European Space Agency (ESA) Planck Satellite
Observing the Cosmic Microwave Background Relic of the Big Bang
Oct 1, 2009
On 14th May 2009 the Planck observatory, built by the European Space Agency (ESA), was launched into space. Now it is in orbit around the Sun, at a distance from the Earth of about 1.5 million kilometres in a special region known as the second Lagrange point. After extensive testing the observatory has begun (September 2009) to gather experimental data. It is intended that it will scan the whole sky, at least twice, during its 15-month mission, and measure the temperature of what is known as the cosmic microwave background (CMB) radiation, which pervades the whole Universe, in all directions.
According to most astronomers, the Universe was formed about 13.7 billion years ago, in an explosion of matter and energy, termed the Big Bang. About 380,000 years after the Big Bang the temperature of the electromagnetic radiation filling the Universe was about 3,000 degrees C. Since that time it has cooled and now has a temperature of about -270 degrees C. However, this temperature is not completely uniform: it has very tiny variations, which Planck will measure, to high precision. It has been designed to measure the temperature to an accuracy of one-millionth of a degree Celsius. These fluctuations in the first stages of the Universe were the starting point for the large-scale structures such as galaxies and galactic clusters that can be seen in the Universe of today.
HFI and LFI Measuring Instruments
In order to capture and analyse this microwave radiation, Planck has been fitted with two instruments – the Low Frequency Instrument (LFI) and the High Frequency Instrument (HFI). Each of these will measure the radiation at a different wavelength. In order to make extremely accurate measurements of the CMB, these instruments have to be cooled to within a fraction of a degree above absolute zero, making the Planck observatory one of the coldest objects in the whole Solar system. This cooling is achieved using liquid helium. Over the time-span of the mission, the helium will gradually escape from the spacecraft, and when it has all gone Planck will warm up and no more measurements can be made.
Main Objectives of Planck Mission
The Planck mission has several main objectives:
- To measure the amount of normal matter. The matter that we see in the Universe, that makes up stars and clouds of dust and gas (nebulae) makes up only a small part (about 5%) of the matter in the Universe. With the observations from Planck, scientists will be able to calculate the total number of atoms of normal matter.
- About 90% of the matter is in a strange form that is not visible – hence it is known as dark matter. Its presence can be detected by its gravitational effect on normal matter. Planck will be used to determine the total amount of dark matter.
- The universe is not only expanding but its rate of expansion is accelerating. Dark energy is believed to account for this acceleration, and Planck will be used to investigate the nature of dark energy, which currently is not well understood.
- The Milky Way galaxy is permeated with a magnetic field. Planck will map this field in detail, and also produce a map of the distribution of clouds of cold dust in the spiral arms.
- Observations of distant galaxies will help to provide an insight into how stars are formed. Clusters of galaxies will be studied to provide clues on how these clusters evolved.
- Currently, there are numerous theories of how the large structures of the Universe e.g. galaxies and clusters of galaxies formed and grew. Studying the detailed measurements of the variations in the CMB, and thus comparing the Universe of how it was billions of years ago with how it is today will allow these theories to be tested.
Results From Planck
Preliminary results indicate that Planck is gathering high-quality data. Eventually there will be sufficient to keep scientists busy with analysis for decades. This will undoubtedly result in answering some of the intriguing questions about the fundamental nature of our Universe.
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