Author Archives: evaschmelmer

First Successful Mission of upGREAT

The far-infrared spectrometer upGREAT, developed and built by a consortium of German research institutes, led by Rolf Güsten from the Max Planck Institute for Radio Astronomy in Bonn, Germany, recently completed its first successful mission onboard SOFIA. The air-borne observatory SOFIA is a joint project of NASA (USA) and DLR (Germany). Four commissioning flights between May 13 and May 22, 2015, showed the performance of upGREAT.

June 12, 2015

upGREAT – a new far-infrared spectrometer for SOFIA

(DLR News 02 June 2015)

Colliding Stars Explain Enigmatic Seventeenth Century Explosion

APEX and Effelsberg observations unravel mystery of Nova Vul 1670

March 23, 2015

Discoveries made with the APEX telescope reveal that the “new” star that European astronomers saw appear in the sky in 1670 was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using modern submillimetre telescopes was needed to finally unravel the mystery more than 340 years later.

A team led by scientists from the Max Planck Institute for Radio Astronomy in Bonn found emission from a fascinating variety of molecules that provides the tell-tale evidence.

The results appear online in the journal Nature on 23 March 2015.

The nova of 1670 recorded by Hevelius. This chart of the position of a nova that appeared in the year 1670 was recorded by the famous astronomer Hevelius and was published by the Royal Society in England in their journal Philosophical Transactions.

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The nova of 1670 recorded by Hevelius. This chart of the position of a nova that appeared in the year 1670 was recorded … [more]

Some of the age’s greatest astronomers, including Hevelius — the father of lunar cartography — and Cassini, carefully documented the appearance of a new star in the skies in 1670. Hevelius described it as “Nova sub capite Cygni” – a new star below the head of the Swan – but astronomers now know it by the name Nova Vul 1670. This object lies within the boundaries of the modern constellation of Vulpecula (The Fox), just across the border from Cygnus (The Swan) and is also referred to as CK Vulpeculae, its designation as a variable star. Historical accounts of novae are rare and of great interest to modern astronomers.

The lead author of the new study, Tomasz Kamiński (at the time of the observations at the Max Planck Institute for Radio Astronomy, Bonn, Germany and now at ESO, Chile) explains: “For many years this object was thought to be a nova but the more it was studied the less it looked like an ordinary nova — or indeed any other kind of exploding star.”

When it first appeared, Nova Vul 1670 was easily visible with the naked eye and varied in brightness significantly over the course of two years. It then disappeared and reappeared twice before vanishing for good. Although well documented for its time, the intrepid astronomers of the day lacked the equipment needed to solve the riddle of the apparent nova’s peculiar performance.

During the twentieth century, astronomers came to understand that most novae could be explained as runaway explosive behaviour of close binary stars. But Nova Vul 1670 did not fit this model well at all and remained a mystery.

Even with ever-increasing telescopic power, for a long time the event was believed to have left no trace, and it was not until the 1980s that a team of astronomers detected a faint nebula surrounding the suspected location of what was left of the star. While these observations offered a tantalising link to the sighting of 1670, they failed to shed any new light on the true nature of the event witnessed over the skies of Europe over three hundred years ago.

Tomasz Kamiński continues the story: “We have now probed the area in the submillimetre and radio wavelengths. We have found that the surroundings of the remnant are bathed in a cool gas rich in molecules, with a very unusual chemical composition.” Among others, the team discovered the molecules CO, CN, HCN, HNC, NH₃, SiO, the ionized molecules N₂H⁺, HCO⁺ and even the organic H₂CO (formaldehyde).

This picture shows the remains of the new star that was seen in the year 1670. It was created from a combination of visible-light images from the Gemini telescope (blue), a submillimetre map showing the dust from the SMA (yellow) and finally a map of the molecular emission from APEX and the SMA (red).

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This picture shows the remains of the new star that was seen in the year 1670. It was created from a combination of … [more]

As well as APEX, the team also used the Submillimeter Array (SMA) and the Effelsberg radio telescope to discover the chemical composition and measure the ratios of different isotopes in the gas. Together, this created an extremely detailed account of the makeup of the area, which allowed an evaluation of where this material might have come from.

What the team discovered was that the mass of the cool material was too great to be the product of a nova explosion, and in addition the isotope ratios the team measured around Nova Vul 1670 were different to those expected to be produced by a nova. But if it wasn’t a nova, then what was it?

The answer is a rare and spectacular collision between two stars, more brilliant than a nova, but less so than a supernova, which produces a so-called red transient. These are a very rare events in which stars explode due to a merger with another star, spewing nuclear material into space, eventually leaving behind only a faint remnant embedded in a cool environment, rich in molecules and dust. This newly recognised class of eruptive stars fits the profile of Nova Vul 1670 almost exactly.

Co-author Karl Menten (Max Planck Institute for Radio Astronomy and Principal Investigator of APEX) concludes: “This kind of discovery is the most fun: something that is completely unexpected!”

The team is composed of Tomasz Kamiński (ESO, Santiago, Chile; Max Planck Institute for Radio Astronomy, Bonn, Germany [MPIfR]), Karl M. Menten (MPIfR), Romuald Tylenda (N. Copernicus Astronomical Center, Toruń, Poland), Marcin Hajduk (N. Copernicus Astronomical Center), Nimesh A. Patel (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA) and Alexander Kraus (MPIfR).

The Atacama Pathfinder Experiment (APEX) is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), Onsala Space Observatory (OSO), and the European Southern Observatory (ESO) to construct and operate a modified prototype antenna of ALMA (Atacama Large Millimetre Array) as a single dish on the Chajnantor plateau at an altitude of 5,100 meters above sea level (Atacama Desert, Chile). The telescope was manufactured by VERTEX Antennentechnik in Duisburg, Germany. The operation of the telescope is entrusted to ESO.

The 100m Radio Telescope Effelsberg is one of the largest fully steerable radio telescopes on earth. It is operated by the Max-Planck-Institut für Radioastronomie in Bonn, Germany and located in a valley approximately 40 km southwest of Bonn. It was used here to observe a number of radio transitions of different molecules, namely SiO, OH, H₂O (water) and NH₃ (ammonia).

Fortifying the Brick and Charming the Snake

Magnetic Fields are crucial in shaping the Cradles of Massive Stars

January 16, 2015

Magnetic fields in massive dark clouds are strong enough to support the regions against collapse due to their own gravity. A study lead by researchers at the Max–Planck–Institut für Radioastronomie in Bonn, Germany, shows for the first time that high magnetization sets the stage for the formation of stars much more massive than the sun. This is demonstrated in observations of polarized dust emission from two of the most massive clouds in our Milky Way, the “Brick” and “Snake”. The results are published in this week’s issue of the “Astrophysical Journal”.

<p><em>The left panel shows the “Brick” as a shadow against the mid–infrared emission from warm gas and dust in the vicinity of the Galactic Center. The background false–color image and white contours in the right panel give the emission of cold dust in the Brick itself. Markers indicate the orientation of the magnetic field deduced from polarization observations. The area shown on the right is indicated by a white box in the left–hand panel.</em></p>

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The left panel shows the “Brick” as a shadow against the mid–infrared emission from warm gas and dust in the vicinity of the Galactic Center. The background false–color image and white contours in the right panel give the emission of cold dust in the Brick itself. Markers indicate the orientation of the magnetic field deduced from polarization observations. The area shown on the right is indicated by a white box in the left–hand panel.
© T. Pillai & J. Kauffmann, based on Spitzer GLIMPSE & MIPSGAL images (NASA / JPL–Caltech / Univ. of Wisconsin) and Hertz data from the CSO (J. Dotson)

Stars much more massive than the Sun (with 8 solar masses or more) live wild and die young. They spew out powerful stellar winds and sometimes explode violently to end up as supernovae. Even their birth is spectacular: massive stars form out of very dense and massive gaseous cores that are deeply embedded within dark clouds of gas and dust. In fact, the high mass of these cores has puzzled researchers for many years: the cores should quickly collapse due to their own gravity and destroy themselves before telescopes on Earth can detect them.

“For the first time we witness how magnetic fields thread a massive cloud and help stabilize the region while it gets ready to form high–mass stars” says Thushara Pillai from the Max–Planck–Institut für Radioastronomie (MPIfR) in Bonn (Germany), the lead author of the study. “The cloud would already be collapsing if there were no magnetic support”, she adds. “In that case the young forming cores would never become massive enough to form stars much larger than the Sun.”

It has long been suspected that magnetic fields help to support clouds against collapse. But magnetic fields are elusive: it is difficult to tease the weak signal from magnetic fields from the noise. Every region has to be observed over several nights to finally achieve a significant detection. The current study therefore only targets two regions. The “Brick” is an unusually dense cloud that is as opaque as its namesake. It resides just a few dozen light years away from the Galactic Center Black Hole in a distance of about 26,000 light years. The nickname of the “Snake” is inspired by its serpent–like shape. This cloud is about 12,000 light years away from Earth. The team used archival data from two telescopes on top of Mauna Kea (Hawaii, USA) to conduct this research, the James Clerk Maxwell Telescope and the Caltech Submillimeter Observatory.

The magnetic field geometry can be studied by observing the dust particles aligned with the magnetic field. These grains emit polarized radiation that can be detected with telescopes. The magnetic field lines are constantly disturbed by random gas motions in the clouds. “You can think of a guitar string being plucked”, suggests Paul Goldsmith, a team member from the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena (California, USA). “On a stringed instrument such as a guitar, the tension in the string tries to hold it straight. In our clouds, the magnetic field tries to do this, and the degree of straightness of the field lines is a measure of the magnetic field strength.” Researchers Chandrasekhar and Fermi already suggested this technique in 1953. But only recently have telescopes become sensitive enough to conduct this experiment throughout the Milky Way.

<p><em>In the left panel the “Snake” is seen as a dark silhouette against the diffuse mid–infrared glow of the Milky Way. The right panel zooms in on a dense section of the cloud that is outlined by a box in the overview panel. The background false–color image and contours indicate emission from cold dust. Markers give the magnetic field orientation derived from polarization observations.</em></p><br /><br /><br />
<p><em> </em></p>

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In the left panel the “Snake” is seen as a dark silhouette against the diffuse mid–infrared glow of the Milky Way. The right panel zooms in on a dense section of the cloud that is outlined by a box in the overview panel. The background false–color image and contours indicate emission from cold dust. Markers give the magnetic field orientation derived from polarization observations.
© T. Pillai & J. Kauffmann, based on Spitzer GLIMPSE & MIPSGAL images (NASA / JPL-Caltech / S. Carey [SSC/Caltech]) and SCUPOL data from the JCMT (P. Redman / B. Matthews)

This study opens a new chapter in research that started in the early 1980’s at the Effelsberg 100m–telescope of the MPIfR. First surveys of dense gas near the center of the Milky Way revealed unusually massive clouds, including the “Brick”. This discovery inspired several follow–up studies, as co–author Jens Kauffmann from the MPIfR explains. “Two years ago we successfully revealed for the first time the internal structure of the Brick. We were surprised to find very little substructure in this cloud: something seemed to stop the gas from clumping up. Now we know that the strong magnetic field might do this.”

The team has now started a project that will observe many more such clouds. This time the researchers will use MPIfR’s APEX telescope. “APEX is currently the only telescope worldwide that is equipped to make these observations”, concludes Thushara Pillai. “It is an exciting possibility to use this observatory to explore more of our Galactic backyard”.

The research team is comprised of Thushara Pillai, Jens Kauffmann and Karl M. Menten (all MPIfR), moreover Jonathan C. Tan (University of Florida), Paul F. Goldsmith (Jet Propulsion Laboratory, California Institute of Technology), and Sean J. Carey (IPAC, California Institute of Technology).

SOFIA Airborne Observatory begins 2015 Science Campaign

First series of flights uses German receiver GREAT

January 15, 2015

SOFIA, the Stratospheric Observatory for Infrared Astronomy, began its third season of science flights on Jan. 13, 2015. SOFIA is a joint project of NASA and the German DLR, a next generation flying observatory fitted with a 2.5-meter (100-inch) diameter telescope that studies the universe at infrared wavelengths. The first flight used the German Receiver for Astronomy at Terahertz Frequencies (GREAT) spectrometer to study the chemical composition and motions of gas in a star-forming region, a young star, and a supernova remnant. The observations at infrared wavelengths allow e.g. to see through interstellar dust to record the spectral signatures of molecules in such regions to study the abundances of molecules and their formation process.

NASA’s Airborne Observatory Begins 2015 Science Campaign

NASA News Release, January 14, 2015

The Age of Stellar Nurseries

Astrochemical Dating with Molecular Line Observations from SOFIA und APEX

November 17, 2014

An international research team led by scientists from the Coordinated Research Center (CRC) 956 “Conditions and Impact of Star Formation” at the University of Cologne has used observations made with the GREAT instrument on board the SOFIA aircraft observatory and the APEX telescope to date the core of an interstellar cloud that is forming a group of Sun-like stars. This work, to which scientists from the University of Helsinki as well as from the Max-Planck-Institutes for Radio Astronomy (MPIfR) and Extraterrestrial Physics (MPE) contributed, is published in this week’s issue of “Nature”.

Our own solar system formed many billion years ago when a dark interstellar cloud started to contract to form our protostar – which later became the Sun. The duration of this first step in stellar evolution has now been determined to last at least 1 million years in the similar system IRAS 16293-2422, a collection of protostars ~400 light years away in the constellation Ophiuchus (background image). This has been achieved by using molecular hydrogen, H<sub>2</sub>, as a chemical clock. As hydrogen is not directly detectable, the chemically closely related species H<sub>2</sub>D<sup>+</sup> has been observed instead in the submm- and far-infrared wavelength range, using the ground-based telescope APEX in the Chilean Andes and the airborne observatory SOFIA.

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Our own solar system formed many billion years ago when a dark interstellar cloud started to contract to form our … [more]

Stars like our Sun and their planetary systems are born inside clouds consisting of dust and molecular gas. Stellar evolution begins with the contraction of dense material in these stellar nurseries until an embryonic star, the protostar, is formed. How this collapse happens exactly, and on what timescales, is not very well understood. Is the gas “free-falling” towards the center due to gravity or is the collapse slowed down by other factors? “Since this process takes much longer than human history, it cannot just be followed as a function of time. Instead, one needs to find an internal clock that allows to read off the age of a particular star forming cloud,” says the leading author Sandra Brünken from the University of Cologne.

The hydrogen molecule (H₂), by far the most abundant molecule in space, could act as such an internal, “chemical” clock. Molecular hydrogen exists in two different forms, called ortho and para, which correspond to different orientations of the spins of the two hydrogen nuclei. In the cold and dense molecular clouds out of which stars are formed, the relative abundance of these two forms changes continuously with time by chemical exchange reactions. Therefore the current abundance ratio observed is a measure of the time elapsed since the formation of H₂, and thereby the molecular cloud itself. Unfortunately, H₂ cannot be directly detected in the very cold interstellar “breeding grounds” of stars. However, H₂D⁺, an ionized variant in which a deuteron particle is attached to the H₂ molecule, can be observed. Indeed, the ortho and para forms of H₂D⁺ emit and absorb at characteristic wavelengths, forming “spectral lines” that are observable with different telescopes. “We knew from our own laboratory experiments and from theory that H₂D⁺ has a very close chemical relation to H₂,” says Stephan Schlemmer from the University of Cologne who proposed the observations. “For the first time we could now observe both variants of H₂D⁺, which allowed us to indirectly determine the ratio of ortho H₂ to para H₂. Reading this chemical clock we find an age of at least one million years for the parental cloud that is right now giving birth to Sun-like stars.” This result is questioning theories of rapid star formation.

