Funding of the Collaborative Research Centre (CRC) 956, entitled „Conditions and Impact of Star Formation – Astrophysics, Instrumentation and Laboratory Research“, has just been extended for another period of 4 years. CRC 956 explores basic star-formation processes and with that is contributing to worldwide exchange of extended knowledge between researchers. It is jointly run by the I. Physikalische Institut der Universität Köln, the Argelander-Institut für Astronomie der Universität Bonn and the Max-Planck-Institut für Radioastronomie in Bonn. [more]
Scaled Extension of the Planetary Walk at the Effelsberg Radio Telescope to the Brighest Star in the Night Sky
September 14, 2018
The 100-m radio telescope of the Max Planck Institute for Radio Astronomy (MPIfR) is located in a valley near Bad Münstereifel-Effelsberg about 40 kilometers southwest of Bonn in the Eifel area. Three astronomical trails in the surroundings of the observatory, named “Planetary Walk”, “Milky Way Walk” and “Galaxy Walk” illustrate the complete cosmic distance scale from nearby planets to distant galaxies. The connection between two of them, the Planetary Walk and the Milky Way Walk, is established by the common target station “Sirius”. In the scale of the Milky Way Walk, Sirius and our sun are neighbouring stations only 90 cm apart. In the scale of the Planetary Walk, the real distance of 8.6 light years between sun and Sirius amounts to 11,000 km, corresponding to the distance between two of MPIfR’s radio telescopes, the 100-m Effelsberg telescope in Germany and the 12-m APEX submillimeter telescope in Chile.
The 100-m radio telescope seen from the courtyard of the visitors’ pavilion. The yellow ball marks the station “Sun” of … [more]
Planet trails (in German: “Planetenwege”) are a nice way to illustrate cosmic distances and sizes within our solar system. They usually consist of nine or ten stations: the sun and eight planets, sometimes also including the dwarf planet Pluto. At the widely used scale of 1 : 1 billion the trail has a total length of almost 6 kilometers (distance between sun and Pluto). The sun scales to a diameter of 1.4 meters, and the Earth to 1.3 cm in a distance of 150 meters from the sun.
The Planetary Walk at the Effelsberg Radio Observatory is a bit smaller in size. Scaled 1 : 7.7 billion it covers the walking distance of about 800 meters from the parking area to the visitors’ pavilion where talks about radio astronomy and the telescope for groups of visitors are taking place. It starts with the dwarf planet Pluto at the parking lot and continues from there to the inner solar system – the rocky planets between Mars and Mercury and the sun itself can all be found at the courtyard of the visitors’ pavilion (Fig. 1).
Pluto (0 m) Visitors‘ Parking Area
Neptune (182 m) Road to Visitors‘ Pavilion
Uranus (389 m) Road to Visitors‘ Pavilion
Saturn (584 m) Road to Visitors‘ Pavilion
Jupiter (665 m) Road to Visitors‘ Pavilion
Mars (736 m) Road to Visitors‘ Pavilion
Earth (746 m) Court of Visitors‘ Pavilion
Venus (752 m) Court of Visitors‘ Pavilion
Mercury (758 m) Court of Visitors‘ Pavilion
Sun (766 m) Court of Visitors‘ Pavilion
Sirius (11,000 km) APEX Telescope, Atacama Desert, Chile
Table: Stations of the Planetary Walk at the Effelsberg Radio Telescope
Two additional walks, the Milky Way Walk and the Galaxy Walk, are extending the cosmic distance scale far beyond the solar system. The Milky Way Walk covers a total distance of 4 kilometers from the village Burgsahr in the nearby Sahrbach valley to a viewing spot immediately in front of the giant dish of the Effelsberg telescope. At a scale of 1 : 1017 (1 : 100 quadrillion) this corresponds to 40,000 light years through our galaxy. The Milky Way Walk includes a total of 18 stations from the outer regions along the sun to the Galactic centre at a distance of 25,000 light years from the sun.
The Galaxy Walk covers the truly large distances in the Universe. It has a total length of 2.6 km, starting in the forest behind the Effelsberg radio telescope and leading to a nearby hut (Martinshütte: the “hut at the edge of the Universe”). At a scale of 1 : 5 x 1022 (1 : 50 sextillions) it includes a total of 14 stations, the most distant one with a light travel time of 12.85 billion years. In other words: we observe light from that distant galaxy (named J1148+5251) coming from a time less than 1 billion years after the formation of the Universe.
In order to connect the three astronomy trails at Effelsberg there are two target stations included in two of the trails. The station “Andromeda Galaxy M 31” is contained in both, Milky Way Walk and Galaxy Walk. It is the closest large-scale spiral galaxy, a twin of our Milky Way at a distance of 2.5 million light years. For the Galaxy Walk that scales to 50 centimeters; Milky Way and Andromeda galaxy are the first two stations only 50 cm apart. At the scale of the Milky Way Walk, however, it corresponds to a distance of 250 kilometers.
The station “Andromeda Galaxy” is mounted at the “Haus der Astronomie” in Heidelberg, 250 km away from Effelsberg. This house is indeed shaped like a spiral galaxy, contains a 1 : 100 scale model of the Effelsberg telescope in its interior and the plaque “M 31” of the Effelsberg Milky Way Walk at the main entrance.
The connecting element between Planetary Walk and Milky Way Walk will be Sirius, the brightest star in the night sky. Sirius is a nearby star at a distance of only 8.6 light years from the sun. Both stations (Sun and Sirius) can be found on the Milky Way Walk: close to the village Binzenbach in the forest, the two plaques are just 90 centimeters apart.
