The first scientific results from ESA’s Planck mission were released at a press briefing today in Paris. The findings focus on the coldest objects in the Universe, from within our Galaxy to the distant reaches of space.
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This image shows the location of the first six fields used to detect and study the Cosmic Infrared Background. The fields, named N1, AG, SP, LH2, Boötes 1 and Boötes 2, respectively, are all located at a relatively high galactic latitude, where the foreground contamination due to the Milky Way’s diffuse emission is less dramatic. Credits: ESA/Planck Collaboration |
If William Shakespeare were an astronomer living today, he might write that “All the Universe is a stage, and all the galaxies merely players.†Planck is bringing us new views of both the stage and players, revealing the drama of the evolution of our Universe.
Following the publication by ESA of the first full-sky Planck image in July last year, today sees the release of the first scientific results from the mission.
These results are being presented by the Planck Collaboration at a major scientific conference in Paris this week, based on 25 papers submitted to the journal Astronomy & Astrophysics.
The basis of many of these results is the Planck mission’s ‘Early Release Compact Source Catalogue’, the equivalent of a cast list.
Drawn from Planck’s continuing survey of the entire sky at millimetre and submillimetre wavelengths, the catalogue contains thousands of very cold, individual sources which the scientific community is now free to explore.
“This is a great moment for Planck. Until now, everything has been about collecting data and showing off their potential. Now, at last, we can begin the discoveries,†says Jan Tauber, ESA Project Scientist for Planck.
We can think of the Universe as a stage on which the great cosmic drama plays out over three acts.
Visible-light telescopes see little more than the final act: the tapestry of galaxies around us. But by making measurements at wavelengths between the infrared and radio, Planck is able to work back in time and show us the preceding two acts. The results released today contain important new information about the middle act, when the galaxies were being assembled.
Planck has found evidence for an otherwise invisible population of galaxies shrouded in dust billions of years in the past, which formed stars at rates some 10–1000 times higher than we see in our own Galaxy today. Measurements of this population had never been made at these wavelengths before. “This is a first step, we are just learning how to work with these data and extract the most information,†says Jean-Loup Puget, CNRS-Université Paris Sud, Orsay, France.
Eventually, Planck will show us the best views yet of the Universe’s first act: the formation of the first large-scale structures in the Universe, where the galaxies were later born. These structures are traced by the cosmic microwave background radiation, released just 380 000 years after the Big Bang, as the Universe was cooling.
However, in order to see it properly, contaminating emission from a whole host of foreground sources must first be removed. These include the individual objects contained in the Early Release Compact Source Catalogue, as well as various sources of diffuse emission.
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The colour composite of the Rho Ophiuchus molecular cloud highlights the correlation between the anomalous microwave emission, most likely due to miniature spinning dust grains observed at 30 GHz (shown here in red), and the thermal dust emission, observed at 857 GHz (shown here in green). The complex structure of knots and filaments, visible in this cloud of gas and dust, represents striking evidence for the ongoing processes of star formation. The composite image (right) is based on three individual maps (left) taken at 0.4 GHz from Haslam et al. (1982) and at 30 GHz and 857 GHz by Planck, respectively. The size of the image is about 5 degrees on a side, which is about 10 times the apparent diameter of the full Moon. Credits: ESA/Planck Collaboration |
Today, an important step towards removing this contamination was also announced. The ‘anomalous microwave emission’ is a diffuse glow most strongly associated with the dense, dusty regions of our Galaxy, but its origin has been a puzzle for decades.
However, data collected across Planck’s unprecedented wide wavelength range confirm the theory that it is coming from dust grains set spinning at several tens of billion times a second by collisions with either fast-moving atoms or packets of ultraviolet light.
This new understanding helps to remove this local microwave ‘fog’ from the Planck data with greater precision, leaving the cosmic microwave background untouched.
“This is a great result made possible by the exceptional quality of the Planck data,†says Clive Dickinson, University of Manchester, UK.
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This image shows one of the newly discovered superclusters of galaxies, PLCK G214.6+37.0, detected by Planck and confirmed by XMM-Newton. This is the first supercluster to be discovered through its Sunyaev-Zel’dovich effect. The effect is the name for the cluster’s silhouette against the cosmic microwave background radiation. Combined with other observations, the Sunyaev-Zel’dovich effect allows astronomers to measure properties such as the temperature and density of the cluster’s hot gas where the galaxies are embedded. The right panel shows the X-ray image of the supercluster obtained with XMM-Newton, which reveals that three galaxy clusters comprise this supercluster. The bright orange blob in the left panel shows the Sunyaev-Zel’dovich image of the supercluster, obtained by Planck. The X-ray contours are also superimposed on the Planck image. Credits: ESA/Planck Collaboration; XMM-Newton image: ESA |
Among the many other results presented today, Planck has shown new details of yet other actors on the cosmic stage: distant clusters of galaxies. These show up in the Planck data as compact silhouettes against the cosmic microwave background.
