Cosmic Background Explorer (COBE)

Cosmic Background Explorer (COBE)

Published: November 7, 2007, 12:00 am
Updated: March 24, 2009, 12:39 pm
Lead Author: Citizendium
Topics: Space Missions Observatories & Telescopes
Content Source: Citizendium

Introduction

COBE or Cosmic Background Explorer satellite, was launched on November 18, 1989. COBE was designed and developed to investigate the origins of the universe and succeeded in producing images of the universe as it would have been in its infancy some 13.7 billion years ago. [1]

Accomplishments

On May 1, 1992 at a meeting of the American Physical Society, one of COBE’s research leaders, George Smoot[2], announced that the precise measurements taken with the COBE showed hot and cold regions throughout the universe with temperature differences of a hundred-thousandth of a degree. “At the time captured in our images, the currently observable universe was smaller than the smallest dot on your TV screen and less time had passed than it takes for light to cross that dot.”

The accomplishments of the COBE were so significant that COBE’s originators, John C. Mather (NASA Goddard Space Flight Center) and George F. Smoot (Lawrence Berkeley National Laboratory and the University of California at Berkeley) were awarded the 2006 Nobel Prize for physics.

Instrumentation

COBE COBE

Figure 1. Artist rendering of the COsmic Background Explorer (COBE). (Source: NASA.)

COBE was developed by NASA's Goddard Space Flight Center to measure the diffuse infrared and microwave radiation from the early universe. To accomplish this, COBE carried three instruments:

  • Diffuse Infrared Background Experiment (DIRBE) to search for the cosmic infrared background radiation;[4][5][6]
  • Differential Microwave Radiometer (DMR) to map the cosmic radiation and variations in the radiation;[7][8]
  • Far Infrared Absolute Spectrophotometer (FIRAS) to compare the spectrum of the cosmic microwave background radiation with blackbody radiation.[9][10]

The extent and precision of the data gathered has shifted the entire field of cosmology. So much so, that the Nobel Foundation of the Royal Swedish Academy of Sciences, went so far as to say, "the COBE-project can also be regarded as the starting point for cosmology as a precision science: For the first time cosmological calculations (like those concerning the relationship between dark matter and ordinary, visible matter) could be compared with data from real measurements. This makes modern cosmology a true science (rather than a kind of philosophical speculation, like earlier cosmology)."[11]

Theoretical Rationale for COBE

Fig. 2. The Cosmic Background Explorer (COBE) spacecraft is the predecessor to the WMAP Project. COBE was assembled in clean rooms at Goddard Space Flight Center in Greenbelt, Maryland. It was launched in 1989 by NASA into an Earth orbit to make a full sky map of the Cosmic Microwave Background (CMB) radiation, leftover from the Big Bang. The cone shield protects the instruments from microwave signal interference from the Earth, Sun and Moon. Fig. 2. The Cosmic Background Explorer (COBE) spacecraft is the predecessor to the WMAP Project. COBE was assembled in clean rooms at Goddard Space Flight Center in Greenbelt, Maryland. It was launched in 1989 by NASA into an Earth orbit to make a full sky map of the Cosmic Microwave Background (CMB) radiation, leftover from the Big Bang. The cone shield protects the instruments from microwave signal interference from the Earth, Sun and Moon.

Fig. 2. The Cosmic Background Explorer (COBE) spacecraft is the predecessor to the WMAP Project. COBE was assembled in clean rooms at Goddard Space Flight Center in Greenbelt, Maryland. It was launched in 1989 by NASA into an Earth orbit to make a full sky map of the Cosmic Microwave Background (CMB) radiation, leftover from the Big Bang. The cone shield protects the instruments from microwave signal interference from the Earth, Sun and Moon. (Source: NASA.)

The initial premise of the COBE research was that the universe had originated in a sudden expansion from a submicroscopically small point, the Big Bang Theory. The competing theory, called the Steady State Theory, maintained that ours was a consistent and unchanging universe which neither grew smaller or bigger and had never come into being—it was timeless with neither end or beginning. The Big Bang theorist maintained that the universe was expanding, it had begun from something else and could conceivably come to an end.

The Big Bang Theory could be supported if there was evidence of background radiation (referred to as cosmic microwave background radiation, CMB radiation) permeating the entire universe—leftover radiation. The leftover radiation would be evidence that the universe had a beginning at which time it had been filled with intense radiation. This state would have been long before the appearance of matter—elements, gases, stars and galaxies. Although CMB radiation was originally predicted in 1948 by Georgiy “George” Antonovich Gamow,[12] it was not until 1964 that Arno A. Penzias and Robert W.Wilson, researchers at AT&T's Bell Laboratory (Holmdel, N. J. USA), discovered that there is CMB radiation evident in all directions from Earth. A clear example is the radiation evident on a TV screen. Much of the black and white static is in fact CMB, photons of energy still cooling after the Big Bang.[13]

Ripples in the space-time fabric

One of the most significant aspects of the COBE data was gathered from the DMR (Differential Microwave Radiomters) which measured difference in radiation. This variation, or anisotropy, in the backgound radiation consists of small temperature fluctuations in the blackbody radiation left over from the Big Bang. The average temperature of CMB radiation radiation is 2.725 degrees Kelvin.[14] The variations in the temperature are very small, thousandths of degrees.

As Smoot has explained, “The tiny temperature variations we discovered are the imprints of tiny ripples in the fabric of space-time put there by the primeval explosion process. Over billions of years, the smaller of these ripples have grown into galaxies, clusters of galaxies, and the great voids in space."

References

  1. Universe Evolution Image from Smoot Group representing the range of time for the COBE background radiation map
  2. Standard Cosmology Gary Scott Watson, Dept. of Physics, Brown University
  3. COBE Science Working Group National Aeronautics and Space Administration
  4. George Smoot Wins Nobel Prize in Physics
  5. DIRBE
  6. DIRBE Galactic plane maps shows various exposures depicting the plane of the galaxy in wavelengths from 1.25 to 12 microns
  7. DIRBE Galactic plane maps shows various exposures depicting the plane of the galaxy in wavelengths from 25 to 240 microns
  8. DMR
  9. DMR images National Aeronautics and Space Administration
  10. FIRAS
  11. FIRAS scientific results National Aeronautics and Space Administration
  12. The Nobel Prize in Physics 2006 (PDF) Information for the public. p. 5. Royal Swedish Academy of Sciences Accessed 30.07.07
  13. Alpher, R. A.; Bethe, H.; Gamow, G. (1948). The Origin of Chemical Elements, Physical Review, vol. 73, Issue 7, pp. 803-804
  14. Traversing the Universe Castelvecchi, D. (2005) “Let it Rain” Symmetry. Vol 2:1, Feb. A Fermilab SLAC publication.
  15. Cosmic Microwave Background Anisotropy Professor Edward L. Wright, UCLA Astronomy faculty.

External Links

Preview Image

 Cosmic Backround Explorer

 

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Citizendium project. Topic editors and authors for the Encyclopedia of the Cosmos may have edited its content or added new information. The use of information from the Citizendium project should not be construed as support for, or endorsement by, that organization for any new information added by EoC personnel, or for any editing of the original content.
Original content retrieved from "http://en.citizendium.org/wiki/COBE_%28astronomy%29"

Citation

Citizendium Project (Contributing Author); Bernard Haisch (Topic Editor). 2008. "Cosmic Background Explorer." In: Encyclopedia of the Cosmos. Eds. Bernard Haisch and Joakim F. Lindblom (Redwood City, CA: Digital Universe Foundation). [First published November 7, 2007].
<http://www.cosmosportal.org/articles/view/135501/>

 

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