alma telescope tour

ALMA Observatory

Top ways to experience nearby attractions

Most Recent: Reviews ordered by most recent publish date in descending order.

Detailed Reviews: Reviews ordered by recency and descriptiveness of user-identified themes such as wait time, length of visit, general tips, and location information.

Also popular with travelers

ALMA Observatory - All You Need to Know BEFORE You Go (2024)

• Sat - Sun 9:00 AM - 1:00 PM
• (8.19 mi) Atacama Lodge
• (8.06 mi) Altos del Lascar
• (8.05 mi) Hostel Towanda
• (8.21 mi) Casa Selti
• (8.28 mi) Restaurant - Lodge Muley

• Log in Register Reset Password Forgot Account
• Account Editor Raw Data

Science Highlight

sci-hi-date

The ALMA Site

A world-class observatory in the desert.

The ALMA Observatory is operated at two distinct sites, far away from comfortable living conditions of modern civilization.

The ALMA antennas are located at the Array Operations Site (AOS) on the Chajnantor plateau of the Chilean Andes at an altitude of 5000 meters, about 40 km east of the village of San Pedro de Atacama. Measurements since 1995 have demonstrated the existence of exceptional atmospheric conditions at this site for observations at millimeter and submillimeter wavelengths, i. e., transparency and stability. 

The ALMA Operations Support Facility (OSF) is the base camp for the every-day, routine operation of the observatory. It is located at an altitude of about 2900 meters, quite high compared to standard living conditions, but still quite acceptable for scientific projects in astronomy of similar scope. However, the OSF does not only serve as the location for operating the Joint ALMA Observatory, it is also the Assembly, Integration and Verification (AIV) station for all the high technology equipment before being moved to the AOS.

The geographical location of ALMA is

latitude: -23.029° ; longitude: -67.755°

The operations support facility (osf).

The OSF is, in many aspects, the center of activities of the ALMA project. The OSF is the focal point of all antenna Assembly-Integration-Verification (AIV) activities. Antenna assembly is done at the OSF site at three separate areas, one each for the antennas provided by North America (VERTEX), Japan (MELCO), and Europe (AEM Consortium).

The OSF is also the center for activities associated with the extension and optimization of ALMA capabilities as well as Principal Investigator (PI) Science observations. During the operations phase of the observatory it is the workplace of the astronomers and of the teams responsible for maintaining proper functioning of all the telescopes.

The Array Operations Site (AOS): The second highest building in the world

The construction of the AOS Technical Building started in October 2005 and the outer shell was completed by mid 2006. Inside construction work was completed in summer 2007. Human operations at the AOS is limited to an absolute minimum, due to the high altitude. The AOS Technical Building houses the ALMA Correlator . Digitized signals received from the radio telescopes are processed here and further transmitted to the data storage facilities located at the OSF.

A High Altitude Road with Super-Highway Dimensions

The construction of the OSF and AOS sites and their access required substantial efforts of the ALMA project. Obviously, there was no access to these two remote locations (see Figure below). The OSF site, located at 2900 meters altitude, is about 15 kilometers away from the closest public road, the Chilean highway No. 23. The AOS is another 28 kilometers away from the OSF site. Thus, one of the first projects to be accomplished by ALMA was to construct an access road not only to the OSF but also to the AOS road, 43 km in length, not only at high altitudes, but also with sufficient width to regularly transport a large number of large radio telescopes with a diameter of 12 meters.

General Weather Statistics

The meteorological conditions on Chajnantor have been monitoried since April 1995. In the period 1995-2004, the data was collected using the NRAO and ESO weather stations and since 2004 similar data has been collected at the weather station at the Atacama Pathfinder EXperiment  (APEX).  The former data can be downloaded from the page  https://science.nrao.edu/facilities/alma/site , which also contains a very detailed description of the site characteristics and links to publications in the ALMA memo letter series, and the latter data can be downloaded from  http://archive.eso.org/wdb/wdb/eso/meteo_apex/form

Figure 3 shows the temperature, humidity, wind speed, and barometric pressure on Chajnantor as function of time of the year. The southern hemisphere winter (June-August) is characterized by lower temperatures, lower humidity, higher wind speeds, and slightly lower pressure compared to the southern hemisphere summer (December-February) conditions.