The astronomical observations were very challenging. The relevant spectral line of para-H₂D⁺ lies in the far infrared wavelength range (at 219 µm), where the Earth’s atmosphere absorbs most of the radiation. “Its first unambiguous detection was only possible due to the unique capabilities of the GREAT (German REceiver for Astronomy at Terahertz Frequencies) instrument on board the SOFIA (Stratospheric Observatory for Infrared Astronomy) aircraft,” says Jürgen Stutzki, whose group at the University of Cologne is involved in the development of GREAT. SOFIA is a joint project between NASA and the DLR (Deutsches Zentrum für Luft- und Raumfahrt) carrying a 2.7 meter diameter telescope as high as 13.7 km, above the atmosphere’s absorbing layers. The team also observed the corresponding rotational line of ortho-H₂D⁺ at mm-wavelengths with the ground-based APEX (Atacama Pathfinder Experiment) telescope located in the Chilean Andes at an altitude of 5100 m. APEX Principal Investigator, the MPIfR’s Karl Menten points out that “It’s great to see the synergy between both telescopes!”

The age of this star-forming cloud, which is located in the Ophiuchus constellation at a distance of around 400 light years, was determined by comparing the data from the telescopes with extensive computer simulations of the chemistry that is changing with time. “The simulations allow us a detailed look at the movement of our H₂D⁺ clock,” explains Jorma Harju of the University of Helsinki. “We find that our new chemical clock is more precise than any of those used previously. Even more importantly, it keeps running when other clocks have already stopped working.” The team is confident that their new method will help to date other stellar birthplaces.

<p>The GREAT far-infrared spectrometer is mounted to the telescope flange, inside the pressurized cabin. During observations GREAT rotates ±20 degrees from the vertical.</p>

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The GREAT far-infrared spectrometer is mounted to the telescope flange, inside the pressurized cabin. During … [more]
© R. Güsten

Background Information:

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a joint project of the National Aeronautics and Space Administration (NASA) and the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR; German Aerospace Centre, grant: 50OK0901). The German component of the SOFIA project is being carried out under the auspices of DLR, with funds provided by the Federal Ministry of Economics and Technology (Bundesministerium für Wirtschaft und Technologie; BMWi) under a resolution passed by the German Federal Parliament, and with funding from the State of Baden-Württemberg and the University of Stuttgart. Scientific operations are coordinated by the German SOFIA Institute (DSI) at the University of Stuttgart and the Universities Space Research Association (USRA) headquartered in Columbia, Maryland, U.S.A.

GREAT, the German Receiver for Astronomy at Terahertz Frequencies, is a receiver for spectroscopic observations in the far infrared spectral regime at frequencies between 1.25 and 5 terahertz (wavelengths of 60 to 220 microns), which are not accessible from the ground due to absorption by water vapor in the atmosphere. GREAT is a first-generation German SOFIA instrument, developed and maintained by the Max-Planck Institute for Radio Astronomy (MPIfR) and KOSMA at the University of Cologne, in collaboration with the Max Planck Institute for Solar System Research and the DLR Institute of Planetary Research. Rolf Guesten (MPIfR) is the principal investigator for GREAT. The development of the instrument was financed by the participating institutes, the Max Planck Society and the German Research Foundation (Deutsche Forschungsgemeinschaft; DFG).

APEX, the Atacama Pathfinder Experiment, is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), Onsala Space Observatory (OSO), and the European Southern Observatory (ESO) to construct and operate a modified prototype antenna of ALMA (Atacama Large Millimetre Array) as a single dish on the Chajnantor plateau at an altitude of 5,100 meters above sea level (Atacama Desert, Chile). The telescope was manufactured by VERTEX Antennentechnik in Duisburg, Germany. The operation of the telescope is entrusted to ESO.

Interstellar Molecules are branching out

Detection of iso-propyl cyanide with ALMA, the Atacama Large Millimeter/submillimeter Array

September 25, 2014

Scientists from the Max Planck Institute for Radio Astronomy (Bonn, Germany), Cornell University (USA), and the University of Cologne (Germany) have for the first time detected a carbon-bearing molecule with a “branched” structure in interstellar space. The molecule, iso-propyl cyanide (i-C₃H₇CN), was discovered in a giant gas cloud called Sagittarius B2, a region of ongoing star formation close to the center of our galaxy that is a hot-spot for molecule-hunting astronomers. The branched structure of the carbon atoms within the iso-propyl cyanide molecule is unlike the straight-chain carbon backbone of other molecules that have been detected so far, including its sister molecule normal-propyl cyanide. The discovery of iso-propyl cyanide opens a new frontier in the complexity of molecules found in regions of star formation, and bodes well for the presence of amino acids, for which this branched structure is a key characteristic.
The results are published in this week’s issue of “Science”.

<p><em>Dust and molecules in the central region of our Galaxy: The background image shows the dust emission in a combination of data obtained with the APEX telescope and the Planck space observatory at a wavelength around 860 micrometers. The organic molecule iso-propyl cyanide with a branched carbon backbone (i-C<sub>3</sub>H<sub>7</sub>CN, left) as well as its straight-chain isomer normal-propyl cyanide (n-C<sub>3</sub>H<sub>7</sub>CN, right) were both detected with the Atacama Large Millimeter/submillimeter Array in the star-forming region Sgr B2, about 300 light years away from the Galactic center Sgr A*. </em></p>

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Dust and molecules in the central region of our Galaxy: The background image shows the dust emission in a combination of … [more]
© MPIfR/A. Weiß (background image), University of Cologne/M. Koerber (molecular models), MPIfR/A. Belloche (montage).

