Thursday 30 July 2015

The Cosmic Microwave Background (CMB)

What is the CMB?

The radiation left from the early stages of the universe is called cosmic microwave background radiation. When the universe was at this early stage, it was soo hot that all atoms in the universe were ions. An ion is an atom that has positive and negative electrical charges. At this point in time the conditions of the universe may have been similar to that of a star; hot, dense and opaque allowing different atoms to pass through it.

Over time as the universe expanded, this gas cooled down. This ofcourse took several hundred thousand years. Radiation that was left behind from the big bang has been able to travel throughout the universe. As this early universe expanded, the radiation red-shifted to longer wavelengths and was therefore in a form to represent different temperatures. The spectrum of the CMB maintains the shape of a Blackbody spectrum. According to writer of 

"Blackbody radiation refers to an object or system which absorbs all radiation incident upon it and re-radiates energy which is characteristic of this radiating system only, not dependent upon the type of radiation which is incident upon it. The radiated energy can be considered to be produced by standing wave or resonant modes of the cavity which is radiating."

The presence of CMB radiation with a Blackbody is a strong indication of the Big Bang theory. 

This above picture is a view of the sky after the foreground glow of the solar system dust has been extracted. This image is dominated by emission from interstellar dust in the Milky Way Galaxy. The two bright objects in the center of the lower right quadrant are nearby galaxies, the Large and Small Magellanic Clouds.


The COBE satellite 
The Cosmic Microwave Background Explorer was launched in 1989. Developed by NASA's Goddard Space Flight Center, its mission was to measure the infrared and microwave radiation from the early universe. COBE made some very precise measurements at different wavelengths. These measurements were from a few micrometer to 1 centimeter. 

The data on the graph above shows small dots, these small dots are the COBE measurement of the CMB at different frequencies. The X-Axis of the graph represents the frequency cycle per centimeter and Y-Axis represents the brightness of the frequency component. The uncertainty in each measurement is less than size of each dot. The left hand side of the curve that just begins to rise represents data points of a blackbody spectrum.  The above observation matches theoretical predictions of the Big Bang almost with perfection. So much so that there can be little doubt that one is seeing the radiation left behind from a hot, dense beginning from an earlier universe. Researches John Mather and George Smoot were awarded Nobel Prize for this work in 2006.

The above mapping shows the Northern and Southern galactic hemispheres,

Images of different regions of the hemispheres, the second image is of our galaxy. The galactic center is the middle bulged.

This graph displays the different magnitudes of the wavelengths from radio waves to X-rays and Gamma rays.

Image of CMB as produced by data collected byt he WMAP.

In 2001 the Wilkinson Microwave Anisotropy Probe (WMAP) made more accurate measurements of the CMB variations.  The above is much more detailed map of the structure of the universe.
In 2013, the European Space Agency (ESA) launched the Planck mission, which went one step further and obtained images in a much higher detail.

The image shows observations of the Cosmic microwave background (CMB) as observed by Planck. The image shows tiny temperature fluctuations that correspond to regions of slightly different densities, representing the seeds of all future structure: the stars, galaxies and nebula's that we have today.

Spiral Galaxy NGC 6503
"Most galaxies are usually in a group close by. A neighboring is never too far away. But this galaxy, known as NGC 6503, has found itself in a very lonely position, at the edge of a strange empty patch of space called the Local Void.
The Local Void is a huge stretch of space that is at least 150 million light-years across. It seems completely empty of stars or galaxies"


Light Echo From Star V838 Monocerotis - April 30, 2002

Star V838 Monocerotis

Hubble Probes Interior of Tarantula Nebula
30 Doradus Nebula, is a giant star-forming region


Early scientists predicted that, the early universe must have begun as a singularity and then expanded as radiation and elementary particles. However what do we mean when we say singularity?

According to the FreeDictionary a singularity is "a hypothetical point in space-time at which matter is infinitely compressed to infinitesimal volume"
This means matter which infinitely falls toward a negative value making it smaller than any real value.

The Big Bang theory is fundamental to our understanding of the universe. So far it has resisted any efforts made by researchers to prove it false, as the CMB provides evidence of the scenario of our early universe.

Nucleus of Galaxy Centaurus A
The above image shows the Nucleus of Galaxy Centaurus A.
Some of the crucial discoveries made by the COBE were:
  • COBE revolutionized our understanding of the early cosmological structure.
  • It measured and mapped the oldest light in the universe -- the cosmic microwave background. This was similar to seeing a baby picture of the universe.
  • The cmb spectrum was measured with a precision of 0.005%.
  • The results confirmed the Big Bang theory of the origin of the universe.
  • The very precise measurements helped eliminate a great many theories about the Big Bang.
  • The mission urged scientists into a new age of precision measurements, providing ground for new research into microwave background by NASA's WMAP mission and ESA's Planck mission, that latter provided much more detailed measurements.

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Goodbye for now and see you next time.

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