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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 05/03/2026

With OpR4 complete, 4MOST now moves into the Survey Programme Validation (SPV) phase, as we move even closer to the start of survey operations!

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 05/03/2026

The Cambridge Astronomical Survey Unit (CASU) also worked to ensure that OpR4 data could be rapidly transformed into usable survey products. “The OpR4 campaign was intense, but ultimately successful...The 4MOST pipelines are now ready, let the science begin.” - Nic Walton and David Murphy (CASU)

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 05/03/2026

“For me the most impressive thing to see was the enthusiasm, competence, and hard work of everyone involved. We have been planning for this moment for the last decade - everyone was present and keen on making it work” - Jakob Walcher (4MOST Operations Manager)

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 05/03/2026

During this phase, teams worked to ensure that 4MOST can automatically generate Observing Blocks and select targets, while also adapting for live observing conditions at Paranal.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 05/03/2026

Operations Rehearsal 4 (OpR4) has now concluded, marking a major milestone towards routine survey operations! Image: Automatically generated and queued OBs during OpR4 (Credit: Jakob Walcher) #4MOST #astronomy #astrophysics

A computer monitor showing the execution sequence scheduling interface at Paranal during OpR4

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 30/01/2026

“Seeing on the first night of OpR4 how one [observing block] gets executed, producing data, while the next one already appears by magic in the execution sequence has been hugely satisfying for everyone involved” - Jakob Walcher (4MOST Operations Manager)

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 30/01/2026

OpR4 is a month-long dress rehearsal to test every process of the survey, from live observations of the night sky to science-ready data products, and all of the infrastructure in between!

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 30/01/2026

After a successful commissioning process, 4MOST has reached the next major milestone before the full survey begins: Operations Rehearsal 4 (OpR4) ✨ Image: Carlos la Fuente launching the first observation for OpR4 (Credit: Jakob Walcher) #4MOST #astronomy #astrophysics

A picture of Carlos la Fuente launching the first observation for OpR4

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 21/12/2025

Lara’s project, titled “Chronicling the Clouds: Chemodynamics of the Most Massive Dwarf Galaxies”, will use 4MOST to explore how these dwarf galaxies formed, evolved, and interacted over billions of years. Check out the full press-release here: www.4most.eu/cms/news/202...

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4MOST

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 21/12/2025

We are delighted to share that Dr Lara Cullinane has been awarded a prestigious Leibniz Junior Research Group based at the Leibniz Institute for Astrophysics Potsdam (@aippotsdam.bsky.social). Image Credit: AIP/Spikermann #4MOST #astronomy #astrophysics

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Leibniz-Gemeinschaft @leibniz-gemeinschaft.de · 12/12/2025

4MOST - Ein neuer Blick ins All. Matthias Steinmetz ( @galacticrave.bsky.social ) von @aippotsdam.bsky.social & @unipotsdam.bsky.social zu Gast bei #TonspurWissen, dem #Podcast von @leibniz-gemeinschaft.de & Rheinischer Post. 👁️🔭🌟 pod.fo/e/364503 #Astrophysik #Astronomie #4MOST @4most-eu.bsky.social

Rechts oben in der Ecke steht in einer weißen Blase "tonspur Wissen“. Am rechten Bildrand ist ein Foto von Matthias Steinmetz zu sehen. Er ist Direktor des Leibniz-Instituts für Astrophysik Potsdam. Das Bild der Person ist schwarz-weiß eingefärbt, um die Konturen der Person beschnitten und zusätzlich weiß umrandet. In einer großen weißen Blase, die mittig-links im Bild platziert ist, steht: "4MOST - Ein neuer Blick ins All. Matthias Steinmetz. Leibniz-Institut für Astrophysik Potsdam ". Der Bildhintergrund ist ein blau-grün eingefärbtes Foto eines Blick ins Weltall mit einer Spiralgalaxie und einem Messkurve.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 11/12/2025

8. The view from back in the Residencia after a long day’s work, watching the incredible VLT laser guide star facility!

A view from the hotel window at night, showing the VLT with orange lasers pointing to the sky from the laser guide star facility.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 11/12/2025

7. Back in the control room checking the raw data for any faults.

Some more computer screens showing different 4MOST diagnostic software.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 11/12/2025

6. A visit to see the 4MOST instrument! “It was like seeing an old friend and a celebrity all in one!”

An image of the VISTA Telescope with the 4MOST instrument mounted on it.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 11/12/2025

4. The 4MOST dayshift control room (next to one of the VLT Unit Telescopes) just after twilight flat calibrations had been taken.

