Tuesday, April 27, 2010

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).

Monday, April 12, 2010

Baby stars in the Rosette cloud

Infrared image of the Rosette molecular cloud. Herschel collects the infrared light given out by dust and this image is a three-colour composite made of wavelengths at 70 microns (blue), 160 microns (green) and 250 microns (red). It was made with observations from Herschel’s Photoconductor Array Camera and Spectrometer (PACS) and the Spectral and Photometric Imaging Receiver (SPIRE). The bright smudges are dusty cocoons containing massive protostars. The small spots near the centre of the image are lower mass protostars.

Credits: ESA/PACS & SPIRE Consortium/HOBYS Key Programme Consortia

Herschel’s latest image reveals the formation of previously unseen large stars, each one up to ten times the mass of our Sun. These are the stars that will influence where and how the next generation of stars are formed. The image is a new release of ‘OSHI’, ESA’s Online Showcase of Herschel Images.

The Rosette Nebula resides some 5,000 light years from Earth and is associated with a larger cloud that contains enough dust and gas to make the equivalent of 10,000 Sun-like stars. The Herschel image shows half of the nebula and most of the Rosette cloud. The massive stars powering the nebula lie to the right of the image but are invisible at these wavelengths. Each colour represents a different temperature of dust, from –263ºC (only 10ºC above absolute zero) in the red emission to –233ºC in the blue.

The bright smudges are dusty cocoons hiding massive protostars. These will eventually become stars containing around ten times the mass of the Sun. The small spots near the centre and in the redder regions of the image are lower mass protostars, similar in mass to the Sun.

ESA’s Herschel space observatory collects the infrared light given out by dust. This image is a combination of three infrared wavelengths, colour-coded blue, green and red in the image, though in reality the wavelengths are invisible to our eyes. It was created using observations from Herschel’s Photoconductor Array Camera and Spectrometer (PACS) and the Spectral and Photometric Imaging Receiver (SPIRE).

Herschel is showing astronomers such young, massive protostars for the first time, as part of the ‘Herschel imaging survey of OB Young Stellar objects’. Known as HOBYS, the survey targets young OB class stars, which will become the hottest and brightest stars.

“High-mass star-forming regions are rare and further away than low-mass ones,” says Frédérique Motte, Laboratoire AIM Paris-Saclay, France. So astronomers have had to wait for a space telescope like Herschel to reveal them.

It is important to understand the formation of high-mass stars in our Galaxy because they feed so much light and other forms of energy into their parent cloud they can often trigger the formation of the next generation of stars.

When astronomers look at distant galaxies, the star-forming regions they see are the bright, massive ones. Thus, if they want to compare our Galaxy to distant ones they must first understand high-mass star-formation here.

“Herschel will look at many other high-mass star-forming regions, some of them building stars up to a hundred times the mass of the Sun,” says Dr Motte, who plans to present the first scientific results from HOBYS at ESA’s annual ESLAB symposium to be held in the Netherlands, 4–7 May.

Source: ESA

Wednesday, March 17, 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.

Tuesday, March 16, 2010

Herschel Science Archive (HSA) and HIPE publicly [9 March 2010] available

We are pleased to announce that as of today the Herschel Science Archive (HSA) has been opened to the world. At the same time the Herschel Integrated Processing Environment (HIPE) software has been made available for public download. For more information use the 'HIPE Download' and 'HSA Access' buttons on the left. [9 March 2010]

HIFI spectral scan of Orion HIFI spectral scan of Orion (blowouts)

HIFI spectral scan of Orion [4 March 2010]

The very successful commissioning and performance verification activities conducted with HIFI have produced a spectacular spectral scan of the Orion nebula. On the left above a spectrum displaying a plethora of lines from a number of molecules obtained in just a couple of hours, displaying the spectral richness so characteristic of Orion. On the right zooming in on smaller regions of the spectrum showing the unprecedented detail uniquely provided by HIFI. For additional information see the SRON and SciTech webpostings.

Friday, March 12, 2010

Herschel-HIFI unveils precursors of life-enabling molecules in Orion Nebula

An artist's view of the Herschel satellite with the at present largest telescope mirror in space, which carries the HIFI instrument.

