Tag Archives: Atacama Cosmology Telescope

Atacama Cosmology Telescope (ACT) data provides an updated view of the cosmic microwave background (CMB)

All Posts, Astronomy, ,

Peter Lobner, 19 March 2025

The Atacama Cosmology Telescope (ACT), is a microwave wavelength telescope located in the Atacama Desert in Chile, at an altitude of 5,190 meters (17,030 ft), making it one of the highest ground-based telescopes in the world. ACT took its final data in 2022 and has since been decommissioned. 

Atacama Cosmology Telescope. 
Sources: (top) NDRIO White Paper, A. Hicks, 2020, (middle) Wikipedia, (bottom) flickr

The Atacama Cosmology Telescope (ACT) Collaboration posted new maps of the cosmic microwave background (CMB) radiation based on the final data collected with the Advanced ACT camera over the period 2017–2022. The CMB is the light released from the primordial universe as atoms first started forming and space became transparent, approximately 380,000 years after the Big Bang. The new maps cover 19,000 square degrees, almost one-half of the total area of the celestial sphere, which measures about 41,253 square degrees.

The above detail from the new ACT map of the CMB radiation shows 
how polarization reveals the movement of primordial gases. 
Source: ACT Collaboration

For more information on the new ACT maps, see the following article in Science:

The complete ACT data release papers are listed here: https://act.princeton.edu

The new CMB map shown above is described in detail here:

The Cosmic Microwave Background Provides a Refined View of Our Universe

All Posts, Astronomy, Astrophysics, Cosmology, , , ,

Peter Lobner, 12 January 2021

The Atacama Cosmology Telescope (ACT) is a six-meter (19.7 foot) radio telescope designed to make high-resolution, microwave-wavelength surveys of the cosmic microwave background (CMB).  It is located at a remote site in the Atacama Desert at an elevation of 5,190 meters (17,030 feet) in northern Chile. 

The ACT site.  Source: ACT Collaboration

ACT observes in three frequency bands (148, 218 and 277 GHz) and has a resolution of 1.3 arc minutes at 148 GHz, near the peak of the CMB spectrum.  This is significantly higher than the 5-10 arc minute resolution of the Planck spacecraft, which observed the CMB from 2009 to 2013 in the frequency range from 30 to 857 GHz. You’ll find a detailed description of the Atacama Cosmology Telescope (ACT) at the following link: https://www.cosmos.esa.int/documents/387566/387653/Ferrara_Dec3_09h20_Devlin_ACT.pdf

I reported on key results of the Planck CMB survey results in my post at the following link: https://lynceans.org/all-posts/the-universe-is-isotropic/

New results from the ACT survey, reported in December 2020, affirm the Planck CMB survey results.  

  • The universe is isotropic
  • The estimate of the age of the universe was refined to 13.77 billion years old ± 0.04 billion years, overlapping uncertainty bands with the 2015 Planck estimate of 13.813 ± 0.038 billion years
  • The value of the Hubble constant was refined to 67.6 kilometers / second / megaparsec, up slightly from the 2018 Planck estimate of 67.4 kilometers / second / megaparsec.  The significant difference from the value derived from astrophysical measurements, 73.5 km / second / megaparsec, remains unexplained.
ACT high resolution image of the isotropic cosmic background radiation covering a section of the sky 50 times the width of a full moon. This image represents a region of space 20 billion light-years across. Source: ACT Collaboration via EarthSky

For more information: