Joris Witstok

Incredible outfit for no doubt an incredible PhD thesis! Congrats Dr Helton 🥳🍾

Currently watching the first light from
@vrubinobs.bsky.social’s 3200 megapixel camera 🤩

A small ancient galaxy started reionizing its surroundings early As the James Webb Space Telescope looks back at the universe’s first billion years, surprises continue to turn up.

A wonderful summary of our results on the enigmatic galaxy GS-z13-1 came out in Physics Today a few days ago!

pubs.aip.org/physicstoday...

Dust Ahead of Schedule: The Surprising UV Bump in a Galaxy at Cosmic Dawn What do you get when baby galaxies crash and light up in UV? A surprising early signature of cosmic dust.

From Niloofar Sharei @astroneal.bsky.social : What do you get when baby galaxies crash and light up in UV? A surprising early signature of cosmic dust. 🔭✨☄️
astrobites.org/2025/04/21/dust-ahead-of-schedule-uv-bump/

🧵 Today is paper day for me! Usually I don’t post about papers but I have a special soft spot for this one: the detection of the Gunn-Peterson trough in high-redshift *galaxies* !!

arxiv.org/abs/2504.02683

#astrosci #extragalactic #cosmology

This is figure 1, which shows NIRCam and NIRSpec/PRISM observations of JADES-GS-z13-1-LA.

A paper in Nature reports observations from the JWST showing one of the earliest known galaxies caught in the act of reionization. The observations place the onset of cosmic reionization to at least 330 million years after the Big Bang. https://go.nature.com/4hLNK12 🧪 🔭

Witnessing the onset of reionization through Lyman-α emission at redshift 13 - Nature Spectroscopy from the JWST Advanced Deep Extragalactic Survey of a galaxy at redshift 13 shows a singular, bright emission line identified as Lyman-α, suggesting the onset of reionization only 330 Myr...

Paper day! And it’s a big one 🥳

Today, a team of researchers led by @joriswitstok.bsky.social — A DAWN fellow @cosmicdawncenter.bsky.social and Post-doc in the PRIMORDIAL group — published a paper in @nature.com reporting the detection of Lyman-alpha emission from a galaxy at redshift 13 (!)

🧵👇

James Webb opdager tidligste tegn på at Universet bliver gennemsigtigt - Cosmic Dawn Center Universets første galakser blev født indhyllet i en “tåget” gas, og kunne ikke ses tydeligt før denne tåge var lettet. Ved hjælp af rumteleskopet James Webb har et internationalt hold af forskere, led...

Earliest sign of the Universe becoming transparent discovered with #JamesWebb.

@joriswitstok.bsky.social et al. detected the escape of your fav UV light, Lyman α, the signature of an ionized bubble, only 330M years after the Big Bang.

🇬🇧 cosmicdawn.dk/news/james-w...
🇩🇰 cosmicdawn.dk/news-in-dani...

A small red dot is in the middle of the image. To its upper left is a face-on spiral galaxy, and to its lower right is an edge-on spiral galaxy. A handful of other small background galaxies are seen against the black background of space.

Using the unique infrared sensitivity of #NASAWebb, researchers can examine ancient galaxies to probe secrets of the early universe. Recently, a bright hydrogen emission from a galaxy in an unexpectedly early time in the universe’s history has been identified. (1/4) 🧵 🔭 🧪

An area of deep space is covered by a scattering of galaxies in many shapes and in colours ranging from blue to whitish to orange, as well as a few nearby stars. A very small square is shown zoomed in, in a box to the left. In the centre a red dot, a faraway galaxy, is marked out by lines and labelled “Redshift (z)=13”, signifying its extreme distance. Two much larger galaxies are labelled “z=0.63” and “z=0.70”. The box is titled “JADES-GS-z13-1”.

Astronomers have identified powerful hydrogen emission in one of the most distant galaxies known — a probable sign that we are seeing some of the first hot stars from the dawn of the Universe ✨

All thanks to the NASA/ESA/CSA James #Webb Space Telescope.

Read more 👉 www.esa.int/Science_Expl...
🔭🧪☄️

James Webb discovers earliest sign of the Universe becoming transparent - Cosmic Dawn Center The first galaxies in the Universe were born enshrouded in a “foggy” gas, and could not be seen clearly until they had cleared up this fog. Using the James Webb Space Telescope, a team of researchers ...

Press releases:
ESA (@esa.int): esawebb.org/news/weic2505/

NASA: webbtelescope.org/contents/new...

DAWN (@cosmicdawncenter.bsky.social): cosmicdawn.dk/news/james-w...

