Dusting for Stars’ Magnetic Fingerprints

ALMA observations of the protoplanetary disk around HD 142527. The white bars show the directions of the magnetic field revealed by the orientation of the dust grains. The strength of the magnetic field is 0.3 milligauss. For comparison, a typical refrigerator magnet has a magnetic field of about 1,000,000 milligauss. Credit: ALMA (ESO/NAOJ/NRAO), S. Ohashi et al. Download image (1.8MB)

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For the first time astronomers have succeeded in observing the magnetic field around a young star where planets are thought to be forming. The team was able to use dust to measure the three-dimensional structure “fingerprint” of the magnetic field. This will help improve our understanding of planet formation. Planets form in turbulent disks of gas and dust called protoplanetary disks around young stars. It is thought that the first step in planet formation is dust grains colliding and sticking together. The movement of the dust grains is influenced by many forces, including magnetism. Thus, understanding the magnetic fields is important for understanding planet formation, but so far it has not been possible to measure the magnetic fields in a protoplanetary disk.

In this research, an international team of astronomers led by Satoshi Ohashi at the National Astronomical Observatory of Japan used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the protoplanetary disk around a young star known as HD 142527. This star is located 512 light-years away in the direction of the constellation Lupus. The team found that the dust grains aligned with the magnetic field lines. This allowed the team to detect and measure the unseen magnetic field lines, much the same way iron filings can reveal the magnetic field around a magnet. The team thinks that the measured three-dimensional structure might create strong turbulence withing the protoplanetary disk.

Now that this method of dusting for a young star’s magnetic fingerprint has been proven to work, the team wants to apply it to more stars, and measure the magnetic field closer to the star to better understand the magnetic conditions where planets are forming.

Source: National Astronomical Observatory of Japan (NAOJ)/Science

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Detailed Article(s)

Magnetic Field in Planet Formation has been Successfully Observed
ALMA

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Release Information

Researcher(s) Involved in this Release

Satoshi Ohashi (National Astronomical Observatory of Japan)

Coordinated Release Organization(s)

National Astronomical Observatory of Japan
RIKEN
Kogakuin University
Ibaraki University
Ashikaga University

Paper(s)

Satoshi Ohashi et al. “Observationally derived magnetic field strength and 3D components in the HD 142527 disk”, in Nature Astronomy, DOI:10.1038/s41550-024-02454-x

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Related Link(s)

ALMA measures size of seeds of planets (December 5, 2016)

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Young star HD 142527

Observations made with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope of the disc of gas and cosmic dust around the young star HD 142527 show vast streams of gas flowing across the gap in the disc. These are created by giant planets guzzling gas as they grow. The dust in the outer disc is shown in red. Dense gas in the streams flowing across the gap, as well as in the outer disc, is shown in green. Diffuse gas in the central gap is shown in blue. The gas filaments can be seen at the three o’clock and ten o’clock positions, flowing from the outer disc towards the center. Credit: ALMA (ESO/NAOJ/NRAO), S. Casassus et al. Hi-res image

Source:  National Radio Astronomy Observatory (NRAO)/Gallery

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Planet Formation around Binary Star

A composite image of the HD 142527 binary star system from data captured by the Atacama Large Millimeter/submillimeter Array shows a distinctive arc of dust (red) and a ring of carbon monoxide (blue and green). The red arc is free of gas, suggesting the carbon monoxide has "frozen out," forming a layer of frost on the dust grains in that region. Astronomers speculate this frost provides a boost to planet formation. Credit: Andrea Isella/Rice University; B. Saxton (NRAO/AUI/NSF); ALMA (NRAO/ESO/NAOJ)

A composite image of the HD 142527 binary star system from data captured by the Atacama Large Millimeter/submillimeter Array shows a distinctive arc of dust (red) and a ring of carbon monoxide (blue and green). The red arc is free of gas, suggesting the carbon monoxide has "frozen out," forming a layer of frost on the dust grains in that region. Astronomers speculate this frost provides a boost to planet formation. The two dots in the center represent the two stars in the system. Credit: Andrea Isella/Rice University; B. Saxton (NRAO/AUI/NSF); ALMA (NRAO/ESO/NAOJ)

