At the largest in-person gathering of astronomers since the launch of JWST, it should be no surprise that the flagship space observatory is getting lots of attention!
The 241st meeting of the American Astronomical Society (AAS) kicked off in Seattle today, with a presentation by Jane Rigby, Operations Project Scientist for JWST at NASA’s Goddard Space Flight Center.
The majority of Rigby’s talk focused on the technical performance of JWST, especially how it has met or exceeded all of its requirements! Not only are all 17 science instrument modes “ready for science,” beginning normal operations in July 2022, but the telescope is outperforming expectations.
JWST can track faster than initially designed, so it can image planets (as evidenced by its beautiful pictures of Jupiter and Neptune) and also managed to capture the fast-moving DART impact! The image quality has been more stable than anticipated, with corrections planned every two days having become unnecessary lately. And the mirror itself was so clean upon launch and deployment (reducing light scattering that can degrade image quality) that the telescope is 5 percent more efficient at collecting light than predicted—a small-sounding number that has a big effect on operations.
Rigby talked about her experience embedded in the team involved with launching and commissioning the observatory. She quipped: “I don’t know why people cheer rockets—they can only blow up!” Instead, she described the excitement as the JWST became the “Christmas present that took six months to unwrap,” launched on December 25, 2021, and requiring months of work to deploy, align, and test.
“JWST is artisanal,” Rigby said. “It was made by hand.” She illustrated that by showing numerous images of engineers and scientists working on the observatory before launch, and she described JWST’s successes as a testament to the thousands of people who dedicated their efforts—in the final phases, of course, during a pandemic—to ensuring that everything worked perfectly.
At the conclusion of her talk, Rigby asked everybody in attendance who had worked on JWST to stand up, and the room filled with applause.
But there was more JWST to come! The meeting’s first press conference attracted a packed house to hear presentations about “Eyes on Galaxies with JWST.”
Among other objectives, JWST was designed to detect light from the very early Universe, including light from the first galaxies to take shape.
A little background…
Astronomers like to talk about a galaxy’s distance in terms of its redshift z. (They prefer z because it’s a measurable quantity, from which attributes such as age and distance can be derived.) More distant galaxies have larger redshifts, thus larger values of z. And because light travels at a finite speed, a more distant galaxy dates back to an earlier epoch in the history of the Universe.
The upshot? Galaxies with high z are young galaxies that we are seeing shortly after the birth of the Universe.
But how high is high z? Good question. Once upon a time, a z of 4 or 5 might have been considered impressive, but the Hubble Space Telescope pushed that out to z of about 11, and JWST promises even more.
Haojing Yan at the University of Missouri wants to take things to z of 20! At least in the title of his talk…
Yan announced a large batch of “candidate galaxies” with z potentially between 11 and 20. As the press release about his work describes, that corresponds to an era about 200 to 400 million years after the Big Bang.
Using a less-then-reliable technique called photometric redshift, Yan and his collaborators studied the early JWST imagery of SMACS 0723-73 (made famous as part of the first image release from JWST last July) and discovered 87 candidates for these high z galaxies. That’s far more than most astronomers would have expected to identify—as Yan put it, most experts would have said they would be “lucky” to find even one!
This is tantalizing, but Yan was clear to note that “photometric redshift is not a confirmation.” For more accurate determination of the galaxies’ redshift (and thus age and distance), there needs to be follow up work measuring the galaxies’ spectra. That’s the way to determine z accurately, but it takes a lot more time and effort to make those measurements.
Yan was confident that such effort would pay off. During the Q&A session at the press conference, he said he’d wager $20 and a tall glass of beer that at least half of his 87 candidates would get confirmed redshifts greater than 11. Indeed, there’s already confirmation for at least one such galaxy from a different team of researchers, so JADES-GS-z13-0 holds the record for most distant galaxy (yet) observed, with a redshift of 13.20.
If we find a lot of galaxies with z greater than 11, then Yan believes “our previously favored picture of galaxy formation in the early universe must be revised.”
Among other things, he noted that, if these galaxies are confirmed, then “galaxies were formed much earlier than we thought… and there are way more galaxies than we expected.” This underscores the important relationship between observations and theory. As Yan said, the data “make our theorists go with observational facts. And I think they are pretty good at it, given the historical record.”
Plenty more JWST galaxy news got shared! Jeyhan Kartaltepe from Rochester Institute of Technology led a group of researchers that categorized the shape and structure of young galaxies in JWST images, discovering far greater diversity and than previously known. James Rhoads from NASA’s Goddard Space Flight Center compared unusual nearby galaxies (which he described as “fossils of earlier forms of galaxy formation,” like coelacanths) to distant galaxies imaged by JWST and noted intriguing similarities. And looking at phenomena much closer to home, Philip Appleton from Caltech’s IPAC facility examined JWST’s incredible imagery of Stephan’s Quintet to understand a violent collision occurring 270 million light years away.
That’s just the first of four days of the AAS meeting! We look forward to sharing more cutting-edge astronomy news for the rest of the week.