Share this page!

Enter URL or ID to Unroll

You can paste full URL like: https://x.com/threadreaderapp/status/1644127596119195649
or just the ID like: 1644127596119195649

How to get URL link on X (Twitter) App

  1. On the Twitter thread, click on or icon on the bottom
  2. Click again on or Share Via icon
  3. Click on Copy Link to Tweet
  4. Paste it above and click "Unroll Thread"!
  5. More info at Twitter Help
Mark McCaughrean Profile picture
Mark McCaughrean
@markmccaughrean
Senior Advisor for Science & Exploration @esa / JWST Science Working Group IDS / Co-founder @spacerockslive / sameusername at 🐘 dot social
Sep 25, 2022 • 32 tweets • 16 min read
Here’s the order of play for my #JWST look at the Orion Nebula & Trapezium Cluster over the coming week.

35 hours of observations spread over 6 days, generating ~3,500 images & ~140GB of data.

Probably worth a bit of background explanation.

1/ First things first.

Most astronomers would think of Orion as something to be observed in December. That's when it's opposite the Sun in the sky & is visible most of the night, culminating around midnight. I've spent many December nights observing Orion from Hawai'i & Chile.

2/
Sep 6, 2022 • 4 tweets • 5 min read
Two spectacular new images of the Sun marking the inauguration of the #InouyeSolarTelescope on Haleakala, Maui.

They show the complementary nature of observing at different wavelengths: @ESASolarOrbiter extends this principle to those invisible from the ground.

HT @PlanRad Image of an 82,500km square region of the Sun at 18km resoluImage of an 82,500km square region of the Sun at 18km resolu @ESASolarOrbiter @PlanRad Be sure to click & view at full-size: they're lovely.

Both show a an 82,500km square region of the Sun at 18km resolution.

L: in the emission line of H-beta at 486nm showing the chromosphere above the surface

R: in the Fraunhofer G-band at 430nm showing surface granulation
Sep 6, 2022 • 5 tweets • 3 min read
Enter the spider's lair 🕸🕷

Great new #JWST image of 30 Doradus, the Tarantula Nebula, in the Large Magellanic Cloud.

Do follow the link & download the full-sized image if you dare – there's a huge amount of superb detail in there when you pan & zoom.

esawebb.org/news/weic2212/ JWST NIRCam mosaic of the Tarantula Nebula, 30 Doradus, in t In the link you'll find NIRCam near-infrared & MIRI mid-infrared images of the Tarantula Nebula & the dense cluster of young stars, NGC2070, at its core, plus NIRSpec near-infrared integral field spectroscopy.

Also check out the @esascience thread:

Aug 25, 2022 • 19 tweets • 12 min read
Another great early science result from #JWST: the first unambiguous detection of CO2 in the atmosphere of an exoplanet.

Seen in one single transit of the planet WASP-39b in front of its star with the @esa-led NIRSpec instrument.

So much more to come.

esa.int/Science_Explor… Image @esa This result comes from one of the Early Release Science programmes & is fully described in a paper that came out on arXiv overnight & will be published in Nature next week.

Congratulations to the large team of authors & everyone who made this possible.

arxiv.org/abs/2208.11692
Aug 24, 2022 • 6 tweets • 3 min read
I believe strongly in the idea of the BBC & many parts of it do a brilliant job.

But it is impossible to deny that its news & current affairs output since Brexit has been heavily compromised by dark political influence, as @maitlis so cogently says.

theguardian.com/media/2022/aug… @maitlis I find Question Time & Newsnight unwatchable now, & the glaring unwillingness in many news programmes to openly confront the deeply-damaging impact of Brexit & government failings during the pandemic & more widely has helped drive an ugly ideological wedge between many Britons.
Aug 23, 2022 • 4 tweets • 1 min read
About that “sound of a black hole” tweet.

An X-ray image of Perseus Cluster shows ripples in hot gas driven by a black hole.

A series of radial profiles in the image generate data curves. The frequencies are multiplied by ~200 quadrillion & then sonified.

So, err, not really. The Chandra webpage gives a good explanation of what was done, but the result really isn’t “the sound of a black hole”.