The quartile data in the figures are based on median values per each hour. The median filter tends to smooth the appearance. The smoothing of the data affects in particular the plot of the wind; in the raw database measurements there are wind gusts of up to 46 m/s, and sustained wind for more than one hour of up to 32 m/s.

Figure 3: Weather statistics (temperature, humidity, wind speed, and pressure) measured at the APEX weather station. Data have been collected over the years 2006-2010. The blue, green, and red bars show the 1st, 2nd, and 3rd quartile of the data. The raw data have a dump rate of 1 minute. From the raw data, the median value per hour was calculated and these median values were sorted per weeks. The thin cyan line shows the tenth largest value in the database, and the thin purple line shows the tenth lowest value among the median values, per week, respectively.

Figure 4: Diurnal variation of temperature (upper row) and wind speed (lower row) in June (left column) and December (right column) as function of Chilean local time (CLT). Data have been collected over the years 2006-2010. The blue, green, and red bars show the 1st, 2nd, and 3rd quartile of the data. The raw data have a dump rate of 1 minute. From the raw data, the median value per hour was calculated and these median values were sorted per time intervals. The thin cyan line shows the tenth largest value in the database, and the thin purple line shows the tenth lowest value among the median values, per time interval.

The diurnal variation of temperature and wind in a representative winter month (June) and in a representative summer month (December) is shown in Figure 4. Typical night-time temperatures range from  -10 to -6 degrees C during winter and -4 to 0 °C during summer. Temperature rises slowly after sunrise, reaching normally around -4 °C during winter time and +4 °C summer time.  Extreme night and day temperatures range from a minimum of -20 °C to a maximum of 12 °C, respectively.

During winter, the wind speed at night time is characterized by steady wind 5-7 m/, increasing after sunrise, reaching 6-11 m/s at 12-14 (CLT), after which the wind speed begins to drop slowly. The wind speed during summer looks slightly different, with a minimum of 2-4 m/s at 22-02 (CLT), gradually increasing up to 19 (CLT), when it reaches 8-10 m/s, after which the wind speed drops relatively abruptly. The latter winter speed pattern normally starts in October and continues until March.

PWV and Atmospheric Transmission

At millimeter and submillimeter wavelengths, pressure broadened molecular spectral lines make the atmosphere a natural limitation to the sensitivity and resolution of astronomical observations. Tropospheric water vapor is the principal culprit. The translucent atmosphere both decreases the signal, by attenuating incoming radiation, and increases the noise, by radiating thermally. Furthermore, inhomogeneities in the water vapor distribution cause variations in the electrical path length through the atmosphere. These variations result in phase errors that degrade the sensitivity and resolution of images made with both interferometers and filled aperture telescopes.

Figure 5 shows the precipitable water vapor (PWV) measured by the APEX radiometer as function of the time of the year. This image shows that during more that 50 % of the time between April and December, the PWV is below 1 mm (green quartile), and during the 5 best months (May-September), the PWV is below 0.5 mm for more than 25% of the time (blue quartile). The instrument uptime was in this period 80%. Lack of data indicate that the shutter was closed due to high humidity, and during these periods the pwv is assumed to be 10mm.

Figure 5: The precipitable water vapor, measured by the radiometer at APEX, as a function of the time of the year. Data presented here have been collected over the years 2007-2010. The blue, green, and red bars show the 1st, 2nd, and 3rd quartile of the data.

Figure 5 shows that the 1 st , 2 nd , and 3 rd  quartile of the PWV in March is 1.6, 3.3, and 5.2 mm, respectively, and the corresponding quartiles for August is 0.4, 0.65, and 1.05 mm.  The transmission plots at these PWVs is shown in Figure 6. This image shows that in March, it is fully possible (from a transparency point of view) to operate in most frequency ranges in the lower frequency ALMA bands, and in August, the upper frequency ALMA bands open up as well.

Figure 6: The zenith atmospheric transmission in March (upper panel) and September (lower panel) represented by the 1 st , 2 nd , and 3 rd  quartile of the PWVs in the two months, respectively. The different colored boxes are the ALMA bands 3-10.

