Author Archives: evaschmelmer

IAU Prize for Doctoral Thesis of Gisela Ortiz

The IAU PhD Prize recognises the outstanding scientific achievement in astronomy by PhD students around the world. There are a series of awards, one for each of the IAU’s nine Divisions, with each division selecting a winner in its own field of astronomy.

The IAU Executive Committee awarded the IAU PhD Prize for 2017 in the Division A Fundamental Astronomy to Gisela Ortiz Leon, Instituto de Radioastronomía y Astrofísica, Mexico, for her research in Ultra-high precision astrometry with centimeter and millimeter very long baseline interferometry.

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Ancient Galaxy Megamergers

ALMA and APEX discover massive conglomerations of forming galaxies in the early Universe

April 25, 2018

Using the ALMA and APEX telescopes in Chile, two international research teams with participation from scientists of the Max Planck Institute for Radio Astronomy in Bonn, Germany, have uncovered startlingly dense concentrations of galaxies that are poised to merge, forming the cores of what will eventually become colossal galaxy clusters.
The results are presented in two research papers to appear in the journals Nature and The Astrophysical Journal.

Artist’s impression of of the actual configuration of galaxies in SPT 2349. Such mergers have been spotted using the ALMA and APEX telescopes and represent the formation of galaxies clusters, the most massive objects in the modern Universe.

© ESO/M. Kornmesser

The Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder Experiment (APEX) have peered deep into space — back to the time when the Universe was one tenth of its current age — and witnessed the beginnings of gargantuan cosmic pileups: the impending collisions of young, starburst galaxies. Astronomers thought that these events occurred around three billion years after the Big Bang, so they were surprised when the new observations revealed them happening when the Universe was only half that age! These ancient systems of galaxies are thought to be building the most massive structures in the known Universe: galaxy clusters.

Two international teams led by Tim Miller from Dalhousie University in Canada and Yale University in the US and Iván Oteo from the University of Edinburgh, United Kingdom, used both telescopes, ALMA and APEX, to uncover startlingly dense concentrations of galaxies that are poised to merge, forming the cores of what will eventually become colossal galaxy clusters.
Peering 90% of the way across the observable Universe, the first team observed a galaxy protocluster named SPT 2349-56. The light from this object began travelling to us when the Universe was about a tenth of its current age.
The individual galaxies in this dense cosmic pileup are starburst galaxies and the concentration of vigorous star formation in such a compact region makes this by far the most active region ever observed in the young Universe. As many as 15 000 stars are born there every year, compared to just one in our own Milky Way.

The Oteo team discovered a similar megamerger formed by ten dusty star-forming galaxies, nicknamed a “dusty red core” because of its very red colour, by combining observations from ALMA and the APEX.
These forming galaxy clusters were first spotted as faint smudges of light, using the South Pole Telescope and the Herschel Space Observatory. Subsequent APEX and ALMA observations showed that they had unusual structure and confirmed that their light originated much earlier than expected — only 1.5 billion years after the Big Bang.

The new high-resolution ALMA observations finally revealed that the two glows spotted by APEX and Herschel are not single objects, but are actually composed of fourteen and ten individual massive galaxies respectively, each within a radius comparable to the distance between the Milky Way and the neighbouring Magellanic Clouds.
The duration of the starburst event in each of the galaxies is short compared to the evolution time scale of the proto-cluster”, explains Axel Weiß from the Max Planck Institute for Radio Astronomy who is co-author on both publications. “The fact that we see so many starburst galaxies in both clusters at the same time suggests either a so far unknown mechanism to trigger the activity over several hundred thousand light years or the presence of gas flows from the cosmic web to replenish the gas supply in the active galaxies.

These discoveries by ALMA are only the tip of the iceberg. Additional observations with the APEX telescope show that the real number of star-forming galaxies is likely even three times higher. Ongoing observations with the MUSE instrument on ESO’s VLT are also identifying additional galaxies”, comments Carlos De Breuck, astronomer at ESO, the European Southern Observatory.

Current theoretical and computer models suggest that protoclusters as massive as these should have taken much longer to evolve. By using data from ALMA, with its superior resolution and sensitivity, as input to sophisticated computer simulations, the researchers are able to study cluster formation less than 1.5 billion years after the Big Bang.
How this assembly of galaxies got so big so fast is a mystery. It wasn’t built up gradually over billions of years, as astronomers might expect. This discovery provides a great opportunity to study how massive galaxies came together to build enormous galaxy clusters“, concludes Tim Miller, a PhD candidate at Yale University and lead author of the paper in Nature.