While various types of molecules have been detected in space, the kind of hydrogen-rich, carbon-bearing (organic) molecules that are most closely related to the ones necessary for life on Earth appear to be most plentiful in the gas clouds from which new stars are being formed. “Understanding the production of organic material at the early stages of star formation is critical to piecing together the gradual progression from simple molecules to potentially life-bearing chemistry,” says Arnaud Belloche from the Max Planck Institute for Radio Astronomy, the lead author of the paper.

The search for molecules in interstellar space began in the 1960’s, and around 180 different molecular species have been discovered so far. Each type of molecule emits light at particular wavelengths, in its own characteristic pattern, or spectrum, acting like a fingerprint that allows it to be detected in space using radio telescopes.

Until now, the organic molecules discovered in star-forming regions have shared one major structural characteristic: they each consist of a “backbone” of carbon atoms that are arranged in a single and more or less straight chain. The new molecule discovered by the team, iso-propyl cyanide, is unique in that its underlying carbon structure branches off in a separate strand. “This is the first ever interstellar detection of a molecule with a branched carbon backbone,” says Holger Müller, a spectroscopist at the University of Cologne and co-author on the paper, who measured the spectral fingerprint of the molecule in the laboratory, allowing it to be detected in space.

But it is not just the structure of the molecule that surprised the team – it is also plentiful, at almost half the abundance of its straight-chain sister molecule, normal-propyl cyanide (n-C₃H₇CN), which the team had already detected using the single-dish radio telescope of the Institut de Radioastronomie Millimétrique (IRAM) a few years ago. “The enormous abundance of iso-propyl cyanide suggests that branched molecules may in fact be the rule, rather than the exception, in the interstellar medium,” says Robin Garrod, an astrochemist at Cornell University and a co-author of the paper.

<p><em>The central region of the Milky Way above the antennas of the ALMA observatory. The direction to the Galactic center is halfway between Antares, the brightest star visible in the picture and the tip of an ALMA antenna in the foreground (second from right).</em></p>

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The central region of the Milky Way above the antennas of the ALMA observatory. The direction to the Galactic center is … [more]
© Y. Beletsky (LCO)/ESO

The team used the Atacama Large Millimeter/submillimeter Array (ALMA), in Chile, to probe the molecular content of the star-forming region Sagittarius B2 (Sgr B2). This region is located close to the Galactic Center, at a distance of about 27,000 light years from the Sun, and is uniquely rich in emission from complex interstellar organic molecules. “Thanks to the new capabilities offered by ALMA, we were able to perform a full spectral survey toward Sgr B2 at wavelengths between 2.7 and 3.6 mm, with sensitivity and spatial resolution ten times greater than our previous survey,” explains Belloche. “But this took only a tenth of the time.” The team used this spectral survey to search systematically for the fingerprints of new interstellar molecules. “By employing predictions from the Cologne Database for Molecular Spectroscopy, we could identify emission features from both varieties of propyl cyanide,” says Müller. As many as 50 individual features for i-propyl cyanide and even 120 for n-propyl cyanide were unambiguously identified in the ALMA spectrum of Sgr B2. The two molecules, each consisting of 12 atoms, are also the joint-largest molecules yet detected in any star-forming region.

The team constructed computational models that simulate the chemistry of formation of the molecules detected in Sgr B2. In common with many other complex organics, both forms of propyl cyanide were found to be efficiently formed on the surfaces of interstellar dust grains. “But,” says Garrod, “the models indicate that for molecules large enough to produce branched side-chain structure, these may be the prevalent forms. The detection of the next member of the alkyl cyanide series, n-butyl cyanide (n-C₄H₉CN), and its three branched isomers would allow us to test this idea”.

“Amino acids identified in meteorites have a composition that suggests they originate in the interstellar medium,” adds Belloche. “Although no interstellar amino acids have yet been found, interstellar chemistry may be responsible for the production of a wide range of important complex molecules that eventually find their way to planetary surfaces.”

“The detection of iso-propyl cyanide tells us that amino acids could indeed be present in the interstellar medium because the side-chain structure is a key characteristic of these molecules”, says Karl Menten, director at MPIfR and head of its Millimeter and Submillimeter Astronomy research department. “Amino acids have already been identified in meteorites and we hope to detect them in the interstellar medium in the future”, he concludes.

GREAT Far-IR Spectrometer Opens Window to New Science Opportunities

4.7 Terahertz Spectroscopy with SOFIA, the airborne observatory

June 11, 2014

With successful commissioning of its high-frequency channel, the GREAT (German Receiver for Astronomy at Terahertz Frequencies) far-infrared spectrometer onboard SOFIA is ready to explore new realms.

First-light observations by the GREAT H-channel on SOFIA: map of planetary nebula NGC 7027 in the neutral oxygen emission line at 63 microns. The effective angular resolution is indicated by the gray circle at lower left.

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First-light observations by the GREAT H-channel on SOFIA: map of planetary nebula NGC 7027 in the neutral oxygen … [more]

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High-resolution spectrum of OI toward the center of NGC 7027 showing complex velocity structure in the outflow.

The new so-called H-channel was first tested during SOFIA flights on May 14, 16, and 17, and confirmed to be working perfectly. It is based upon an extremely sensitive superconductive detector and a novel “quantum cascade” terahertz laser. With that receiver added, the GREAT instrument is now capable of high-resolution spectroscopy of astrophysically important lines of atomic neutral oxygen [OI] at a wavelength of 63 μm (frequency of 4.74 TeraHertz).

