Thread by @markmccaughrean

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 🙂

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.

Later images confirmed what we suspected, namely that the jet was emitting in lines of shocked molecular hydrogen – the first pure H2 outflow from a young star ever found. This image is from the Calar Alto 3.5m telescope in the 2.12 micron line of H2.

In this image, the very young protostar driving the jet is in the gap between the two halves, invisible in the near-IR & only seen at much longer sub-millimetre & millimetre wavelengths, deeply embedded in gas & dust.

The protostar & outflow have become a bit of a poster child for the very early stages of star formation, & have been studied with many infrared & (sub)millimetre telescopes. The new #JWST programme led by Alessio Caratti o Garatti in Dublin will add greatly to our understanding.

So, we'll be taking new near-IR images in a 2 lines of shocked H2 & another of shocked Fe (yup), plus some continuum filters to isolate the lines & measure stars locally. They'll cover roughly the same region as the discovery image, but with ~30 x higher spatial resolution 😬

In addition to much more detail in the jet, showing lumps & clumps of shocked gas, we'll be comparing to our older data, including a lovely image from the VLT in 2006 that I'm not sharing here (yet), to see how the jet has has expanded from the protostar over several decades.

Then in separate observations, we'll be pointing the NIRSpec & MIRI IFUs at just the main bow shock at the left-hand end of the jet, to get imaging spectroscopy which'll let us analyse the chemistry & physics as the jet crashes at ~100km/s into the surrounding molecular cloud.

This collaboration between Alessio, Tom Ray, Ewine van Dishoeck et al. of the MIRI team & me, using a total of ~24 hrs of guaranteed time on HH211 should give us some great insight into the shocked interface between the jet & cloud, & the impact on the environment.

And for those interested in what we made of those discovery & follow-up observations, here's the paper I wrote in 1994 with my long-standing collaborators John Rayner & Hans Zinnecker: adsabs.harvard.edu/full/1994ApJ..…

Only four years later, I got involved in what was then known as the Next Generation Space Telescope or NGST, later named JWST. And here we are, 24 years after that, finally awaiting the first images of HH211 with this amazing machine. Talk about time dilation.

And this is just the beginning: within the next 10 weeks or so, we'll be getting JWST H2 images of the even more spectacular HH212 protostellar outflow & of the inner Orion Nebula in 12 different IR filters.

More on those as they get scheduled, but the deluge is imminent.

Coda: the discovery of HH211 was a complete accident. John Rayner & I were observing on the UH 88" in 1990 & Hans Zinncker phoned us up from Germany to say we should look at IC348, a young star cluster – that was the kind of science we were doing together.

So we went to Dan Gezari's trusty "Catalog of Infrared Observations", a book listing all IR observations ever made to that point, with positions, wavelengths, & brightnesses. Yep, those were the days.

We looked up IC348, found a coordinate & pointed the IR camera there.

However, because the catalogue was ordered in increasing Right Ascension, the first coordinate we found was for a deeply obscured IR source found in an old survey quite some way west of the IC348 star cluster. It wasn't in our field-of-view at all.

We saw the embedded source – it's the bright thing in the middle of the first image in this thread. But we also saw that elongated object & new we were on to something – we forgot about the IC348 star cluster that night & imaged this new discovery.

We called it IC348-IR for a while, but a year or so later, we discovered another jet elsewhere.

Because it was found in the 2.12 micron line of H2, we persuaded Bo Reipurth to give us the number HH212 in his catalogue of Herbig-Haro objects, shocked gas linked to young stars.

HH also stood for the H2 molecule & as 212 is a symmetric number, it was a great fit to that very symmetric jet.

And then, because we had discovered the IC348-IR jet earlier, it became HH211.

Simples 🤷‍♂️

I'll also be imaging HH212 soon with JWST & in an interesting loop, my ESA colleague Catarina Alves de Oliviera will be observing the real IC348 star cluster.

We're also working together on spectroscopy of very low mass brown dwarfs in Orion, so there's plenty to come.

Whoops: greasy fingers. We’ll be imaging HH211 in *three* near-IR lines of H2 & one of iron.

To complete this thread, here’s another on the Catalog of Infrared Observations. Which in turn quotes this thread. Things could get very recursive 😬

https://twitter.com/markmccaughrean/status/1560391102556930048