Sonification of data sets like images, spectra, particle hit rates, etc. is fine for outreach & accessibility, but it’s important not to mislead or confuse.
Aug 21, 2022 • 27 tweets • 40 min read
Wave-particle duality.

#JWST senses light from distant stars & galaxies as photons, their energy liberating electrons in the detectors.

But the light also has wave-like properties, interacting with the geometry of the telescope optics to create diffraction patterns. An image of a bright star as seen with JWST, its light diffr This is a full-resolution blow-up of the star 2MASS J17554042+6551277, used for focus measurements in March 2022. Data processing by @gbrammer & @CosmicSprngJWST, with some enhancement by me in LightRoom.
Aug 18, 2022 • 4 tweets • 2 min read
And for the old school infrared observers, here’s my copy of Dan Gezari’s Catalog of Infrared Observations & the listing for IC348-IR where we pointed the telescope in 1990 & discovered HH211 👇

(This is the third edition from 1993, but same observations of IC348-IR 🙂) ImageImage Dan’s catalogs were utterly essential in pre-internet days. A complete listing of every IR astronomical observation ever published to that date, with names, coordinates, wavelengths, beam sizes, fluxes etc, plus a full bibliography of all of the papers. About 1000 pages long.
Aug 18, 2022 • 21 tweets • 5 min read
The cosmic vertigo you feel when you hear that your first #JWST observation has been scheduled 😱

Ten days from now, the protostellar jet HH211 will be imaged with NIRCam in 9 filters.

Here's the image we made when we discovered it 32 years ago.

I suspect it'll look better 🙂 ImageImage The discovery was made using the University of Hawai'i 88 inch telescope on Maunakea, with a 256 x 256 pixel IR array & an image scale of 0.75"pixel. The image is a three-colour JHK (1-2.5 micron) colour composite.
Jul 18, 2022 • 11 tweets • 5 min read
While semantically correct, this headline sensationalises reality.

Yes, the micrometeoroid hit on #JWST's C3 primary segment caused permanent damage.

But the *effect* of that damage is minimal & the telescope remains within its design specifications.

Very well within. The article itself is a bit more nuanced, but still overplays the effect. If you go to page 23 of the observatory commissioning report, you'll get the balanced picture.

stsci.edu/files/live/sit…
Jul 17, 2022 • 6 tweets • 3 min read
Nice #JWST piece by @MonicaGrady, including a welcome nod to the role played by Europe & Canada, alongside the US.

One minor nitpick though (forgive me, Monica 😬), but the last thing the primary mirror segments are is flat. Very smooth, but not flat 🙂

theguardian.com/commentisfree/… I mean, in this case I’m sure it’s just a slight misphrasing, but it is interesting that many people don’t seem to realise that the primary mirror isn’t flat, but is very precisely curved in a concave parabolic shape to focus light towards the secondary mirror.
Jul 16, 2022 • 19 tweets • 4 min read
Who remembers my “adventures” with Avis at Frankfurt Airport?

They mixed my contract for someone else’s, someone who got caught speeding several times & I ended up with their police fines.

Took months & lawyers to sort out.

Well, let’s talk about Munich Airport today 🙄

1/ Of course, I didn’t rent with Avis this time – that’s never happening again, so I switched to Hertz.

I picked up a car from them at Munich Airport on Thursday, drove it to Alpbach in Austria, & returned it today.

2/
May 7, 2022 • 7 tweets • 3 min read
Finally caught a glimpse of some of the European bison that roam around the Zuid-Kennemerland national park just north of Zandvoort 🦬🙂

This pair were splashing around in a small pond, then wandered off into the dunes.

As seen during this evening’s 90km ride.

#cyclinglife 🚴‍♂️ The Kraansvlak herd of bison or “wisent” have free run of quite a large area of the dunes & are monitored as part of a rewilding research project. Despite the old idea that they’re predominantly forest animals, they do very well in this setting.

wisenten.nl/en
Mar 30, 2022 • 11 tweets • 4 min read
Perhaps the most distant known star, detectable by Hubble thanks to gravitational lensing.

Or is it a star in our own Milky Way that just happens to lie on the lensing caustic?