First-light spectra were obtained towards planetary nebula NGC 7027 (Figure 1). That nebula is an expanding bubble of gas expelled by a dying star with approximately twice the mass of our Sun, 3,000 light-years away in the constellation of Cygnus. The nebula has been extensively studied at other wavelengths, but only GREAT can resolve the velocities of the expanding envelope in the [OI] line. The spectrum (Figure 2) represents only 2 minutes of integration, illustrating the superb sensitivity of the GREAT instrument carried into the stratosphere by SOFIA.

The GREAT far-infrared spectrometer (gold vertical structure in the foreground) is mounted to SOFIA's telescope during the observatory's first southern hemisphere deployment.

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The GREAT far-infrared spectrometer (gold vertical structure in the foreground) is mounted to SOFIA’s telescope during … [more]

GREAT is a Principal Investigator-class instrument for SOFIA, developed and maintained by the Max Planck Institute for Radio Astronomy (PI: Rolf Guesten) and KOSMA at the University of Cologne (Co-I: Juergen Stutzki), in collaboration with the DLR Institute of Planetary Research (Co-I: Heinz-Wilhelm Huebers) and the Max Planck Institute for Solar System Research (Co-I: Paul Hartogh).

SOFIA is a joint project of NASA and the German Aerospace Center (DLR). The aircraft is based at NASA Armstrong Flight Research Center that manages the program. NASA Ames Research Center at Moffett Field, Calif., manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Md., and the German SOFIA Institute (DSI) at the University of Stuttgart.

Hidden Nurseries in the Milky Way

APEX reveals cradles of massive star-formation throughout our Galaxy

May 10, 2014

APEX, the Atacama Pathfinder Experiment, is a telescope of 12 m diameter at an exceptional site on Earth: the Chajnantor plateau is located 5100 m above sea level in the Atacama desert in Chile. It was used to map the whole inner part of the plane of our Milky Way, ranging from the Southern constellations of Vela and Carina all the way to the Northern constellations of Aquila and the great Cygnus rift. The APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) mapped the Galactic Plane at a wavelength of 0.87 mm. Cold interstellar dust emits strongly in this part of the electromagnetic spectrum, called the sub-millimeter range, while it is blocking visible and infrared wavelengths. The survey has revealed an unprecedented number of cold dense clumps of gas and dust as the cradles of massive stars, thus providing a complete view of their birthplaces in the Milky Way. Based on this census, an international team of scientists led by Timea Csengeri from the Max Planck Institute for Radio Astronomy in Bonn has estimated the time scale for these nurseries to grow stars. This has been found to be a very fast process: with only 75,000 years on average it is much shorter than the corresponding time scales typically found for nurseries of lower mass stars.

The ATLASGAL survey coverstwo thirds of the surface area of the Galaxy within 50,000 light years of the Galactic center. Thus it includes practically all (97%) of the star-formation within the Solar Circle, i.e. the inner Galaxy. The image displays a part of ATLASGAL, a region located between the giant molecular complexes called W33 and M17 in the Sagittarius constellation. Zooms in color scale show the 3-color emission from the mid-infrared GLIMPSE survey, and sub-millimeter dust emission from ATLASGAL is shown in red and traced with contours. One region corresponds to a cold, pristine massive clump (upper left inset), and another one to a young massive star (upper right inset). Both objects have sizes of only a few light-years across. In the lower right inset we present a schematic of the Milky Way and show the position of the Solar Circle (green) and region of the Galaxy covered by ATLASGAL (shaded region).

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The ATLASGAL survey coverstwo thirds of the surface area of the Galaxy within 50,000 light years of the Galactic center … [more]

Stars significantly more massive than the Sun end their fast and furious lives in violent supernova explosions producing the heavy elements in the Universe. Throughout their lives, their powerful stellar winds and high-energy radiation shape their local environments and have a significant impact on the appearance and future evolution of their host galaxies. These stars form at the densest and coldest places in the Milky Way deeply embedded in dust cocoons, which are so dense that they absorb most of the radiation from the young stars within. It is in these dense cocoons of gas and dust, hidden from visible and infrared wavelengths, where the next generation of stars are being born.

An international team of astronomers used the APEX telescope with its sub-millimeter camera, LABOCA, built at the Max Planck Institute for Radio Astronomy (MPIfR), to survey the inner Galaxy to search for the birthplaces of the most massive stars currently forming in the Milky Way. The APEX telescope is located on the Chajnantor Plateau in Chile at 5100 m altitude, which is one of the few places on Earth where observations at sub-millimeter wavelengths are possible. The ATLASGAL survey covers more than 420 square degrees of the Galactic plane, which corresponds to 97% of the inner Galaxy within the Solar circle. Thus it includes large sections of all four spiral arms, and approximately two thirds of the entire molecular disc of the Milky Way (see lower right inset of Fig. 1). This data set therefore includes the majority of all massive star forming nurseries in the Galaxy and is being used to construct a 3D map of the Milky Way.

The APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) provides an unprecedented census of the cold and dense environments where the most massive stars in our Galaxy begin their lives. The material in these stellar nurseries is so dense that optical and infrared light emitted from the embedded young high-mass stars cannot escape. Therefore, the earliest stages of star formation are effectively hidden at these short wavelengths and longer wavelengths are required to probe these regions. The ATLASGAL survey detects emission at sub-millimeter wavelengths, which is dominated by emission from cold dust. It provides a detailed view of the birthplaces where the next generation of massive stars is being formed.