Artist impression of the HD 142527 binary star system based on data from the Atacama Large Millimeter/submillimeter Array (ALMA). The rendition shows a distinctive arc of dust (red) embedded in the protoplanetary disk. The red arc is free of gas, suggesting the carbon monoxide has "frozen out," forming a layer of frost on the dust grains in that region. Astronomers speculate this frost provides a boost to planet formation. The two dots in the center represent the two stars in the system. Credit: B. Saxton (NRAO/AUI/NSF)

ALMA reveals planet-forming potential of protoplanetary disk

Using ALMA, astronomers have taken a new, detailed look at the very early stages of planet formation around a binary star. Embedded in the outer reaches of a double star's protoplanetary disk, the researchers discovered a striking crescent-shape region of dust that is conspicuously devoid of gas. This result, presented at the AAAS meeting in Washington, D.C., provides fresh insights into the planet-forming potential of a binary system.

Astronomers struggle to understand how planets form in binary star systems. Early models suggested that the gravitational tug-of-war between two stellar bodies would send young planets into eccentric orbits, possibly ejecting them completely from their home system or sending them crashing into their stars. Observational evidence, however, reveals that planets do indeed form and maintain surprisingly stable orbits around double stars.

To better understand how such systems form and evolve, astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) took a new, detailed look at the planet-forming disk around HD 142527, a binary star about 450 light-years from Earth in a cluster of young stars known as the Scorpius-Centaurus Association.

The HD 142527 system includes a main star a little more than twice the mass of our Sun and a smaller companion star only about a third the mass of our Sun. They are separated by approximately one billion miles: a little more than the distance from the Sun to Saturn. Previous ALMA studies of this system revealed surprising details about the structure of the system's inner and outer disks.

"This binary system has long been known to harbor a planet-forming corona of dust and gas," said Andrea Isella, an astronomer at Rice University in Houston, Texas. "The new ALMA images reveal previously unseen details about the physical processes that regulate the formation of planets around this and perhaps many other binary systems."

Planets form out of the expansive disks of dust and gas that surround young stars. Small dust grains and pockets of gas come together under gravity, forming larger and larger agglomerations and eventually asteroids and planets. The fine points of this process are not well understood, however. By studying a wide range of protoplanetary disks with ALMA, astronomers hope to better understand the conditions that set the stage for planet formation across the Universe.

ALMA's new, high-resolution images of HD 142527 show a broad elliptical ring around the double star. The disk begins incredibly far from the central star -- about 50 times the Sun-Earth distance. Most of it consists of gases, including two forms of carbon monoxide (13CO and C180), but there is a noticeable dearth of these gases within a huge arc of dust that extends nearly a third of the way around the star system.

This crescent-shaped dust cloud may be the result of gravitational forces unique to binary stars and may also be the key to the formation of planets, Isella speculates. Its lack of free-floating gases is likely the result of them freezing out and forming a thin layer of ice on the dust grains.

"The temperature is so low that the gas turns into ice and sticks to the grains," Isella said. "This process is thought to increase the capacity for dust grains to stick together, making it a strong catalyst for the formation of planetesimals, and, down the line, of planets."

"We've been studying protoplanetary disks for at least 20 years," Isella said. "There are between a few hundred and a few thousand we can look at again with ALMA to find new and surprising details. That's the beauty of ALMA. Every time you get new data, it's like opening a present. You don't know what's inside."

HD 142527 will be the subject of an upcoming paper led by Rice postdoctoral fellow Yann Boehler, who is working in Isella’s group.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

 
Contact:

Charles Blue, NRAO Public Information Officer
(434) 296-0314; 
Email:  cblue@nrao.edu

Source: National Radio Astronomy Observatory (NRAO) 

ALMA Reveals Planetary Construction Sites

PR Image eso1549a

Artist’s impression of a transitional disc around a young star

PR Image eso1549b

Schematic view of a transitional disc around a young star
 

PR Image eso1549c

ALMA imaging of the transitional disc HD 135344B

PR Image eso1549d

ALMA imaging of the transitional disc DoAr 44

Videos

 

PR Video eso1549a

Artist’s impression of a transitional disc around a young star

PR Video eso1549b

Artist’s impression of a transitional disc around a young star

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New evidence for young planets in discs around young stars

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found the clearest indications yet that planets with masses several times that of Jupiter have recently formed in the discs of gas and dust around four young stars. Measurements of the gas around the stars also provide additional clues about the properties of those planets.