<p><em>Montage with three views of </em><em>the observations of SPT 2349, </em><em>a distant group of interacting and merging galaxies in the early Universe. The left image is a wide view from the South Pole Telescope that reveals just a bright spot. The central view is from Atacama Pathfinder Experiment (APEX) that reveals more details. The right picture is from the Atacama Large Millimeter/submillimeter Array (ALMA) and shows that the object is actually a group of 14 merging galaxies in the process of forming a galaxy cluster.</em></p> <p><em> </em></p>
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Montage with three views of the observations of SPT 2349, a distant group of interacting and merging galaxies in the early Universe. The left image is a wide view from the South Pole Telescope that reveals just a bright spot. The central view is from Atacama Pathfinder Experiment (APEX) that reveals more details. The right picture is from the Atacama Large Millimeter/submillimeter Array (ALMA) and shows that the object is actually a group of 14 merging galaxies in the process of forming a galaxy cluster.
© ESO/ALMA (ESO/NAOJ/NRAO)/Miller et al.

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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 metres 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 Atacama Large Millimeter/submillimeter Array (ALMA) is an international partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan, together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. ALMA -the largest astronomical project in existence- is a single telescope of revolutionary design, composed of 66 high precision antennas located on the Chajnantor plateau, 5000 meters altitude in northern Chile.

MPIfR affiliations: Axel Weiß is co-author in both publications and Maria Strandet, who just received her PhD in the IMPRS research school at MPIfR, is co-author in the Nature paper.

https://www.mpifr-bonn.mpg.de/pressreleases/2018/6

The Far Side of the Milky Way

Mapping Spiral Structure for an Improved Picture of our Home Galaxy

October 12, 2017

Astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and the Harvard-Smithsonian Center for Astrophysics have directly measured the distance to a star-forming region on the opposite side of our Milky Way Galaxy from the Sun, using the Very Long Baseline Array. Their achievement reaches deep into the Milky Way’s terra incognita and nearly doubles the previous record for distance measurement within our Galaxy.
Their results are published in the 13 October issue of the journal Science.

<p class="Body"><em>Artist’s view of the Milky Way with the location of the Sun and the star forming region (maser source G007.47+00.05) at the opposite side in the Scutum-Centaurus spiral arm.   </em></p>
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Artist’s view of the Milky Way with the location of the Sun and the star forming region (maser source G007.47+00.05) at[more]

© Bill Saxton, NRAO/AUI/NSF; Robert Hurt, NASA.

Distance measurements are crucial for an understanding of the structure of the Milky Way. Most of our Galaxy’s material, consisting principally of stars, gas, and dust, lies within a flattened disk, in which our Solar System is embedded. Because we cannot see our Galaxy face-on, its structure, including the shape of its spiral arms, can only be mapped by measuring distances to objects elsewhere in the Galaxy.

The astronomers used a technique called trigonometric parallax, first applied by Friedrich Wilhelm Bessel in 1838 to measure the distance to the star 61 Cygni in the constellation of the Swan. This technique measures the apparent shift in the sky position of a celestial object as seen from opposite sides of the Earth’s orbit around the Sun. This effect can be demonstrated by holding a finger in front of one’s nose and alternately closing each eye — the finger appears to jump from side to side.

Measuring the angle of an object’s apparent shift in position this way allows astronomers to use simple trigonometry to directly calculate the distance to that object. The smaller the measured angle, the greater the distance is. In the framework of the Bar and Spiral Structure Legacy (BeSSeL) Survey, it is now possible to measure parallaxes a thousand times more accurate than Friedrich Bessel. The Very Long Baseline Array (VLBA), a continent-wide radio telescope system, with ten dish antennas distributed across North America, Hawaii, and the Caribbean, can measure the minuscule angles associated with great distances. In this case, the measurement was roughly equal to the angular size of a baseball on the Moon.
“Using the VLBA, we now can accurately map the whole extent of our Galaxy,” says Alberto Sanna, of the Max Planck Institute for Radio Astronomy in Germany (MPIfR).

The new VLBA observations, made in 2014 and 2015, measured a distance of more than 66,000 light-years to the star-forming region G007.47+00.05 on the opposite side of the Milky Way from the Sun, well past the Galaxy’s center in a distance of 27,000 light-years. The previous record for a parallax measurement was about 36,000 light-years.
“Most of the stars and gas in our Galaxy are within this newly-measured distance from the Sun. With the VLBA, we now have the capability to measure enough distances to accurately trace the Galaxy’s spiral arms and learn their true shapes,” Sanna explains.

