Ραδιοτηλεσκόπιο ALMA: Η ψυχή της ερήμου Ατακάμα

ALMA OBSERVATORY: THE SOUL OF THE ATACAMA DESERT

AUGUST 16th 2024 | Marilenia Zoi

“The universe is full of magical things patiently waiting for our wits to grow sharper.”
–Eden Phillpotts

* Alma in Spanish translates to "soul"

Image 1: The Atacama Large Millimeter/submillimeter Array in the Atacama Desert, Chile.
Source: NRAO

This article will take us to the Atacama Desert in Chile. When one thinks of a desert, images of dryness and unbearable heat come to mind, and perhaps the thought that a desert is not a suitable place for human activity. However, in the Atacama Desert is located the ALMA Observatory (Atacama Large Millimeter/submillimeter Array), which takes advantage of the light that bathes the desert area and provides us with significant information about our cosmic origins.

The History of ALMA

The idea of constructing the ALMA radio telescope dates back to the early 1980s, shortly after the completion of the Nobeyama 45-meter radio telescope. Scientists at Japan's National Astronomical Observatory (NAOJ) were not content with the success of their latest project and continued to seek ways to deepen their understanding of the universe. Thus, in collaboration with the European Southern Observatory (ESO) and the National Radio Astronomy Observatory (NRAO), studies and construction of the radio telescope began in the 1990s. The first observations were made in 2011, and it was completed in 2013 at a total cost of $1.4 billion, starting full operations with 16 antennas, each 12 meters in diameter.

Image 2: Image of an ALMA antenna being transported to the installation site.
Source: Thales

What is ALMA?

Today, the Atacama Large Millimeter/submillimeter Array consists of 66 antennas, which detect and study radio waves with wavelengths ranging from 0.32 to 3.6 mm. Of its total antennas, 50 are 12 meters in diameter and are part of the main array, functioning together as a single telescope (an interferometer¹). The remaining antennas form a compact array of 4 antennas, each 12 meters in diameter, and 12 antennas, each 7 meters in diameter. These antennas are spread over distances ranging from 150 meters to 16 kilometers.

The purpose of ALMA is to provide observers with the clearest possible images of various phenomena related to the early universe, such as star formation or molecular clouds.².

Image 3: The Atacama Large Millimeter/submillimeter Array in the Atacama Desert, Chile.
Source: Universe Today

Significant Findings

Solar System A variety of celestial bodies within our solar system, such as moons, asteroids, comets, and planets, have been studied by ALMA.

In 2019, ALMA astronomers aimed to deepen our understanding of Jupiter's interior, beneath its colorful and diverse clouds. Using radio waves, they managed to capture images of the planet's atmosphere 50 kilometers below the visible cloud layer.

Image 4: Image of Jupiter
Source: ALMA Observatory

Planets: In 2014, while observing the young star HL Tauri, ALMA observers made groundbreaking discoveries regarding planet formation. The image of HL Tauri’s bright, concentric rings provided the most indisputable evidence of the ongoing formation of planets within protoplanetary disks and led to the conclusion that planets form faster than previously thought.

The search for answers about planet formation did not stop there. In 2018, the results of a study, in which scientists from around the world partook, were published, based on images of 20 nearby protoplanetary disks. The most notable conclusions from this study were that giant planets, like Uranus for example, take shape much faster than previously believed and tend to form at astonishingly far distances from their system's star.

Image 5: The protoplanetary disk around the star HL Tauri.
Source: ALMA Observatory

Star Formation: Stars form from molecular clouds or stellar nurseries. A stellar nursery can produce thousands of newborn stars as long as it exists. Stellar nurseries have been discovered in a variety of shapes and sizes, which influence the stars that are formed.

In 2018, ALMA, along with other telescopes, revealed the internal web of stellar nurseries in the Orion Nebula. This web consists of red filaments, which can only be detected by telescopes operating in the millimeter wavelength range and are not visible in optical and infrared light, making ALMA one of the few telescopes capable of capturing it.

In 2021, astronomers, with the help of ALMA, expanded their studies to map our cosmic neighborhood and discover variations in star-forming galaxies.

Image 6: The internal web of stellar nurseries in the Orion Nebula. The red frozen gas acts as a cradle for new stars.
Source: ALMA Observatory

Star Death: Stars reach their end in various ways. Some end in supernovae⁴Others become red giants⁵ and then begin to lose mass by ejecting gas and particles, eventually forming a planetary nebula. ALMA observers have made significant discoveries regarding both cases of star deaths.

In 2017, in collaboration with NASA's Hubble and the Chandra X-ray Observatory, an in-depth study of Supernova 1987A, which shocked astronomers thirty years earlier, was conducted, offering new images and data.

In 2020, while observing some red giants, ALMA scientists debunked the theory that gas around them is necessarily spherical. If they interact with another star or exoplanet, their shape changes.

Image 7: Supernova 1987A as depicted by each collaborating telescope.
Source: ALMA Observatory

Galaxy Formation: Oxygen did not always exist in the universe. It was created within stars and explosively released at the end of their lives.