As these dusty corners of our Galaxy are very difficult to access, such surveys provide the large scale coverage to search for the stellar nurseries forming the most massive stars in our Galaxy. “Our team has now analyzed this survey revealing the largest sample of the so-far hidden places of massive star-formation”, states Timea Csengeri from MPIfR, the lead author of the study. “We have identified many new potential sites where the most massive stars currently form in our Galaxy.”

Providing an unprecedented statistics, scientists reveal that the processes to build up the cold, dense sites where the most massive stars in our Galaxy form, occur rapidly, taking place within only 75,000 years, which is much shorter than the corresponding timescales in nurseries of lower mass –stars like our Sun. This is the first global indication that star-formation is a fast process in our Galaxy.

“We characterized these places to search for signatures revealing how massive stars form within them,” continues James Urquhart, also from MPIfR. “The fast and furious life of the most massive stars was already known. And now we could also show that it is initiated by a pretty short infancy within their stellar cocoons.” The lifetime of massive stars is about 1000 times shorter than the lifetime of stars like the Sun, and the new results reveal that they also form on short timescales and in a much more dynamic star formation process.

APEX and the night sky. The image shows the southern part of the Milky Way including the pointer stars, the Southern Cross and the Eta Carina region (bright reddish nebula above the cross). The ATLASGAL survey covers the southern Milky Way to the Carina region.

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APEX and the night sky. The image shows the southern part of the Milky Way including the pointer stars, the Southern … [more]

“Only telescopes at exceptional locations, such as the high and dry Chajnantor Plateau in Chile at 5100 m are capable to observe in this frequency range”, adds Frederic Schuller from ESO, co-author of the study. “This is the largest area in the sky surveyed from a ground-based telescope in the sub-millimeter wavelength regime”.

“ATLASGAL also provides a “finding chart” for the most extreme dust cocoons, where the innermost processes of stellar birth can be studied at much higher angular-resolution with the new ALMA interferometer, located just next to the APEX telescope” concludes Friedrich Wyrowski, the APEX project scientist at MPIfR.

SOFIA Has Gone South

Airborne Observatory Investigates the Southern Sky from New Zealand

July 18, 2013

For the first time SOFIA, the “Stratospheric Observatory for Infrared Astronomy”, has been deployed to the southern hemisphere. Based at the airport of Christchurch, New Zealand for three weeks, SOFIA has started to study celestial objects that are uniquely observable on southern flight routes. On the morning of July 18 New Zealand time, SOFIA landed after the first of its planned 9 science flights that included studies of the Magellanic Clouds, neighbours to the Milky Way galaxy, and of the circumnuclear disk orbiting the black hole in the center of our Galaxy. The GREAT instrument used in these flights has been developed by a consortium of German research institutes led by Rolf Güsten (Max Planck Institute for Radio Astronomy).

SOFIA, the "Stratospheric Observatory for Infrared Astronomy" has been deployed to a base at Christchurch, New Zealand, for a series of science flights to observe astronomical targets in the southern sky. The image shows SOFIA in the United States Antarctic Program (USAP) area of Christchurch International Airport.

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SOFIA, the “Stratospheric Observatory for Infrared Astronomy” has been deployed to a base at Christchurch, New Zealand … [more]

As a joint project between NASA and the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR), SOFIA carries a telescope with an effective diameter of 2.5 meters in a modified Boeing 747SP aircraft and is thus the world’s largest airborne observatory. SOFIA flies at altitudes as high as 13,700 meters (45,000 feet) to provide access to astronomical signals at far-infrared wavelengths that would otherwise be blocked due to absorption by water vapor in the atmosphere.

A crew of about 60 scientists, technicians, and engineers from the U.S. and Germany plus two shifts of NASA pilots will operate SOFIA while based in New Zealand.

The GREAT (German Receiver for Astronomy at Terahertz Frequencies) far-infrared spectrometer, developed jointly by the MPI für Radioastronomie, Bonn, and the Universität zu Köln, will be mounted on the telescope during the entire deployment.

“The more than 30 publications of scientific results from the first observing campaigns with SOFIA’s first generation of instruments, GREAT and (U.S.) FORCAST, in 2011 in the northern hemisphere have already demonstrated the tremendous scientific potential of this observatory,” said Alois Himmes, DLR’s SOFIA program manager. “The current (and future) deployments to New Zealand will expand this potential substantially,” he added.

Some targets for astronomical investigations are only visible from the Earth's southern hemisphere. This photo of the southern sky, taken at Cerro Paranal in the Chilean Atacama Desert, shows a total of three galaxies: stars and gas from the inner Milky Way and the two Magellanic Clouds. The Large and Small Magellanic Clouds, two dwarf galaxies accompanying the Milky Way, are both targets of the first science flights of SOFIA starting from Christchurch, New Zealand.

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Some targets for astronomical investigations are only visible from the Earth’s southern hemisphere. This photo of the … [more]

On July 12 the airplane flew from its usual home at Palmdale, Califfornia (U.S.A.), via Hawaii, to New Zealand where it will be based until August 02. The scientific targets for the southern deployment of SOFIA include the Large and Small Magellanic Clouds, as well as objects in the central regions of the Milky Way. The two Magellanic Clouds, dwarf galaxies in the close neighbourhood of our Galaxy, are easily visible with the naked eye in the southern sky (Figure 2, they are named after explorer Ferdinand Magellan, one of the first Europeans to report seeing them). Their relative proximity allows detailed investigation of the stellar life cycles, from protostars to supernova remnants. Sites of prominent star formation will be studied during the deployment – sites well known from optical studies but barely explored at far-infrared wavelengths. For a number of science objectives the telescope will be pointing at the Milky Way’s center, which is much better and longer accessible from the southern hemisphere than from the north.