Planets are found around nearly every star, but astronomers still do not fully understand how — and under what conditions — they form. To answer such questions, they study the rotating discs of gas and dust present around young stars from which planets are built. But these discs are small and far from Earth, and the power of ALMA was needed for them to reveal their secrets.

A special class of discs, called transitional discs, have a surprising absence of dust in their centres, in the region around the star. Two main ideas have been put forward to explain these mysterious gaps. Firstly, the strong stellar winds and intense radiation could have blown away or destroyed the encircling material [1]. Alternatively, massive young planets in the process of formation could have cleared the material as they orbit the star [2].

The unparalleled sensitivity and image sharpness of ALMA have now allowed the team of astronomers, led by Nienke van der Marel from the Leiden Observatory in the Netherlands to map the distribution of gas and dust in four of these transitional discs better than ever before [3]. This in turn has allowed them to choose between the two options as the cause of the gaps for the first time.

The new images show that there are significant amounts of gas within the dust gaps [4]. But to the team’s surprise, the gas also possessed a gap, up to three times smaller than that of the dust.

This could only be explained by the scenario in which newly formed massive planets have cleared the gas as they travelled around their orbits, but trapped the dust particles further out [5].

“Previous observations already hinted at the presence of gas inside the dust gaps,” explains Nienke van der Marel. “But as ALMA can image the material in the entire disc in much greater detail than other facilities, we could rule out the alternative scenario. The deep gap points clearly to the presence of planets with several times the mass of Jupiter, creating these caverns as they sweep through the disc.”

Remarkably, these observations were conducted utilising just one tenth of the current resolving power of ALMA, as they were performed whilst half of the array was still under construction on the Chajnantor Plateau in northern Chile.

Further studies are now needed to determine whether more transitional discs also point towards this planet-clearing scenario, although ALMA’s observations have, in the meantime, provided astronomers with a valuable new insight into the complex process of planetary formation.

“All the transitional discs studied so far that have large dust cavities also have gas cavities. So, with ALMA, we can now find out where and when giant planets are being born in these discs, and compare these results with planet formation models,” says Ewine van Dishoeck, also of Leiden University and the Max Planck Institute for Extraterrestrial Physics in Garching [6]. “Direct planetary detection is just within reach of current instruments, and the next generation telescopes currently under construction, such as the European Extremely Large Telescope, will be able to go much further. ALMA is pointing out where they will need to look.”

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Notes

[1] This process, which clears the dust and gas from the inside out, is known as photoevaporation. 

[2] Such planets are difficult to observe directly (eso1310) and previous studies at millimetre wavelengths (eso1325) have failed to achieve a sharp view of their inner, planet-forming zones where these different explanations could be put to the test. Other studies (eso0827) could not measure the bulk of the gas in these discs. 

[3] The four targets of these investigations were SR 21, HD 135344B (also known as SAO 206462), DoAr 44 and Oph IRS 48. 

[4] The gas present in transitional discs consists primarily of hydrogen, and is traced through observations of the carbon monoxide — or CO — molecule. 

[5] The process of dust trapping is explained in an earlier release (eso1325). 

[6] Other examples include the HD 142527 (eso1301 and here) and J1604-2130 transitional discs.

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More Information

This research was presented in a paper entitled “Resolved gas cavities in transitional disks inferred from CO isotopologs with ALMA”, by N. van der Marel, et al., to appear in Astronomy & Astrophysics in December 2015.

The team is composed of N. van der Marel (Leiden University, Leiden, the Netherlands; Institute for Astronomy, University of Hawaii, Honolulu, USA), E. F. van Dishoeck (Leiden University, Leiden, the Netherlands; Max Planck Institute for Extraterrestrial Physics, Garching, Germany), S. Bruderer (Max-Planck Institute for Extraterrestrial Physics, Garching, Germany), S. M. Andrews (Harvard-Smithsonian Center for Astrophysics, Massachusetts, USA), K. M. Pontoppidan (Space Telescope Science Institute, Baltimore, Maryland, USA), G. J. Herczeg (Peking University, Beijing, China), T. van Kempen (Leiden University, Leiden, the Netherlands) and A. Miotello (Leiden University, Leiden, the Netherlands).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes.

VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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Links

• Research paper in Astronomy & Astrophysics 
• Photos of ALMA

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Contacts

Nienke van der Marel
Institute for Astronomy, University of Hawaii
Honolulu, USA
Email: nmarel@ifa.hawaii.edu

Ewine van Dishoeck
Leiden Observatory
Leiden, The Netherlands
Tel: +31 71 527 5814
Email: ewine@strw.leidenuniv.nl

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: ESO

ALMA Sheds Light on Planet-Forming Gas Streams

PR Image eso1301a
Artist’s impression of the disc and gas streams around HD 142527

 PR Image eso1301b
ALMA observations of the disc and gas streams around HD 142527

PR Image eso1301c
Side-by-side comparison of ALMA observations and 

artist’s impression of the disc and gas streams around HD 142527

PR Video eso1301a
Artist’s impression of the disc and gas streams around HD 142527

Videos

PR Video eso1301a
Artist’s impression of the disc and gas streams around HD 142527

  PR Video eso1301b
The young star HD 142527 (zoom)

Tantalising signs of flows feeding gas-guzzling giant planets

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope have seen a key stage in the birth of giant planets for the first time. Vast streams of gas are flowing across a gap in the disc of material around a young star. These are the first direct observations of such streams, which are expected to be created by giant planets guzzling gas as they grow. The result is published on 2 January 2013 in the journal Nature.

The international team of astronomers studied the young star HD 142527, over 450 light-years from Earth, which is surrounded by a disc of gas and cosmic dust — the remains of the cloud from which the star formed. The dusty disc is divided into an inner and an outer part by a gap, which is thought to have been carved by newly forming gas giant planets clearing out their orbits as they circle the star. The inner disc reaches from the star out to the equivalent of the orbit of Saturn in the Solar System, while the outer disc begins about 14 times further out. The outer disc does not surround the star uniformly; instead, it has a horseshoe shape, probably caused by the gravitational effect of the orbiting giant planets.

According to theory, the giant planets grow by capturing gas from the outer disc, in streams that form bridges across the gap in the disc.

“Astronomers have been predicting that these streams must exist, but this is the first time we’ve been able to see them directly,” says Simon Casassus (Universidad de Chile, Chile), who led the new study. “Thanks to the new ALMA telescope, we’ve been able to get direct observations to illuminate current theories of how planets are formed!”

Casassus and his team used ALMA to look at the gas and cosmic dust around the star, seeing finer details, and closer to the star, than could be seen with previous such telescopes. ALMA’s observations, at submillimetre wavelengths, are also impervious to the glare from the star that affects infrared or visible-light telescopes. The gap in the dusty disc was already known, but they also discovered diffuse gas remaining in the gap, and two denser streams of gas flowing from the outer disc, across the gap, to the inner disc.

“We think that there is a giant planet hidden within, and causing, each of these streams. The planets grow by capturing some of the gas from the outer disc, but they are really messy eaters: the rest of it overshoots and feeds into the inner disc around the star” says Sebastián Pérez, a member of the team, who is also at Universidad de Chile.

The observations answer another question about the disc around HD 142527. As the central star is still forming, by capturing material from the inner disc, the inner disc would have already been devoured, if it was not somehow topped up. The team found that the rate at which leftover gas streams onto the inner disc is just right to keep the inner disc replenished, and to feed the growing star.

Another first is the detection of the diffuse gas in the gap. "Astronomers have been looking for this gas for a long time, but so far we only had indirect evidence for it. Now, with ALMA, we can see it directly," explains Gerrit van der Plas, another team member at Universidad de Chile.

This residual gas is more evidence that the streams are caused by giant planets, rather than even larger objects such as a companion star. "A second star would have cleared out the gap more, leaving no residual gas. By studying the amount of gas left, we may be able to pin down the masses of the objects doing the clearing.” adds Pérez.

What about the planets themselves? Casassus explains that, although the team did not detect them directly, he is not surprised. “We searched for the planets themselves with state-of-the-art infrared instruments on other telescopes. However, we expect that these forming planets are still deeply embedded in the streams of gas, which are almost opaque. Therefore, there may be little chance of spotting the planets directly.”