Figure 7: The diurnal variation of the PWV in March (upper panel) and August (lower panel).

The PWV also has a diurnal pattern. Taking March and August 2010 as two examples of an (late) Altiplanic month and Southern winter month, respectively, it can be shown (see Figure 7) that the PWV peaks at 19 (CLT) in both winter and summer, but the absolute scale differs; During 50% of the time in March 2010 the PWV was below 1.8 mm, and during August 2010, the PWV was below 0.7 mm 50% of the time. It should however be noted that these numbers vary greatly from year to year.

Phase Fluctuations/Stability at Chajnantor

Tropospheric phase stability was measured directly using two phase monitors (site test interferometers, STI), one built by NRAO and one by ESO, and located in Chajnantor. These observed unmodulated beacons broadcast from geostationary satellites and measure the phase difference between the signals received by two 1.8 m diameter antennas 300 m apart. Because the atmosphere is non-dispersive away from line centers, the results can be scaled to millimeter and submillimeter wavelengths. From the phase time series, the RMS path fluctuations on a 300 m baseline, the power law exponent of the phase structure function, and the velocity at which the turbulent water vapor moves over the array were obtained. The NRAO STI operated almost continuously since May 1995 until August 2005, and the ESO STI from June 1998 until July 2005. The data is analyzed to derive the path fluctuations AT THE ZENITH for a 300m baseline using 10 minutes time bins, to guarantee that the phase screens have had enough time to cross over the STI baseline completely.

The results of both STIs are as follows (fluctuations at zenith for 10 minute bins):

A merged statistical plot of the information obtained with the NRAO STI is as follows:

The plots in the upper row (from left to right) show the monthly median, the comparison of the monthly median as a function of year and the median diurnal variation of the path fluctuation RMS, respectively. There is a clear correlation of increased phase fluctuations with Altiplanic winter and with time of day (larger fluctuations during day time, peaking near local noon).

The plots in the lower row (from left to right) show the cumulative distributions of the fluctuations, the slope of the dependency of the fluctuations with baseline lenght and the crossing time of the STI baseline, respectively. The plots suggest that the fluctuations are never pure Kolmogorov, and that a possible mixture of layers, different layer velocities, etc may be occurring at the AOS.

References:

Otarola A., Holdaway M., Nyman L-E., Radford S.J.E., Butler B. J (2005-02-01),  ATMOSPHERIC TRANSPARENCY AT CHAJNANTOR: 1973-2003 , ALMA Memo # 512

Neal Evans, John Richer, Seiichi Sakamoto, Christine Wilson, Diego Mardones, Simon Radford, Selby Cull, Robert Lucas (2005-07-03),  Site Properties and Stringency,  ALMA Memo # 471

Alison Stirling, John Richer, Richard Hills, Adrian Lock (2005-04-05),  Turbulence Simulations of Dry and Wet Phase Fluctuations at Chajnantor. Part I: The Daytime Convective Boundary Layer , ALMA Memo # 517

• Accessibility
• Privacy Statement

By continuing to use this website, you are giving consent to our use of cookies. For more information on how ESO uses data and how you can disable cookies, please view our privacy policy .

Press Release

Revolutionary alma image reveals planetary genesis.

6 November 2014

This new image from ALMA, the Atacama Large Millimeter/submillimeter Array, reveals extraordinarily fine detail that has never been seen before in the planet-forming disc around a young star. These are the first observations that have used ALMA in its near-final configuration and the sharpest pictures ever made at submillimetre wavelengths. The new results are an enormous step forward in the observation of how protoplanetary discs develop and how planets form.

For ALMA’s first observations in its new and most powerful mode, researchers pointed the antennas at HL Tauri — a young star, about 450 light-years away, which is surrounded by a dusty disc [1] . The resulting image exceeds all expectations and reveals unexpectedly fine detail in the disc of material left over from star birth. It shows a series of concentric bright rings, separated by gaps  [2] .

"These features are almost certainly the result of young planet-like bodies that are being formed in the disc. This is surprising since such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image,"  said Stuartt Corder, ALMA Deputy Director.

