Planck satellite on a mission to the beginning of the Universe – Niels Bohr Institute - University of Copenhagen

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18 May 2010

Planck satellite on a mission to the beginning of the Universe

”The mission is going perfectly and we are getting very good data which might explain what happened during the creation of the Universe and how and why the world looks as it does”, explains a happy but enigmatic researcher with the Discovery Center at the Niels Bohr Institute, Pavel Naselsky, for there are great things in store, but the final results must wait a little longer yet.

The Planck satellite's mission is to observe all
the way back to childhood of the Universe and
measure the cosmic microwave radiation, which
can unravel completely new details about the early
Universe 300.000 years after Big Bang.

The ESA satellite Planck was launched on the 14th of May 2009. Its mission is to observe back to childhood of the Universe and measure the cosmic microwave radiation with unprecedented accuracy. Microwave radiation came into existence at the birth of the Universe (Big Bang) and its very early development and contains a wealth of information about the fundamental physical processes that guided the evolution of the very early Universe.

It took 50 days for the satellite to reach its position in space (the so-called Lagrange-point L2), 1.5 million kilometres from the Earth, and then approximately half a year was needed to adjust it as it is its extreme accuracy in measurement with a precision of 0.00001 degrees C, which will revolutionise cosmology. The plan was that the satellite would remain in its position and observe for a year and then the mission would end. 

”But by a stroke of pure luck the satellite came out of Earth’s orbit quickly and this saved so much fuel that the mission can continue for an additional year, so it will give us twice as much data”, explains,” Pavel Naselsky, associate professor with the Discovery Center at the Niels Bohr Institute at the University of Copenhagen.

Sophisticated experiment

The reason why the satellite uses fuel in space – unlike other satellites, is because it not just remains still in space, but needs to change direction every hour as well as rotate once a minute on its own axis. These movements mean that it scans the entire surrounding Universe in the course of six months. This means that instead of getting a limited telescopic view out in one direction, you now get a complete and very detailed map of the Universe in all directions. Planck has a very sophisticated detector system that measures the cosmic microwave radiation at nine different frequencies in intervals from 23 Ghz to 857 Ghz.

New images of the Orion cloud using the Planck
satellite’s microwave observations reveal the
complex physical forces in the formation of new
stars. The images show the separate physical
processes, where the emission of electrons from
gas is affected by the galaxy’s magnetic field and
reacts with spinning dust particles. As a result of
gravity the gas and dust cloud contracts and finally
collapses and becomes a star, which is a big ball of
glowing gas. Planck can measure the very small
amounts of heat which the icy dust particles emit in
the earliest stages of a star being born. 

The Universe’s primordial soup

Just after the Big Bang, so long before the Earth, Sun, stars and galaxies, the Universe was a primordial soup – a dense cloud of hot plasma and tremendous energy. There were no atoms, only free protons and electrons. Everything was completely dark.

But the primordial Universe expands, the dense mass spreads and cools. After approximately 300,000 years the universe has cooled down to approximately 3000 degrees C and now the electrons can begin to bond with the protons to form the first atoms, hydrogen. The light can begin to escape as heat radiation and this is what we see now as cosmic radiation, which now - 13 billion years later, has a temperature of 2.7 degrees Kelvin (approximately minus 270 degrees C).

But the microwave radiation is not evenly distributed, it ‘clumps’ slightly (approx. 1/100,000 difference in the temperature). These irregularities (or anisotropy as the physicists say) in the observed temperature across the sky is a measure for how the mass was distributed when the radiation was released. These small fluctuations in size and amplitudes at the last scattering surface tell us about the galaxies formation right from very distant past, when the Universe was about 300.000 years old.

Mysteries of the universe

By studying the irregularities in the temperature distribution
of the cosmic microwave radiation in the very early Universe,
researchers can clear up many of the great mysteries of the
Universe – such as, what caused the Big Bang to happen and
create the entire Universe?

By studying the irregularities in the temperature distribution of the cosmic microwave radiation in the very early Universe, researchers can clear up many of the great mysteries of the Universe – such as, what caused the Big Bang to happen and create the entire Universe? How and when did it happen?

And what makes up the Universe? – only approximately 4 percent of the Universe is made up of the visible celestial bodies like stars, planets and galaxies, the rest is unknown – like dark matter, which is invisible, but nevertheless, according to calculations, accounts for the vast majority of the Universe’s mass along with dark energy, which we also don’t know what it is. If you can explain that, you can determine whether the Universe will continue to expand for eternity or whether it will contract in a reverse process to the Big Bang, a phenomena which might be called the 'Big Crunch'.


Only approximately 4 percent of the Universe is
made up of the visible celestial bodies like stars,
planets and galaxies, the rest is unknown – like
dark matter, which is invisible, but nevertheless,
according to calculations, accounts for the vast
majority of the Universe’s mass along with dark
energy, which we also don’t know what it is.

From measurements using NASA’s Wilkinson Microwave Anisotropi Probe (WRAP) it is known that it is very improbable that the universe will contract again, but the future of the Universe is less predictable than one thought. This is due to the existence of the 'dark energy' which everything indicates there are large quantities of in our Universe and which like a kind of vacuum energy causes the expansion of the Universe to accelerate. 

Greatest Achievement
In addition to investigation of the dark matter and the dark energy phenomena the Planck Mission is also studying special cosmic gravitational waves, which radiate out from the early Universe.

Currently there is an American project LIGO that is searching for gravitational waves from the Earth’s 'environs', that is to say the centre of the Milky Way and from binary stars, i.e. two stars that spin faster and faster around each other. With the Planck satellite the cosmic gravitational waves can be studied all the way back to their origins – the Big Bang, through their imprint on the polarisation of the cosmic microwave radiation.

"It would perhaps be the greatest achievement in the understanding of our Universe, that we at Planck would be able to measure the gravitational waves of the Universe, which are directly linked to the Big Bang and cosmic inflation (the extremely rapid expansion of the Universe in the very first moments)", explains Pavel Naselsky, and he expects in the future we will have an entirely new understanding of the origin of the Universe in the coming years.