27, 39, 93, 145, 225, 280 GHz

Happy 60th birthday to physicist Uroš Seljak, born on 13 May 1966 in Slovenia, who coined the term "B-mode" and figured out with others that we could probe the era of inflation with the Cosmic Microwave Background in 1996-1997. 30 years later, we (and others) are on the hunt for them!

Congrats to Simons Observatory members Colin Hill and @msyriac.bsky.social for receiving the Breakthrough New Horizons Prize in Physics for work on CMB lensing! Our LAT is raring to go and image the gravitational lensing of the CMB deeper than ever before! (Credit: SO/O. Kusiak/K. Perez Sarmiento)

How many viscachas is too many? Answer: more than we can fit here—because this still isn’t enough! 🐾 These fluffy mountain summit residents have been hopping, sunbathing, and keeping an eye on us while NSF–DOE Rubin Observatory captures the cosmos! 🔭🧪

Are you, or do you know a student, who would be interested in a one-week summer school on the cosmic microwave background? The @simonsfoundation.org is organising one this July in NYC, with accommodation and travel support available! Apply by April 4th here: www.simonsfoundation.org/event/cmb-su...

POV: You're an observatory 🔭 in a remote part of the world but somehow aren't worried about this whole "oil price spike" thing. An important part of our Advanced Simons Observatory grant was to make our observatory mostly #SolarPowered Image credit: Dr Benjamin Schmitt, U Penn

Our Large Aperture Telescope making friends last December.🧪🔭 Nuestro Telescopio de Gran Apertura haciendo un amigo el pasado diciembre. Image Credit: Federico Nati

The Northeastern US wasn't the only place with snowfall last weekend... It also snowed at our site, nestled at 5200m above sea level in the Atacama desert! ¡El fin de semana pasado nevó en nuestro observatorio, situado a 5200 m sobre el nivel del mar en el desierto de Atacama!🔭 Image: Niklas Tampier

On the sixth day of CMBmas my telescope gave to me: Six SATs a-funding FIVE SCORE PAPERS Four parts of Stokes Three fine SATs 🔭 Two optics designs and a low PWV We have a new paper out, presenting how we are expanding the SAT side of SO, to detect B-modes ever better. arxiv.org/abs/2512.15833

On the fifth day of CMBmas my telescope gave to me: FIVE SCORE PAPERS Four parts of Stokes Three fine SATs 🔭 Two optics designs and a low PWV We have already published more that 100 papers describing the instruments and forecasting their performance! See them at that link:

On the fourth day of CMBmas, my telescope gave to me: Four Stokes components Three working SATs 🔭 Two optics designs and a low PWV Any light can be decomposed into the four so-called Stokes parameters: total intensity I, two linear polarizations Q and U, and circular V. SO measures I, Q and U.

On the third day of CMBmas, my telescope gave to me: Three working SATs 🔭 Two optical designs and a low PWV Last winter, we fixed a cracked lens in one of our Small Aperture Telescopes. We put it back on its' platform and it's now scanning the sky again. (Timelapse made by Josh Borrow, UPenn)

On the first day of CMBmas, the observatory Had a low PWV Telescopes like us are inconvenienced by water in the atmosphere emitting/blocking microwaves (same reason why a microwave heats food well). Luckily, the #Atacama desert has one of the lowest Precipitable Water Vapour amounts Earth.

Thrilled to join the Simons Observatory with Duke University as a member institution! @simonsobservatory.org today.duke.edu/2025/10/capt...

The @simonsobservatory.org was recently highlighted on BBC Four's The Sky at Night program: https://www.bbc.co.uk/programmes/m002j9vz #science #astronomy #cosmology

Excited to announce the latest recipients of our Targeted Grants in Mathematics and Physical Sciences (MPS) and Targeted Grants to Institutions: https://www.simonsfoundation.org/2025/08/27/2025-targeted-grants-to-institutes-and-targeted-grants-in-mps-announced/ #science #math

Tonight! 🧪📺

UK people! If you tune in to BBC Four at 22:00 BST this Monday, you will see us on The Sky at Night! www.bbc.co.uk/programmes/m... (plus other features on @vrubinobs.bsky.social and DESI) #scicomm

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, 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"

OK, who was throwing a rave inside the Large Aperture Telescope 🔭? (Image credit: Prof. Suzanne Staggs, Princeton)

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!

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!

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/)

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

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/

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.

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!

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.

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

As we are putting the finishing touches on our Large Aperture Telescope 🔭, now might be a good time to explain what science goals it serves. The problem is that there are many to choose from! (Image credit: Mark Devlin) 1/8

Fog can't stop us from installing our last mirror 🔭 Image credit: Toby Satterthwaite

Do not flip 6m secondary mirrors without experienced PI supervision and heavy duty equipment. Do not try this at home. 🔭 Image credit: Mark Devlin

Orion diving into the @simonsobs.bsky.social Large Aperture Telescope from my visit to the site a few weeks ago. Looking forward to first light soon!

Big day! The primary mirror is in the LAT! Credit: Elle Shaw

The M1 mirror (primary) being lifted into the Simons Observatory LAT telescope. #cosmology

First light? The LAT M1 mirror exposed to the sky for the first time in Chile after opening the shipping box. If the weather cooperates it could be installed in the telescope today. #cosmology @simonsobs.bsky.social

PSA: Lift 6m mirrors with your crane, not with your back

SATs and stars 📸 Elle Shaw, Felipe Carrero