RT: Today's Google Doodle features Mexican astronomer, Guillermo Haro, famous for the discovery with George Herbig of the eponymous HH objects, patches of nebulosity linked to young stars. Here's a (proper) thread about some of my work in this field. 1/ google.com/doodles/guille… 
In the early 1990s, John Rayner, Hans Zinnecker, & I discovered two Herbig-Haro objects, collimated jets of gas emerging at hundreds of kilometres per second from invisible protostars perhaps only 10–100 thousand years old, deeply embedded in their natal gas & dust. 2/
Both jets were discovered on big telescopes using infrared cameras with narrow-band filters at 2.12 microns. Molecular hydrogen in the outflow gets mechanically shocked up to thousands of degrees & glows brightly in a ro-vibrational line (v=1–0 S(1)) at that wavelength. 3/
The second jet we discovered (bear with me) was in 1990. John & I were observing on the University of Hawaii 88 inch telescope on Mauna Kea when Hans called us from Europe & said "take some images of IC348". He didn't give us any more details. Typical Hans 🙄 4/
What he meant us to look at was the young stellar cluster, IC348, in Perseus. But this was pre-internet & when we looked in Dan Gezari's famous (paper 😵) Catalog of Infrared Observations, we found an object called IC348-IR & pointed the telescope to those coordinates. 5/
But IC348-IR was a bright Infrared source with some associated nebulosity discovered in 1974 by Steve Strom, some way from the stellar cluster. When we imaged the region in H2, we found a remarkable double-lobed jet nearby, later given the catalogue name HH211. 6/
We published this discovery in a paper in 1994. HH211 has since been extensively studied, showing that the H2 emission lies along the edges of a highly-collimated jet seen in SiO & other species, emerging from a young protostar right in the middle. 7/ articles.adsabs.harvard.edu/cgi-bin/nph-ia…
More on the discovery of our other jet a bit later: it's dinner time. But do tune in: this has an equally convoluted history, but is even more beautiful 👍🚀🛰 8/
OK, back. A couple more HH211 facts. a) It was the first ever jet discovered through infrared imaging. b) As seen in the picture in tweet 6, the jet is ~0.15 parsecs or ~0.5 light years long, i.e. ~500 times the diameter of our Solar System (out to Neptune's orbit). Big 😵 9/
Now to the other HH jet. In the late 80's, we were at the 3.8m UK Infrared Telescope also on Mauna Kea, using one of the very first IR cameras for astronomy, IRCAM: both John & I worked had on it for our PhD's. 10/
Hans was interested in young, cold protostar candidates that had been discovered by the US-UK-NL infrared space mission, IRAS, & he used IRCAM to look at one such source, IRAS 05413–0104 (that's its coordinate), near the Horsehead nebula in Orion. 11/
Hans saw two dots of near-infrared light at that location on the sky & concluded that IRAS 05413–0104 was a protobinary stellar system, quite a find. He excitedly wrote up the discovery in some conference papers. However, he was wrong. 12/
A few years later in 1993, John & I were at the IRTF, a 3m infrared telescope also on Mauna Kea, built to take IR data of solar system objects to accompany NASA's interplanetary missions. That night, Hans asked us to re-observe IRAS 05413–0104 with higher resolution. 13/
We did & because the IRTF's newer IR camera had a bigger field-of-view than IRCAM, we saw that those two dots were just the innermost in a symmetric linear series of features on the sky. Very exciting. 14/
A year later, we observed it again on the Calar Alto 3.5m telescope in southern Spain, mapping out the full extent of this amazing object. Here it is in later images from the ESO VLT on Paranal. Full-res version on Flickr. 15/ flickr.com/photos/markmcc…
This object got the name HH212, but not at all by chance. Hans asked Bo Reipurth, the HH catalogue keeper, to give us that number because 212 refers to the shocked molecular hydrogen emission line at 2.12 microns & because it's a symmetric number, like the jet itself. 16/
And that's why the other jet was called HH211, because we published it before we published the HH212 paper, even though the first observation was made later. Confused? I think we all are 😧 17/
The HH212 paper was published in 1998 in a journal beginning with the letter N. You might be able to grab a copy here. 18/ dropbox.com/s/3usfeyhpm82y…
HH212 is a stunning object, with a series of knots & bow shocks almost completely symmetrically placed on either side of an invisible protostar. Altogether, it spans ~0.5pc or 1.6 light years, almost halfway from the Sun to Proxima Centauri, our nearest stellar neighbour. 19/
Because of the symmetry, we assume that the jet features are linked to episodic "burps" from the protostar. We've been observing it repeatedly, to watch it expand over time. It's moving at hundreds of km/s but at such great distances, the observed motions are small. 20/
Both HH211 & HH212 are fantastic laboratories in which to observe very early star formation. Weirdly, at the same time as most material is falling in via a disk to form the new star in the centre, a fraction of it is being ejected in jets from that star & disk. Why? How? 21/
It could be linked to the removal of angular momentum as rotating material falls in, with magnetic fields in the disk winding up & providing a mechanism for ejection. It's a topic of very active observational & theoretical research still, as below. 22/ arxiv.org/pdf/1711.00384…
Anyway, that's perhaps enough for this thread, inspired by Google's doodle in honor of Guillermo Haro, half of the Herbig-Haro name used for jets & outflows from protostellar objects. 23/
One last thing. HH211 & HH212 will be among the objects observed with JWST in its first year after launch. With the MIRI team, we'll be doing a comprehensive near/mid-IR imaging & spectroscopy study of HH211 & I'll be doing very deep, detailed imaging of HH212. 24/
So expect some fantastic new images & science from these amazing protostellar jets soon. If you made it all the way to the end of this epic thread, then you'll also have the patience to wait a bit longer for them, I hope 👍🚀🛰 25/25
Please unroll this thread, @threadreaderapp.