The Planck Collaboration has identified 189 so far, including 20 previously unknown clusters that are being confirmed by ESA’s XMM-Newton X-ray observatory.
By surveying the whole sky, Planck stands the best chance of finding the most massive examples of these clusters. They are rare and their number is a sensitive probe of the kind of Universe we live in, how fast it is expanding, and how much matter it contains.
“These observations will be used as bricks to build our understanding of the Universe,†says Nabila Aghanim, CNRS-Université Paris Sud, Orsay, France.
“Today’s results are the tip of the scientific iceberg. Planck is exceeding expectations thanks to the dedication of everyone involved in the project,†says David Southwood, ESA Director of Science and Robotic Exploration.
“However, beyond those announced today, this catalogue contains the raw material for many more discoveries. Even then, we haven’t got to the real treasure yet, the cosmic microwave background itself.â€
Planck continues to survey the Universe. Its next data release is scheduled for January 2013 and will reveal the cosmic microwave background in unprecedented detail, the opening act of the cosmic drama, a picture of the beginning of everything.
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I'm certainly looking forward to the Planck results as well!
As far as the cosmic infrared background is concerned, Herschel will also do a very good job of finding new foreground sources.
Marchis: “…we can now say that stars in our Milky Way galaxy are more likely to host small exoplanets since 75% of the Kepler catalog exoplanets are smaller than Neptune, with a peak of exoplanets only 2-3 times larger than Earth.
I'm going to copy and paste two small texts on light. It is really very interesting:
What kinds of light come from astronomical objects?
In our everyday human experience, we see that light has measurable properties. It has intensity (brightness), and it has color. The intensity gives an indication of the number of light “waves” or “particles” (called photons) coming from an object. The color is a measure of the energy contained in each photon. The colors of the rainbow (red, orange, yellow, green, blue, violet) denote the energies of light waves that our human eyes can see and interpret. This “color” or “energy” range is called the visible spectrum. Red photons of light have the least energy, violet photons carry the most energy. Until fairly recently, all of our astronomical knowledge came from the detailed study of visible light from astronomical objects.
Notice that radio, TV, and microwave signals are all light waves; they simply lie at energies that your eye doesn't respond to. On the other end of the scale, beware the high energy UV, x-ray, and gamma-ray photons! Each one carries a lot of energy compared to their visible- and radio-wave brethren. They're the reasons you should wear sunblock in the summer, for example.
When we look at the Universe in light of different energies, we probe different kinds of physical conditions — and we can see new kinds of objects! For example, high-energy gamma-ray and X-ray telescopes tend to see the most energetic dynamos in the cosmos, such as active galaxies, the remnants from massive dying stars, accretion of matter around black holes, and so forth. Visible light telescopes best probe light produced by stars (it's no accident that human eyes have adapted to be sensitive to “ROYGBIV” light like they are — after all, that's where most of the Sun's energy comes out). Going to even lower energies and longer wavelengths, infrared and microwave radio telescopes best probe dark, cool, obscured structures in the Universe: dusty star-forming regions, dark cold molecular clouds, the primordial radiation emitted by the formation of the Universe shortly after the Big Bang. Only through studying astronomical objects at many different wavelengths are astronomers able to piece together a coherent, comprehensive picture of how the Universe works!
And one more:
How do we see color? Sensing light
We perceive color when the different wavelengths composing white light are selectively interfered with by matter (absorbed, reflected, refracted, scattered, or diffracted) on their way to our eyes, or when a non-white distribution of light has been emitted by some system.
Visible light is merely a small part of the full electromagnetic spectrum, which extends from cosmic rays at the highest energies down through gamma rays, X- rays, the ultraviolet, the visible, the infrared, and radio waves to induction-heating and electric-power-transmission frequencies at the lowest energies. Note that this is the energy per quantum (photon if in the visible range) but not the total energy; the latter is a function of the intensity in a beam.
We can detect the range of light spectrum from about 400 nanometers (violet) to about 700 nanometers (red). We perceive this range of light wavelengths as a smoothly varying rainbow of colors — the visual spectrum.
I'm certainly looking forward to the Planck results as well!
As far as the cosmic infrared background is concerned, Herschel will also do a very good job of finding new foreground sources.