Simons Observatory

A group of about a hundred people arrayed outdoors on a lawn in front of a multi-story brick building detailed with oxidized copper panels. The sky is grey but they are smiling

A roundel with written "Simons Observatory" on top and "Face-2-face Manchester 2025" at the bottom. The roundel shows the Manchester skyline in grey on a black background. A stylized telescope at the bottom left shines a light at a white and orange pixel-art bee.

We're having our collaboration meeting this week! Many of our members went to the University of Manchester, many more are online. Kudos to the local team for an adorable logo (with a pun in it of course) 🐝-modes are the sweetest honey! #AstroSci

At @simonsobservatory.org, Bluefors cooling tech powers ultra-sensitive telescopes mapping the #CosmicMicrowaveBackground —the faint afterglow of the Big Bang.

Take a dive into this ambitious #Cosmology project:
bluefors.com/stories/big-...

#Astrophysics #Astronomy #PhysicsSky #CoolForProgress

Hey, that's us! 🔭☄️

Cool results from our cousins at the South Pole Telescope! 🔭 With our Large Aperture Telescope, we hope to reach a similarly exquisite sensitivity as they do on their green patch over a large sky area (that I crudely outlined in blue).

Eternal Sky Film About Jim Simons and the Simons Observatory Now Streaming Eternal Sky, a documentary about the lead-up to the construction of the Simons Observatory in Chile’s Atacama Desert, is now available for streaming.

Eternal Sky, a documentary about our co-founder Jim Simons and the @simonsobservatory.org, is now available for streaming: www.simonsfoundation.org/2025/05/13/e... #science #astronomy #cosmology

Hoy se cumplen 60 años de la publicación del descubrimiento del Fondo Cósmico de Microondas por Arno Penzias y Robert Wilson! 🥳

Compartimos la columna de nuestro investigador @csifon.bsky.social resumiendo la importancia de este descubrimiento

"LAT llama a casa"

A night photo of a large building-sized telescope. The building is in two parts: a big u-shaped structure is mounted on a pivot, and itself ensnares a smaller brick-shaped box that can swivel with a hole in it. Some rocks in the background are visible in yellow, illuminated by an unseen source. Red safety lights at the bottom of the U element and ice blue light from within the telescope's opening complete the scene

OK, who was throwing a rave inside the Large Aperture Telescope 🔭?

(Image credit: Prof. Suzanne Staggs, Princeton)

A front view of one of the SO Small aperture telescopes from up close. The top half of the image is filled by a conical structure we are looking into: its inside is covered with a white, wallpaper looking structure. There is snow piled up on the bottom lip of the cone. At the end of the cone is an aluminium foil cover. Beneath and behind the cone you can see a white metal platform that holds the rest of the telescope, including its mount. Various surfaces are covered in snow, black cables meander around the scene. In the background, a deep blue sky and a shiny screen that provides additional sun and terrain shielding.

We had snow last week at our site! Our telescopes 🔭 like being cold, our teams not so much. Here you are looking inside the sun-shield of one of the SO SATs, the actual lenses and the focal plane sit beneath that shiny cover, cooled to cryogenic temperatures.
Image credit: Dr Elle Shaw, UT Austin

"A beginning is the time for taking the most delicate care that the balances are correct."
-Frank Herbert, Dune

Our Rubin colleagues are starting an exciting commissioning period in Chile, like us with our LAT!

The Simons Observatory LAT with its aperture open, looking at the sky at night. Red safety lights illuminate the bottom of the telescope structure, while a few stars shine in the background.

This week, we are trying to assess performance of our Large Aperture Telescope by looking at the planet Mars. For our telescope, it appears as a point, so we can understand our optical response and pointing by observing it.
Image credit: Mark Devlin. ☄️🔭

@evevavagiakis.bsky.social introduces Large™️ @simonsobservatory.org telescope to a standing room only crowd at @astronomyontap.bsky.social Durham!

Inflation

Fun fact: Three out of the eight schools in the Elite Eight of the Women's March Madness are members of the Simons Observatory: Duke, USC, and UT Austin. 🏀 If you want your team to get good, consider convincing your institution to join us! (Of course, there is a relevant xkcd: xkcd.com/1365/)

Simons Observatory Large Aperture Telescope Achieves First Light Milestone Simons Observatory Large Aperture Telescope Achieves First Light Milestone on Simons Foundation

The @simonsobservatory.org recently completed the installation of its Large Aperture Telescope, joining its three Small Aperture Telescopes. These telescopes will collect the most precise measurements yet of the universe’s oldest light. www.simonsfoundation.org/2025/03/17/s... #science #astronomy

If you're curious about the LAT's abilities, here's a thread from a few weeks ago:

A green dot (Mars) surrounded by a white ring on a purple background. A faint white x pattern is visible

One of the mirrors being lowered by crane inside the white box that constitutes the LAT housing. Behind it is the barren landscape of the Atacama desert

We have first light on our Large Aperture Telescope! www.simonsfoundation.org/2025/03/17/s...
After installing our mirrors over the last few weeks, we have started looking at the sky. We are still tuning the telescope, but we can already make maps of objects in the sky, like Mars. ☄️🔭🧪

¡La nueva página del Observatorio Simons ya está disponible! Por ahora solo en inglés, pronto viene la versión en castellano. ¿Qué les parece? ¡Déjennos sus comentarios!

simonsobservatory.org/institutions/

A drone view of the Atacama desert on a clear day with the SO site in the foreground.

