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Phase: Past

Launch Date: May 14, 2009

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Program(s):Physics of the Cosmos

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The ESA-led Planck mission, formerly called COBRAS/SAMBA and renamed in honor of the German scientist Max Planck, allows astronomers to address some of the most fundamental questions in cosmology and astrophysics. These question include the geometry and contents of the universe, how the universe grew immediately after its birth, and how the stage was set for the universe to evolve into structures that we see today, such as galaxies.

Comparison of CMB results from COBE, WMAP and Planck
Comparison of CMB results from COBE, WMAP and Planck.
Image Credit: NASA/JPL-Caltech/ESA

Like its predecessor, NASA’s Wilkinson Microwave Anistropy Probe (WMAP), Planck was designed to achieve these goals by making a careful measurement of the Cosmic Microwave Background (CMB), the remnant background radiation left over from the Big Bang. The CMB is remarkably uniform over the entire sky, with an effective current temperature of 2.7 degrees kelvin. But the CMB is not completely smooth-- there exist fluctuations in temperature at the tiny level of one part per 100,000. Tiny as they are, it is from these very fluctuations that the current large-scale structures of the universe grew.

Planck imaged these tiny fluctuations in the CMB over the whole sky with unprecedented sensitivity and angular resolution. It resolved structures down to 5 arcminutes in angular size on the sky, and detected temperature variations at the microkelvin level. Planck also measured the polarization of the CMB radiation, which among other things tells us about the early history of star formation.

Dust Glow (upper left), Carbon Monoxide Gas (upper right), Careening Particle (lower left), Captured in Magnetic Fields (lower right)
New Dynamic Portrait of the Milky Way.
Components making up the main image include: Dust Glow (upper left), Carbon Monoxide Gas (upper right), Careening Particle (lower left), Captured in Magnetic Fields (lower right).
Image Credit: ESA/NASA/JPL-Caltech

The Planck mission collected and characterized radiation from the Cosmic Microwave Background (CMB) using sensitive microwave receivers operating at extremely low temperatures. The Planck spacecraft was 4.2 meters high and had a maximum diameter of 4.2 meters, with a launch mass of around 1.8 tons. The two scientific instruments in Planck were:

  • The LFI (Low Frequency Instrument), an array of coherent microwave receivers based high electron mobility transistor amplification.
  • The HFI (High Frequency Instrument), an array of microwave detectors using bolometers equipped with neutron transmutation doped germanium thermistors.

Planck was an ESA-led mission with substantial contributions from NASA. For reasons of cost effectiveness, ESA launched Planck together with Herschel, an infrared space telescope, on an Ariane-5 launch vehicle on May 14, 2009. The two spacecraft separated soon after launch and operated independently. In October 2013 the Planck was passivated and put into a heliocentric orbit to avoid any interference with future missions.


Milky Way's Magnetic Fingerprint
Milky Way's Magnetic Fingerprint
Darker regions correspond to stronger polarized emission, and the striations indicate the direction of the magnetic field projected on the plane of the sky.
Copyright: ESA and the Planck Collaboration

The Planck mission has enhanced our understanding of the universe.

  • The age of the universe is 13.8 billion years old.
  • The universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy.
  • The Hubble constant was measured to be 67.80 ±.77 (km/s)/Mpc.
  • The simplest model of inflation was validated, giving the Lambda-CDM model stronger support.
  • New maps from Planck uncover the 'polarized' light from the early universe across the entire sky, revealing that the first stars were formed much later than previously thought - the Dark Ages ended 550 million years after the Big Bang.
  • Planck made the most extensive catalog of the largest galaxy clusters.

Last Updated: April 17, 2015

Related Links
  • ESA Planck Website -
  • Science@ESA - Planck video -
  • Planck's View of the Universe video (ESA) -
  • Revealing CMB video (ESA) -