“ When we first saw this image we were astounded at the spectacular level of detail. HL Tauri is no more than a million years old, yet already its disc appears to be full of forming planets. This one image alone will revolutionise theories of planet formation, ” explained Catherine Vlahakis, ALMA Deputy Program Scientist and Lead Program Scientist for the ALMA Long Baseline Campaign.

HL Tauri’s disc appears much more developed than would be expected from the age of the system. Thus, the ALMA image also suggests that the planet-formation process may be faster than previously thought.

Such high resolution can only be achieved with the long baseline capabilities of ALMA and provides astronomers with new information that is impossible to collect with any other facility, even the NASA/ESA Hubble Space Telescope. “The logistics and infrastructure required to place antennas at such distant locations required an unprecedented coordinated effort by an expert international team of engineers and scientists,” said ALMA Director, Pierre Cox. “These long baselines fulfill one of ALMA’s major objectives and mark an impressive technological, scientific and engineering milestone.”

Young stars like HL Tauri are born in clouds of gas and fine dust, in regions which have collapsed under the effects of gravitation, forming dense hot cores that eventually ignite to become young stars. These young stars are initially cocooned in the remaining gas and dust, which eventually settles into a disc, known as a protoplanetary disc.

Through many collisions the dust particles will stick together, growing into clumps the size of sand grains and pebbles. Ultimately, asteroids, comets and even planets can form in the disc. Young planets will disrupt the disc and create rings, gaps and holes such as those seen in the structures now observed by ALMA [3] .

The investigation of these protoplanetary discs is essential to our understanding of how Earth formed in the Solar System. Observing the first stages of planet formation around HL Tauri may show us how our own planetary system may have looked more than four billion years ago, when it formed.

“ Most of what we know about planet formation today is based on theory. Images with this level of detail have up to now been relegated to computer simulations or artist’s impressions. This high resolution image of HL Tauri demonstrates what ALMA can achieve when it operates in its largest configuration and starts a new era in our exploration of the formation of stars and planets,” says Tim de Zeeuw, Director General of ESO.

[1] Since September 2014 ALMA has been observing the Universe using its longest ever baselines, with antennas separated by up to 15 kilometres. This Long Baseline Campaign will continue until 1 December 2014. The baseline is the distance between two of the antennas in the array. As a comparison, other facilities operating at millimetre wavelengths provide antennas separated by no more than two kilometres. The maximum possible ALMA baseline is 16 kilometres. Future observations at shorter wavelengths will achieve even higher image sharpness.

[2] The structures are seen with a resolution of just five times the distance from the Sun to the Earth. This corresponds to an angular resolution of about 35 milliarcseconds — better than what is routinely achieved with the NASA/ESA Hubble Space Telescope.

[3] In visible light, HL Tauri is hidden behind a massive envelope of dust and gas. ALMA observes at much longer wavelengths, which allows it to study the processes right at the core of this cloud.

More information

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, Czechia, 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”.

• Science paper
• More about ALMA
• Photos of ALMA
• Videos of ALMA
• ALMA brochure
• The movie ALMA — In Search of our Cosmic Origins
• The ALMA Photo Book In Search of our Cosmic Origins – The Construction of the Atacama Large Millimeter/submillimeter Array
• More press releases based on ALMA data
• Catalog of Circumstellar Discs

Catherine Vlahakis Joint ALMA Observatory Santiago, Chile Tel: +56 9 75515736 Email: [email protected]

Valeria Foncea Rubens Joint ALMA Observatory Santiago, Chile Tel: +56 2 24676258 Email: [email protected]

Richard Hook ESO education and Public Outreach Department Garching bei München, Germany Tel: +49 89 3200 6655 Cell: +49 151 1537 3591 Email: [email protected]

Connect with ESO on social media

About the Release

• For Educators
• For Scientists

• Announcement: March 13, 2023 at 9:28 am EDT

A Decade of Unveiling the Hidden Universe: ALMA at 10

On March 13 th , 2023, astronomers around the world will mark the 10 th anniversary of the inauguration of the Atacama Large Millimeter/submillimeter Array (ALMA), the world’s largest radio telescope. Over the past decade, the international ALMA collaboration— led by the U.S. National Science Foundation ’s National Radio Astronomy Observatory (NRAO), the European Southern Observatory (ESO), and the National Astronomical Observatory of Japan (NAOJ)— has revolutionized our understanding of the Universe and unveiled its secrets, from the formation of planets, stars, and galaxies to deciphering the chemistry of the cosmos, and even taking part in capturing the first images of black holes. 

