In most of our articles, we have looked at the worlds in our own solar system, or orbiting relatively nearby stars. There’s so much going on in our neighborhood, it’s easy to get nearsighted and forget that astronomy reaches much further now. This time, we’re going to take a longer journey, not only through space, but through time as well. We’re going to hop in our time machine and go back to the very dawn of the universe, when it was only a small fraction of its present age. Our time machine is called the Planck observatory, and it’s a space telescope launched by the European Space Agency last year. By observing the Cosmic Microwave Background, it sees the universe as it was at the tender age of only 380,000 years- and in doing that, it may allow us to understand how everything that we see around us today came into being. The Planck mission has the ambitious goal of compiling two separate sky maps of the Cosmic Microwave Background (CMB), the “bang!” of the Big Bang, which is still resounding through the universe.
In addition to this, Planck is also undertaking a few other observations of nearer things, such as parts of our own Milky Way galaxy. As the most sensitive instrument of its kind, it can see things with a greater clarity, resolution and range of wavelengths than ever before, and scientists have several targets selected for it.
The rocket that took Planck into space was an Ariane 5, the ESA’s standard launch vehicle. The launch took place on May 14, 2009, from the ESA spaceport in Kourou, French Guiana. As a cost-saving measure, Planck was launched along with another probe, the Herschel infrared observatory. These two probes separated from their launcher soon after reaching space. Both of them were sent on a course that would eventually lead them to the second Lagrangian point (L2), situated about 1.5 million km. from Earth in the opposite direction from the sun.
These two probes will operate independently of each other, but the science they do will be complementary. The Herschel infrared observatory is also an interesting subject, and will be examined further in a future article at this site. For now, we will concentrate on Planck.
The Planck satellite weighed about 1900 kg. at launch, and has a boxy shape about 4.2 meters on a side. It is equipped with a 1.5-meter-wide mirror which focuses radiation from the sky and sends it to two detectors known as the Low Frequency Instrument and the High Frequency Instrument.
The Low Frequency Instrument (LFI) performs observations of the microwave sky in the range of frequencies from 27 to 77 GHz. It is composed of 22 tuned radio receivers which work like the transistors in a radio, amplifying the signal and converting it into a voltage. The High Frequency Instrument (HFI) performs observations in the range from 84 GHz to 1 THz. It has 52 bolometric detectors , devices capable of measuring very small amounts of heat energy. The results from these two instruments are complementary, and go together to form the total mission results.
The instruments are very sensitive to heat, and the probe’s designers had to include a cooling system and various other measures to ensure a stable, low temperature. In fact, the reason why Planck orbits the sun at the L2 point, rather than orbiting Earth, is that both Earth and the moon give off too much heat. Planck had to get some distance away from them, or their heat would have spoiled the observations.
Planck is equipped with its own thrusters, and these were used for three course correction maneuvers. The third of these maneuvers took place on July 2, and injected the probe into its orbit around the L2 point.
Because of the temperature constraint, it was necessary to put the probe through a cooling process before it could go into operation. The instruments hit their lowest temperature, 0.1K above absolute zero, in the first week of July. During the cooling period, all of the satellite’s subsystems were also turned on and tested.
Planck was designed to give answers to some of the most fundamental questions in cosmology: how did the universe begin, how did it evolve to the state that it is in today, and how will it evolve in the future? The Cosmic Microwave Background carries information about the processes that took place in those early moments of existence, and by analyzing it, scientists can look through a window in time, to the moment right after creation.
This information takes the form of tiny temperature fluctuations in the CMB, about a millionth of one degree. This is the equivalent of detecting the body heat of a rabbit sitting on the moon from Earth.
Planck’s first task was the First Light Survey, which was really just a chance to check the sensitivity of the instruments and make sure they could perform as expected. The scientists were delighted to find that the quality of the data was excellent.
Since then, Planck has been working on its first All-Sky Survey. This began in mid-August 2009, and is being completed now. As of mid-March 2010, 98% of the sky had been observed by Planck, and 100% sky coverage is expected by late May 2010.
However, before the raw data can be turned into sky maps of the CMB, it will require a lot of delicate adjustments and careful analysis. About two years will be need to refine the information and obtain the scientific results. Even then, the resulting maps will provide decades of work for cosmologists and astrophysicists as they continue to study and analyze them.