The VLBA observations measured the distance to a region where new stars are being formed. Such regions include areas where molecules of water and methanol act as natural amplifiers of radio signals — masers, the radio-wave equivalent of lasers for light waves. This effect makes the radio signals bright and readily observable with radio telescopes.
The Milky Way has hundreds of such star-forming regions that include masers. “So we have plenty of ‘mileposts’ to use for our mapping project. But this one is special: Looking all the way through the Milky Way, past its center, way out into the other side”, says the MPIfR’s Karl Menten.

The astronomers’ goal is to finally reveal what our own Galaxy looks like if we could leave it, travel outward perhaps a million light-years, and view it face-on, rather than along the plane of its disk. This task will require many more observations and much painstaking work, but, the scientists say, the tools for the job now are in hand. How long will it take?
“Within the next 10 years, we should have a fairly complete picture,” predicts Mark Reid of the Harvard-Smithsonian Center for Astrophysics.

[DF/njn]

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The research team consists of Alberto Sanna of the Max Planck Institute for Radio Astronomy (MPIfR), the first author, along with colleagues Mark Reid and Thomas Dame of the Harvard-Smithsonian Center for Astrophysics and Karl Menten and Andreas Brunthaler, also of the MPIfR. They report their findings in the 13 October issue of the journal Science.

The Long Baseline Observatory (LBO) runs the “Very Long Baseline Array” (VLBA) as a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

The BeSSeL Survey (Bar and Spiral Structure Legacy Survey) is a VLBA Key Science project. The survey is named in honor of Friedrich Wilhelm Bessel (1784-1846) who measured the first stellar parallax in 1838. The goal of the survey is to study the spiral structure and kinematics of the Milky Way.

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Distance determination by measuring the angle of apparent shift in an object’s position, as seen from opposite sides of[more]

Mapping Cold Dust in the Universe

ATLASGAL Survey of Southern Milky Way Completed

February 24, 2016

Spectacular new images of the Milky Way have been released to mark the completion of the APEX Telescope Large Area Survey of the Galaxy. The APEX telescope in Chile, a collaboration between the Max Planck Institute for Radio Astronomy in Bonn, Germany, the Swedish Onsala Space Observatory, and the European Southern Observatory, has mapped the full area of the Galactic Plane visible from the southern hemisphere for the first time at submillimetre wavelengths (between infrared light and radio waves) and in finer detail than recent space-based surveys. The pioneering 12-metre APEX telescope allows astronomers to study the cold Universe: gas, dust and other celestial objects that are only a few tens of degrees above absolute zero.
<p><em>Three areas of the Galactic plane as seen by the APEX LABOCA camera merged with large-scale images from the Planck satellite. Above: 6 x 3 degree field centered on the Galactic centre (constellation: Sagittarius). The bright source left of the middle is Sgr B2. Lower left: Field towards constellation &ldquo;Scorpius&rdquo; with NGC 6334 as brightest source (overlap with Fig. 2). Lower right: field towards constellation &ldquo;Scutum&rdquo;. </em></p>
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Three areas of the Galactic plane as seen by the APEX LABOCA camera merged with large-scale images from the Planck[more]
© ATLASGAL-Konsortium/Csengeri et al. 2016, A&A 585, A104.

APEX, the Atacama Pathfinder EXperiment telescope, is located at 5100 metres altitude on the Chajnantor Plateau in Chile’s Atacama region. The APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) took advantage of the unique characteristics of the telescope to provide a detailed view of the distribution of cold dense gas along the plane of the Milky Way galaxy. The complete survey includes most of the regions of star formation in the Milky Way.

The ATLASGAL maps cover an area of sky 140 degrees long and 3 degrees wide. This survey is the single most successful APEX large programme with more than 69 associated science papers already published, and its legacy will expand much further with all the reduced data products now available for the full astronomical community.
At the heart of APEX are its sensitive instruments. One of these, LABOCA (the LArge BOlometer Camera), the largest such detector in the southern hemisphere, was used for the ATLASGAL survey. LABOCA, built at the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, measures incoming radiation by registering the tiny rise in temperature it causes and can detect emission from the cold dark dust bands obscuring the stellar light.
“If we combine the high spatial resolution ATLASGAL data with observations from ESA’s Planck satellite, the resulting data reach space quality with a 20 times higher resolution”, says Axel Weiß from MPIfR. This allows astronomers to detect emission spread over a larger area of sky and to estimate the fraction of dense gas in the inner Galaxy. The ATLASGAL data were also used to create a complete census of cold and massive clouds where new generations of stars are forming.