Nevertheless, the astronomers aim to find out more about the suspected planets by studying the gas streams as well as the diffuse gas. The ALMA telescope is still under construction, and has not yet reached its full capabilities. When it is complete, its vision will be even sharper, and new observations of the streams may allow the team to determine properties of the planets, including their masses.

More information

This research was presented in a paper, “Flows of gas through a protoplanetary gap”, to appear in the journal Nature on 2 January 2013.

The team is composed of S. Casassus (Universidad de Chile, Chile; Millennium Nucleus for Protoplanetary Disks — Ministry of Economy, Chilean Government), G. van der Plas (Universidad de Chile, Chile), S. Pérez M. (Universidad de Chile, Chile), W. R. F. Dent (Joint ALMA Observatory, Chile; European Southern Observatory, Chile), E. Fomalont (NRAO, USA), J. Hagelberg (Observatoire de Genève, Switzerland), A. Hales (Joint ALMA Observatory, Chile; NRAO, USA), A. Jordán (Pontificia Universidad Católica de Chile, Chile), D. Mawet (European Southern Observatory, Chile), F. Ménard (CNRS / INSU, France; Universidad de Chile, Chile; CNRS / UJF Grenoble, France), A. Wootten (NRAO, USA), D. Wilner (Harvard-Smithsonian Center for Astrophysics, USA), A. M. Hughes (U. C. Berkeley, USA), M. R. Schreiber (Universidad Valparaiso, Chile), J. H. Girard (European Southern Observatory, Chile), B. Ercolano (Ludwig-Maximillians-Universität, Germany), H. Canovas (Universidad Valparaiso, Chile), P. E. Román (University of Chile, Chile), V, Salinas (Universidad de Chile, Chile).

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

• Research paper

• Simulation video of the streams and gap in a protoplanetary disc created by two planets. The view rotates to keep one of the planets in the same apparent position. Credit: S. Casassus et al.

• Simulation video of the stream and gap in a protoplanetary disc created by one planet. The view rotates to keep the planet in the same apparent position. Credit: S. Casassus et al.

• More about ALMA at ESO

• The Joint ALMA Observatory

Contacts

 Simon Casassus
 Universidad de Chile
 Santiago, Chile
 Tel: +56 2 9771137
 Email: scasassus@u.uchile.cl

 Douglas Pierce-Price
 ESO Public Information Officer
 Garching, Germany
 Tel: +49 89 3200 6759
 Email: dpiercep@eso.org

 John Stoke
 National Radio Astronomy Observatory (NRAO)
 Charlottesville, USA
 Tel: +1 434 244 6816
 Email: jstoke@nrao.edu

ALMA Opens Its Eyes

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Antennae Galaxies composite of ALMA and Hubble observations

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Antennae Galaxies composite of ALMA and Hubble observations

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ALMA view of the Antennae Galaxies

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Antennae Galaxies, side-by-side comparison of ALMA and VLT observations

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The Antennae Galaxies in the constellation of Corvus

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Wide-field view of the region around the Antennae Galaxies

More Images

PR Image eso1137g - PR Image eso1137h

Nineteen ALMA antennas on the Chajnantor plateau

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ALMA antennas on the Chajnantor Plateau, seen from nearby Cerro Toco

Videos

PR Video eso1137d
Zooming on ALMA’s view of the Antennae Galaxies

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Panning across the ALMA and Hubble views of the Antennae Galaxies (crossfade)

PR Video eso1137f
Panning across the ALMA and Hubble views of the Antennae Galaxies

The full release, images and videos are available on:
http://www.eso.org/public/news/eso1137/

The most powerful millimetre/submillimetre-wavelength telescope in the world opens for business and reveals its first image

Humanity's most complex ground-based astronomy observatory, the Atacama Large Millimeter/submillimeter Array (ALMA), has officially opened for astronomers. The first released image, from a telescope still under construction, reveals a view of the Universe that cannot be seen at all by visible-light and infrared telescopes. Thousands of scientists from around the world have competed to be among the first few researchers to explore some of the darkest, coldest, furthest, and most hidden secrets of the cosmos with this new astronomical tool.

At present, around a third of ALMA’s eventual 66 radio antennas, with separations up to only 125 metres rather than the maximum 16 kilometres, make up the growing array on the Chajnantor plateau in northern Chile, at an elevation of 5000 metres. And yet, even under construction, ALMA has become the best telescope of its kind — as reflected by the extraordinary number of astronomers who requested time to observe with ALMA.

