Planck Casts New Light on Stellar Formation

A series of recent experiments has revealed that, more often than not, the halos of dark matter surrounding massive galaxy clusters are flattened and shaped like a cigar. Until now, astrophysicists believed that the mysterious stuff, which is believed to be five times more abundant than regular matter around the Universe, would clump up in rounded spheres. However, observations appear to paint a different picture, and experts are currently working on models that would help explain that.

The discovery could finally lead to studies that would result in the direct detection of the peculiar type of matter, whose existence can only be inferred from the gravitational pull it exerts on normal matter around it. “There are clear theoretical predictions that we expect dark mater halos to be flattened like this. It's a very beautiful, very clean and direct measurement of that,” explains expert Graham P. Smith, who is based at the University of Birmingham, in the United Kingdom. He is also a coauthor of the new study, which will appear in an upcoming issue of the esteemed scientific publication Monthly Notices of the Royal Astronomical Society.

In the new studies, the investigators looked at about 20 galaxy clusters, which are massive collections of galaxies, held together by strong gravitational interactions. In order to see the effect dark matter has on the largest organized structures in the Universe, the researchers used gravitational lensing. This observations technique analyzes how much light is bent when mass wraps time-space in order to determine the mass of celestial objects beyond. The Mauna Kea, Hawaii-based Subaru Telescope was used for the study, and the team took advantage of the Prime Focus Camera above all other instruments.

“What we're probing with these gravitational lensing observations is the dark matter distribution, because the dark matter dominates the mass on these large scales,” Smith says. The research team in charge of the study was led by National Astronomical Observatory of Japan expert Masamune Oguri and University of Tokyo scientist Masahiro Takada. The cigar-like shapes of these dark matter halos have been predicted in computer models of the cold dark matter theory, but thus far they have not been evidenced in practice in such a large number of galaxy clusters, Space reports.

“Precise measurements of the Cosmic Microwave Background are crucial to cosmology, and to understanding how our Universe formed and evolved. Attaining the highest-sensitivity (a few parts per million), highest-angular resolution (5 arcminutes) maps of the CMB – the goal of the Planck mission – requires the removal of the 'foreground' emission arising from the Milky Way. The information gleaned during this process is providing, as a by-product, a unique view of the processes that led to the formation of the stars in the galaxies that populate our Universe,” ESA officials write in a press release.

Planck maps the sky in nine frequencies using two state-of-the-art instruments, designed to produce high-sensitivity, multi-frequency measurements of the diffuse sky radiation: the High Frequency Instrument (HFI) includes the frequency bands 100 – 857 GHz, and the Low Frequency Instrument (LFI) includes the frequency bands 30-70 GHz. The first Planck all-sky survey began in August 2009 and is 98% complete (as of mid-March 2010).

Planck sees tapestry of cold dust

The image spans about 50° of the sky. It is a three-colour combination constructed from Planck’s two highest frequency channels (557 and 857 GHz, corresponding to wavelengths of 540 and 350 micrometres), and an image at the shorter wavelength of 100 micrometres made by the IRAS satellite. This combination visualises dust temperature very effectively: red corresponds to temperatures as cold as 10° above absolute zero, and white to those of a few tens of degrees. Overall, the image shows local dust structures within 500 light-years of the Sun.

Credits: ESA and the HFI Consortium, IRAS

Giant filaments of cold dust stretching through our Galaxy are revealed in a new image from ESA’s Planck satellite. Analysing these structures could help to determine the forces that shape our Galaxy and trigger star formation.

Planck is principally designed to study the biggest mysteries of cosmology. How did the Universe form? How did the galaxies form? This new image extends the range of its investigations into the cold dust structures of our own Galaxy.

	Planck scanning the sky

The image shows the filamentary structure of dust in the solar neighbourhood – within about 500 light-years of the Sun. The local filaments are connected to the Milky Way, which is the pink horizontal feature near the bottom of the image. Here, the emission is coming from much further away, across the disc of our Galaxy.

The image has been colour coded to discern different temperatures of dust. White-pink tones show dust of a few tens of degrees above absolute zero, whereas the deeper colours are dust at around –261°C, only about 12 degrees above absolute zero. The warmer dust is concentrated into the plane of the Galaxy whereas the dust suspended above and below is cooler.

Planck's newly imaged region shown in box

“What makes these structures have these particular shapes is not well understood,” says Jan Tauber, ESA Project Scientist for Planck. The denser parts are called molecular clouds while the more diffuse parts are ‘cirrus’. They consist of both dust and gas, although the gas does not show up directly in this image.