An external view of the control room building, next to one of the VLT Unit Telescopes.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 11/12/2025

3. Inside the 4MOST dayshift control room, where raw data are reduced and inspected.

A set of computer screens inside the control room, showing different 4MOST control software.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 11/12/2025

2. Commuting from the ESO Residencia (the astronomers’ hotel) to the observatory.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 11/12/2025

Join Jessica Pilling from the University of Sussex for a day in her life commissioning the 4MOST instrument! Credit: J. Pilling #4MOST #astronomy #astrophysics #telescope #observatory 1. Arrival at Paranal observatory 🔭

A Paranal Observatory sign on the way to the observatory

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 19/11/2025

"Commissioning has been a really intense and fun experience so far. This new team based model of commissioning telescopes is a fantastic opportunity for young researchers like me and I’m loving every moment of it." - Sam Philipsborn

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 19/11/2025

Commissioning is well underway at 4MOST! Sam Philipsborn, a PhD student from the University of Sussex, is one of the team members working tirelessly to ensure that 4MOST is performing as expected. Image Credit: S. Philipsborn #4MOST #astronomy #astrophysics #telescope #observatory

A view of mountains at Paranal, with the 4MOST facility visible on one of the peaks.

Sam Philipsborn standing next to the 4MOST sign at the VISTA telescope.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 31/10/2025

Meet the team commissioning 4MOST! Over the next two months, they’ll observe thousands of targets to study how the instrument performs and ensure it meets expectations ahead of full science operations. #4MOST #astronomy #astrophysics #telescope #observatory

A group photo of the 4MOST Commissioning Team

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 24/10/2025

With three spectrographs, and a hexagonal field-of-view of 4.2 square degrees, 4MOST will gather spectra of over 20 million stars and galaxies during its first five years of surveys.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 24/10/2025

4MOST in motion! Mounted on ESO’s VISTA telescope in Chile, this wide-field, fibre-fed spectroscopic facility can observe over 2000 targets at once, capturing their light and splitting it into spectra for analysis. Video: AIP/A. Saviauk Audio: LofCosmos #4MOST #astronomy #astrophysics

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Rubin LSST:UK @lsstuk.bsky.social · 23/10/2025

Congratulations to @4most-eu.bsky.social which has achieved First Light, splitting the light into 18,000 spellbinding colour components. 🎉 Read more about this multi-tasking telescope, which will collect the largest ever spectroscopic sample of supernovae. 🔭 tinyurl.com/2wnw86zd

tinyurl.com

Portsmouth and Southampton scientists help secure the first capture of light in all its colours from cosmic objects

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 23/10/2025

4MOST will capture thousands of these spectra at once, helping us map the structure and evolution of the Universe!

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 23/10/2025

Each peak and dip reveals what elements are present, how fast the object is moving, and how far away it lies. In this example spectrum of an active galactic nucleus (AGN, the region around a massive black hole) you can see strong emission lines from magnesium (Mg), oxygen (O), and hydrogen (Hγ, Hβ).

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 23/10/2025

When light from a star or galaxy enters one of 4MOST’s 2400 fibres, it is split into its colours and dispersed across the detectors, creating a spectrum, a detailed record of brightness versus wavelength. Credit: AIP/R. de Jong, CRAL/J.-K. Krogager #4MOST #astronomy #astrophysics

A spectrum of an active galactic nucleus showing peaks for Mg, O, and H emission lines. The x-axis is wavelength, and the y-axis is intensity.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 22/10/2025

We’re so lucky to have such an incredible team, and we can’t wait to share our exploration of the Universe with you, 2400 spectra at a time!

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 22/10/2025

Pictured here are just a portion of the 4MOST collaboration, an international group of astronomers and engineers responsible for 4MOST’s design, construction, and the upcoming research being conducted by our Consortium and Community surveys.

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University of Southampton @unisouthampton.bsky.social · 22/10/2025

Revolutionary new space telescope @4most-eu.bsky.social has captured its first data from the universe. Our scientists are part of the team behind the super-scope and say it’ll reveal how galaxies and black holes formed. Read more 👉 tr.ee/ba4NEs

The VISTA 4MOST, a large, intricate astronomical device, housed inside an industrial facility. The structure features a prominent circular component with visible wiring and metal framework, supported by a sturdy blue frame with stairs and a raised platform for access.

The VISTA mountain top observatory stands on rocky terrain under a clear night sky, with the Milky Way stretching across and a bright planet shining above.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 22/10/2025

"We cannot exactly predict what breakthroughs 4MOST will bring, but I really look forward to all the excitement of getting our hands on the data. Let’s get ready for the next fifteen years!"

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 22/10/2025

"A project like this is only possible by the dedication, determination, and strong collaboration of many people, bringing their diverse knowledge and mentality."

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 22/10/2025

"Little did those photons know that they would one day meet the fibres of 4MOST, forming the spectra of our First Light."

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 22/10/2025

"Fifteen years ago, a bunch of photons began their journey to Earth. At the same time, a team from institutes across the globe were aligning to build a next-generation multi-object spectrograph."