“ATLASGAL provides exciting insights into where the next generation of high-mass stars and clusters form. By combining these with observations from Planck, we can now obtain a link to the large scale structures of giant molecular clouds”, remarks Timea Csengeri, also from MPIfR, responsible for combining the LABOCA and Planck data.

The APEX telescope recently celebrated ten years of successful research on the cold Universe. It plays an important role not only as pathfinder, but also as a complementary instrument for ALMA, the Atacama Large Millimeter/submillimeter Array, also on the Chajnantor Plateau. APEX is based on a prototype antenna constructed for the ALMA project, and it has found many targets that ALMA can study in great detail.

“ATLASGAL has allowed us to have a new and transformational look at the dense interstellar medium of our own Milky Way”, says Leonardo Testi from ESO, who is a member of the ATLASGAL team and the European Project Scientist for the ALMA project. “The new release of the full survey opens up the possibility to mine this marvelous dataset for new discoveries. Many teams of scientists are already using the ATLASGAL data to plan for detailed ALMA follow-up.”

“Modern astronomy always uses a multi-wavelength approach. ATLASGAL adds a view at the cold Universe, revealing the cradles of stars”, concludes Karl Menten from MPIfR, the APEX principal investigator.

<p><em>Image of the Milky Way in the direction of the constellation Scorpius with the NGC 6334 (Cat&rsquo;s Paw Nebula, upper left) and the emission nebula RCW 120 (upper right). The APEX data, at a wavelength of 0.87 millimetres, shows up in red and the background blue image was imaged at shorter infrared wavelengths by the NASA Spitzer Space Telescope as part of the GLIMPSE survey.</em></p>
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Image of the Milky Way in the direction of the constellation Scorpius with the NGC 6334 (Cat’s Paw Nebula, upper left)[more]
© ESO/APEX/ATLASGAL consortium/NASA/GLIMPSE consortium

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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 metres 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.

ATLASGAL , the APEX Telescope Large Area Survey of the Galaxy, is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Max Planck Institute for Astronomy (MPA), ESO, and the University of Chile.

ALMA, the Atacama Large Millimeter/submillimeter Array, is a partnership of the ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

https://www.mpifr-bonn.mpg.de/pressreleases/2016/3

Hot Science of the Cold Universe

The “Atacama Pathfinder Experiment” in Chile starts its second decade

February 09, 2016

During 10 years of operation, the Atacama Pathfinder Experiment (APEX) 12 m submillimeter telescope has significantly contributed to a wide variety of astronomy science areas, ranging from the discoveries of new interstellar molecules to large and deep imaging of the submillimeter sky, leading to insights into star formation from our Milky Way to distant starburst galaxies in the early Universe.

On the occasion of this anniversary, a celebration was held at the APEX base station in Sequitor, San Pedro de Atacama, including a visit to the APEX telescope at the Chajnantor plateau, 5100 m above sea level.

Guests of the event visiting the 12 m APEX telescope, 5100 m above sea level in the Chilean Atacama desert.
Guests of the event visiting the 12 m APEX telescope, 5100 m above sea level in the Chilean Atacama desert.

The Atacama Pathfinder Experiment (APEX) is a radio telescope of 12 m diameter for observations at submillimeter wavelengths. It was built at a very specific site, the Chajnantor plateau in the Atacama desert in Northern Chile, at an altitude of more than 5000 m above sea level, thus providing access to the otherwise blocked submillimeter range of the electromagnetic spectrum. The Chajnantor plateau also hosts the telescopes of the Atacama Large Millimeter/submillimeter Array (ALMA).

On January 25-26, the 10th anniversary of APEX was celebrated at the APEX base station in Sequitor, San Pedro de Atacama, at a better accessible altitude of only 2500 m above sea level. A number of special guests were present at the occasion, including the German ambassador in Chile, Rolf Schulze, the President of the Max-Planck-Gesellschaft, Prof. Martin Stratmann, and the Director General of the European Southern Observatory (ESO), Prof. Tim de Zeeuw. For the partners in the APEX collaboration, principal investigator Prof. Karl Menten and APEX project manager Dr. Rolf Güsten from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, and Prof. John Conway, Director of the Swedish Onsala Space Observatory (OSO) were attending the event. Fig. 1 shows the group of visitors at the high-altitude APEX site.