ALMA’s decade of success was preceded by Early Science Observations in 2011, nearly a full two years before the telescope was inaugurated. This test period for ALMA yielded complex and beautiful images which revealed star formation and violent galaxy mergers in the Antennae Galaxies at a level of detail no other telescopes on Earth had ever attained. These pre-inaugural observations allowed ALMA to grow into what it is today. 

“Since its first light, ALMA has not only changed our understanding of the Universe, but also the way in which we look at it,” said Tony Beasley, Director of NRAO and AUI Vice President for radio astronomy. “In order to look deeper into the Universe and to see things that no other telescopes can see with such clarity, like water hiding out in the disks of young stars , and the supermassive black hole in the heart of the Milky Way, we have continuously developed cutting-edge technology, including some of the fastest supercomputing processors in the world.”  

ALMA consists of 66 antennas, spread over up to 16 kilometers— nearly 10 miles— on the Chajnantor Plateau of the Chilean Andes at 5,000 meters— or 16,404 feet— above sea level. The technology that makes the telescope special is borne of an international collaboration of 21 countries from across North America, Europe, and East Asia. NRAO’s Central Development Laboratory (CDL) is responsible for the development of the Band 6 receiver , ALMA’s most scientifically productive receiver, which was approved for upgrades in 2021. ALMA was also approved earlier this year for the development of a new central correlator and digital transmission system , upgrades that will eventually increase the system bandwidth by a factor of four, and that will be carried out by NRAO and several other partners. This technology, and other innovations like it, have supported ALMA-user scientists to produce more than 3,000 scientific publications to date. That’s nearly one publication per day for a decade.

“ALMA has captured the world’s imagination since it unveiled its first images more than a decade ago, and it has opened new windows on the Universe that could not have been opened otherwise,” said Karen Marrongelle, U.S. National Science Foundation Chief Operating Officer. “Our commitment to ALMA now and for the future is the same as it was then: to develop the technology that unlocks and expands our knowledge of the Milky Way and every other galaxy in our Universe.”

Among ALMA’s most notable contributions are the first clear pictures of planet formation, observed around the young star HL Tau by scientists from ALMA’s partner regions and led by NRAO in 2014, and supermassive black holes M87* and SgrA* , observed by the Event Horizon Telescope (EHT) collaboration in 2019 and 2022, respectively. 

“ALMA has transformed our understanding of the Universe and opened new research frontiers,” said Sean Dougherty, Director of ALMA. “We are very proud of the accomplishments of the past decade and excited about the discoveries over the next ten years.”

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

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (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 Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Media Contacts:

Amy C. Oliver Public Information Officer, ALMA Public Information & News Manager, NRAO +1 434 242 9584 [email protected]

Nicolás Lira Education and Public Outreach Coordinator Joint ALMA Observatory, Santiago – Chile +56 2 2467 6519 [email protected]

More News From Atacama Large Millimeter/submillimeter Array

The Atacama Large Millimeter/submillimeter Array (ALMA), renowned for observing the cosmos’s darkest and most distant corners, has taken a…

Jupiter’s moon Io is the most volcanically active place in the solar system. During its 1.8-day orbit, this moon…

The U.S. National Science Foundation National Radio Astronomy Observatory (NSF NRAO) and Associated Universities, Inc. (AUI) are proud to celebrate the remarkable achievements of two local students, Iris and Camila, as they embark on their journeys into STEM (Science, Technology, Engineering, and Mathematics) careers.

Astronomers have discovered the secrets of a starburst galaxy producing new stars at a rate much faster than our…

More News Related to People and Events

The VLA Spring Open House promises a day filled with enriching experiences, including guided tours, captivating talks, educational activities, and a variety of local food options.