“Even in this very early phase ALMA already outperforms all other submillimetre arrays. Reaching this milestone is a tribute to the impressive efforts of the many scientists and engineers in the ALMA partner regions around the world who made it possible,” said Tim de Zeeuw, Director General of ESO, the European partner in ALMA.

ALMA observes the Universe in light with millimetre and submillimetre wavelengths, roughly one thousand times longer than visible-light wavelengths. Using these longer wavelengths allows astronomers to study extremely cold objects in space — such as the dense clouds of cosmic dust and gas from which stars and planets form — as well as very distant objects in the early Universe.

ALMA is radically different from visible-light and infrared telescopes. It is an array of linked antennas acting as a single giant telescope, and it detects much longer wavelengths than those of visible light. Its images therefore look quite unlike more familiar pictures of the cosmos.

The ALMA team has been busy testing the observatory’s systems over the past few months, in preparation for the first round of scientific observations, known as Early Science. One outcome of their tests is the first image published from ALMA, albeit from what is still very much a growing telescope. Most of the observations used to create this image of the Antennae Galaxies were made using only twelve antennas working together — far fewer than will be used for the first science observations — and with the antennas much closer together as well. Both of these factors make the new image just a taster of what is to come. As the observatory grows, the sharpness, efficiency, and quality of its observations will increase dramatically as more antennas become available and the array grows in size [1].

The Antennae Galaxies are a pair of colliding galaxies with dramatically distorted shapes. While visible light shows us the stars in the galaxies, ALMA’s view reveals something that cannot be seen in visible light: the clouds of dense cold gas from which new stars form [2]. This is the best submillimetre-wavelength image ever made of the Antennae Galaxies.

Massive concentrations of gas are found not only in the hearts of the two galaxies but also in the chaotic region where they are colliding. Here, the total amount of gas is billions of times the mass of our Sun — a rich reservoir of material for future generations of stars. Observations like these open a new window on the submillimetre Universe and will be vital in helping us understand how galaxy collisions can trigger the birth of new stars. This is just one example of how ALMA reveals parts of the Universe that cannot be seen with visible-light and infrared telescopes.

ALMA could accept only about a hundred or so projects for this first nine-month phase of Early Science. Nevertheless, over the last few months, keen astronomers from around the world have submitted over 900 proposals for observations. This ninefold level of oversubscription is a record for a telescope. The successful projects were chosen based on their scientific merit, their regional diversity, and also their relevance to ALMA’s major science goals.

"We are living in a historic moment for science and particularly for astronomy, and perhaps also for the evolution of humanity, because we start to use the greatest observatory under construction at the moment," said Thijs de Graauw, Director of ALMA.

One of the projects chosen for ALMA Early Science observations was that of David Wilner from the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts, USA. Wilner said, “My team hunts for the building blocks of solar systems, and ALMA is uniquely equipped to spot them.”

His team’s target is AU Microscopii, a star 33 light-years away that is only 1% of the age of our Sun. “We will use ALMA to image the ‘birth ring’ of planetesimals that we believe orbits this young star. Only with ALMA, however, can we hope to discover clumps in these dusty asteroid belts, which can be the markers of unseen planets.” Wilner and his team will share their data with a European team who also requested ALMA observations of this nearby, dust-ringed star.

Any hunt for habitable planets around other stars often begins with a hunt for water in those distant solar systems. Debris discs, the swarms of dust, gas, and rocks around stars, are suspected also to contain craggy ice chunks filled with frozen water, gas, and possibly even organic molecules — the astrochemistry of life.

Simon Casassus, from the University of Chile, and his team will use ALMA to observe the gas and dust disc around HD142527, a young star that is 400 light-years away. “The dusty disc around this star has a very large gap, which may have been carved by the formation of giant planets,” said Casassus. “Outside the gap, this disc contains enough gas to make about a dozen Jupiter-sized planets. Inside the gap, a young gaseous giant planet could still be forming, if there is gaseous material available.” Their ALMA observations will measure the mass and physical conditions of gas interior to the gap. “Thus, ALMA gives us a chance to observe planet formation, or its most recent wake,” said Casassus.