“In designing and operating APEX, ESO, OSO and the Max-Planck-Society set a perfect example of how long-term international collaboration can push the limits in astronomy”, said Martin Stratmann, President of the Max-Planck-Gesellschaft. Within the last ten years, about 2000 scientists have used data obtained with APEX for their science projects, resulting in more than 500 publications. Major APEX results include the discovery of five new molecules in the interstellar medium and also large surveys like ATLASGAL (the “APEX Telescope Large Area Survey of the Galaxy”), or LESS (the “LABOCA Survey of the Extended Chandra Deep Field South”).  Both have used the Large APEX Bolometer Camera (LABOCA) to measure the star formation activity in the Milky Way and at early epochs of the Universe. The APEX telescope and its access to the southern sky, in particular the inner part of the Milky Way and the Magellanic Clouds, is visualized in Fig. 2.

“It’s a great pleasure to celebrate a decade of astronomy with APEX, and ESO is very proud to be a member of this partnership. Not only is APEX an amazingly productive telescope in its own right, but it also wonderfully complements its more recent neighbour on Chajnantor, ALMA”, said ESO’s Director General, Tim de Zeeuw.

The APEX project was initiated by Karl Menten, Director at the MPIfR and head of its Millimeter and Submillimeter Astronomy Research department. The outstanding personal commitment of Karl Menten and Rolf Güsten was honored by Martin Stratmann at the 10-year anniversary ceremony in Sequitor: “I am deeply impressed by the passion and dedication that has led to the design and installation of APEX in 2003. Right at the very beginning of operation, APEX had proven its significance in studying the southern celestial hemisphere.”   Indeed, Menten recalls: “Right from the start, APEX has delivered wonderful data. And now, after ten years of research, APEX continues its important role not only as a pathfinder, but also as a complementary instrument for both, the ALMA interferometer here at Chajnantor and for the airborne observatory SOFIA.”

“From the engineering point of view, APEX has been a big success and its performance surpassed our expectations right from the beginning”, said Rolf Güsten. “Within the last ten years, we have continuously improved the performance of the telescope. Today the suite of state-of-the-art receivers and camera systems places the facility at the leading edge of submillimeter astronomy.” This continuous stream of innovative technology, constantly opening new scientific opportunities had always been an integral part of the project’s philosophy.

“The collaboration over the last ten years between three very different institutions has worked extremely well, each bringing its own strengths to the project. APEX has an exciting future, both doing its own unique science and in supporting ALMA observations”, said John Conway, the Director of OSO.

With the official opening of the ALMA, the importance of APEX has even increased in providing the complementary instrument to the high-resolution interferometer in order to image the large scale structure of molecular clouds and to select the target sources for a detailed investigation. “Whatever can be detected with APEX, can be imaged with superb precision with ALMA”, explained Karl Menten. “APEX truly is a pathfinder!”  The importance of the telescope’s complementary role to ALMA’s mission was also stressed by Martin Stratmann: “Astronomy and astrophysics have always been core elements of our research portfolio. However, the size and diversity of experiments led to fundamental changes in the way we approach our questions in practice. Nowadays, breakthroughs demand for a large network of complementary telescopes and instruments. APEX’ role as a pathfinder shows how the Max-Planck-Gesellschaft can strike out in a new and promising direction.”
Central part of the Galactic plane as seen by the APEX LABOCA camera merged with large-scale images from the Planck satellite (upper image). Southern part of the Milky Way including Southern Cross and the Eta Carina region (bright reddish nebula to the left and above the cross) and the two Magellanic Clouds (left of the telescope).
© Upper part: APEX Team/Csengeri et al. 2016; Lower part: ESO/Y. Beletsky (Optical Sky Image); ESO (APEX telescope); Composite image in the lower part created by C. Urquhart.

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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 metres 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.

First Successful Mission of upGREAT

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

Colliding Stars Explain Enigmatic Seventeenth Century Explosion

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. Zoom Image

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

 

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). Zoom Image

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

 

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

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 &ldquo;Brick&rdquo; as a shadow against the mid&ndash;infrared emission from warm gas and dust in the vicinity of the Galactic Center. The background false&ndash;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&ndash;hand panel.</em></p> Zoom Image

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 &ldquo;Snake&rdquo; is seen as a dark silhouette against the diffuse mid&ndash;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&ndash;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>&nbsp;</em></p> Zoom Image

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

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.

The Age of Stellar Nurseries

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 &ndash; 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. Zoom Image

Our own solar system formed many billion years ago when a dark interstellar cloud started to contract to form our … [more]
© Martina Markus & Oskar Asvany, based upon: NASA/Carla Thomas, C. Durán/ESO/APEX (MPIfR/ESO/OSO), ESO/Digitized Sky Survey 2/Davide De Martin, ESO/ L. Calçada, Bill Saxton, NRAO/AUI/NSF)

 

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 &plusmn;20 degrees from the vertical.</p> Zoom Image

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.