The National Radio Astronomy Observatory (NRAO) marked its presence for the third consecutive year at the prestigious New Mexico Governor’s STEM Challenge

This International Women’s Day, the National Radio Astronomy Observatory (NRAO) celebrates the selection of Dr. Patricia (Trish) Henning as the next Associate Director for New Mexico Operations

Over the course of two scientific meetings, held in 2022 and 2023, German astronomers have collected 41 highly compelling science cases involving 57 unique authors from 19 German institutions, all aspiring to use the ngVLA.

ALMA Opens Its Eyes

3 October, 2011 / Read time: 12 minutes

The most powerful millimeter/submillimeter-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 competed to be the first few researchers to explore some of the darkest, coldest, farthest, and most hidden secrets of the Cosmos with this new astronomical tool.

“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, ALMA Director.

At present, around a third of ALMA’s eventual 66 radio antennas make up the growing array on the Chajnantor plateau in northern Chile, at an elevation of 5,000 meters. And yet, even under construction, ALMA has become the best telescope of its kind – as reflected by the extraordinary number of astronomers who requested to observe with ALMA.

“The 'M' in ALMA stands for 'millimeter/submillimeter' waves, because ALMA views the Universe in these long wavelengths of light, much longer than the optical light we see with our eyes,”  said Alison Peck, ALMA Deputy Project Scientist.  “With millimeter and submillimeter waves, we can watch star and planet formation, investigate astrochemistry, and detect the light that is finally reaching us from the Universe’s earliest galaxies.”

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 —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 is 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 submillimeter-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 submillimeter 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.  “It was absolutely tremendous to receive more than nine hundred project proposals from astronomers from throughout the world wanting to use ALMA in this first ever science period!”  said Lewis Ball, ALMA Deputy Director.  “That represents a level of demand which is unprecedented across any ground-based or space telescope .” The successful projects were chosen based on their scientific merit, their regional diversity, and also their relevance to ALMA’s major science goals.

One of the projects chosen for ALMA Early Science observations was that of David Wilner of 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 disks, 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 disk around HD142527, a young star that is 400 light years away. “ The dusty disk 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 disk 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.

Father away, 26,000 light years from us in the center 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 tantalizing views of Sgr 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 .”

ALMA is capable of seeing cosmic dust, the cold ashes from exploded stars. Like the black outlines in a child’s coloring 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 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 Plateau in the harsh Atacama Desert. Each new, climate-armored antenna will join the array and be linked via fiber 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 millimeter/submillimeter wave radio antennas working together as one and built by ALMA’s multinational partners in North America, East Asia, and Europe.

Thijs de Graauw, ALMA Director, said:  “Today marks the recognition of the successful coalition of thousands of people from all over the world all working with the same goal: to build the world’s most advanced radio telescope to see into the Universe’s coldest, darkest places, where galaxies and stars and perhaps the building blocks of life are created.”

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (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 Ministry of Science and Technology (MOST) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. 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.

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

[3]  1.7x1016 operations per second.

Join our Newsletter

Image title.

Here goes image description

Share Image

• For Educators
• For Scientists

The Atacama Large Millimeter / submillimeter Array

• What is ALMA?
• What is ALMA used For?
• Cosmology & the Distant Universe
• Galaxies & Active Galactic Nuclei
• The Interstellar Medium
• The Origin of Planets & Solar Systems
• Event Horizon Telescope
• Who Operates ALMA?
• An International Partnership

What Makes ALMA So Powerful?

• The Correlator

ALMA Technology

Ask radio astronomy engineers about the early conversations they had with astronomers on their ideal design for a millimeter-wave telescope array, and they will tell you that the astronomers wanted the impossible. Accurately combining high-frequency waves from several dozen dish antennas in the extreme climate of the Chilean Andes had never been attempted – for good reason.

And yet, now ALMA stands as a masterpiece of engineering, the most complex astronomical observatory ever achieved on Earth, thanks to those same engineers who pushed technology into innovations the world had never seen.

