Guide to the Cosmos
Making the Wonders of our Universe Accessible to Everyone.

Planck Satellite Refines Cosmic Measurements

Initial results from the Planck satellite provide superb measurements of the CMB and refined values of the age and composition of the universe.
The Planck satellite, launched in 2009 by the European Space Agency (ESA), is the latest effort to understand the beginning of our universe by studying the Cosmic Microwave Background (CMB).
The CMB is our universe’s “first light” — the first radiation to escape from the primordial fireball that emerged from the Big Bang. The CMB that we observe today has been flying through space at the speed of light for nearly 14 billion years, carrying with it the image of the most remote reaches of our universe. It shows us what the universe looked like when it was only 380,000 years old, 36,000 times younger than it is today.
Back then the universe was a uniform soup of hot hydrogen and helium gas, without stars, galaxies, or planets. Temperatures and densities were extremely homogeneous, varying by only 1 part in 100,000. Yet those minute variations were critical to our future — over the eons, the slightly denser regions developed into the rich life-enabling structures we see today.
The following images reveal the advance of science in the last three generations of CMB satellite missions.


CMB image from NASA’s COBE satellite, launched in 1989.



CMB image from NASA’s WMAP satellite, launched in 2001.


CMB image from ESA’s Planck satellite, launched in 2009.


The fine details of the CMB are a rich source of cosmic information that scientists extract using power spectrum analysis. The power spectrum basically measures “clumpiness” — the power spectrum of an oil painting reveals what brush sizes the artist used and how often each size was used. In the Planck power spectrum shown below, each measurement is represented by a red dot with a vertical line indicating its uncertainty (the longer the line, the more uncertainty), and the green band represents the fitted prediction of the Inflationary Big Bang theory. The match is spectacular.




Combining Planck data with prior measurements, our current best estimates are:

Age of our Universe

13.819±0.058 billion yrs

Current Expansion Rate 

46,500±1000 mph per million light-yrs

Percentage of Normal Matter


Percentage of Dark Matter


Percentage of Dark Energy


Amazingly, we now know the age of the universe to better than ½% precision.
The Planck satellite was named in honor of the Nobel Prize winning German physicist, Max Planck (1858-1947), who originated quantum mechanics, developed the theory of black body radiation, and was Einstein’s greatest supporter. The CMB is the most pristine example of black body radiation ever discovered.
The Planck satellite sampled 9 frequency bands using 22 radio wave detectors and 52 advanced bolometers produced by NASA-JPL/Caltech, which ran at just 0.1 degrees above absolute zero temperature (–459.67ºF). This extended sampling facilitated discriminating point sources, such as galaxies, from the cosmic background radiation.
The orbits of the WMAP and Planck satellites were particularly interesting. Both were sent to the second Lagrange point (L2 shown below) of the Earth-Sun system. At each of five Lagrange points, Earth’s gravity and the Sun’s gravity combine to yield a quasi-stable orbit with a period of one Earth year. Satellites near L2 are far enough from Earth to minimize interference from terrestrial radiation, yet remain close enough to facilitate communication.
L2 is 1.5 million km (930,000 miles) from Earth in the direction opposite the Sun. Because orbits at L2 are only quasi-stable, Planck orbited L2 at an average distance of 400,000 km (250,000 miles).



Having completed its mission in August, the Planck satellite has been sent off into an Earth-avoiding orbit.
Analysis of Planck’s data is far from complete, so we expect further updates. Of special interest will be Planck’s measurements of the polarization of CMB light.
Best Regards,
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