One of the things they’ll be looking for will be confirmation of the current theory of how the universe formed. This is one of those sticky moments in science when the scientific authorities have a theory that explains everything beautifully, but they don’t have a shred of evidence to support it- or to disprove it, for that matter. The theory is called the inflation model, and the condensed version runs something like this:
(What came before the Big Bang, we have no idea. All of our theories of the evolution of the universe deal with what happened after that event, and if anything came earlier, we probably will never know about it.)
The universe begins as an extremely small point. During the first millionth of a second of its existence, it rapidly expands, or “inflates.” After this initial burst of expansion, it continues to grow at a slower rate, and as it grows, the thermal energy which it contains becomes spread out over a larger area. This means that the universe cools as it expands.
When the temperature of the universe drops to 1000 GeV (about 10 million million degrees) the natural forces appear: gravity, electromagnetism, and the strong and weak nuclear forces. Quarks, the things that will form matter, appear and wander freely through the universe. As the universe keeps cooling, these quarks will eventually combine to form protons and neutrons, but it will still be too hot for them to capture electrons and make real elements. Since electrons aren’t being captured to form atoms, they are free to interact with photons (light particles). Because of this, a photon can’t travel very far without encountering an electron, and light does not propagate freely. Because of this, the universe is dark. It is only after 300,000 years that the universe cools enough to allow protons to capture electrons and form hydrogen atoms, which finally allows light to propagate freely. Light comes to the universe, and that first burst of light is the Cosmic Microwave Background.
Matter begins to form clots due to gravity, and as these clots grow, the universe takes on a more familiar appearance. Stars form, and these form galaxies.
Fast-forward to today, and we see around us a universe filled with structures. Galaxies form clusters, clusters form sheets and streamers spanning vast distances. Where did all the structure come from? If the universe all expanded out of one tiny point, why isn’t it uniform? Why is matter gathered in some areas, while it seems to be more diffuse in other places?
The inflation theory explains the elaborate structures in the universe, which result from an uneven distribution of matter, by saying that they are the expansion of tiny variations in the original point from which it all expanded, and the expansion happened so suddenly that those variations were preserved, in vastly greater size, as the unevenness of matter in the universe today.
In other words, there has always been an unevenness in the distribution of matter and energy (as well as dark matter and dark energy). This goes all the way back to the first instant of expansion, and since the CMB comes from close to the first moment (300,000 years is not very long in universal terms) it should have this unevenness, too. It should also carry various other information from that early time, which Planck’s instruments can coax from it. As a snapshot of the universe at a young age, it should have things to tell us about how the universe started, and how it got like it is today.
These are the kind of cosmic questions that Planck was designed to address. Along the way, it will also do some viewing closer to home. In fact, just a few days ago, the ESA released spectacular pictures taken by Planck showing filaments of cold dust only a few hundred lightyears away. In addition to its work relating to the CMB, Planck will be doing studies of this nature, investigating structure and evolution on a galactic scale.
Planck is just getting started, and the clarity and resolution of the data so far promises great things for the future. The questions that it addresses are of the most fundamental nature: how did it all begin, and how did it get like it is now? You can’t get more cosmic than that.
As new data comes in from Planck, you can find it here.
Sources:
ESA Space Science: Planck Overview at website of European Space Agency: esa.int/esaSC/120398_index_0_m.html
ESA Planck homepage at website of European Space Agency: esa.int/SPECIALS/Planck/index.html
“Planck at a Glance: ESA’s Microwave Observatory” at website of European Space Agency: esa.int/SPECIALS/Planck/SEMWN20YUFF_0.html
ESA Planck: Science Objectives at website of European Space Agency: esa.int/SPECIALS/Planck/SEM0P20YUFF_0.html
ESA Planck: Planck Highlights at website of European Space Agency: esa.int/SPECIALS/Planck/SEMKO20YUFF_0.html
ESA Planck: Instruments at website of European Space Agecny: esa.int/SPECIALS/Planck/SEMBU20YUFF_0.html
ESA Planck: Launch and Early Operations at website of European Space Agency: esa.int/SPECIALS/Planck/SEMB030YUFF_0.html
ESA Science and Technology: Planck at website of European Space Agency: sci.esa.int/science-e/www/area/index.cfm?fareaid=17
ESA News: “Planck Sees Tapestry of Cold Dust” at website of European Space Agency: esa.int/esaCP/SEMMN9CKP6G_index_0.html
ESA Space Science: “So How Everything Start?— a Timeline for the Universe” at website of European Space Agency: esa.int/esaSC/SEMC6TS1VED_index_0.html