What makes ALMA so extraordinary is its manifold of innovative technologies. By the time an observer receives data from ALMA, its waves have been processed through the inventions and constructions of thousands of skilled people from around the world.

Antennas: The “Eyes” of ALMA

Using the same technical and scientific specifications, each of the three partner nations came up with its own different design for the robotic, armor-clad antennas.

We worked with Vertex, RSI, a company based in Germany but owned by General Dynamics Corporation, to design our 12-meter dish antennas. Their unique features are a spider-web feed support to hold the secondary mirror and an elevation gear that is driven by a track system. Our dishes are bolted together and their backs are enclosed to provide crawlspace maintenance over the many years ALMA is expected to operate.

Our European partners worked with the AEM Consortium (Alcatel Alenia Space France, Alcatel Alenia Space Italy, European Industrial Engineering S.r.L., MT Aerospace) to design their 12-meter antennas with a magnetic sweep drive and dishes that are glued together. Their secondary mirror sits on four smooth poles, and their dishes are covered entirely by a conical backing to increase wind resistance and reduce joints that can expand and contract in extreme temperature changes.

Our East Asian partners worked with MELCO (Mitsubishi Electric Corporation) to design a 12-meter antenna with a bolted dish, spider-webbed feed legs, and a magnetic drive elevation gear. They also designed the twelve 7-meter dish antennas in miniature, but with the smooth, four-poled feed legs, that sit on the same pedestal drive bases as their 12-meter cousins. The surfaces of all of these dishes, to accurately reflect millimeter and submillimeter waves, are smooth to less than the thickness of a human hair. The amazing panels are bolted on and hand adjusted to this accuracy.

These receivers were built around the world, with each partner contributing designs and construction. The giant cooler keeps them to nearly the temperature of space — hundreds of degrees below zero — to block their electronics from creating heat that the receivers detect as radio noise.

The receivers can detect wavelengths from 8.6 to 0.3 mm (frequencies from 35 GHz up to 950 GHz). When ALMA was in its design phase, the specifications for these receivers were beyond what had ever been possible. In operation now, the receivers perform even better than those specifications.

ALMA’s antennas do not work alone. They must function as a whole of up to 66 antennas. Just as your eyes are separated by a certain distance, the antennas in the array are separated by varying distances. Imagine a pair of eyes 10 miles across! For us to make any sense of what ALMA “sees,” we have to process its collected data from its many pairs of “eyes.

The Correlator: the “Brain” of ALMA

Complex electronics accurately stitch ALMA’s individual wave detections together into one dataset. The first step in this process is to have exact measurements of where and when the antenna picked up its waves. On each antenna is a clock that timestamps the data using a kind of atomic metronome, or rhythm-keeping device, kept near the supercomputer. The timekeeping waves from this central oscillator beam out to each of ALMA’s antennas. Onboard the antennas, a local oscillator injects this timekeeping beat into a microscopic mixer with the waves coming through the receiver, and a mixed-down signal is digitized and sent back along the fiber into the supercomputer.

Inside the supercomputer, at speeds reaching 17 quadrillion mathematical operations every second, every antenna’s signal is paired with every other antenna’s signal. This is called “correlation,” and it is the secret of how all radio telescope arrays achieve such amazing images.

The so-called correlator Correlator A specialized supercomputer that multiplies the data from two antennas and averages the result over time. Essentially the correlator only selects the data that is spotted and analyzed by both antennas, which means the data that isn’t spotted by both is dropped. assembles the data into cubes, slices of the signal divided by frequency, that can be hundreds of layers thick. Astronomers process those data in a software package designed by radio astronomers and software developers for ALMA called CASA.

ALMA in the News

The Atacama Large Millimeter/submillimeter Array (ALMA), renowned for observing the cosmos’s darkest and most distant corners, has taken a…

Jupiter’s moon Io is the most volcanically active place in the solar system. During its 1.8-day orbit, this moon…

The U.S. National Science Foundation National Radio Astronomy Observatory (NSF NRAO) and Associated Universities, Inc. (AUI) are proud to celebrate the remarkable achievements of two local students, Iris and Camila, as they embark on their journeys into STEM (Science, Technology, Engineering, and Mathematics) careers.