For the Planetary Walk it is a different story: the distance of about 9 light years to Sirius scales to 11,000 kilometers! At the same scale, the dwarf planet Pluto is less than 800 meters away from the Sun. For the space probe Voyager 1, the most distant device built by mankind, it is less than 3 km in that scale, but even for the nearest star, Proxima Centauri, the distance is already more than 5000 km!
Coincidence by chance: the required value of 11,000 km for Sirius nicely meets the distance between two radio telescopes of the Max Planck Institute for Radio Astronomy, the 100-m radio telescope at Effelsberg and the APEX telescope in the Atacama desert in Chile which is jointly run by the MPIfR, the European Southern Observatory ESO and the Swedish Onsala Observatory.
The station “Sirius” of the Planetary Walk is mounted directly at the APEX site on the Chajnantor plateau 5100 m above sea level in the Atacama desert (Fig. 2). Sirius is the brightest star in the night sky, and it is visible from both sites, Effelsberg in Germany as well as APEX in Chile.
Since there is no general access to the APEX telescope on Chajnantor, Sirius is also presented in the nearby village San Pedro de Atacama, 2500 m above sea level. The San Pedro office of Alain Maury’s San Pedro de Atacama Celestial Explorations (SPACE) on Caracoles 400-2 presents the plaque in three different languages (Spanish, English and German).
“It is great that Sirius enables us to close the last remaining gap between our astronomical walks at the Effelsberg telescope”, concludes Norbert Junkes from MPIfR who regularly uses the cosmic distance scale in his talks for visitor groups at the Effelsberg site. “From the planets to stars and star forming regions in our Galaxy and further on to other galaxies, almost to the edge of the Universe – our three walks cover the complete range.”
Computer models of a fly-by show amazing resemblance to outer solar system features
August 09, 2018
The findings are published in the present issue of „The Astrophysical Journal“.
Artist’s concept of a solar system in the making with a protoplanetary disk surrounding a young star.
A near catastrophy billions of years ago might have shaped the outer parts of the solar system, while leaving the inner regions basically untouched. Researchers from the Max Planck Institute for Radio Astronomy in Bonn and their collaborators found that a close fly-by of another star can explain many of the features observed in the outer solar system. „Our group has been looking for years at what fly-bys can do to other planetary systems never considering that we actually might live right in such a system”, says Susanne Pfalzner, the leading author of the project. “The beauty of this model lies in its simplicity.”
The basic scenario of the formation of the solar system has long been known: our Sun was born from a collapsing cloud of gas and dust. In the process a flat disk was formed where not only large planets grew but also smaller objects like the asteroids, dwarf planets etc. Due to the flatness of the disk one would expect that the planets orbit in a single plane unless something dramatic happened afterwards. Looking at the solar system right to the orbit of Neptune everything seems fine: most planets move on fairly circular orbits and their orbital inclinations vary only slightly. However, beyond Neptune things become very messy. The biggest puzzle is the dwarf planet Sedna, which moves on an inclined, highly eccentric orbit and is so far outside, that it could not have been scattered by the planets there.
Just outside Neptune’s orbit another strange thing happens. The cumulative mass of all the objects dramatically drops by almost three orders of magnitude. This happens at approximately the same distance where everything becomes messy. It might be coincidental, but such conincidences are rare in Nature.
Susanne Pfalzner and her co-workers suggest that a star was approaching the Sun at an early stage, ‘stealing’ most of the outer material from the Sun’s protoplanetary disk and throwing what was left over into inclined and eccentric orbits. Performing thousands of computer simulations they checked what would happen when a star passes very close-by and perturbs the once larger disk. It turned out that the best fit for today’s outer solar systems comes from a perturbing star which had the same mass as the Sun or somewhat lighter (0.5-1 solar masses) and flew past at approximately 3 times the distance of Neptune.
However, the most surprising thing for the researchers was that a fly-by does not only explain the strange orbits of the objects of the outer solar system, but also gives a natural explanation for several unexplained features of our Solar System, including the mass ratio between Neptune and Uranus, and the existence of two distinct populations of Kuiper Belt objects.
“It is important to keep exploring all the possible avenues for explaining the structure of the outer solar system. The data are increasing but still too sparse, so theories have a lot of wiggle room to develop”, says Pedro Lacerda from the Queen’s University in Belfast, a co-author of the paper. “There is a certain danger that one theory crystallises as truth, not because it explains the data better but because of other pressures. Our paper shows that a lot of what we currently know can be explained by something as simple as a stellar fly-by.”
The big question is the likelihood for such an event. Nowadays, fly-bys even hundreds of times more distant are luckily rare. However, stars like our Sun are typically born in large groups of stars which are much more densely packed. Therefore, close fly-bys where significantly more common in the distant past. Performing another type of simulations, the team found that there was a 20%-30% chance of experiencing a fly-by over the first billion years of the Sun’s life.
This is no final proof that a stellar fly-by caused the messy features of the outer Solar System, but it can reproduce many observational facts and seems relatively realistic. So far it is the simplest explanation and if simplicity is a sign for validity this model is the best candidate so far.
„In summary, our close fly-by scenario offers a realistic alternative to present models suggested to explain the unexpected features of the outer solar system“, concludes Susanne Pfalzner. „It should be considered as an option for shaping the outer solar system. The strength of the fly-by hypothesis lies in the explanation of several outer solar system features by one single mechanism.“
Simulation of the stellar intruder scenario for a mass of 0.5 solar masses and a perihelion distance of 100 astronomical units or 15 billion kilometers for the perturbing star (three times the distance between Sun and Neptune). … [more]
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.
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.
© 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.
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.
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.
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.
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.
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.
ATLASGAL Survey of Southern Milky Way Completed
February 24, 2016
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.
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).
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.
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.
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
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.