In 2018, studies on galaxy formation were conducted by detecting the most distant oxygen molecules. These molecules were discovered 13.28 billion light-years away, in the galaxy MACS1149-JD1, leading to the conclusion that stars formed unexpectedly 250 million years after the Big Bang. ALMA's findings indicated that oxygen had already been released in MACS1149-JD1 from dead stars 500 million years after the Big Bang.

Image 8: The galaxy MACS1149-JD1, as captured by ALMA and Hubble.³.
Source: ALMA Observatory

Black Holes: The ALMA observatory, in collaboration with other radio telescopes, created an Earth-sized interferometer, the Event Horizon Telescope, to capture the first image of a black hole in 2019. This is the black hole at the center of the M87 galaxy.

Image 9: The first image of a black hole.
Source: ALMA Observatory

Recent Developments

Higher Image Resolution: The ALMA team upgraded to Band 10 by increasing the distance between antennas, aiming for clearer images from its observations. With these improvements, the radio telescope can detect objects on the Moon's surface as small as 10 meters!

Image 10: The highest resolution image captured by ALMA, depicting the star R Leporis, which belongs to our galaxy.
Source: Space.com

Planet Formation Around Twin Stars⁶: ALMA scientists studied the protoplanetary disks of two twin systems, D.F. Tau and F.O. Tau. In the D.F. Tau system, only one protoplanetary disk is magnetically locked with its star, while the other has detached. This is explained by the fact that the star that lost its disk rotates rapidly. However, the same does not apply to the F.O. Tau system, where the stars move more slowly and have more circular orbits. There, both disks remain magnetically locked to their stars.

The conclusion drawn is that more stable conditions, as in the case of the F.O. Tau system, favor planet formation.

Image 11: The twin star system DF Tau.
Source: Space.com

Discovery of Molecular Species in a Distant Galaxy ALMA scientists, after conducting research on the galaxy NGC 253, which is a cradle of star formation, discovered over a hundred molecular species. This discovery is noteworthy because never before have so many been found beyond our galaxy. These molecular species provide important information about the different stages of star life.

Epilogue

The ALMA radio telescope still has much to offer to the astronomical community. This is evident from its continuous groundbreaking discoveries and the evolution of its capabilities, as it provides increasingly clearer images over time. As long as the observatory's astronomers remain curious and driven by the desire to understand the universe more deeply, humanity will eagerly await ALMA's new findings.

Glossary of Terms

INTERFEROMETER: A combination of a number of instruments placed at distant voltages, for the purpose of obtaining high definition images.

MOLECULAR CLOUD: A cloud in which the conditions for the formation of molecules are favorable.

HUBBLE: NASA telescope, which has been in orbit around Earth since 1990.

SUPERNOVA: Otherwise, a supernova star. It is about the explosion of a star just before it reaches the end of its life.

RED GIANT: A star can turn into a red giant one stage before it dies. It gains enormous volume, its mass dilutes and its surface temperature drops. After that, it starts to lose its ground.

TWIN STARS: Twin stars are called those that revolve around each other.

Editorial Review: Despoina Kasimoglou
Scientific Review: Despoina Kasimoglou
Translation: Despoina Kasimoglou

BIBLIOGRAPHY

ALMA Observatory, “About ALMA, at first glance”, https://www.almaobservatory.org/en/about-alma/, [πρόσβαση 05/08/2024]
NAOJ (National Astronomical Observatory of Japan), “Milestones”, https://alma-telescope.jp/en/milestones, [πρόσβαση 05/08/2024]
The Editors of Encyclopaedia Brittanica, “Atacama Large Millimeter Array”, https://www.britannica.com/topic/Atacama-Large-Millimeter-Array, [πρόσβαση 05/08/2024]
ALMA Observatory, “Discoveries”, https://www.almaobservatory.org/en/about-alma/how-alma-works/early-discoveries/, [πρόσβαση 11/08/2024]
Event Horizon Telescope, “Astronomers Reveal First Image of the Black Hole at the Heart of Our Galaxy”, https://eventhorizontelescope.org/blog/astronomers-reveal-first-image-black-hole-heart-our-galaxy, [πρόσβαση 13/08/2024]
Mark Thompson (2023), “A New Technique Has Dramatically Improved ALMA’s Resolution”, https://www.universetoday.com/164335/a-new-technique-has-dramatically-improved-almas-resolution/, [πρόσβαση 13/08/2024]
Robert Lea (2024), “Massive radio telescope array investigates the birth of planets around twin stars”, https://www.space.com/twin-star-system-alma-investigation, [πρόσβαση 13/08/2024]
ALMA Observatory, “A Glimpse by Molecules – a Production Line Inside a Busy Star Factory in a Starburst Galaxy”, https://alma-telescope.jp/en/news/starfactory-202403, [πρόσβαση 13/08/2024]
Καστανάς, Π. (2020), Προς τ’ άστρα, Αθήνα: ΚΑΚΤΟΣ