The Deutsches SOFIA Institut (DSI) of the University of Stuttgart manages the German contributions to SOFIA’s mission operations and scientific observations. A crew of 13 DSI colleagues will support the observatory’s first southern deployment with their expertise regarding the Infrared Telescope. “We plan to conduct up to three scientific flights per week,” explains Holger Jakob, head of the German telescope team. “Thus we will be quite busy during the deployment.”

The high spectral resolving power of the GREAT instrument is designed for studies of the interstellar gas and the stellar life cycle, from a protostar’s early embryonic phase when still embedded in its parental cloud, to deaths of evolved stars when their outer envelopes are ejected back to space, providing gas enriched with heavy elements that is “recycled” into later generations of stars and planets. “With the GREAT instrument on SOFIA the newest technology can be used for astronomical applications. This provides a continuing basis for astrophysical investigations in this particularly important wavelength range of far-infrared astronomy, following up on the successful ESA-mission Herschel” says Prof. Jürgen Stutzki, Universität zu Köln.

“The GREAT success to address new exiting science at far-infrared wavelengths has been demonstrated during SOFIA’s earlier, northern hemisphere science flights. Now we are turning the instrument to new frontiers such as the Magellanic Clouds, which are relatively deficient in heavy elements, including the Tarantula nebula (also known as 30 Doradus), the most active starburst known in the Local Group of Galaxies”, adds Rolf Güsten from the Max-Planck-Institut für Radioastronomie in Bonn, leader of the group of German researchers who developed GREAT.

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The GREAT far-infrared spectrometer (gold vertical structure in the foreground) is mounted to SOFIA’s telescope during … [more]

SOFIA’s deployment to the southern hemisphere shows the remarkable versatility of this observatory, the product of years of fruitful collaboration and cooperation between the U.S. and German space agencies”, says Paul Hertz, director of NASA’s Astrophysics Division. “This is just the first of a series of SOFIA scientific deployments envisioned over the course of the mission’s planned 20-year lifetime,” he concludes.

“We had a very successful flight tonight, excellent data on all targets”, said GREAT project leader Rolf Güsten immediately after the first science flight finished at Christchurch International Airport. “I have never seen a far-infrared sky as transparent as tonight – a few micron water only. That’s almost space!”

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GREAT, the German Receiver for Astronomy at Terahertz Frequencies is a receiver for spectroscopic observations in the far infrared spectral regime at frequencies between 1.25 and 5 terahertz (wavelengths of 60 to 220 microns), which are not accessible from the ground due to absorption by water vapor in the atmosphere. GREAT is a first-generation German SOFIA instrument, developed and maintained by the Max-Planck Institute for Radio Astronomy (MPIfR) and KOSMA at the University of Cologne, in collaboration with the Max Planck Institute for Solar System Research and the DLR Institute of Planetary Research. Rolf Guesten (MPIfR) is the principal investigator for GREAT. The development of the instrument was financed by the participating institutes, the Max Planck Society and the German Research Foundation (Deutsche Forschungsgemeinschaft; DFG).

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a joint project of the National Aeronautics and Space Administration (NASA) and the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR; German Aerospace Centre, grant: 50OK0901). The German component of the SOFIA project is being carried out under the auspices of DLR, with funds provided by the Federal Ministry of Economics and Technology (Bundesministerium für Wirtschaft und Technologie; BMWi) under a resolution passed by the German Federal Parliament, and with funding from the State of Baden-Württemberg and the University of Stuttgart. Scientific operations are coordinated by the German SOFIA Institute (DSI) at the University of Stuttgart and the Universities Space Research Association (USRA) headquartered in Columbia, Maryland, U.S.A.

SOFIA and the Southern Sky:
There is a number of unique objects in the southern sky, which are not visible from the Earth’s northern hemisphere. The nearest star, Alpha Centauri, in a distance of only 4.3 light years is among them, and also one of the best-known constellations in the sky, the Southern Cross. The Southern Cross together with the two pointer stars, Alpha and Beta Centauri, is actually forming a landmark in the southern sky which is similarly popular for people in the Southern hemisphere as the Big Dipper (constellation Ursa Major) for people in the Northern hemisphere. Fig. 2 shows the Southern cross within the band of the Milky Way in the left part.
Other unique targets of the southern sky include the two nearest galaxies, the Magellanic Clouds, in distances of 160,000 light years (Large Magellanic Cloud, LMC) and 200,000 light years (Small Magellanic Cloud, SMC) and the nearest galaxy with an active nucleus, Centaurus A, in a distance of 12 million light years. The central area of our Milky Way is higher above the horizon and much better visible from the southern hemisphere.
During its first scientific flight from Christchurch/New Zealand, SOFIA has already targeted both, the Magellanic Clouds and the center of the Milky Way.

Orion’s Hidden Fiery Ribbon

May 15, 2013

Picture Release No. 1321 of European Southern Observatory (ESO). A dramatic new image of cosmic clouds in the constellation of Orion reveals what seems to be a fiery ribbon in the sky. The orange glow represents faint light coming from grains of cold interstellar dust, at wavelengths too long for human eyes to see. It was observed by the MPIfR-built & ESO-operated Atacama Pathfinder Experiment (APEX) in Chile.