Searching for Our Cosmic Origins

The early universe may have gone through “inflation”, i.e., rapid exponential expansion. This can lead to ripples in space-time that leave a distinct pattern in how the CMB light is polarized.  The Simons Observatory may detect this smoking gun signature if the energy scale of inflation is large enough.  SO will also test other signatures of inflation, such as departures from Gaussianity in the distribution of density fluctuations.

Not all fundamental particles may be detectable in laboratories and accelerators. Very weakly interacting light particles would affect the expansion of the early universe, leading to detectable changes to the distribution of CMB fluctuations.  SO will place tight constraints on such new particles by carefully measuring the number of light particles in the universe (expected to comprise only the three neutrino species in the standard model of the universe).

SO will explore the Dark Universe through multiple methods.  Using gravitational lensing of the CMB, the otherwise invisible “dark matter” distribution can be mapped to high fidelity. This can allow cosmologists to infer the particle nature of dark matter and measure the unknown mass of neutrinos, shedding light on the properties of these poorly-understood particles.  Cross-correlations with optical and infrared surveys will also allow reconstruction of the evolution of dark matter over cosmic time, allowing cosmologists to test theories of dark energy and cosmic acceleration. Counting the number of galaxy clusters as a function of mass and time gives another complementary probe of neutrinos and dark energy.

SO will map the distribution of hot ionized gas, infer the statistical properties of the intergalactic medium, and detect galaxy clusters across its surveyed area. This will allow astrophysicists to understand how galaxies form and evolve over cosmic time. In particular, SO will dramatically improve the precision at which we understand the “feedback” imprinted by active galactic nuclei (i.e., supermassive black holes) on cosmic structure formation.

SO will produce high-sensitivity, arcminute-resolution maps of the Milky Way at a wide range of frequencies, including in polarization. This will allow us to learn about the properties of interstellar dust in our galaxy, the structure of magnetic fields permeating it, and turbulence in the interstellar medium due to high-energy stellar processes. SO will also potentially detect the statistical signature of Oort clouds and debris disks around other star systems.

SO will map half the sky repeatedly every 1-2 days, opening a new microwave-frequency window into the transient and time-evolving universe. It will track over time the energy output of supermassive black holes at the centers of hundreds or thousands of galaxies. It will perform searches for a wide variety of transient signals, including stellar flares, gamma ray bursts, and tidal disruption events. It will set constraints on the existence of a possible ninth Solar System planet and allow new insights into the composition of asteroids.