Cambridge (@cambridgeuni.bsky.social): www.cam.ac.uk/research/new...

I've been lucky to work on this amazing data together with Peter Jakobsen (also at @cosmicdawncenter.bsky.social), Roberto Maiolino, @renskerens.bsky.social, @aasaxena.bsky.social, and many others.

Special thanks goes to @kevinhainline.bsky.social, Brant Robertson, Ben Johnson, @sandrotacchella.bsky.social, and others, who orchestrated the initial search leading to the discovery of this galaxy.

JADES The JWST Advanced Deep Extragalactic Survey (JADES) is exploring the universe of high-redshift galaxies using the transformative opportunity of the James Webb Space Telescope.

Needless to say this was a huge team effort by the JADES collaboration, and would not have been possible without key contributions from a large number of international scientists.

JADES website (with interactive image viewer): jades-survey.github.io

A lighthouse galaxy shines unexpectedly through the fog of the cosmic dawn Ancient UV light illuminates how galaxies and black holes first formed.

This also implies the galaxy contains a remarkably powerful source of extreme ultraviolet radiation, either in the form of extraordinarily massive, hot stars or a supermassive black hole rapidly consuming nearby gas.

As illustrated beautifully in the News & Views article by Michele Trenti:

In JADES-GS-z13-1, JWST has confirmed one of the most distant galaxies known to date. But unlike any other similarly distant galaxy, it shows a very clear, telltale signature that can only be seen once the surrounding fog has fully lifted.

While the Universe right after the Big Bang was blisteringly hot, a rapid expansion and cooldown subsequently rendered it opaque to energetic ultraviolet light. This ‘fogginess’ was gradually cleared out when bright starlight from the first galaxies started a process known as cosmic reionisation.

Using the James Webb Space Telescope (JWST), we identified bright hydrogen emission from a galaxy at an unexpectedly early time in cosmic history. But why is this result so surprising?

Image credits: ESA/Webb, NASA, CSA, STScI, J. Olmsted (STScI), S. Carniani (Scuola Normale Superiore), P. Jakobsen

Unexpected, bright hydrogen emission caught astronomers by surprise While the Universe right after the Big Bang was blisteringly hot, a rapid expansion and cooldown subsequently rendered it opaque to energetic ultraviolet light. This ‘fogginess’ was gradually cleared ...

Unexpected, bright hydrogen emission caught astronomers by surprise 🔭😳

I'm proud to have led a study reporting this surprising result, which is now published in @nature.com. Read more in this Behind the paper post and in the thread below! 👇

Oxygen discovered in most distant known galaxy Two different teams of astronomers have detected oxygen in the most distant known galaxy, JADES-GS-z14-0. The discovery, reported in two separate studies, was made possible thanks to the Atacama…

📣 Using ALMA 📡, in which ESO is a partner, astronomers have discovered oxygen in the most distant known galaxy!

This record-breaking detection is making scientists rethink how quickly galaxies formed in the early Universe 🤔

Read more: www.eso.org/public/news/...

🔭 🧪 ☄️

Proud to have been part of Katherine's first PhD paper 👏👏 Her detailed study of a distant galaxy reveals what is likely an ongoing merger in a complex system containing both young and old stellar populations with new evidence for the presence of small carbonaceous grains – read more below!

How do we learn about the anatomy of the most distant galaxy we currently know of? 🩻

Read more below! 👇

Had a wonderful time visiting the Kapteyn Astronomical Institute in Groningen last week. Congratulations to Roberto for being this year’s Blaauw professor and thanks to everyone at Kapteyn for your hospitality!

Don't fancy an Eerlijk Eten maaltijdbox?

Reminder about next year's conference on obscured star formation at the Kavli Institute for Cosmology, Cambridge (22-26 April), organised by Jan Scholtz and me. Abstract submission closes soon! sites.google.com/cam.ac.uk/sf...

Looking forward to learning more about the origin and fate of cosmic dust this week in Gothenburg ✨ #CosmicDustSweden2023

This seemed like a good first opportunity to dive into Blue Sky – thanks @emily.space for setting me up and @ojhall.bsky.social for providing the invite code!

Star Formation 2024 A hybrid (online & on-site) meeting focusing on hidden and elusive star formation, from the local Universe to high redshift, and an occasion to remember Richard Hills

Jan Scholtz, myself et al. are excited to announce an upcoming conference at the Kavli Institute for Cosmology. "Raising the veil on star formation near and far" is a meeting dedicated to Richard Hills, remembering his contributions to understanding obscured star formation across cosmic time: