From The MPG Institute for Astronomy [MPG Institut für Astronomie](DE): “Planet-forming disks evolve in surprisingly similar ways”
Max Planck Institut für Astronomie (DE)
From The MPG Institute for Astronomy [MPG Institut für Astronomie](DE)
May 06, 2022
Markus Nielbock
Press and public relations officer
+49 6221 528-134
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Max Planck Institute for Astronomy, Heidelberg
Sierk van Terwisga
+49 6221 528-227
terwisga@mpia.de
Max Planck Institute for Astronomy, Heidelberg
The demographics of hundreds of planet-forming disks within a thousand light-years reveal how their masses vary with age.
This artistic impression illustrates what planet-forming disks around young stars often look like. They initially consist of dust and gas configured into rings of dense material. In time, the solid components grow into pebbles which eventually can evolve into planets. Since the ALMA observations used in this study are only sensitive to millimetre-sized dust grains, evolved disks with larger objects or even planets produce a relatively faint signal from the remnant material. The new results indicate that without external irradiation, such disks evolve similarly. After about a million years, most of them do not have enough mass to produce large planets like Jupiter. However, such planets may already have formed there. Image: MPIA graphics department.
A group of astronomers, led by Sierk van Terwisga from the Max Planck Institute for Astronomy, have analysed the mass distribution of over 870 planet-forming disks in the Orion A cloud.
By exploiting the statistical properties of this unprecedented large sample of disks and developing an innovative data processing scheme, they found that far away from harsh environments like hot stars, the decline in disk mass only depends on their age. The results indicate that, at least within 1000 light-years of the Earth, planet-forming disks and planetary systems evolve in similar ways.
Some of the most exciting questions in present-day astronomical research are: What do other planetary systems look like? How comparable is the Solar System to other planetary systems? A team of astronomers have now contributed crucial clues to solving this puzzle. “Up to now, we didn’t know for sure which properties dominate the evolution of planet-forming disks around young stars”, says Sierk van Terwisga, who is a scientist at the Max Planck Institute for Astronomy in Heidelberg, Germany. He is the lead author of the underlying research article published in Astronomy & Astrophysics today. “Our new results now indicate that in environments without any relevant external influence, the observed disk mass available for forming new planets only depends on the age of the star-disk system”, van Terwisga adds.
The disk mass is the key property when studying the evolution of planet-forming disks. This quantity determines how much material is available to be transformed into planets. Depending on the disk age, it may also provide clues about the planets already present there. External effects like irradiation and winds from nearby massive stars obviously impact the disk survival. However, such environments are rare, and those processes do not reveal much about the disks themselves. Instead, astronomers are more interested in internal disk properties such as age, chemical composition, or the parental cloud dynamics from which the young stars with their disks emerged.
To disentangle the various contributions, the team of astronomers selected a large and well-known region of young stars with disks, the Orion A cloud. It is approximately 1350 light-years away from Earth. “Orion A provided us with an unprecedented large sample size of more than 870 disks around young stars. It was crucial to be able to look for small variations in the disk mass depending on age and even on the local environments inside the cloud,” Álvaro Hacar, a co-author and scientist at The University of Vienna [Universität Wien](AT), explains. The sample stems from earlier observations with the Herschel Space Telescope, which permitted identifying the disks
Combining several wavelengths provided a criterion to estimate their ages. Since they all belong to the same cloud, the astronomers expected little influence from chemistry and cloud history variations. They also avoided any impact from massive stars in the nearby Orion Nebula Cluster (ONC) by rejecting disks closer than 13 light-years.
To measure the disk mass, the team employed the Atacama Large Millimeter/Submillimeter Array (ALMA) located on the Chajnantor Plateau in the Chilean Atacama Desert.

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Observatory (CL).
ALMA consists of 66 parabolic antennas, functioning as a single telescope with a tunable angular resolution. The scientists applied an observing mode that allowed them to target each disk efficiently at a wavelength of about 1.2 millimetres. The cold disks are bright in this spectral range. On the other hand, the central stars’ contribution is negligible. With this approach, the astronomers determined the disks’ dust masses. However, the observations are insensitive to objects much larger than a few millimetres, e.g. rocks and planets. Therefore, the team effectively measured the mass of the disk material capable of forming planets.
Before calculating the disk masses, the astronomers combined and calibrated the data from several dozens of ALMA telescopes. This task becomes quite a challenge when dealing with large data sets. Using standard methods, it would have taken months to process the collected data. Instead, the team developed a new method using parallel computers. “Our new approach improved the processing speed by a factor of 900,” co-author Raymond Oonk from the collaborating IT service provider SURF points out. The 3000 CPU hours required to finish the task and prepare the data for subsequent analysis elapsed in less than a day.
Altogether, Orion A contains planet-forming disks, each with dust amounting to up to a few hundred Earth-masses. However, from the 870 disks, only 20 hold dust equivalent to 100 earths or more. In general, the number of disks declines rapidly with mass, with a majority containing less than 2.2 Earth-masses of dust. “In order to look for variations, we have dissected the Orion A cloud and analysed these regions separately. Thanks to the hundreds of disks, the sub-samples were still sufficiently large to yield statistically meaningful results”, van Terwisga explains.
Indeed, the scientists found minor variations in the disk mass distributions on scales of tens of light-years within Orion A. However, all of them can be explained as an age effect, meaning within a few million years, disk masses tend to decline towards older populations. Within the error margins, clusters of planet-forming disks of the same age exhibit the same mass distribution. It is not at all surprising to find the dust mass in planet-forming disks to decrease in time. After all, dust is one of the raw materials for planets. Hence, planet formation certainly reduces the amount of free dust. Other well-known processes are dust migration towards the disk centre and dust evaporation by irradiation from the host star. Still, it is surprising to see such a strong correlation between disk mass and age.
All those disks emerged from the same environment that now constitutes the Orion A cloud. How does this compare to other young star-disk populations? The astronomers addressed this question by comparing their results to several nearby star-forming regions with planet-forming disks. Except for two, all of them nicely fit the mass-age relation found in Orion A. “Altogether, we think our study proves that at least within the next 1000 light-years or so, all populations of planet-forming disks show the same mass distribution at a given age. And they seem to be evolving in more or less the same way”, van Terwisga concludes. The result may even hint at the formation of stunningly similar planetary systems.
As a next step, the scientists will look at possible impacts from nearby stars on smaller scales of a few light-years. While they avoided the strong radiation field caused by the massive stars in the ONC, there are potentially fainter field stars that may affect the dust in neighbouring disks and alter the disk mass statistics. Such contributions may explain some of the deviations found in the disk mass to age relation. The results can help strengthen the overall picture of a planet-forming disk evolution dominated by age.
Additional information
The team consists of S. E. van Terwisga (Max Planck Institute for Astronomy, Heidelberg, Germany), A. Hacar (Department of Astrophysics, University of Vienna, Austria), E. F. van Dishoeck (Leiden Observatory [Sterrewacht Leiden](NL), Leiden University [Universiteit Leiden](NL); The MPG Institute for Extraterrestrial Physics [MPG Institut für Extraterrestrische Physik]( DE) , R. Oonk (SURF, Leiden, The Netherlands; LObs; Netherlands Institute for Radio Astronomy (ASTRON), Dwingeloo, The Netherlands), and S. Portegies Zwart (LObs).
The Atacama Large Millimeter/Submillimeter Array (ALMA) is a partnership between the European Southern Observatory (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).
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Max Planck Institute for Astronomy campus, Heidelberg (DE)
The MPG Institute for Astronomy [MPG Institut für Astronomie] (DE) is a research institute of the MPG Society for the Advancement of Science [MPG Gesellschaft zur Förderung der Wissenschaften e. V.] (DE). It is located in Heidelberg, Baden-Württemberg, Germany near the top of the Königstuhl, adjacent to the historic Landessternwarte Heidelberg-Königstuhl astronomical observatory. The institute primarily conducts basic research in the natural sciences in the field of astronomy.
In addition to its own astronomical observations and astronomical research, the Institute is also actively involved in the development of observation instruments. The instruments or parts of them are manufactured in the institute’s own workshops.
The founding of the institute in 1967 resulted from the insight that a supra-regional institute equipped with powerful telescopes was necessary in order to conduct internationally competitive astronomical research. Hans Elsässer, an astronomer, became the founding director in 1968. In February 1969, a first group of 5 employees started work in the buildings of the neighbouring Königstuhl State Observatory. The institute, which was completed in 1975, was initially dedicated to the preparation and evaluation of astronomical observations and the development of new measurement methods.
From 1973 to 1984, it operated the Calar Alto Observatory on Calar Alto near Almería together with Spanish authorities.
