Simons Observatory

Currently under construction in Chile’s Atacama Desert, the Simons Observatory (SO) is a next-generation observatory that will look for signs of cosmic inflation and answer fundamental questions about the origin of the Universe. Scientific topics SO will help address include:

Primordial Universe

Affected by gravity and amplified by inflation, primordial fluctuations in the density of matter and energy have led to the growth of the large-scale structures we see in the Universe today. SO will measure the cosmic microwave background (CMB) fluctuations with unprecedented precision so that we will be able to distinguish between many different models of inflation, test the standard model of cosmology, and possibly discover new, exotic particles.

Neutrino Physics

Neutrinos are among the most elusive particles: We do not know how massive they are, and the current model of particle physics cannot explain how their mass is created. SO will provide a robust measurement of neutrino masses through gravitational lensing, the counting of galaxy clusters, and the energy change in CMB photons as they pass through galaxy clusters.

Dark Energy and the Cosmological Constant

Dark energy, which is responsible for the observed accelerated expansion of the Universe, makes up about 70% of the Universe. The simplest way to describe dark energy is the cosmological constant. SO will provide very precise measurements of the current expansion rate, called the Hubble constant (H0), that will help confirm or resolve the discrepancies in H0 measured by different probes. If the discrepancy in H0 is confirmed, we will need to revise the our standard model of cosmology.

Reionization and Galaxy Evolution

"Cosmic reionization” refers to the time when energetic photons emitted by the first stars and galaxies ionized the ordinary matter (mostly hydrogen) in the Universe. By studying patterns imprinted on the CMB signal by free (ionized) elections, SO will deepen our understanding of reionization, putting constraints on the onset and duration of this physical process. Additionally, SO will provide key insights into galaxy formation by accurately measuring the energy gain of CMB photons as they pass through through giant clusters of galaxies filled with hot gas of electrons.

Galactic Science

In addition to observing distant galaxies and the CMB, SO will measure emission from the interstellar medium of our own Galaxy. This provides us with a unique opportunity to obtain more information on the dust, gas, and magnetic fields in the Milky Way. SO will be able to map magnetic fields in various interstellar environments, shedding light on the physical mechanisms behind Galactic emission, such as the role magnetic fields play in driving star formation from cold, dense clouds, the composition of interstellar dust, and the population of energetic cosmic-ray electrons.

Once the construction is completed, SO will consist of the following telescopes:

• A large-aperture telescope (LAT) that has a 6-meter diameter aperture to explore the CMB at small angular scales
• Three small-aperture telescopes (SATs), each with seven 6” detector wafers, to study the CMB at large angular scales

SO is a collaboration between the Simons Foundation, the founding universities and laboratories (University of Pennsylvania, Princeton University, UC San Diego, UC Berkeley, and the Lawrence Berkeley National Laboratory) and collaborating institutions across the globe. KIPAC researchers will be actively using the SO data to explore frontier questions about the early Universe through the studies of CMB, galaxy clusters, and dark matter. For more information on SO, please visit the Simons Observatory website.