
so thank you so much, Methot.
All right, everyone,
have a cosmically awesome day out there.
(upbeat music)