The Source of Cosmic Microwave Background

Researchers at Max Planck Institute for Extraterrestrial Physics and other institutions have used data from the Herschel Space Telescope to resolve a portion of the Cosmic Microwave Background (CMB) into its constituent sources. Using images in the far infrared range taken by the Photodetector Array Camera and Spectrometer (PACS) instrument aboard Herschel, these scientists have pinpointed approximately 60% of the galaxies forming the CMB in a section of the sky within the constellation Ursa Major.
A far infrared picture of a portion of the constellation Ursa Major (Source: Max Planck Institute for Extraterrestrial Physics)
A far infrared picture of a portion
of the constellation Ursa Major
(Source: Max Planck Institute for
Extraterrestrial Physics)

Scientists first explored the CMB in the early 1990s using NASA’s COBE explorer designed specifically to explore the background radiation of the universe. COBE experimentally measured far infrared radiation originating from all directions with equal intensity. Scientists believed this radiation was generated by galaxies forming in the early universe and attempted to isolate individual sources using infrared space telescopes but their resolution was not sufficient for the task until the PACS instrument was launched on Herschel in May 2009.

Managed by the European Space Agency, Herschel is the largest space telescope ever built with a primary mirror measuring 3.5 meters in diameter. PACS was designed to observe radiation with wavelengths ranging from 70 to 160 micrometers, the portion of the infrared spectrum where most of the CMB radiation falls.

PACS was focused on a portion of the sky within the constellation Ursa Major for 30 hours in October, resulting in the first infrared image that clearly shows a large number of individual sources of radiation instead of an aggregate radiation signature combining most of these signals. The PACS image of this region shows not only point sources, but an indication of relative distance thanks to redshift effects in the image. Scientists estimate that nearly 60% of the point sources are resolved in this image and hope to improve that percentage in subsequent observations.

TFOT has previously reported on the Herschel Space Telescope including an overview of the telescope as a whole and descriptions of each of its three major scientific instruments and a report on the first images returned from the observatory after its launch. TFOT has also reported on other experiments and instruments designed to observe the Cosmic Microwave Background including an experiment designed by NIST and several research universities to test the polarization of the CMB radiation in hopes of proving that cosmic inflation occurred immediately following the Big Bang, computer simulations designed to study the large scale structure of the universe (including the CMB) near the Milky Way galaxy, and a report on the 2006 Nobel Prize in Physics awarded to George Smoot and John Mather for their work with COBE.

Read more about the PACS image and the Cosmic Microwave Background in this Max Planck Institute for Extraterrestrial Physics press release.

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