There are many forces at work in the Galaxy to help shape the molecular clouds and cirrus into these filamentary patterns. For example, on large scales the Galaxy rotates, creating spiral patterns of stars, dust, and gas. Gravity exerts an important influence, pulling on the dust and gas. Radiation and particle jets from stars push the dust and gas around, and magnetic fields also play a role, although to what extent is presently unclear.

Bright spots in the image are dense clumps of matter where star formation may take place. As the clumps shrink, they become denser and better at shielding their interiors from light and other radiation. This allows them to cool more easily and collapse faster.

Filamentary structures on large and small scales in the Milky Way

ESA’s Herschel space telescope can be used to study such regions in detail, but only Planck can find them all over the sky. Launched together in May 2009, Planck and Herschel are both studying the coolest components of the Universe. Planck looks at large structures, while Herschel can make detailed observations of smaller structures, such as nearby star-forming regions.

One puzzle to be solved is why there is similar filamentary structure on both the large and the small scale. “That’s a big question,” says Tauber.

The new image is a combination of data taken with Planck’s High Frequency Instrument (HFI), at wavelengths of 540 micrometres and 350 micrometres, and a 100-micrometre image taken in 1983 with the IRAS satellite.

The HFI data were recorded as part of Planck’s first all-sky survey at microwave wavelengths. As the spacecraft rotates, its instruments sweep across the sky. During every rotation, they cross the Milky Way twice. Thus, in the course of Planck’s mission to precisely map the afterglow of the big bang, it is also producing exquisite maps of the Galaxy.

Herschel and Planck in the classroom

To mark the launch of the Herschel and Planck space observatories, ESA has participated in the production of a wide-ranging series of educational materials related to these two cornerstones of its science programme.

These materials were originally disseminated to German teachers through a collaboration with the German “Wissenschaft in die Schulen!” (WiS! - Science into Schools!) project and the “Sterne und Weltraum” magazine. ESA is now making them available online through its education website.

The launch of Herschel and Planck on 14 May 2009 marked the beginning of a new era in observational astronomy. When they reach their operational orbits later in the year, Herschel will provide new insights into the births of stars and galaxies, while Planck will map the Cosmic Microwave Background – the relic radiation of the Big Bang – with unprecedented accuracy. The first observatory to cover the entire range from far-infrared to sub-millimetre wavelengths and bridge the two, Herschel will explore further in the far-infrared than any previous mission, studying otherwise invisible dusty and cold regions of the cosmos, both near and far.

WiS! recognised the importance of this scientific milestone by dedicating a special edition of “Sterne und Weltraum” to the pair of pioneering missions. This issue included numerous articles written by scientists involved in the missions, as well as didactical material written by educational experts in the field. The teaching materials, mainly aimed at secondary school students, covers various mission-related topics such as orbits, Lagrange points, the Big Bang and electromagnetic radiation.

The articles and corresponding exercises can be downloaded in English and in German from the ESA Education website. The original publication, which was made available to teachers during workshops in Germany, included a DVD that contained three educational videos. These can also be found on the ESA Education website.

“Wissenschaft in die Schulen!”

The “Wissenschaft in die Schulen!” project started in 2005 with support from the German Klaus Tschira Foundation, a non-profit organisation designed to support research and public understanding of science and mathematics. Through close collaboration with the magazine “Sterne und Weltraum”, it includes a wide range of interesting subjects derived from recent astronomical research and space travel for use in lessons.

Thanks to the publisher Spektrum der Wissenschaft, the project has developed teaching materials for lower and upper secondary classes, based on subjects covered in its monthly scientific magazines. These materials are made available to a wide audience through a magazine and a website. Teachers can now find 80 lessons online on the “Wissenschaft in die Schulen!” website.

Herschel and Planck educational materials

Planck Chills Out

Artist's concept of Planck in space, with Earth in the background. Image credit: ESA› High-resolution JPEG (1.5MB)

June 12, 2009

A JPL-developed and -built cooler on the Planck spacecraft has chilled the mission's low-frequency instrument down to its operating temperature of a frosty 20 Kelvin (minus 424 degrees Fahrenheit). The so-called hydrogen sorption cooler was turned on June 4 and achieved the target temperature of 20 Kelvin eight days later. The cooler is part of a chain of coolers that works together to ultimately chill the high-frequency instrument down to 0.1 Kelvin -- an event scheduled to take place in a few weeks.

Planck is currently on its way to its final orbit at the second Lagrange point, which is located about 1.5 million kilometers (930,000 miles) from Earth, on the opposite side of our planet from the sun. Once there, it will look back to the dawn of time to study the birth of our universe.