The HIFI spectrum of the Orion Nebula, superimposed on a Spitzer image of Orion. A characteristic feature is the spectral richness: among the organic molecules identified in this spectrum are water, carbon monoxide, formaldehyde, methanol, dimethyl ether, hydrogen cyanide, sulphur oxide, sulphur dioxide and their isotope analogues. It is expected that new molecules will also be identified. This spectrum is the first glimpse at the spectral richness of regions of star and planet formation. It harbours the promise of a deep understanding of the chemistry of space once the complete spectral surveys are available.

Credit: ESA, HEXOS and the HIFI consortium

Press Release of the University of Cologne, Max Planck Institut für Radioastronomie, Bonn, and Max Planck Institut für Sonnensystemforschung, Lindau:

ESA’s Herschel Space Observatory has revealed the chemical fingerprints of potential life-enabling organic molecules in the Orion Nebula, a nearby stellar nursery in our Milky Way galaxy. This detailed spectrum, obtained with the Heterodyne Instrument for the Far Infrared (HIFI) - one of Herschel's three innovative instruments - demonstrates the gold mine of information that Herschel-HIFI will provide on how organic molecules form in space. Several German Institutes contributed essential parts to the HIFI instrument: the Universität zu Köln and two Max Planck Institutes: Radioastronomie (Bonn) and Sonnensystemforschung (Lindau).

Striking features in the HIFI spectrum include a rich, dense pattern of “spikes”, each representing the emission of light from a specific molecule in the Orion Nebula. This nebula is known to be one of the most prolific chemical factories in space, although the full extent of its chemistry and the pathways for molecule formation are not well understood. By sifting through the pattern of spikes in this spectrum, astronomers have identified a few common molecules that appear everywhere in the spectrum. The identification of the many other emission lines is currently ongoing.

By clearly identifying the lines associated with the more common molecules, astronomers can then begin to tease out the signature of particularly interesting molecules that are the direct precursors to life-enabling molecules. A characteristic feature of the Orion spectrum is the spectral richness: among the molecules that can be identified in this spectrum are water, carbon monoxide, formaldehyde, methanol, dimethyl ether, hydrogen cyanide, sulphur oxide, sulphur dioxide and their isotope analogues. It is expected that new organic molecules will also be identified.

“This HIFI spectrum, and the many more to come, will provide a virtual treasure trove of information regarding the overall chemical inventory and on how organics form in a region of active star formation. It harbours the promise of a deep understanding of the chemistry of space once we have the full spectral surveys available,” said Edwin Bergin of the University of Michigan principal investigator of the HEXOS Key Programme on Herschel.

Unprecedented high resolution

HIFI was designed to provide extremely high-resolution spectra and to open new wavelength ranges for investigation, which are inaccessible to ground-based telescopes. “It is astonishing to see how well HIFI works," said Frank Helmich, HIFI principal investigator of SRON Netherlands Institute for Space Research. "We obtained this spectrum in a few hours and it already beats any other spectrum, at any other wavelength, ever taken of Orion. Organics are everywhere in this spectrum, even at the lowest levels, which hints at the fidelity of HIFI. The development of HIFI took eight years but it was really worth waiting for.”

Identification of the many spectral features visible in the Orion spectrum with transitions of particular molecular species requires sophisticated tools such as the Colgone Database of Molecular Spectroscopy (CDMS), which collect the laboratory data of several hundred moelcular species and precise line predictions. “The high spectral resolution of HIFI shows the breath-taking rechness of molecular species, which are present, despite of the hostile environment, in the stellar nurseries and sites for planet formation”, says Jürgen Stutzki, HIFI-co-principle investigator at the Universität zu Köln.

ESA project Herschel:

Herschel is one of ESAs cornerstone missions, a space observatory with science instruments provided by European-led Principal Investigator consortia, with important contributions from NASA on the US side. One of the three instruments on board Herschel is HIFI, the Heterodyne Instrument for the Far-Infrared, .an ultra-sensitive, high resolution spectrometer designed and built by a nationally-funded consortium led by SRON Netherlands Institute for Space Research. The consortium includes partners from 25 institutes and 13 different nations. German institutes have provided key components for HIFI: the local oscillator, built at the MPI für Radioastronomie, Bonn, superconducting detectors with sensitivity close to the fundamental quantum limit, built at the Universität zu Köln. HIFI carries the classical radio frequency technique of heterodyne-mixing into a for orders of magnitude higher fequency regime, namely the Far-Infrared spectral range. A further essential component, the Acousto Optical Spectrometer (AOS), was developed in collaboration between the Universität zu Köln and the Max Planck Institut für Sonnensystemforschung, Lindau.