We have a brand new website! simonsobservatory.org Go check it out for information on what we do, recent publications, and cool images. 🧪🔭

Good luck out there SPHEREx! May your non-gaussianity constraints have low uncertainty.

Mapa del cielo mostrando el área que observará el Observatorio Simons en comparación a DES, DESI, Euclid y Rubin.

Hoy publicamos dos artículos en el repositorio #arXiv. En el primero de ellos (arxiv.org/abs/2503.00636) discutimos los principales objetivos científicos de nuestro LAT (recuerden: Large Aperture Telescope, Telescopio de Gran Apertura), que observará la mitad del cielo

two weeks, two readout harnesses for advanced @simonsobs.bsky.social!

A figure with four panels showing oscillating, roughly exponential lines in different colors between blue and yellow. The caption reads: Figure 1. Logarithmic profiles of five monochromatic co-polar beam maps generated for each of the 93 (top left), 145 (top right), 225 (bottom left), and 280 GHz bands (bottom right), using TICRA TOOLS software. Each set of (five) maps is produced at frequencies of uniform spacing across the full frequency range of the corresponding band. All bands are assumed to have 25% fractional width, and all beam maps are generated for a detector on the center of the focal plane of a simulated three-lens refracting telescope.

The second preprint is about our small aperture telescopes. We ran simulations to forecast how much of a problem shifts in the shape of our beam within a band (color corrections/chromaticity) would be for our cosmological analysis. arxiv.org/abs/2503.01791 This project was led by Nadia Dachlythra.🔭☄️

A timeline of the LAT's status between 2020 and 2034. Construction lasts until 2025, the LAT gets upgraded sometimes in 2028, sensitivity raises with time to 2.5 microK/arcmin over 20000 square degrees. 3d renders show the LAT and the focal plane getting filled up

We have two preprints out on the arXiv today 🔭☄️!
The first one is about an #NSFFunded upgrade to our Large Aperture Telescope, roughly doubling the number of detectors in it: arxiv.org/abs/2503.00636 enabling us to probe the sky deeper than ever. The paper was led by Susan Clark and Colin Hill.

Our collaboration is not just about building the telescopes: a lot of work goes into developing tools to analyze the data we collect.

Figure 1

Figure 2

Figure 3

Figure 4

PROTOCALC, A W-band polarized calibrator for CMB Telescopes: application to Simons Observatory and CLASS. Gabriele Coppi et. al. https://arxiv.org/abs/2502.14473

Cover of an MIT Kids Press book called "I'm a neutrino - Tiny particles in a big Universe." Some doodly neutrinos are tumbling in front of a pastel spiral galaxy

P.S. At this point, since @evevavagiakis.bsky.social is not writing this post, I can mention her children's book with adorable little neutrinos if you want to learn more about them. www.penguinrandomhouse.com/books/706338... 9/8

So you can use the largest objects in the Universe (the CMB and large scale structure) to weigh the lightest elementary particles (neutrinos) which is the coolest thing ever. There's a lot more we can do with the LAT but this thread is already fairly long, so let's save it for next time. 8/8

A series of curves of the CMB lensing power spectrum with changing colors matching to specific sums of neutrino masses. The caption below it says: The effect of massive neutrinos on the matter power spectrum and CMB lensing power spectrum. Top Left: The effect of neutrino mass on the matter power spectrum. Top Right: The change to the matter power spectrum relative to the case with massless neutrinos. Bottom Left: The projected matter power spectrum observed through CMB lensing shows the same suppression with neutrino mass. Bottom Right: The relative change to the lensing potential power spectrum.

This is a scale-dependent effect, so we know how to identify it. It is also sensitive to the mass of the relativistic particles zipping through. That includes neutrinos! (Image from the CMB-S4 science book arxiv.org/abs/1610.02743) 7/8

a cartoon of a man holding a sword with the words " i can 't pull me dow defying gravity " below Alt: The green witch from wicked holding a broom with the words " They can't pull me down defying gravity " below

We expect some of it will be missing, because some matter will be defying gravity. It turns out if you are going at relativistic speeds, you're not very sensitive to the pull of your typical dark matter blob. 6/8

We can also compare the measured lensing to predictions of the statistical properties it should have if the large-scale structure of the universe only consisted of normal matter and dark matter that gradually assembled into the "cosmic web" of the previous picture. 5/8