The good news: #JWST will get a spectrum & tell us one way or the other 🤷‍♂️

bbc.com/news/science-e… The authors have ruled out the latter by suggesting that a star in our own galaxy would likely have moved a bit in the 3.5 years since its discovery.

Perhaps, but in a semi-random distribution of motions, not all stars move tangentially; some will move mostly radially.
Jan 24, 2022 • 27 tweets • 13 min read
Venus & Mercury, closer to the Sun, orbit more quickly, in 225 & 88 Earth days, respectively.

Mars is further out & takes 687 days to orbit; Jupiter 4332, Saturn 10759, Uranus 30685, & Neptune 60,189 days.

Ditto for non-planets like Pluto. Cough 😳

Image: Wikipedia/WP

18/ The relationship between the distance of a planet from the Sun & its orbital period was discovered by Johannes Kepler.

His third law says the square of the orbital period of a planet is proportional to the cube of its orbital semi-major axis.

19/
Jan 24, 2022 • 19 tweets • 8 min read
A few hours from now, #JWST will make its Mid-Course Correction 2 (MCC-2) burn, injecting it into its operational orbit around the Sun-Earth L2 point, ~1.5 million kilometres away.

What, why, how, when?!

A thread.

1/ First, a reminder: #JWST was launched on #Ariane5 #VA256 from Europe's spaceport in French Guiana on 25 December 2021. The #Ariane5 put it on a near-perfect trajectory towards L2 & two subsequent JWST Mid-Course Corrections have tweaked that.

2/
Jan 8, 2022 • 34 tweets • 10 min read
As the start of the last major #JWST deployment approaches, the starboard primary mirror wing, it's time for a thread about what that helps enable – excellent spatial resolution.

It's #SharpnessSaturday (yes, the hashtag symbol also denotes a "sharp" in music 🙂) So what do we mean by "spatial resolution"?

It's a way of quantifying the sharpness of an image scene, the amount of detail visible at small scales, or at some rather fundamental level, how close two things can be in a scene & still be separated.

2/
Jan 8, 2022 • 4 tweets • 3 min read
And … as one third of you got right, the correct answer is “Glass” 🙂

Yes, even though the beryllium mirrors of #JWST are coated with a highly infrared reflective 100nm layer of gold, that in turn is coated with a thin layer of SiO2 (aka silica) to protect it from dings.

1/ Gold is soft & easily scratched, hence the overcoat. Silica is used in many applications, but in this form, it’s reasonable to refer to it as glass.

Of course, almost all photons hitting #JWST pass straight through before hitting & getting reflected by the gold, but still.

2/
Jan 7, 2022 • 14 tweets • 6 min read
Today’s the day – #JWST starts spreading the wings around its eyes 👀

And yes, I know this joke would make more sense if this was a pit viper rather than a cobra, but they don’t have a deployable hood 🐍🤷‍♂️

1/ That is, cobras are members of the elapid family of snakes, whereas pit vipers, including rattlesnakes, are from the crotaline family.

And what pit vipers share with boas & pythons is an ability to sense the infrared, which cobras lack.

2/
Jan 6, 2022 • 12 tweets • 4 min read
Morning. As we near the end of #JWST’s deployments (& how mad is that?! 😱), the big focus (😉) will naturally be on the primary mirror wings swinging into place 🔭

But don’t forget the aft deployable radiator, key to the instruments keeping their cool as they do science 😎

1/ Unfortunately I don’t have time today for a megathread on the physics of the radiator, as I’m going to be driving my son back to university in Groningen.

But there’s one equation to keep in mind with the ADR: sigma.A.T^4

2/
Jan 2, 2022 • 38 tweets • 10 min read
As we wait for the #JWST sunshield tensioning to begin after a day of well-deserved down time for the mission team, let’s talk in a bit more detail about how having a big, cold telescope helps us detect faint things.

Yes, folks, it’s Signal-To-Noise Sunday 😬

1/ Now, a health & safety warning – this could get a bit technical, maybe mathematical, & possibly even quantum mechanical 😱

I don’t know – I haven’t planned this thread at all, so it’ll just come out as a stream of consciousness. But hopefully a semi-intelligible one 🤷‍♂️🙂

2/