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 22/10/2025

Our PI, Roelof de Jong, reflects on 15 years of dedication, collaboration, and discovery leading to 4MOST First Light. Image Credit: R. de Jong #4MOST #Astronomy

A picture of the 4MOST PI, Roelof de Jong.

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ESO @eso.org · 21/10/2025

1/ The 4MOST instrument installed on our VISTA telescope in Chile completed its first test observations. @4most-eu.bsky.social will help us unravel our galactic history, explore dark matter, and more. www.eso.org/public/annou... 🔭 🧪 #instrumentation 📷 AIP/A. Saviauk

A view of the VISTA telescope and its 4MOST instrument. The structure is grey, with several cables visible around it. The telescope is viewed from above and is located inside a building with metallic walls.

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Durham University @durham.ac.uk · 21/10/2025

First light for 4MOST! 🔭 Global telescope collaboration @4most-eu.bsky.social captures its first light, beginning a scientific journey to reveal how galaxies and stars form and evolve. Discover Durham’s role in this project 👉 www.durham.ac.uk/news-events/... @icc-durham.bsky.social

durham.ac.uk

New Telescope Captures First Light in Chile - Durham University

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Leibniz-Institut für Astrophysik Potsdam (AIP) @aippotsdam.bsky.social · 21/10/2025

A new telescope facility is born 🌟, #4MOST captured its first starlight 💫 An impressive example of international cooperation. 4MOST can analyse the light from 2,400 objects simultaneously in 18,000 colours. www.aip.de/news/4most-f... @eso.org @4most-eu.bsky.social @aippotsdam.bsky.social

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Max Planck Institute for Extraterrestrial Physics @mpe-garching.bsky.social · 21/10/2025

🤩The @4most-eu.bsky.social (#4MOST) facility on @eso.org VISTA telescope in Chile achieved first light. #MPE scientists played a leading role in developing the Operations System, enabling to link #eROSITA’s X-ray universe with large-scale structure of galaxies. ➡️ More: www.mpe.mpg.de/8102833/news...

mpe.mpg.de

4MOST Begins its Journey of Cosmic Discovery

4MOST embarks on a cosmic journey, capturing spectra of thousands of celestial objects simultaneously, unlocking secrets of the universe.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 21/10/2025

This marks the start of 4MOST's journey to explore our Galaxy and beyond, and we are very excited to bring you all along with us!

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 21/10/2025

4MOST simultaneously collected light from 2000 objects, including the Sculptor galaxy, the globular cluster NGC 288, and the active core of a distant galaxy, revealing their detailed chemical signatures.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 21/10/2025

First Light for 4MOST! The 4-metre Multi-Object Spectroscopic Telescope (4MOST) has captured its very first spectra! Video Credit: AIP/R. de Jong, AIP/K. Riebe, AIP/A. Saviauk, CRAL/J.-K. Krogager

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First Light for 4MOST!

YouTube video by 4-meter Multi-Object Spectroscopic Telescope

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 18/10/2025

Sneak peek time! 👀 Each dot in this image is a target star or galaxy that will be captured in our First Light! Soon, each of these dots will turn into spectra, revealing the chemical signature of each of these objects! Image Credit: R. de Jong #4MOST #astronomy #telescope #observatory #science

A hexagonal map showing the focal plane of the 4MOST instrument, with many coloured dots showing fibre positions for first light, each marking where light from a star or galaxy will be collected.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 16/10/2025

The glasses aren’t raised just yet… but they’re standing by. Preparations for 4MOST First Light are in full swing, and the team on the mountain clearly have everything ready for the big day! 🥂 📷: R. de Jong #4MOST #telescope #astronomy #astrophysics #science #observatory

Bottles of sparkling wine placed in front of the 4MOST instrument, symbolising celebration as the team prepares for first light.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 14/10/2025

The road has been winding, but the destination is now in sight! 4MOST is almost at first light! Stay tuned 👀 📷: F. Laurent #4MOST #telescope #astronomy #astrophysics #science #observatory

A yellow road sign showing a winding arrow standing on a desert mountain road leaning towards the 4MOST site, symbolising the twists and turns of the journey to first light.

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 10/10/2025

3/3: The nine 4MOST Extragalactic Community Surveys explore the Universe beyond the Milky Way. Together they will probe galaxy evolution, the baryon cycle, strong lensing, quasar feedback, and the large-scale structure of the cosmos! 📷: A. Saviauk/AIP #WorldSpaceWeek #4MOST #extragalactic

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4-meter Multi-Object Spectroscopic Telescope (4MOST) @4most-eu.bsky.social · 10/10/2025

2/3: The nine 4MOST Extragalactic Community Surveys explore the Universe beyond the Milky Way. Together they will probe galaxy evolution, the baryon cycle, strong lensing, quasar feedback, and the large-scale structure of the cosmos! 📷: A. Saviauk/AIP #WorldSpaceWeek #4MOST #extragalactic

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