Calar Alto Astronomical Observatory 3.5 meter Telescope, located in Almería province in Spain on Calar Alto, a 2,168-meter-high (7,113 ft) mountain in Sierra de Los Filabres(ES)
This largest observatory on the European mainland was used equally by astronomers from both countries until 2019. On 23 May 2019, the regional government of Andalusia and the MPG signed a transfer agreement for the 50% share in the observatory. Since then, it has been owned exclusively by Spain.
Since 2005, the MPIA has been operating the Large Binocular Telescope (LBT) together with partners from Germany, Italy and the USA and equipping it with measuring instruments.
LBT-U Arizona Large Binocular Telescope Interferometer, or LBTI, is a ground-based instrument connecting two 8-meter class telescopes on Mount Graham, Arizona, USA, Altitude 3,221 m (10,568 ft.) to form the largest single-mount telescope in the world. The interferometer is designed to detect and study stars and planets outside our solar system. Credit: NASA/JPL-Caltech.
Two scientific questions are given priority at the MPIA. One is the formation and development of stars and planets in our cosmic neighbourhood. The resonating question is: Is the Sun with its inhabited planet Earth unique, or are there also conditions in the vicinity of other stars, at least the numerous sun-like ones among them, that are conducive to life? On the other hand, the area of galaxies and cosmology is about understanding the development of today’s richly structured Universe with its galaxies and stars and its emergence from the simple initial state after the Big Bang.
The research topics at a glance:
• Star formation and young objects, planet formation, astrobiology, interstellar matter, astrochemistry
• Structure and evolution of the Milky Way, quasars and active galaxies, evolution of galaxies, galaxy clusters, cosmology
Together with the Center for Astronomy at The Ruprecht Karl University of Heidelberg [Ruprecht-Karls-Universität Heidelberg](DE), the Heidelberg Institute for Theoretical Studies (HITS) and the Department of Astro- and Particle Physics of the MPI for Nuclear Physics (MPIK), the MPIA in Heidelberg is a globally renowned centre of astronomical research.
Since 2015, the MPIA has been running the “Heidelberg Initiative for the Origins of Life” (HIFOL) together with the MPIK, the HITS, the Institute of Geosciences at Heidelberg University and the Department of Chemistry at The Ludwig Maximilians University of Munich [Ludwig-Maximilians-Universität München](DE). HIFOL brings together top researchers from astrophysics, geosciences, chemistry and the life sciences to promote, strengthen and combine scientific research towards the prerequisites for the emergence of life.
Structure
• Galaxies and Cosmology Department
• Planet and Star Formation Department
• Atmospheric Physics of Exoplanets
• Technical Departments
Instrumentation
The MPIA also builds instruments or parts of them for ground-based telescopes and satellites, including the following:
• Calar Alto Observatory (Spain)[above]
• La Silla Observatory of the European Southern Observatory (The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL))
European Southern Observatory(EU) La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.
• Paranal Observatory and E-ELT (ESO)
Paranal Observatory pictured with Cerro Paranal in the background. The mountain is home to one of the most advanced ground-based telescopes in the world, the VLT. The VLT telescope consists of four unit telescopes with mirrors measuring 8.2 meters in diameter and work together with four smaller auxiliary telescopes to make interferometric observations. Each of the 8.2m diameter Unit Telescopes can also be used individually. With one such telescope, images of celestial objects as faint as magnitude 30 can be obtained in a one-hour exposure. This corresponds to seeing objects that are four billion (four thousand million) times fainter than what can be seen with the unaided eye.
European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile at an altitude of 3,060 metres (10,040 ft).
• Large Binocular Telescope [above]
• Infrared Space Observatory (The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU))
ESA Infrared Space Observatory.
• Herschel Space Observatory (ESA, The National Aeronautics and Space Agency (US))
European Space Agency Herschel spacecraft active from 2009 to 2013.
• James Webb Space Telescope (NASA, ESA.CSA)
National Aeronautics Space Agency/European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/ Canadian Space Agency [Agence Spatiale Canadienne](CA) James Webb Infrared Space Telescope(US) annotated, finally launched December 25, 2021, ten years late.
The MPIA is also participating in the Gaia mission.
European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganisation](EU) GAIA satellite.
Gaia is a space mission of the European Space Agency (ESA), in which the exact positions, distances and velocities of around one billion Milky Way stars are determined.
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MPG Society for the Advancement of Science [MPG Gesellschaft zur Förderung der Wissenschaften e. V.] is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.
According to its primary goal, the MPG Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014) MPG Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.
The MPG Institutes focus on excellence in research. The MPG Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the MPG institutes fifth worldwide in terms of research published in Nature journals (after Harvard University, The Massachusetts Institute of Technology, Stanford University and The National Institutes of Health). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by The Chinese Academy of Sciences [中国科学院](CN), The Russian Academy of Sciences [Росси́йская акаде́мия нау́к](RU) and Harvard University. The Thomson Reuters-Science Watch website placed the MPG Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.
The MPG Society and its predecessor Kaiser Wilhelm Society hosted several renowned scientists in their fields, including Otto Hahn, Werner Heisenberg, and Albert Einstein.
History
The organization was established in 1911 as the Kaiser Wilhelm Society, or Kaiser-Wilhelm-Gesellschaft (KWG), a non-governmental research organization named for the then German emperor. The KWG was one of the world’s leading research organizations; its board of directors included scientists like Walther Bothe, Peter Debye, Albert Einstein, and Fritz Haber. In 1946, Otto Hahn assumed the position of President of KWG, and in 1948, the society was renamed the Max Planck Society (MPG) after its former President (1930–37) Max Planck, who died in 1947.
The MPG Society has a world-leading reputation as a science and technology research organization. In 2006, the Times Higher Education Supplement rankings of non-university research institutions (based on international peer review by academics) placed the MPG Society as No.1 in the world for science research, and No.3 in technology research (behind AT&T Corporation and The DOE’s Argonne National Laboratory.
The domain mpg.de attracted at least 1.7 million visitors annually by 2008 according to a Compete.com study.
MPG Institutes and research groups
The MPG Society consists of over 80 research institutes. In addition, the society funds a number of Max Planck Research Groups (MPRG) and International Max Planck Research Schools (IMPRS). The purpose of establishing independent research groups at various universities is to strengthen the required networking between universities and institutes of the Max Planck Society.
The research units are primarily located across Europe with a few in South Korea and the U.S. In 2007, the Society established its first non-European centre, with an institute on the Jupiter campus of Florida Atlantic University (US) focusing on neuroscience.
The MPG Institutes operate independently from, though in close cooperation with, the universities, and focus on innovative research which does not fit into the university structure due to their interdisciplinary or transdisciplinary nature or which require resources that cannot be met by the state universities.
Internally, MPG Institutes are organized into research departments headed by directors such that each MPI has several directors, a position roughly comparable to anything from full professor to department head at a university. Other core members include Junior and Senior Research Fellows.
In addition, there are several associated institutes:
International Max Planck Research Schools
International Max Planck Research Schools
Together with the Association of Universities and other Education Institutions in Germany, the Max Planck Society established numerous International Max Planck Research Schools (IMPRS) to promote junior scientists:
• Cologne Graduate School of Ageing Research, Cologne
• International Max Planck Research School for Intelligent Systems, at the Max Planck Institute for Intelligent Systems located in Tübingen and Stuttgart
• International Max Planck Research School on Adapting Behavior in a Fundamentally Uncertain World (Uncertainty School), at the Max Planck Institutes for Economics, for Human Development, and/or Research on Collective Goods
• International Max Planck Research School for Analysis, Design and Optimization in Chemical and Biochemical Process Engineering, Magdeburg
• International Max Planck Research School for Astronomy and Cosmic Physics, Heidelberg at the MPI for Astronomy
• International Max Planck Research School for Astrophysics, Garching at the MPI for Astrophysics
• International Max Planck Research School for Complex Surfaces in Material Sciences, Berlin
• International Max Planck Research School for Computer Science, Saarbrücken
• International Max Planck Research School for Earth System Modeling, Hamburg
• International Max Planck Research School for Elementary Particle Physics, Munich, at the MPI for Physics
• International Max Planck Research School for Environmental, Cellular and Molecular Microbiology, Marburg at the Max Planck Institute for Terrestrial Microbiology
• International Max Planck Research School for Evolutionary Biology, Plön at the Max Planck Institute for Evolutionary Biology