Sunday, December 6, 2009

Log: (09-29-2009 - 11-25-2009)

25 November 2009 (L+195, DOY 329)

The findings of the HIFI investigation team and the proposed plan for bringing HIFI back in operation were presented to the ESA Director of Science and Robotic Exploration and others in a briefing meeting held in ESTEC on 25 November 2009. The plan presented was endorsed, and is now the adopted way forward.

[G. Pilbratt, Herschel Project Scientist, posted 27 November 2009]

19 November 2009 (L+189, DOY 323)

The plan for bringing HIFI back in operation is now on the table, and subject to formal approval in the coming week. The plan consists of performing a number of software updates in the coming weeks, followed by a full instrument switch-on in January 2010, after which HIFI operations will resume. See information provided on the SRON website.

[G. Pilbratt, Herschel Project Scientist, posted 20 November 2009]

26 October 2009 (L+165, DOY 299)

The HIFI failure investigation team set-up at ESA in support of the Principal Investigator effort in SRON is finalising its work and a draft report is currently under review within the team. The content of this report will be presented to the ESA Director General and the Director of Science and Robotic Exploration this week. Due to the capability to perform extended tests on fully representative hardware and software on the ground, and to the excellent cooperation between the PI team and ESA specialists, the investigation has arrived at a complete and consistent failure scenario which can explain the observable evidence. Some further consolidating investigations on this scenario are still on-going but the picture that has emerged is the following:

A Single Event Upset (SEU) in the Random Access Memory (RAM) of the Local Oscillator Control Unit (LCU) microcontroller would be at the origin of a chain reaction that eventually results in an unplanned emergency switch off of sensitive instrument components. Designed to protect the local oscillators against damage from undervoltage on the spacecraft 28 V bus, this switch was thrown while the 28 V bus was alive. The resulting load transient in the internal power system of the LCU associated with this mode change created a stress in the power converters, leading to a permanent failure of one of the diodes.

Before the restart of the instrument on the redundant signal chain can be performed, changes in the operation and protection logic of the instrument must be implemented and validated in on-board software to prevent re-occurrence of such a sequence of events.

Although the detailed investigations have uncovered some marginalities in the stress applied to certain diodes in the internal power system of the LCU, laboratory tests have shown these diodes to be quite resilient against the short overvoltage spikes they are subjected to during nominal instrument operations. The investigation team is confident that HIFI can perform nominally for the remainder of the mission if the required corrective actions are implemented.

[J. Riedinger, Herschel Mission Manager and co-chair of the ESA investigation team]

5 October 2009 (L+144, DOY 278)

Progress towards re-enabling HIFI

Today, SRON have added an entry to their top level web page (www.sron.nl), in which they report about the progress that is being made towards re-enabling HIFI operations. Despite the progress which is undoubtedly made by the joint HIFI/ESA investigation team, the HIFI Project Manager cautions that switching the instrument back on may still be a few weeks in the future: We must ensure that we have taken all conceivable measures to minimise the risk of such a chain of events from happening again. One of these measures may require changes in on-board software, the validation of which would have to be performed with the utmost care.

[J. Riedinger, Herschel Mission Manager]

29 September 2009 (L+138, DOY 272)

First science data distributed to the users community

Yesterday 28 September Herschel reached another important milestone: the first set of observations corresponding to the so-called 'Science Demonstration Phase" were made available to their owners. This delivery took place several weeks ahead of the originally planned schedule and marks the start of the transition from the Performance Verification Phase to the Routine Phase of operations.

The observations (six so far only) were conducted on 12 September 2009 and successfully processed with the latest version of the pipeline as implemented in a dedicated version of HIPE that was also distributed to the observers. They are SPIRE scan maps of a variety of astronomical sources including a galactic HII region, a proto-planetary nebula, a supernova remnant, and a couple of galaxy clusters. This is the first of the observing modes released to the users community following its early validation during the Performance Verification Phase.

If there are no major contingencies, we expect to be running the Science Demonstration Phase at full speed during the second half of October and the whole month of November, as initially planned, first with PACS and SPIRE AORs, and then with HIFI as well, once the instrument resumes operations and completes its own performance and verification phase, delayed because of the problems already reported in this (B)log.

[P. Garcia-Lario, HSC ESAC, posted 30 September 2009]