Further away, 26 000 light-years from us in the centre of our galaxy, sits Sagittarius A*, a supermassive black hole four million times the mass of our Sun. Gas and dust between it and us hide it from our optical telescopes. However, ALMA is tuned to see through the galactic murk and give us tantalising views of Sagittarius A*.

Heino Falcke, an astronomer at Radboud University Nijmegen in the Netherlands, said “ALMA will let us watch flares of light coming from around this supermassive black hole, and make images of the gas clouds caught by its immense pull. This will let us study this monster’s messy feeding habits. We think that some of the gas may be escaping its grip, at close to the speed of light.”

Like the black outlines in a child’s colouring book, cosmic dust and cold gas trace out structures inside galaxies, even if we can’t see those galaxies clearly. At the outer fringes of our visible Universe lie the mysterious starburst galaxies, bright islands in an otherwise calm, dark cosmos. ALMA will hunt for cold gas and dust tracers here, as far back as a few hundred million years after the Big Bang, at a time astronomers call “cosmic dawn”.

Masami Ouchi of the University of Tokyo in Japan will use ALMA to observe Himiko, a very distant galaxy churning out at least 100 Suns’ worth of stars every year and surrounded by a giant, bright nebula. “Other telescopes cannot show us why Himiko is so bright and how it has developed such a huge, hot nebula when the ancient Universe all around it is so calm and dark,” said Ouchi. “ALMA can show us the cold gas deep in Himiko’s star-forming nebula, tracing the movements and activities inside, and we will finally see how galaxies started forming at the cosmic dawn.”

During its Early Science observations, ALMA will continue its construction phase in the Chilean Andes, high on the remote Chajnantor Plain in the harsh Atacama Desert. Each new, climate-armoured antenna will join the array and be linked via fibre optic cabling. The views from each distant antenna are assembled into one large view by one of the world’s fastest special-purpose supercomputers, the ALMA correlator, which can perform 17 quadrillion [3] operations per second.

By 2013, ALMA will be an up to 16-km wide array of 66 ultra-precision millimetre/submillimetre wave radio antennas working together as one telescope and built by ALMA’s multinational partners in Europe, North America and East Asia.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Notes

[1] The quality of images from an interferometric telescope like ALMA depends on both the separations and the number of the antennas. Larger separations mean that sharper images can be created and if more antennas are working together more detailed images can be produced. More information about ALMA and interferometry can be found at: http://www.eso.org/public/teles-instr/alma/interferometry.html.

[2] The observations were made at specific wavelengths of millimetre and submillimetre light, tuned to detect carbon monoxide molecules in the otherwise invisible hydrogen clouds, where new stars are forming.

[3] 1.7x10¹⁶ operations per second.

More information

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

ESO ALMA pages
Pictures of ALMA
JAO’s ALMA web pages
NRAO’s ALMA web pages
NAOJ’s ALMA web pages

List of the 112 highest priority projects selected for ALMA Early Science, including titles, investigators, and short descriptions (PDF)

Contacts

Paola Andreani
European ARC Manager, ESO
Garching, Germany
Tel: +49 89 3200 6576
Email: pandrean@eso.org

Douglas Pierce-Price
ESO Public Information Officer
Garching, Germany
Tel: +49 89 3200 6759
Email: dpiercep@eso.org

Lars-Åke Nyman
Head of Science Operations, Joint ALMA Observatory
Santiago, Chile
Tel: +56 2 467 6127
Email: lnyman@alma.cl

William Garnier
Education and Public Outreach Officer, Joint ALMA Observatory
Santiago, Chile
Tel: +56 2 467 6119
Email: wgarnier@alma.cl

Mark McKinnon
North American ALMA Project Manager
USA
Tel: +1 434-296-0229
Email: mmckinno@nrao.edu

Tania Burchell
Science Writer, National Radio Astronomy Observatory
Charlottesville, USA
Tel: +1 434 244 6812
Email: tburchel@nrao.edu

Sachiko K. Okumura
East Asian ARC Manager, National Astronomical Observatory of Japan
Japan
Tel: +81 422 34 3782
Email: sachiko.k.okumura@nao.ac.jp

Masaaki Hiramatsu
Education & Public Outreach Officer, National Astronomical Observatory of Japan
Japan
Tel: +81 422 34 3900 ext.3150
Email: hiramatsu.masaaki@nao.ac.jp