• International Max Planck Research School “From Molecules to Organisms”, Tübingen at the Max Planck Institute for Developmental Biology
• International Max Planck Research School for Global Biogeochemical Cycles, Jena at the Max Planck Institute for Biogeochemistry
• International Max Planck Research School on Gravitational Wave Astronomy, Hannover and Potsdam MPI for Gravitational Physics
• International Max Planck Research School for Heart and Lung Research, Bad Nauheim at the Max Planck Institute for Heart and Lung Research
• International Max Planck Research School for Infectious Diseases and Immunity, Berlin at the Max Planck Institute for Infection Biology
• International Max Planck Research School for Language Sciences, Nijmegen
• International Max Planck Research School for Neurosciences, Göttingen
• International Max Planck Research School for Cognitive and Systems Neuroscience, Tübingen
• International Max Planck Research School for Marine Microbiology (MarMic), joint program of the Max Planck Institute for Marine Microbiology in Bremen, the University of Bremen, the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, and the Jacobs University Bremen
• International Max Planck Research School for Maritime Affairs, Hamburg
• International Max Planck Research School for Molecular and Cellular Biology, Freiburg
• International Max Planck Research School for Molecular and Cellular Life Sciences, Munich
• International Max Planck Research School for Molecular Biology, Göttingen
• International Max Planck Research School for Molecular Cell Biology and Bioengineering, Dresden
• International Max Planck Research School Molecular Biomedicine, program combined with the ‘Graduate Programm Cell Dynamics And Disease’ at the University of Münster and the Max Planck Institute for Molecular Biomedicine
• International Max Planck Research School on Multiscale Bio-Systems, Potsdam
• International Max Planck Research School for Organismal Biology, at the University of Konstanz and the Max Planck Institute for Ornithology
• International Max Planck Research School on Reactive Structure Analysis for Chemical Reactions (IMPRS RECHARGE), Mülheim an der Ruhr, at the Max Planck Institute for Chemical Energy Conversion
• International Max Planck Research School for Science and Technology of Nano-Systems, Halle at Max Planck Institute of Microstructure Physics
• International Max Planck Research School for Solar System Science at the University of Göttingen hosted by MPI for Solar System Research
• International Max Planck Research School for Astronomy and Astrophysics, Bonn, at the MPI for Radio Astronomy (formerly the International Max Planck Research School for Radio and Infrared Astronomy)
• International Max Planck Research School for the Social and Political Constitution of the Economy, Cologne
• International Max Planck Research School for Surface and Interface Engineering in Advanced Materials, Düsseldorf at Max Planck Institute for Iron Research GmbH
• International Max Planck Research School for Ultrafast Imaging and Structural Dynamics, Hamburg
Max Planck Schools
• Max Planck School of Cognition
• Max Planck School Matter to Life
• Max Planck School of Photonics
Max Planck Center
• The Max Planck Centre for Attosecond Science (MPC-AS), POSTECH Pohang
• The Max Planck POSTECH Center for Complex Phase Materials, POSTECH Pohang
Max Planck Institutes
Among others:
• Max Planck Institute for Neurobiology of Behavior – caesar, Bonn
• Max Planck Institute for Aeronomics in Katlenburg-Lindau was renamed to Max Planck Institute for Solar System Research in 2004;
• Max Planck Institute for Biology in Tübingen was closed in 2005;
• Max Planck Institute for Cell Biology in Ladenburg b. Heidelberg was closed in 2003;
• Max Planck Institute for Economics in Jena was renamed to the Max Planck Institute for the Science of Human History in 2014;
• Max Planck Institute for Ionospheric Research in Katlenburg-Lindau was renamed to Max Planck Institute for Aeronomics in 1958;
• Max Planck Institute for Metals Research, Stuttgart
• Max Planck Institute of Oceanic Biology in Wilhelmshaven was renamed to Max Planck Institute of Cell Biology in 1968 and moved to Ladenburg 1977;
• Max Planck Institute for Psychological Research in Munich merged into the Max Planck Institute for Human Cognitive and Brain Sciences in 2004;
• Max Planck Institute for Protein and Leather Research in Regensburg moved to Munich 1957 and was united with the Max Planck Institute for Biochemistry in 1977;
• Max Planck Institute for Virus Research in Tübingen was renamed as Max Planck Institute for Developmental Biology in 1985;
• Max Planck Institute for the Study of the Scientific-Technical World in Starnberg (from 1970 until 1981 (closed)) directed by Carl Friedrich von Weizsäcker and Jürgen Habermas.
• Max Planck Institute for Behavioral Physiology
• Max Planck Institute of Experimental Endocrinology
• Max Planck Institute for Foreign and International Social Law
• Max Planck Institute for Physics and Astrophysics
• Max Planck Research Unit for Enzymology of Protein Folding
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